magnetic and spectroscopic studies of … · relative basicity of the tmpyp isomers 35 ......

MAGNETIC

METAL

AND SPECTROSCOPIC STUDIES OF TRANSITION

COMPLEXES OF WATER SOLUBLE PORPHYRINS

a t h e s i s by

D a v id Wood

submitted for the degree of Doctor of Philosophy of the University

of London and for the Diploma of Membership of Imperial College

C h e m is t r y D e p a r tm e n t

I m p e r i a l C o l l e g e

London SW7 2AY JANUARY 1985

ABSTRACT

Tetra (4-N-methyl) t e t ra p y r id y l porphyrin (abbreviated : p-TMPyP)

and the related (3-N-methyl) and (3 -N -e thy l ) compounds were synthesised

by adaptations of the l i t e r a t u r e methods .

The pK values for water , a x ia l ly coordinated to the Fe***

complexes , were determined spectrophotometrically as a function of

temperature and ionic strength . The pH and ionic strength dependent

dimerisation of the F e * *1 complexes was investigated using magnetic

suscept ib i l ty measurements and spectrophotometry .

The formation constants for the complexes of Fe***p-TMPyP with

f luor ide , azide , cyanide and some nitrogenous bases were determined

by spectrophotometric and magnetic t i t r a t i o n . The competition from

buffer coordination was investigated and in some cases was corrected

for . Computer programs were w r i t ten to evaluate these formation

constants . 1H NMR spectroscopy was also used to fol low quan t i ta t ive ly

cyanide coordination and ESR spectroscopy was used to establ ish the

coordination of f lu o r id e .

Variable temperature magnetic suscept ib i i ty and 1H NMR

measurements were used to fo llow the coordination of water to

N i i r m-TMPyP . Thermodynamic parameters and rate constants were

determined .

The revers ib le coordination of dioxygen to Mn**m-TMPyP was

investigated using ESR spectroscopy .

A q u a l i t a t i v e determination of the r e la t iv e s t a b i l i t i e s of

Co^m-TMPyP complexes with imidazoles , pyridines , amines ( including

b io log ica l buffers) and azide in aqueous solution was made using ESR

spectroscopy . The e f fe c t of adding poly alcohols was investigated .

The reaction of Co^m-TMPyP with dioxygen was followed using ESR and

NMR spectroscopy and the mechanism was considered .

2

A C K N O W L E D G E M E N T S

The h e l p and g u id a n c e o f my s u p e r v i s o r ,

P r o f Dennis Evans , i s acknow ledged w i t h g r a t i t u d e .

My th a n k s a l s o go t o t h e f o l l o w i n g p e o p le .

The t e c h n i c a l s t a f f f o r t h e i r s k i l l e d a s s i s t a n c e and

i n p a r t i c u l a r t o Sue Johnson f o r her c h e e r f u l h e l p i n

o p e r a t i n g t h e B ru k e r WM250 .

P e t e r Beardwood f o r h is w e l l i n f o r m e d a d v ic e on ESR

s p e c t r o s c o p y and m ic r o c o m p u t in g .

John W h i te h o u s e and Bob R o l l i n s f o r t h e i r h i n t s on

FORTRAN programming .

L i o n e l M i lg r o m f o r t h e b e n e f i t o f h i s e x p e r i e n c e i n

p o r p h y r i n s y n t h e s i s .

F i n a l l y t o O l i v i a Howes and L e s le y C l a r k e f o r t h e i r

c a r e f u l p r o o f r e a d i n g o f t h i s t h e s i s .

T h is work was c a r r i e d ou t w i t h t h e f i n a n c i a l

a s s i s t a n c e o f th e S c ie n c e R esearch C o u n c i l .

3

CONTENTS

Page

Abstract 2

Acknowledgements 3

Contents 4

L ist of tables and f igures 9

Symbols and abbreviations 12

Introduction : some general considerations

0.1. Porphyrins and metalloporphyrins 16

0.2. Aggregation 19

0.3. Magnetic properties of f i r s t row t rans i t ion metal

complexes of TMPyP 24

0.4. The Evans' Method 26

Chapter 1 : aqueous solution e q u i l ib r i a of FeTMPyP

1.1. Simple aqueous solution behaviour

1. 1. 1. Introduction 33

1.1.2. Relative bas ic i ty of the TMPyP isomers 35

1. 1. 3. Axial water hydrolysis 36

1. 1. 4. Oimerisation 45

1. 1. 5. Solution sus c e p t ib i l i t y of measurements 52

1. 1. 6. Summary of equil ibr ium constant evaluations 62

1. 1. 7. Experimental 63

4

2. Complexes with other l igands

1.2.1. Introduction 67

1. 2.2. V is ib le absorption spectra 67

1. 2. 3. Magnetic t i t r a t io n s 71

1 . 2 . ; . Complexes with imidazoles 79

1.2.5. Complexes with DMAP and SCN 96

1.2.6. Azide complex 99

1.2.7. Fluoride complex 106

1.2.8. Cyanide complexes

1 . 2.8. 1 Introduction 112

1. 2. 8. 2 . Spectrophotometric t i t r a t i o n , pH 3.75 - 7.2 112

1 . 2 . 8 . 3 . Spectrophotometric t i t r a t i o n , pH 7.9 - 10.0 121

1 . 2.8.4 T i t ra t io n followed by NMR 129

inCOCM Magnetic t i t r a t i o n s 133

1. 2. 8. 6 . Comparison of cyano complex formation constants 1 ; 2

1.2.9. Summary of values u ;

1.2.10. FeI I TMPyP h 5

1.2.11. Experimental h 9

1.3. Synthesis and analysis

1. 3.1. Preparation of FeT(M,Et)PyP 153

1.3.2. Analysis of FeTMPyP for iron 156

1. 3. 3. Analysis of cyanide solutions 158

5

Page

Chapter 2 : some reactions of MnTMPyP and NiTMPyP

2.1. Introduction 160

2.2. MnTMPyP


2. 2. 2. 1H NMR of MnI H TMPyP 160

2. 2. 3. Reaction of Mn** porphyrins with dioxygen 164

2. 2. 4. Synthesis 169

2.3. NiTMPyP


2. 3. 2. Spectrophotometric pH t i t r a t i o n 172

2. 3. 3. L a b i l i t y of ax ia l water 172

2. 3. 4. Suscept ib i l i ty measurements 173

2. 3. 5. Direct observation of 1H NMR 176

2. 3. 6. Other systems 182

2. 3. 7. Summary of results for NiTMPyP 182

2. 3. 8. Synthesis 183

6

Page

Chapter 3 : Reactions of CoTMPyP with dioxygen and other ligands

3.1. Introduction 186

3.2. Suscept ib i l i ty measurements 187

3.3. ESR spectra 187

3.4. Reaction with dioxygen followed by ESR spectroscopy 196

3.5. Reaction with ind iv idual ligands 200

3.6. Complexes in methanol solution 212

3.7. ESR parameters 214

3.8. Reaction with dioxygen followed by 1H NMR

and ESR spectroscopy 217

3.9. Other studies 223

3.10. Synthesis and p u r i f i c a t io n 225

Preparation , puruf icat ion and analysis

4.1. Carbonate free NaOH 229

4.2. Imidazoles 229

4.3. Free base porphyrins 229

4.4. Ethyl p-toluene sulphonate 234

7

Page

Appendix 1 : FeTMPyP

1.1 Spectrophotometric t i t r a t i o n s 237

1.2 To calculate pK._ from magnetic moment data 239A21.3 Spectrophotometric determination of dimerisation constant 241

1.4 To calculate the magnetic moment of dimeric FeTMPyP 246

1.5 Theory and computer program for calculat ing magnetic

moment var ia t ion with pH 247

1.6 Ef fect of buffer coordination 250

1.7 Magnetic t i t r a t i o n s 255

1.8 Spectrophotometric t i t r a t i o n 270

1.9 Theory and computer program for the evalution of

NMR in tegra l data 281

Appendix 2 : NiTMPyP

2.1 Magnetic moments 290

2.2 1H NMR chemical sh i f ts 295

2.3 1H NMR l in e ha l f widths 299

References 304

8

LIST OF TABLES AND FIGURES

Table T itle Pagi

0.1 Chemical shifts of m-TMPyP 21

0.2 Reference mixtures for susceptibility measurements 29

1 .1 pK. values of TMPyP A 35

1 .2 pK values for Fe^TIM .EtlPyP A1 40

1 .3 Dimerisation constant for Fe p-TMPyP 51

1 .4 Extinction coefficients of Fe p-TMPyP complexes 70

1 .5 Correction for buffer coordination 78

1 .6 $2 values for coordination of imidazoles 79

1 .7 Determination of K’ for cyanide coordination 116

1 .8 Determination of K1 for cyanide coordination 120

1 .9 values for coordination of cyanide 138

1.10 Evaluation of p’ as a function of Kz ef f 139

1.11 P2 values by magnetic t itra tio n 144

2. 1 pKt values for MnTMPyP A 160

2.2 *H NMR Chemical shifts of MnI H TMPyP 161

2.3 ESR parameters for Mn**TMPyP and Mn**TPP 165

2.4 Magnetic moment of NiTMPyP 176

2.5 1H NMR NiTMPyP chemical shifts 180

2.6 Pyrrole peak half width data 181

3.1 ESR parameters of Co^TMPyP complexes 214

3.2 ESR parameters for dioxygen adducts 216

3.3 NMR chemical shifts of Co^TMPyP complexes 220

9

Figure T itle Pag<

0. 1 Porphyrin structure 17

0.2 13C NMR of m-TMPyP 22

0.3 Metalloporphyrin energy level diagram 25

1 . 1 FeTMPyP system of equilibria 34

1 .2 Determination of pK.. valuesA 1 41

1 .3 Visible absorption spectra of FeTMPyP 47

1.4 Spectrophotometric determination of KQ for FeTMPyP 49

1.5 Variation of Fe p-TMPyP magnetic moment with pH 54

1.6 Titration of Fe p-TMPyP with NaOH 59

1.7 Visible absorption spectra of Fe p-TMPyP complexes 68

1.8 Titration of Fe p-TMPyP with imidazole in 0. 1 M buffer 76

1 .9 Titration of Fe p-TMPyP with imidazoles 85

1.10 Titration of Fe p-TMPyP with DMAP and KSCN 97

1.11 Magnetic titra tio n of FeTMPyP with NaN 100

1.12 Visible absorption and ESR spectra of the

FeTMPyP azide complex 104

1 .13 Spectrophotometric t itra tio n of FeTMPyP with KF 107

1 . 14 Titration of FeTMPyP with KF followed by ESR 108

1.15 Magnetic titra tio n of FeTMPyP with KF 110

1.16 Spectrophotometric t itra tio n of FeTMPyP with cyanide ,

pH 3.75 114

1 .17 Spectrophotometric t itra tio n of FeTMPyP with cyanide ,

pH 7.9 - 10.0 125

10

1.18 T itration of FeTMPyP with pH 3.75 cyanide ,

followed by 1H NMR 130

1.19 Magnetic titra tio n of FeTMPyP with cyanide ,

pH 7.20 - 3.75 13B

1.20 Magnetic titra tio n of Fe^TMPyP with imidazole 147

2.1 250 M Hz 1H NMR of Mn1XTMPyP 162

2.2 Reaction of Mn^TMPyP and dioxygen followed by ESR 166

2.3 Temperature dependent magnetic susceptibility of NiTMPyP 175

2.4 250 M Hz *H NMR of NiTMPyP 177

2.5 NiTMPyP pyrrole proton NMR data 179

3.1 ESR spectrum of Cu^TMPyP and a free radical impurity 189

3.2 PCo(O) and PCo(N) type ESR spectra 190

3.3 Effect of solvent on the ESR spectrum of Co^TMPyP 193

3.4 Effect of glycerol on Co^TMPyP ESR spectra 195

3.5 Reaction of Co^TMPyP with 0 followed by ESR 197

3.6 ESR spectra of the *NH and ^NH complexes of Co^TMPyP 201

3.7 ESR spectra of some Co^TMPyP te rtia ry amine complexes 203

3.8 Formation of the PCo**(Im) complex followed by ESR 207

3.9 Reaction of Co^TMPyP with 02 followed by 1H NMR 218

A 1.1 To solve equation {9} for CPFe(CN) ] 276n

Figure Tit l e Page

11

S Y M B O L S A N D A B B R E V I A T I O N S U S E D

S p e c t r o p h o t o m e t r i c t i t r a t i o n s

S u b s c r i p t M is for m o n o m e r ; s u b s c r i p t D is for d i m e r ;

s u b s c r i p t C is for c o m p l e x and s u b s c r i p t T is for o v e r a l l

( a v e r a g e ) .

S u b s c r i p t 0 r e f e r s to t h e i n i t i a l v a l u e and s u b s c r i p t 100

r e f e r s to to the f i n a l v a l u e . The l a c k of such a s u b s c r i p t

m e a n s any p a r t i c u l a r p o i n t of t h e t i t r a t i o n .

A A b s o r b a n c e

- 1 - 1e E x t i n c t i o n c o e f f i c i e n t in c m m o l 1 ; c o n c e n t r a t i o n

r e f e r s to CFeJ for b o t h a n d z.AD M

1 P ath l e n g t h in cm

A W a v e l e n g t h

M a g n e t i c T i t r a t i o n s

S u b s c r i p t M is f o r m o n o m e r ; s u b s c r i p t D is for d i m e r ;

s u b s c r i p t C is for c o m p l e x and s u b s c r i p t T is for o v e r a l l

( a v e r a g e ) .

A f S e p a r a t i o n of r e f e r e n c e p e a k s a f t e r c o r r e c t i o n

p M a g n e t i c m o m e n t

X M a g n e t i c s u s c e p t i b i l i t y

p q is per i r o n c e n t r e but x D is per m o l e of d i m e r

m o l e c u l e s .

C o m p u t e r P r o g r a m s

S u b s c r i p t cal r e f e r s to c a l c u l a t e d and s u b s c r i p t e x p r e f e r s

to e x p e r i m e n t a l .

<

1 2

GeneralCHES 2 - ( C y c l o h e x y l a m i n o ) e t h a n e s u l p h o n i c acid

CD] C o n c e n t r a t i o n of d i m e r i c i ron p o r p h y r i n

D MAP 4 - N ',N ‘ d i m e t h y l a m i n o p y r i d i n e

DSS 3 - {t r i m e t h y l s i y l ) - 1 - p r o p a n e s u l p h o n a t e

[ Fe ] T T o t a l c o n c e n t r a t i o n of i r o n

F e D e u t Iron D e u t e r o p o r p h y r i n - IX

F e D S S Iron D e u t e r o p o r p h y r i n - IX d i s u l f o n i c acid

F e P r o t Iron P r o t o p o r p h y r i n - IX

H E P E S N - 2 - H y d r o x y e t h y l p i p e r a z i n e - N ‘-2-

e t h a n e s u l p h o n i c a c i d

H MDS H e x a m e t h y l d i s i l o x a n e

I I o n i c s t e n g t h

Im I m i d a z o l e

K mW I o n i c p r o d u c t of w a t e r

= 1 . 008 x 1 0 " 14 m o l 2l ” 2 at 25° C

LHS L e f t h a n d s i d e

MES 2 (N - m o r p h o l i n o )- e t h a n e s u l p h o n i c a cid

PFe ( OH ) ■( OH )

PNi(OH2 )2PFe r e p r e s e n t s an i r o n p o r p h y r i n and PNi r e p r e s e n t s a

n i c k e l p o r p h y r i n . T h e m o l e c u l a r f o r m u l a in p a r e n t h e s i s

r e f e r to a x i a l l y c o o r d i n a t e d m o l e c u l e s .

o - p h e n o r t h o p h e n a n t h r o l i n e

pip P i p e r i d i n e

P I P E S P i p a r a z i n e - N N ‘- b i s 2 - e t h a n e s u l p h o n i c

a cid

P TFE P o l y t e t r a f l u o r o e t h y l e n e

py P y r i d i n e

RHS R i g h t hand s i d e

s a l e n Bis - s a l i c y l i d e n e - e t h y l e n e d i a m i n e

TAPP Para t e t r a ( t r i m e t h y l ammoniumphenyl ) p o r p h y r i n

TCP P Para t e t r a c a r bo x y p h e n y l p o r p h y r i n

m-TEtPyP Meta t e t r a ( N - e t h y l p y r i d y l ) p o r p h y r i n

TMPP T e t r a ( p - m e t h o x y p h e n y l ) p o r p h y r i n

m-TMPyP Meta t e t r a ( N - m e t h y l p y r i d y l ) p o r p h y r i n

p-TMPyP Para t e t r a ( N - m e t h y l p y r i d y l ) p o r p h y r i n

I f u n s p e c i f i e d t h e p ar a i s o m e r i s i m p l i e d

TMS T e t r a m e t h y l s i l a n e

TPP T e t r a p h e n y l p o r p h y r i n

TPyP T e t r a p y r i d y l p o r p h y r i n

t p p s 3 T r i ( s u l p h o p h e n y l ) p h e n y l p o r p h y r i n

T P P S T e t r a ( s u l p h o p h e n y l ) p o r p h y r i n

Tr i s T r i s ( h y d r o x y m e t h y l ) - m e t h y l a m i n e

TTP T e t r a t o l y l p o r p h y r i n

I N T R O D U C T I O N

Some g e n e r a l c o n s i d e r a t i o n s

0 . 1 . P o r p h y r i n s a n d m e t a l l o p o r p h v r i n s

P o r p h y r i n s a l l have t h e same cor e o f f o u r p y r r o l e s

j o i n e d v i a t h e i r a carbons by f o u r m e t h i n e

b r i d g e s ( F i g u r e 0 . 1 ) . M e t a l i o ns can be i n c o r p o r a t e d by

c o o r d i n a t i o n f rom t h e f o u r c e n t r a l n i t r o g e n atoms . T h i s

i n v o l v e s l o s s o f two p r o t o n s f rom two o f t h e s e n i t r o g e n

atoms .

M e t a l l o p o r p h y r i n s have been s t u d i e d by many w o r k e r s

and t h i s work has been r e v i e w e d i n two e x c e l l e n t books

e d i t e d r e s p e c t i v e l y by Smi th ( 1 ) and D o l p h i n ( 2a) . These

sub st ances occur n a t u r a l l y i n hemoglob i n and cy t ochromes ,

where t h e y p e r f o r m e s s e n t i a l f u n c t i o n s i n oxygen and

e l e c t r o n t r a n s p o r t . The c l o s e l y r e l a t e d c o r r i n m o l e c u l e

occurs i n v i t a m i n B a n d i n c h l o r o p h y l l s . As ide f ro m t h e

b i o l o g i c a l r e l e v a n c e o f t h e s e m o l e c u l e s , t h e d i v e r s e r e d o x

and c o o r d i n a t i o n c h e m i s t r y i s o f i n t e r e s t i n i t s e l f .

M e t a l l o p o r p h y r i n s have a s t r o n g v i s i b l e chromophore and a r e

somet imes p a r a m a g n e t i c . As a r e s u l t a v a r i e t y o f

s p e c t r o s c o p i c t e c h n i q u e s have been used t o s t udy them .

Most o f t h e work on m e t a l l o p o r p h y r i n s has been done

i n o r g a n i c s o l v e n t s , u s i n g both n a t u r a l and s y n t h e t i c

p o r p h y r i n s . Aqueous s o l u t i o n work i s more r e l e v a n t t o

n a t u r a l l y o c c u r r i n g p o r p h y r i n s , wh ic h g e t t h e i r w a t e r

s o l u b i l i t y f rom c a r b o x y l i c a c i d s i d e c h a i n s . Work done

w i t h such systems has been o f l i m i t e d use because t he

n a t u r a l p o r p h y r i n s show a s t r o n g t e n d e n c y t o a g g r e g a t e i n

aqueous s o l u t i o n ( 3 - 6 )

F i g u r e 0 . 1 shows w a t e r s o l u b l e d e r i v a t i v e s o f TPP

t h a t have been made ( 7 ) by a t t a c h i n g c a r b o x y l a t e o r

FIGURE 0.1 Porphyin SmuCTURE

P o s it io n s of s u b s t i t u t i o n

17

s u l p h o n a t e groups a t t h e p h e n y l groups . However t h e

c a r b o x y l i c a c i d groups do no t g i v e w a t e r s o l u b i l i t y i n a c i d

s o l u t i o n where t h e y become p r o t o n a t e d . TMPyP i s a

d e r i v a t i v e o f TPyP and g e t s i t s w a t e r s o l u b i l i t y f rom f o u r

q u a r t e r n a r y p y r i d i n e s .

TMPyP and i t s m e t a l l o complexes have appeared i n a

d i v e r s i t y o f a p p l i c a t i o n s . In p a r t i c u l a r , i n b i o c h e m i c a l

s t u d i e s ( 8 - 1 4 ) , i n a wa sh i ng powder f o r m u l a t i o n ( 15 ) , i n

t he d e t e r m i n a t i o n o f l ow l e v e l s o f m e t a l s i n w a t e r ( 1 6 , 1 7 )

and as p a r t o f an u n d e r g r a d u a t e l a b o r a t o r y e x e r c i s e ( 1 8 ) .

D e s p i t e t h e many s t u d i e s i n v o l v i n g complexes o f

TMPyP , t h e i r aqueous s o l u t i o n b e h a v i o u r i s not w e l l

u n d e r s t o o d . T h i s work a t t e m p t s t o c l a r i f y t he many

c o n t r a d i c t o r y r e p o r t s and t o f u r t h e r t h e u n d e r s t a n d i n g o f

t h e s e u s e f u l aqueous systems . TMPyP was chosen i n

p r e f e r e n c e t o t h e o t h e r w a t e r s o l u b l e p o r p h y r i n s because o f

i t s l a c k o f a g g r e g a t i o n i n aqueous s o l u t i o n . Th is p r o p e r t y

o f TMPyP i s d i s c u s s e d i n more d e t a i l be l ow .

0 . 2 . A g g r e g a t i o n

0 . 2 . 1 . I n t r o d u c t i o n

P o r p h y r i n s and m e t a l l o p o r p h y r i n s may a s s o c i a t e i n

s o l u t i o n by Van d e r Waals a t t r a c t i o n s between t h e f l a t

f a c e s o f t h e m o l e c u l e s ( 1 9 ) . T h i s process i s g e n e r a l l y

r e f e r r e d t o as a g g r e g a t i o n . V a r i o u s methods , c o v e r i n g a

w ide r a nge o f c o n c e n t r a t i o n s , have been used t o

i n v e s t i g a t e t h e p o s s i b l e a g g r e g a t i o n o f TMPyP . The r e s u l t s

o f o t h e r w o r k e r s a r e d i s c u s s e d be l ow t o g e t h e r w i t h some 1 H

1 3and C NMR measurements c a r r i e d out as p a r t o f t h i s work .

0 . 2 . 2 . F l u o r e s c e n c e

Kano e t a l ( 2 0 ) have obser ved t h a t i n t h e r an ge

- 7 - 5 o2 x 1 0 t o 1 x 10 M (25 C) t h e f l u o r e s c e n c e e m i s s i o n

sp e c t ru m o f TMPyP i s a s i n g l e band . On d i l u t i o n t o

~8 M (2 5 ° C ) o r i n c r e a s i n g t h e t e m p e r a t u r e t o

°C ( 1 0 " 6 M) two bands were obser ved . Use o f aqueous

1 M Na Cl as s o l v e n t made no d i f f e r e n c e . The two band

spe ct rum was a s s i g n e d t o t h e monomer by compar i son t o t h e

spe ct r um o f TPPS. . I t was c onc l uded t h a t TMPyP i s— 8

d i m e r i s e d a t c o n c e n t r a t i o n s above 10 M .

0 . 2 . 3 . S p e c t r o P h o t o m e t r i c and t e m p e r a t u r e jump measurements

P a s t e r n a c k e t a l ( 7 ) c o n c l u d e f rom t h e i r s t u d i e s

o - 7(25 C , pH 0 , pH 7 . 5 , pH 14 , p o r p h y r i n concn 10 t o

- 510 M ) t h a t TCPP and TPPS3 a g g r e g a t e i n aqueous s o l u t i o n- 7 -5whereas TMPyP does n o t . I n t h e range 10 t o 5 x 10 M

TMPyP complexes w i t h N i , Cu and Zn were f ound ( 21 ) no t t o

a g g r e g a t e , wher eas TCPP complexes w i t h N i and Cu d i d

19

i t s m e t a l l o complexes a g g r e g a t e . P a s t e r n a c k ( 23) has

r e p o r t e d t h a t Fe* * * TMPyP does not a g g r e g a t e under t h e

c o n d i t i o n s employed ( 2 5 ° C , pH 2 . 1 , I = 0 . 05M , p o r p h r y n

- 6 - 4concn 2 x 1 0 t o 3 x 1 0 M) . I t has been

suggest ed ( 2 1 , 2 2 ) t h a t f i v e or s i x c o o r d i n a t e

m e t a l l o p o r p h y r i n s do not t e n d to a g g r e g a t e whereas f r e e

base p o r p h y r i n s and f o u r c o o r d i n a t e m e t a l l o p o r p h y r i n s t e n d

t o a g g r e g a t e .

0 . 2 . 4 . and ^3 C NMR s p e c t r a

1 1 3H and C NMR c h e m i c a l s h i f t s and l i n e w i d t h s have

been used i n o t h e r s t u d i e s ( 1 b , 24) t o i d e n t i f y p o r p h y r i n

1 3a g g r e g a t e s and s i m i l a r a dd u c t s . I n t h i s work t he C and

1 oH NMR s p e c t r a o f a m-TMPyP s o l u t i o n i n D2 0 (23 C ,

pD = 6 . 9 , p ho spa t e b u f f e r ) a r e shown ( F i g u r e 0 . 2 ) and t h e

c h e m i c a l s h i f t s f o r d i f f e r e n t c o n c e n t r a t i o n s of p o r p h y r i n

and f o r sodium t o s y l a t e o n l y a r e shown i n T a b l e 0 . 1 .

Ass ignments a r e made by c ompa r i son o f t h e sodium t o s y l a t e

spe ct r um w i t h t h e p o r p h y r i n s p e c t r a . A l l o f t h e peaks

a s s i g n e d t o t h e p o r p h y r i n d i d no t change t o w i t h i n 0 . 0 5 ppm

on d i l u t i o n o f t h e p o r p h y r i n . Th i s r e s u l t suggest s t h a t

t h e p o r p h y r i n does not change i t s s t a t e o f a g g r e g a t i o n ( i f- 2any) a t t h e h i g h e r c o n c e n t r a t i o n s o f 1 x 1 0 and

- 22 x 1 0 M . W i t h one e x c e p t i o n t h e peaks a ss i g n e d t o t h e

t o s y l a t e i o n s h i f t e d u p f i e l d w i t h an i n c r e a s e i n p o r p h y r i n

c o n c e n t r a t i o n . T h i s may be due t o an a s s o c i a t i o n between

t h e p o r p h r i n and t o s y l a t e i o n . The p o r p h y r i n r i n g c u r r e n t

c ou ld a l t e r t h e r e s o n a n c e s o f t h e t o s y l a t e i o n . I t was

a g g r e g a t e . K r i s h n a m u r t h y ( 2 2 ) f o u n d t h a t T P P S . a n d s o m e o f

2 0

n o t i c e d t h a t t h e DSS 1H NMR i s broadened by FeTMPyP . I t

may be t h a t s u l p h o n a t e s form i on p a i r s w i t h c a t i o n i c TMPyP

and i t s m e t a l d e r i v a t i v e s .

T a b l e 0 .1 Ch emi ca l s h i f t s o f m-TMPvP

0 . 0 2 M 0. 01 M 0 . 0 8 Mm-TMPyP m-TMPyP Na t o s y l a t e Comment s

1 H NMR

9 . 55 9 . 6 0 —

9 . 25 9 . 2 3 —

9 . 1 7 9 . 1 9 —

9. 11 — —

8 . 9 2 8 . 9 3 —

8 . 5 0 8 . 5 2 —

8 . 44 8 . 4 4 —

8. 41 — —

8 . 3 5 8 . 3 4 —

6 . 84 7 . 01 7 . 596 . 74 6 . 91 7 . 4 96 . 04 6 . 3 3 7 . 2 65 . 94 6 . 23 7 . 0 73 . 5 6 3 . 5 6 3 . 56 D i o x a n— 3 . 2 0 — I m p u r i t y1 . 07 1 . 33 2 . 1 8

1 3C NMR

149. 61 1 4 9 . 6 4148 . 32 1 4 8 . 3 5146 . 00 1 4 6 . 0 3141. 91 1 4 2 . 2 3 1 4 3 . 1 2141 . 76 1 4 1 . 7 9140. 21 1 4 0 . 21 1 4 0 . 6 8129 . 18 1 2 9 . 3 8 1 3 0 . 1 8127. 71 1 27 . 71125. 41 1 2 5 . 5 6 1 2 6 . 2 4113 . 77 1 1 3 . 8 0

6 7 . 4 0 6 7 . 4 0 6 7 . 4 0 D i oxan49. 61 4 9 . 6 1

2 7 . 5 0 I m p u r i t y2 0 . 3 2 2 0 . 5 3 2 1 . 26

F o s t e r ( 2 5 ) has noted t h e c o n c e n t r a t i o n dep enden t

1H NMR s p e c t r a o f t h e a n i o n i n p-TMPyP t e t r a t o s y l a t e .

T hi s i s a l s o a s s i g n e d t o an i on p a i r i n g between the

t o s y l a t e i o n and p-TMPyP .

21

F I G URL 0.2 13c NMR OF fn-TMPyP

0.0 2 M

0.0 8 M

m-TMPyP tos y la te

Na tosylate

160 HO 120 100 80 60 40 20 0

Chemical shift / ppm

f 0 6.9 (phosphate) . 23°C

0 . 2 . 5 . C o n c l u s i o n s

From t h e work c o n s i d e r e d h e r e i t seems t h a t TMPyP

does not change i t s s t a t e o f a g g r e g a t i o n , i f any , o v e r

- 2 - 7t h e c o n c e n t r a t i o n r an ge 10 t o 10 M . I f a d i m e r i c

a g g r e g a t e were t o become s t a b l e a t about 10 ^ M , as

Kano ( 20 ) sug ges t s , t hen more h i g h l y a g g r e g a t e d s p e c i e s

a r e e xp e c t e d t o become s t a b l e w i t h i n c r e a s i n g

c o n c e n t r a t i o n . In t o t a l , i t would appear t h a t TMPyP does

not a g g r e g a t e . The ESR s t u d i e s o f P i l b r o w e t a l ( 26 ) have

i n d i c a t e d t h a t Co* * TPPS. a g g r e g a t e s whereas s i m i l a r work ,

done her e , does not i n d i c a t e t h a t Co^TMPyP a g g r e g a t e s .

No e v i d e n c e i s known f o r a g g r e g a t i o n o f t h e TMPyP complexes

w i t h Mn , Fe , Co and N i .

2 3

0 . 3 . M a g n e t i c p r o p e r t i e s o f f i r s t row t r a n s i t i o n m e t a l

complexes o f IMPvP

From s i m p l e c r y s t a l f i e l d t h e o r y ( 2 7 ) t h e e n e r g y

l e v e l d i a g r a m i n F i g u r e 0 . 3 i s p r e d i c t e d f o r t h e 3d

o r b i t a l s i n complexes r a n g i n g f rom o c t a h e d r a l t h r o u g h

t e t r a g o n a l y d i s t o r t e d o c t a h e d r a l t o square . The e l e c t r o n s

i n d i c a t e d a r e f o r a N i * * i o n . For a g i v e n complex between

4 7t h e two e x t r e m e s , i t i s seen t h a t f o r d t o d i on s t h e r e

i s a c h o i c e o f a r r a n g e m e n t o f e l e c t r o n s i n t h e 3d

o r b i t a l s . The t o t a l number o f u n p a i r e d s p i n s depends on

t h e r e l a t i v e s i z e o f t h e s e p a r a t i o n s between t h e 3d o r b i t a l

ene rg y l e v e l s and t h e e n e r g y r e q u i r e d t o p a i r t h e s p i n s i n

t h e s e o r b i t a l s .

I n aqueous s o l u t i o n wher e two w a t e r m o l e c u l e s a r e

c o o r d i n a t e d a x i a l l y ( z a z i s ) , l ow sp i n C o * 1 or C o * * * and

h i gh s p i n Mn* * or Mn * * * complexes o f TMPyP a r e o bs er ved .

In g e n e r a l , s t r o n g l i g a n d s such as c y a n i d e a r e r e q u i r e d t o

g i v e l o w s p i n Mn* * or Mn * * * complexes ( 28 ) .

The F e * * and F e * * * complexes o f TMPyP a l s o have two

a x i a l w a t e r m o l e c u l e s and a r e both h i gh s p i n . S t r o n g e r

a x i a l l i g a n d s g i v e l o w s p i n F e * * / F e * * * complexes and f o r

a x i a l l i g a n d s o f i n t e r m e d i a t e s t r e n g t h an e q u i l i b r i u m

between s p i n s t a t e s i s p o s s i b l e .

N i * * TMP yP i s l o w s p i n (S = 0) i n i t s f o u r c o o r d i n a t e

squar e form , due t o t h e s e p a r a t i o n o f t h e two h i g h e s t

e n e rg y 3d o r b i t a l s ( F i g u r e 0 . 3 ) . Wi th two a x i a l w a t e r or

i m i d a z o l e m o l e c u l e s t h e complex i s h i gh s p i n (S = 1) . Near

o c t a h e d r a l N i * * complexes a r e t y p i c a l l y h i gh s p i n ( 2 9 - 3 2 ) .

24

FIGURE 0.3 Metalloporphyrin energy level diagram

noCJl

Energy

2g = = W

Octahedral Tetragonal distortion

dx2_y2

xy

d22

*i 11 - dxz • yz

x Y

The X and Y axis are in the plane of the molecule and the zax i s is the axis of symmetry

Square

0 . 4 . The E v a n s ' Method

T h i s t e c h n i q u e f o r meas ur ing t h e m a g n e t i c

s u s c e p t i b i l i t y o f d i l u t e p a r a m a g n e t i c s o l u t i o n s i s used

t h r o u g h o u t t h i s work . A c o n s i d e r a t i o n o f t h e method i s

t h e r e f o r e p r e s e n t e d a t t h i s p o i n t .

0 . 4 . 1 . Theor y

I t has been shown ( 33 ) t h a t i n c . g . s u n i t s , t h e mass

s u s c e p t i b i l i t y x o f a s o l u t e i s g i v e n by

where

Af =

f =

m =

3 Af

2tt f m+ Y „ +*0

xo (do ■ Vm

- 3

Fr equ ency s e p a r a t i o n o f two r es on anc es

O s c i l l a t e r f r e q u e n c y o f NMR s p e c t r o m e t e r

c o n c e n t r a t i o n o f p a r a m a g n e t i c s o l u t e (g cm “ )

mass s u s c e p t i b i l i t y o f t h e s o l v e n t

d e n s i t y o f t h e s o l v e n t

d e n s i t y o f t h e s o l u t i o n

James ( 3 4 ) has g i v e n t h e f u l l d e r i v a t i o n o f t h i s

e q u a t i o n and t e s t e d some a p p r o x i m a t i o n s o f i t . The

c o r r e c t e d p a r a m a g n e t i c mass s u s c e p t i b i l i t y o f t h e s o l u t e ,

c o r rX i s a p p r o x i m a t e d t o t h e f i r s t t e r m o f t h e e x p r e s s i o n ,

so

3 A fc o r r

2 tr f m

James used t h e f u l l and s i m p l i f i e d e x p r e s s i o n s f o r

f e r r i c t r i s ( d i t h i o c a r b a m a t e s ) and f ound t h a t t he

26

c o r r1 l . So t h e c o r r e c t e d m o l a r s u s c e p t i b i l i t y , x k, . i sMg i v e n by

d i f f e r e n c e s i n m a g n e t i c m o m e n t s c a l c u l a t e d w e r e l e s s t h a n

c o r rM

3Af A

2tt f m

Where A i s t h e r e l a t i v e m o l e c u l a r mass .

NB :

So

m/A

c o r r

[ s o l u t e ]

3 Af

i n mol cm- 3

M 2tt f [ s o l u t e ]c . g . s . u n i t s

I n o r d e r t o use c o n c e n t r a t i o n i n m o l l and o t h e r w i s e- 3

c o n v e r t f rom cgs t o SI u n i t s a f a c t o r o f x 10 i s

i n t r o d u c e d .

So coorM

6Af x 10 -3

f [ s o l u t e ]

Where [ s o l u t e ] i s n u m e r i c a l l y i n m o l l -1

S . I . u n i t s

Us ing NMR s p e c t r o m e t e r s w i t h s u p e r c o n d u c t i n g

s o l e n o i d s t h e m a g n e t i c f i e l d i s p a r a l l e l t o t h e NMR t u b e .

T h i s i n t r o d u c e s a d o u b l i n g o f t h e r a t i o A f / f and hence f o r

t h e above e q u a t i o n s t h e e f f e c t i v e v a l u e o f f i s d o u b l e t h e

a c t u a l v a l u e .

27

I f S . I . u n i t s a r e used f o r xk,M t h e m a g n e t i c

moment i s g i v e n by

_„_ „„ / c o r r ~M = 797 . G6 y j xM • T

„ . „ c o r r .S u b s t i t u t i n g f o r x . A g i v e s t h e same e x p r e s s i o n ,Mi r r e s p e c t i v e o f which system o f u n i t s i s used

M 6 1 . 79Af T

f [ s o l u t e ]

0 . 4 . 2 . A p p a r a t u s

A Wi lmad 517 c o a x i a l NMR t ub e was used f o r some

measurements . 200 p i o f t h e p a r a m a g n e t i c s o l u t i o n was

p l a c e d i n t h e i n n e r t u b e and 200 p i o f t h e s o l v e n t was

p l a c e d i n t h e o u t e r a n n u lu s . Both s o l u t i o n s c o n t a i n a

r e f e r e n c e s ub s t a n c e w h ic h shou ld no t i n t e r a c t

p r e f e r e n t i a l l y w i t h t h e p a r a m a g n e t i c s o l u t e . Th i s

a r r a n g e m e n t i s p a r t i c u l a r l y s u i t a b l e where t h e t e m p e r a t u r e

i s v a r i e d . Any s h i f t s caused by changes i n s o l v e n t

d e n s i t y , w i t h changes i n t e m p e r a t u r e , a r e matched i n both

compar tments . D i f f e r e n c e s i n s h i f t a r e t hus due t o changes

i n p a r a m a g n e t i c s u s c e p t i b i l i t y .

For m a g n e t i c t i t r a t i o n s a n o t h e r a r r a n g e m e n t i s more

c o n v e n i e n t . The p a r a m a g n e t i c s o l u t i o n , w i t h an i n e r t

r e f e r e n c e s ub s t a n c e i s p l a c e d i n a nor mal 5 mm d i a m e t e r NMR

t u b e . The e x t e r n a l r e f e r e n c e , wh ich need no t be t h e same

as t h e i n t e r n a l r e f e r e n c e , i s c o n t a i n e d i n a s e a l e d

c a p i l l a r y t u b e , mounted c o a x i a l l y us i ng PTFE s pa cer s (NMR

L t d ) . The e x t e r n a l r e f e r e n c e was d i l u t e d t o g i v e an NMR

r e s o n a n c e o f c o mp a ra b l e i n t e n s i t y t o t h e i n t e r n a l

28

r e f e r e n c e . For t h i s purpose a c o c k t a i l o f s o l v e n t s was

used wh ich s h i f t e d t h e e x t e r n a l r e f e r e n c e a few H e r t z down

f i e l d o f t h e i n t e r n a l r e f e r e n c e f o r t h e s o l v e n t a l o n e .

T h i s a v o i d s i n a c c u r a c i e s due t o t h e nea r c o a l e s c e n c e o f t h e

two r e so n a n c e s . T h i s i n i t i a l s e p a r a t i o n i s s u b t r a c t e d t o

g i v e t h e a c t u a l s e p a r a t i o n Af .

I t i s much e a s i e r t o shake t h e NMR t u b e t o mix up t h e

r e a g e n t s i f a c e n t r a l s e a l e d c a p i l l a r y i s used f o r t h e

e x t e r n a l r e f e r e n c e . S e v e r a l e x t e r n a l r e f e r e n c e m i x t u r e s

wer e used d e p e n d i n g on t h e i n t e r n a l s o l v e n t .

T a b l e 0 . 2 R e f e r e n c e m i x t u r e s f o r s u s c e p i b i l t v mea suremnts

I n t e r n a l R e f e r e n c e E x t e r n a l R e f e r e n c e ( c a p i l l i a r y )

1 X t - b u t y l a l c o h o l ( aq) 12 X t - b u t y l a l c o h o l38 X CHBrso x c h c i ; c c i 2

1 X DSS ( aq) 25 X HMDS8 X CHBr

67 x c h c i : c c i 2

1 X HMDS i n benzene 27 X HMDS73 X benzene

0 . 5 X (CH ) NCI ( aq) 15 X DMSO3 * 85 X CHBr^

T i t r a t i o n o f a l i g a n d s o l u t i o n i n t o t h e NMR tube

changes t h e b u l k d i a m a g n e t i c s u s c e p t i b i l i t y . T h i s means

t h a t t h e c o r r e c t i o n , A f ' , t o be s u b t r a c t e d t o g i v e t hema c t u a l s e p a r a t i o n , Af , v a r i e s t h r o u g h o u t t h e t i t r a t i o n .

Af = s e p a r a t i o n measured - A f ^

29

James ( 34 ) found t h a t t h e v a r i a t i o n o f Af* w i t hm

t i t r e M was l i n e a r up to a f i n a l l i g a n d / p o r p h y r i n r a t i o o f

100 / 1 . So f o r most e x p e r i m e n t s t h e v a l u e o f A f ' i s g i v e nm

by

( A f ‘ - A f *)oo oA f = Af * + M. ------------------------m om MOO

Af * r e f e r s t o t h e s e p a r a t i o n i n t h e absence o f a

p a r a m a g n e t i c s o l u t e and M r e f e r s t o t h e t i t r e o f l i g a n d

s o l u t i o n . S u b s c r i p t s a r e <> f o r no t i t r e , <» f o r maximum

t i t r e and m f o r i n t e r m e d i a t e t i t r e .

For h i s t i d i n e and DMAP t i t r a t i o n s o f aqueous

FeTMPyP , t h e f i n a l c o n c e n t r a t i o n s o f l i g a n d were

c o m p a r a t i v e l y l a r g e . I n t h e s e cases a b l a n k t i t r a t i o n was

c a r r i e d ou t i n t h e absence o f any p a r a m a g n e t i c s o l u t e . The

v a l u e s o f A f ’ were p l o t t e d a g a i n s t t h e c o n c e n t r a t i o n o f m

t i t r a n t l i g a n d and a smooth c u r ve was drawn t h r o u g h t he

d a t a p o i n t s . The v a l u e s o f A f ^ f o r each p o i n t i n t he

t i t r a t i u o n were r ead f rom t h i s g raph .

0 . 4 . 3 . Ch o i ce o f r e f e r e n c e s u b s t a n c e

The Evans* method r e q u i r e s t h a t t h e r e f e r e n c e

s u b s t a n c e be e v e n l y d i s t r i b u t e d t h r o u g h o u t space w i t h

r e s p e c t t o t h e s u b s t r a t e . OSS i n an F e J I I TMPyP s o l u t i o n

gave a much broadened NMR r e s o n a n c e , wh ich may have been

due t o non random a s s o c i a t i o n o f DSS and FeTMPyP . S e v e r a l

r e f e r e n c e s u b s t a n c e s have been compared a g a i n s t each

o t h e r . The r e s u l t s b e l ow a r e f o r a F e I I i : TMPyP s o l u t i o n and

t h e r e s u l t s f o r a N i * * TMP y P s o l u t i o n a r e i n c h a p t e r 2 .

3 0

Results

R e f e r e n c e S e p a r a t i o n / H z M

T e t r a m e t h y l 6 5 . 2 3 4 6 . 0 8ammonium c h l o r i d eP e n t a e r y t h r i t o l 6 3 . 5 0 6 6 . 0 0t - b u t y l a l c o h o l 6 2 . 5 7 3 5 . 9 6

The d i f f e r e n c e i n t h e s e p a r a t i o n s and hence t h e

a p p a r e n t m a g n e t i c moments a r e s i g n i f i c a n t compared t o t he

e x p e r i m e n t a l e r r o r i n measurement . T h i s i n d i c a t e s t h a t t he

measurements made u s i n g t - b u t y l a l c o h o l as a r e f e r e n c e may

not be e x a c t l y e q u a l t o t h e a c t u a l m a g n e t i c moment .

However we know t h a t t h e a p p a r e n t m a g n e t i c moment o f 5 . 9 6

cor re s po nd s t o 100 l monomer .

0 . 4 . 4 . E x p e r i m e n t a l

A 0 . 2 5 M b u f f e r s o l u t i o n was made by d i s s o l v i n g 40 p i

cone D C 1 and 27 mg o f sodium f o r m a t e i n 1 . 6 ml D^O . The pD

was c a l c u l a t e d t o be 3 . 7 5 . Three r e f e r e n c e s ,

p e n t a e r y t h r i t o l ( 1 . 3 mg) , t e r a m e t h y l ammonium c h l o r i d e

( 1 . 1 mg) and t - b u t y l a l c o h o l (1 p i ) were added , so t h a t

t h e r e l a t i v e s h i f t s c o u ld be obser ved under i d e n t i c a l

c o n d i t i o n s .

The r e l a t i v e c h e m i c a l s h i f t s were e s t a b l i s h e d by

a dd ing e x t r a amounts o f each r e f e r e n c e t o t h e b u f f e r

s o l u t i o n and f o l l o w i n g t h e change i n i n t e n s i t i e s , u s i n g a

P e r k i n Elmer R32 NMR s p e c t r o m e t e r .

500 p i o f t h i s s o l u t i o n was used t o make a

- 3 I I I4 . 1 5 x 10 M Fe p-TMPyP s o l u t i o n . The c o a x i a l NMR tube

t e c h n i q u e , w i t h a B r u k e r WM250 NMR s p e c t r o m e t e r , was used

ot o measure t h e a p p a r e n t m a g n e t i c moment a t 35 C .

CHAPTER 1

Aqueous s o l u t i o n e q u i l i b r i a o f FeTMPyP

32

1 . 1 . S i mpl e aqueous s o l u t i o n b e h a v i o u r

1 . 1 . 1 . I n t r o d u c t i o n

T h i s s e c t i o n i s con cer ned w i t h t h e pH and

c o n c e n t r a t i o n d ep enden t e q u i l i b r i a o f Fe* * * TMPyP i n s i m p l e

aqueous s o l u t i o n .

Even b u f f e r s such as T r i s , wh ich n o r m a l l y c o o r d i n a t e

v e r y w e a k l y w i t h m e t a l i o n s , c o o r d i n a t e s i g n i f i c a n t l y w i t h

FeTMPyP . T h i s e f f e c t i s d i s c u s s e d i n more d e t a i l i n t h e

f o l l o w i n g s e c t i o n on e q u i l i b r i a w i t h o t h e r l i g a n d s . No

b u f f e r s were used i n t h e e x p e r i m e n t s t o d e t e r m i n e t h e

e q u i l i b r i u m c o n s t a n t s i n t h i s s e c t i o n .

There i s much d i s c r e p a n c y i n t h e l i t e r a t u r e o v e r t h e

i n t e r p r e t a t i o n o f t h e aqueous s o l u t i o n b e h a v i o u r o f

FeTMPyP . The system o f e q u i l i b r i a , i n F i g u r e 1.1 ,

a d e q u a t e l y e x p l a i n s t h e o b s e r v a t i o n s i n t h e l i t e r a t u r e

w i t h o u t i n v o k i n g u n p r e c e d e n t e d s p e c i e s . Even f o r t h o s e

a u t h o r s ( 2 3 , 3 5 ) who use t h i s or an e q u i v a l e n t

i n t e r p r e t a t i o n , t h e r e i s l i t t l e c o n s i s t e n c y between t he

v a l u e s f o r t h e v a r i o u s e q u i l i b r i u m c o n s t a n t s . S i n c e a

knowledge o f t h e s e v a l u e s i s e s s e n t i a l t o t he

i n t e r p r e t a t i o n o f more c o m p l i c a t e d systems , a r e v a l u a t i o n

o f t h e s e p a r a m e t e r s was made .

Presumabl y due t o t h e d i f f i c u l t y i n p r e p a r i n g pure

c r y s t a l l i n e samples , t h e r e have been no s t r u c t u r a l

d e t e r m i n a t i o n s f o r t h e w a t e r s o l u b l e meso s u b s t i t u t e d i r o n

p o r p h y r i n s . However t h e s t r u c t u r e o f t h e p - oxo b r i d g e d

(Fe s a l e n J ^ O . p y ^ has been d e t e r m i n e d ( 36 ) . The f e r r i c ions

a r e d i s p l a c e d f rom t h e b e s t c o o r d i n a t i o n p l a n e o f t h e s a l en

and t h e f e r r i c i o n s a r e f i v e c o o r d i n a t e , t h e p y r i d i n e s not

3 3

F I G U R E 1 . 1 F e T M P y P SYSTEM OF E Q U I L I B R I A

K A 1 KA2

P F e (OH ^ ^ P F e ( O H 2 )(OH)

X *- H+ X \)

+

— P Fe(OH)-H

1/2 P F e - O - F e P

A 1

A2

NB: Q

[ P F e ( OH ) (OH) ] [H + ]

[ P F e ( OH 2 ) ]

[ P F e ( OH ) 2 ] C H+ ]

[ P F e ( OH 2 ) ( OH ) ]

[ P F e -O - F e P ] C H + ] 2

CPFe( OH2 ) 2 ] 2

[ P F e - O - F e P ]

CPFe( OH) ( OH ) ] 2

b e i n g c o o r d i n a t e d . By a n a l o g y the f e r r i c ions in the

F e T M P y P d i m e r are p r o b a b l y a l s o f i v e c o o r d i n a t e , w i t h o u t

w a t e r m o l e c u l e s in the o u t e r a x i a l p o s i t i o n s . It has been

s u g g e s t e d (23) t h a t the m o n o m e r d e p i c t e d by P F e ( O H 2 ) 2 has a

fiv e c o o r d i n a t e f e r r i c ion , w i t h o n l y one a x i a l l y

c o o r d i n a t e d w a t e r m o l e c u l e . The c o o r d i n a t i o n of w a t e r

m o l e c u l e s d o e s not a f f e c t t h e d e f i n i t i o n of any of the

e q u i l i b r i a in F i g u r e 1.1 .

34

1 . 1 . 2 . R e l a t i v e b a s i c i t y o f t h e TMPvP i somers

A compar i son o f t h e meta and para i somer s o f t h e f r e e

base p o r p h y r i n i s o f i n t e r e s t a t t h i s p o i n t s i n c e i t a l l o w s

p r e d i c t i o n s t o be made c o n c e r n i n g r e s u l t s t o be d i s c u s s e d

l a t e r . pKt v a l u e s f o r t h e r e a c t i o n be low were c o l l e c t e d A

from s e v e r a l sou rc es .

„ ka ♦ ■H TMPyP ^ - ~ HgTMPyP + H

Where H ^TMPyP i s t h e f r e e base p o r p h y r i n .

T a b l e 1.1 pK v a l u e s o f TMPyP A

p-TMPyP m-TMPyP R e f e r e n c e

1 . 4 ( 1 = 0 . 2 M) , 2 . 2 ( 1 = 2 . 0 M) — 371 . 8 ( 1 = 0 . 7 M) — 381 . 6 2 . 0 391 . 4 1 . 8 401 . 8 ( 1 = 0 . 2 M) 2 . 4 ( 1 = 0 . 2 M) 4 1

The v a l u e o f pK^ i s v e r y i o n i c s t r e n g t h dep en de n t as

shown by B a k e r ' s ( 3 7 ) v a l u e s f o r p-TMPyP and a t t e n t i o n

should be p a i d t o i o n i c s t r e n g t h when compar i sons a r e

made . However m-TMPyP i s i n v a r i a b l y a c c e p t e d as be i ng more

b a s i c t han p-TMPyP . W i l l i a m s and H a mb r i gh t ( 40 ) p o i n t out

t h a t m-TMPyP i s 2 . 5 t i m e s as b a s i c as p-TMPyP and

a c c o r d i n g l y e x t r a p l a n a r l i g a n d s a r e e x p e c t e d t o b i nd l e s s

s t r o n g l y t o Co** *m-TMPyP t h a n t o C o * * * p - TM P yP . T h i s i s

borne out by t h e i r r e s u l t s and t h e same argument a p p l i e s t o

Fe* * *m-TMPyP compared t o F e * * * p - T M P y P . The more s t r o n g l y

t h e w a t e r i s c o o r d i n a t e d t o F e 111 t h e more e a s i l y i t i s

d e p r o t o n a t e d and so t h e l o w e r t h e v a l u e o f p KA„ f o r t h eA1c o o r d i n a t e d w a t e r . The p r e d i c t e d o r d e r f o r pK^ i s t hus :

3 5

Fe p-TMPyP < Fe m-TMPyP

The s t r o n g e r t h e p - o x o b r i d g e i n t he f e r r i c p o r p h y r i n

d i m e r t h e h i g h e r s hou l d be i t s t e n d en c y t o r emai n d i m e r i s e d

i n s o l u t i o n . So on e l e c t r o n i c grounds Fe* * * m-TMPyP i s

e x p e c t e d to d i m e r i s e l e s s r e a d i l y t han F e * * * p - T M P y P .

McLendon and B a i l e y ( 42 ) have a l s o c o n s i d e r e d t h e

s t r e n g t h o f c o o r d i n a t i o n o f l i g a n d s t o m e t a l l o p o r p h y r i n s .

The d e g r e e o f occupancy o f t h e d 2 ,d and d o r b i t a l sz xz yz

was c a l c u l a t e d . The e f f e c t i v e cha rg e a l o n g t h e Z a x i s was

shown t o c o r r e l a t e w i t h t h e b i n d i n g o f a x i a l h y d r o x i d e .

1 . 1 . 3 . A x i a l w a t e r h y d r o l y s i s

1 . 1 , 3 . 1 . C o n s i d e r a t i o n o f o t h e r work

The e q u i l i b r i u m under c o n s i d e r a t i o n i s :

KP F e ( OH2 ) ^ PF e ( 0 H2 ) ( 0 H) + H +

K u r i h a r a e t a l ( 3 5 ) have f o l l o w e d pH t i t r a t i o n s o f

aqueous FeTMPyP u s i n g s p e c t r o p h o t o m e t r y . The c o n d i t i o n s o f

t h e i r e x p e r i m e n t w er e :

0 .1 M Na_ SO. , 7 . 0 8c. 4 x 1 0" 6 M FeTMPyP

A c e t a t e pH 3 - 6

Phosphate pH 4 . 5 - 7 . 2

Phosphate / B o r a t e pH 5 . 8 - 9

I r r e s p e c t i v e o f t h e w a v e l e n g t h ( 403 , 424 , 440 and

596 nm) two i n f l e x i o n p o i n t s were seen i n t h e ab s or b a nc e

v e r s u s pH graph a t a b o u t pH 5 . 7 and pH 12 . S i n c e t h e l ow

c o n c e n t r a t i o n s t a b i l i s e s monomer ic FeTMPyP , t h e s e v a l u e s

36

The s p e c i e s formed a t h i g h pHc or r e s p o n d t o pl< and p l ^ *

was seen t o decompose by about 50 l o v e r 48 hours . Two

Beer * s Law t e s t s a t pH 2 ( C FeTMPyP] = 2 . 5 x 1 05

6 ( [FeTMPyP] - 51 X 10" M) and a t pH 13. = 5 x 10

1 X 1 o " 5 M) showed no change i n t h e s t a t e o f a s s o c i a t i o n .

The a u t h o r s s t a t e t h a t t h e b u f f e r s a f f e c t e d t h e i r

e l e c t r o c h e m i c a l r e s u l t s and t h a t pho spha t e a p p r e c i a b l y

d ep r e s s e d t h e ab s or b a nc e a t pH 6 . The b u f f e r s p r o b a b l y

c o o r d i n a t e d s i g n i f i c a n t l y t o t h e FeTMPyP . C o n s i d e r i n g t h i s

and t h e d i f f e r e n t i o n i c s t r e n g t h employed , t h e pK^ r e s u l t

agr ee s s u r p r i s i n g l y w e l l w i t h t h e v a l u e o b t a i n e d i n t h i s

work ( d i s c u s s e d be l ow) .

P a s t e r n a c k e t a l ( 2 3 ) conduc t ed s p e c t r o p h o t o m e t r i c pH

t i t r a t i o n s under t h e f o l l o w i n g c o n d i t i o n s .

I = 0 . 05 M , pH = 2 - 7 , 2 5° C

1 ) 403 nm C FeTMPyP ] = 8 X io~6 M

2) 403 nm C FeTMPyP] = 9 X 1 0 - 5 M

3 ) 595 nm C FeTMPyP ] = 9 X 1 0 ' 5 M

No c l e a r i s o b e s t i c p o i n t s were o b s e r ve d . The d a t a

cou ld be matched up t o pH 5 u s i n g t h e f i r s t h y d r o l y s i s s t e p

o n l y or up t o pH 6 u s i n g bo t h h y d r o l y s i s s t e ps t o g e t h e r .

The r e s u l t s wer e :

PKA1 = 4 . 7 ± 0 . 2

pK.. = 6 . 5 ± 0 . 3 A2

D i m e r i s a t i o n was s ug ges t ed as t h e r ea s on f o r t he

mismatch o f a c t u a l and c a l c u l a t e d r e s u l t s above pH 6 .

However t h i s was not t a k e n i n t o acc o un t i n t h e c a l c u l a t i o n

37

o f pK v a l u e s and so t h e s e r e s u l t s a r e dub ious .

MCD ( 43 ) and ESR ( 35 ) s p e c t r a have been i n t e r p r e t e d

as i n d i c a t i n g t h a t t h e monomer ic s p e c i e s s t a b i l i s e d by h i g h

pH i s l ow s p i n . T h i s i s i n c o n s i s t e n t w i t h G o f f and

M o r g a n ' s ( 19 ) r e p o r t t h a t t h e m a g n e t i c moment o f F e * * * TMPyP

i n 1M NaOH was 4 . 7 . T h i s was a t t r i b u t e d to t h e f o r m a t i o n

o f PF e ( OH) 2 . From t h i s r e s u l t an e s t i m a t e o f 12 . 7 can be

made ( see a p p e n d i x 1 . 2 ) f o r pK ^ *

H a r t z e l l e t a l ( 44 ) have used s p e c t r o p h o t o m e t r i c and

ESR measurements t o i n v e s t i g a t e t h e b e h a v i o u r o f t h e

r e l a t e d FeTCPP i n aqueous s o l u t i o n . They propose a sys tem

o f e q u i l l i b r i a q u i t e d i f f e r e n t t o t h a t proposed f o r FeTMPyP

i n t h i s work . They used t h e f o l l o w i n g e q u i l i b r i a t o

e x p l a i n t h e i r r e s u l t s

K HPFe-O- FeP + H+ - PFe -O- FeP

From ESR measurements logK^ = 9 . 5 8 ± 0 . 3 7

V KPFe-O- FeP + H+ - - PFe -O- FeP

^ A-

From ESR measurements l o g K 2 = 6 . 3 4 ± 0 . 1 5

From s p e c t r o p h o t o m e t r i c mesurements

l o g K 2 = 6 . 7 2 ± 0 . 3 0

C o n d i t i o n s

S p e c t r o p h o t o m e t r i c

CFeTCPP] = 5 x 10~5 - 12 x 10~5 M

I = 0. 1 M , Temp = 18°C

ESR

[FeTCPP] = 5 x 10~3 M

I = 0 .1 M , Temp < 10°C

38

The a u t h o r s a ck now led ge t h a t t h e p aqua b r i d g e d d i m e r

i s u n p r e c e d e n t e d .

The ESR s p e c t r a f o r FeTCPP i n t h e absence o f

i m i d a z o l e a r e both h i g h s p i n monomer ic f e r r i c p o r p h y r i n

t y p e s p e c t r a . The two s p e c t r a do not c o r r e s p o n d t o t h e

same s p e c i e s and t h e pH 12 . 4 s pe c t rum may be due t o two

s p e c i e s . T h i s s u p p o r t s t h e i d e a o f a n o t h e r pH d e p e n d e n t

e q u i l i b r i u m t a k i n g p l a c e between pH 6 . 5 and pH 12 . 4 . By

a n a l o g y w i t h t h e FeTMPyP system t h e pH 6 . 5 spe c t r um may be

f rom PFe( OH2 ) ( OH) and t h e pH 12 . 4 spe c t rum f rom a m i x t u r e

o f t h i s and P F e ( O H ) 2 and some p oxo d i m e r .

The a u t h o r s r e p o r t t h a t an i n c r e a s e i n t h e a r e a o f

t h e gx band o f t h e ESR s p e c t r u m w i t h i n c r e a s i n g pH i s

i n d i c a t i v e o f a r e d u c t i o n i n a n t i f e r r o m a g n e t i c c o u p l i n g on

go i ng f rom a hydroxo t o an oxo b r i d g e . T h i s seems an

u n l i k e l y e v e n t .

The d i f f e r e n c e i n t h e e x t i n c t i o n c o e f f i c i n t s f o r t h e

a and (3 bands o f t h e v i s i b l e spe c t rum , a t pH 8 . 5 and

pH 1 3 . 0 , i s f u r t h e r e v i d e n c e o f a second pH d e p en de n t

e q u i l i b r i u m i n t h a t r e g i o n .

. - 5The a d h e r e n c e t o Beer s Law i n t h e r e g i o n 1 . 5 x 10

- 4 .t o 1 . 9 x 10 M i s c o n s i s t e n t w i t h t h e FeTCPP b e i n g

c o m p l e t e l y d i m e r i s e d or c o m p l e t e l y monomer ic i n t h a t

r e g i o n .

The e q u i l i b r i u m d e s c r i b e d by H a r t z e l l ' s K c a n a l s o

be d e s c r i b e d by

k mP F e ( OH^) 2 ^ ... j PF e ( 0 H2 ) ( 0 H ) + H+

PKA1 ■ 6 - 72

3 9

The v a l u e o f PK14 i s o f t h e same o r d e r as t h e v a l u eA 1

f o r FeTMPyP , d e t e r m i n e d i n t h i s work .

1 . 1 . 3 . 2 . 1 . E v a l u a t i o n o f d K . . v a l u e s

I n t h i s work v a l u e s o f p K ^ were r e d e t e r m i n e d

s p e c t r o p h o t o m e t r i c a l l y a t v a r i o u s t e m p e r a t u r e s and i o n i c

s t r e n g t h s . Graphs o f l o g { ( A - Aq ) / ( A ^ qq - A) } v e r s u s pH

were drawn to d e t e r m i n e pK . „ v a l u e s ( see a p p e n d i x 1.1 andA1

F i g u r e 1 . 2 ) .

T a b l e 1 . 2 Pl<A1 v a l u e s f o r F e T ( M , E t ) P y P

P o r p h y r i nI o n i c

S t r e n g t h / M T emp/ °CWave

Length /nm Slope <ij*;

i a iii

Fe p-TMPyP 0 . 0 0 1 9 400 1 . 04 4 . 8 9

0 . 2 5 1 8 4 0 2 . 5 1 . 08 5 . 5 0

0 . 3 0 3 1 400 1 . 1 0 5 . 59

Fe m-TMPyP 0 . 2 5 20 396 0 . 9 9 5 . 8 2

0 . 2 5 32 396 1 . 03 5 . 74

0 . 3 0 30 3 9 6 . 5 1 . 02 5 . 78

Fe m-TEtPyP 0 . 2 5 20 3 9 7 . 5 1 . 00 5 . 75

40

FIGURE 1 .2 D etermination of p ka1 values

1.1.3.2.2. Results

Fe p-TMPyP ( 1= 0 . 0 M ,

pH Absorbance

2 . 5 7 0 . 9 1 23 . 53 0 . 8 9 43 . 9 8 0 . 8 6 84 . 27 0 . 8 3 24 . 53 0 . 7 8 24 . 7 7 0 . 7 2 84 . 99 0 . 6 7 15 . 2 9 0 . 6 0 55 . 52 0 . 5 6 06 . 1 3 0 . 4 8 4

Fe p-TMPyP ( 1= 0 . 2 5 M ,

pH Absorbance

2 . 3 2 0 . 8 8 14 . 0 2 0 . 8 7 34 . 5 8 0 . 8 3 95 . 0 9 0 . 7 6 25 . 6 2 0 . 6 9 25 . 9 9 0 . 6 0 26 . 8 0 0 . 4 9 28 . 1 0 0 . 4 7 8

Fe p-TMPyP ( I = 0 . 3 0 M .

pH Absorbance

3 . 60 0 . 7 9 14 . 43 0 . 7 7 85. 01 0 . 7 2 95 . 2 5 0 . 6 9 25 . 51 0 . 6 3 95 . 7 4 0 . 5 8 96 . 1 7 0 . 5 1 26 . 3 5 0 . 4 9 96. 71 0 . 4 7 38 . 4 0 0 . 4 5 5

Fe m-TMPyP ( I = 0 . 2 5 M .

pH Absor bance

3 . 5 8 0 . 8 4 74 . 47 0 . 8 3 25 . 0 2 0 . 7 9 45 . 2 3 0 . 7 6 95 . 5 2 0 . 7 2 35 . 8 0 0 . 6 6 26 . 0 8 0 . 6 0 86 . 51 0 . 5 3 17. 01 0 . 4 7 2

1 9 °C )

l o g { ( A - AQ) / ( A 100" A) }

- 1 . 3 5 8 - 0 . 9 4 0 9 - 0 . 6 3 8 5 - 0 . 3 6 0 3 - 0 . 1226

0 . 1 1 0 2 0 . 4 0 4 4 0 . 6 6 5 7

18°C )

l o g { ( A - A0 > / l A 100“ A >>

-1 . 694 - 0 . 9 3 4 3 - 0 . 3 7 7 8 - 0 . 0 5 4 0

0 . 4 7 2 5 1 . 444

3 1 °C )

l o g { ( A - AQ) / ( A 1 00 - A ) *

- 1 . 3 9 5 3 - 0 . 6 4 5 4 - 0 . 3 7 9 1 - 0 . 0 8 3 0

0 . 1 7 8 2 0 . 6 8 9 7 0 . 8 2 1 9 1 . 2 4 7 2

20°C )

l o g { ( A - A0 > / (A 1 0 o" A * *

- 1 . 380 - 0 . 7 8 3 6 - 0 . 5 8 0 7 - 0 . 3 0 6 3 - 0 . 0 1 1 6

0 . 2 4 4 9 0 . 7 2 8 8

4 2

Fe m-TMPyP (I 0.25 M 3 2 ° C )

pH Absorbance

3 . 5 4 0 . 7 3 94 . 1 2 0 . 7 3 24 . 9 2 0 . 7 0 05 . 2 7 0 . 6545 . 51 0 . 6 1 65 . 7 5 0 . 5 6 25 . 8 8 0 . 5 4 7? 0 . 4 6 46 . 8 0 0 . 4 4 38 . 8 5 0 . 4 0 4

Fe m-TMPyP ( I = 0 . 3 0 M .

pH Absorbance

3 . 0 0 0 . 7 5 94 . 00 0 . 7 5 24 . 5 2 0 . 7 3 94 . 9 9 0 . 7 0 85 . 2 8 0 . 6 6 95 . 51 0 . 6 2 85 . 7 7 0 . 5 7 75 . 9 9 0 . 5 2 86 . 4 0 0 . 4 4 96 . 7 5 0 . 4 1 17 . 51 0 . 3 7 5

Fe m-TEtPyP ( I = 0 . 2 5 M

pH Absorbance

3 . 5 8 0 . 9 6 14 . 1 0 0 . 9 5 24 . 5 6 0 . 9 3 55 . 04 0 . 8 9 15 . 31 0 . 8 5 85 . 5 2 0 . 8 1 15 . 8 0 0 . 7 6 56 . 0 6 0 . 6 9 56 . 4 7 0 . 6 0 47 . 01 0 . 5 6 2

l o g { (A - AQ) / ( A 100“ A ) *

- 1 . 6 7 0 8 - 0 . 8 8 0 2 - 0 . 4 6 8 5 - 0 . 2 3 6 4

0 . 0 4 9 3 0. 12800.66120 . 8 8 0 2

3 0 ° C )

l o g { (A - a q ) / ( A 1oq- a )>

- 1 . 7 3 1 2 - 1 . 260 1 - 0 . 8 1 4 9 - 0 . 5141 - 0 . 2 8 5 8 - 0 . 0 4 5 3

0 . 1789 0 . 6 2 2 1 0 . 9 8 5 3

2 0°C )

l o g { (A - AQ) / ( a 10Q- a ) >

- 1 . 637 - 1 . 1 5 7 - 0 . 6 7 2 1 - 0 . 4 5 8 5 - 0 . 2201 - 0 . 0 1 5 2

0. 3010 0 . 9 2 9 4

I t i s not n e c e s s a r y t o know CFeT( M, E t ) PyP] t o e v a l u a t e

l o g { ( A - a 0 > / < a 10 o " A ) } * However t h e c o n c e n t r a t i o n i s about_ g

10 M i n a l l cases .

4 3

Two p a i r s o f r e s u l t s i n d i c a t e t h e e f f e c t o f i n c r e a s e d

i o n i c s t r e n g t h on t h e v a l u e o f pl<A1 . I n c r e a s e s o f 4 . 8 9 t o

5 . 5 0 and 5 . 7 4 t o 5 . 7 8 r e s u l t f rom i o n i c s t r e n g t h i n c r e a s e s

f rom 0 . 0 t o 0 . 2 5 M and 0 . 2 5 t o 0 . 3 0 M . The l a t t e r i n c r e a s e

i s a much s m a l l e r e f f e c t . T h i s e f f e c t i s i n d i c a t i v e o f a

s t a b i l i s a t i o n o f t h e more h i g h l y charged PF e ( 0 H2 ) 2 compared

to PF e ( 0 H2 ) ( 0 H ) w i t h i n c r e a s e d i o n i c s t r e n g t h . T h i s

e x p l a n a t i o n c o u ld be t e s t e d by d e t e r m i n i n g t h e PKA1 'f o r

FeTPPS, as a f u n c t i o n o f i o n i c s t r e n g t h . S i n c e FeTPPS, i s4 4a n i o n i c , l o s s o f a p r o t o n i n c r e a s e s t he t o t a l p o r p h y r i n

c h a rg e . An i n c r e a s e i n i o n i c s t r e n g t h i s thus e x p e c t e d t o

d e c r e a s e t h e v a l u e o f p K4 . f o r FeTPPS. . The e f f e c t o f

t e m p e r a t u r e on t h e v a l u e o f pK A i s seen by t h e d e c r e a s e o f

5 . 8 2 t o 5 . 7 4 on i n c r e a s i n g t h e t e m p e r a t u r e f rom 20 t o

o .32 C . The v a l u e o f PKA 1S not v e r y s e n s i t i v e t o

t e m p e r a t u r e , t h e s e r e s u l t s c o r r e s p o n d to

1 .1 . 3 . 2 . 3 . Discussion of results

d ( pKA1 )

dT0 . 0 7 / ° C

The p KA„ v a l u e s o f 5 . 5 0 , 5 . 7 5 and 5 . 8 2 , a t 0 . 2 5 MA 1

i o n i c s t r e n g t h a t comp a ra b le t e m p e r a t u r e s , g i v e the

f o l l o w i n g o r d e r f o r t h e t h r e e d i f f e r e n t f e r r i c p o r p h y r i n s :

Fe p-TMPyP < Fe m-TEtPy,P < Fe m-TMPyP

Fe m-TMPyP i s p r e d i c t e d on e l e c t r o n i c grounds t o have

a h i g h e r p K ^ v a l u e t h a n Fe p-TMPyP . The d i f f e r e n c e of

0 . 3 2 ( 1 = 0 . 2 5 M) c o r r e s p o n d s t o a f a c t o r o f 2 i n K 4 „ .A1

44

1 . 1 . 4 . D i m e r i s a t i o n

1 . 1 . 4 . 1 . C o n s i d e r a t i o n o f o t h e r work

The e q u i l i b r i u m under c o n s i d e r a t i o n i s :

K2 PFe( OH2 ) ( OH) * jj PFe-O-FeP + 3 H2 0

S e v e r a l a u t h o r s have r e p o r t e d s t u d i e s o f t h e

d i m e r i s a t i o n o f FeTMPyP .

P a s t e r n a c k e t a l ( 2 3 ) o bs er ved marked d e v i a t i o n s f ro m

B e e r ’ s Law f o r FeTMPyP under t h e f o l l o w i n g c o n d i t i o n s

[FeTMPyP] = 3 x 1o " 7 - 1 x 10~4 M

4 2 5 nm

pH 9 . 0 and pH 9 . 8

The d a t a was e v a l u a t e d w i t h r e s p e c t t o t h e

e q u i l i b r i u m be l ow to g i v e v a l u e s o f 10 . 5 x 1 0 5 (pH 9 . 0 ) and

7 . 0 x 1 0 5 (pH 9 . 8 ) m o l ” 11 f o r Kp

K2 P Fe ( OH) ^ P - ( H O) PFe - O- FeP (O H) + H2 0

The p r e d o m i n a n t monomer ic form was e r r o n e o u s l y

assumed t o be P F e ( 0 H ) 2 , w h i c h i s t h e i r b a s i s f o r i n f e r r i n g

h y d r o x i d e c o o r d i n a t e d t o t h e d i m e r i c FeTMPyP . S i n c e no H +

occur s i n t h e proposed e q u i l i b r i u m , c o r r e s p o n d s t o t h e

Kp d e f i n e d h e r e , a l t h o u g h t h e v a l u e i s c o n s i d e r a b l y l a r g e r

t han t h a t d e t e r m i n e d i n t h i s work . Mossbauer d a t a and a

m a g n e t i c moment o f 2 . 5 w er e c i t e d as e v i d e n c e f o r a p oxo

b r i d g e d d i m e r .

F or sh ey and Kuwana ( 4 5 ) r e p o r t t h a t t h e i r c y c l i c

v o l t a m m e t r y d a t a i s c o n s i s t e n t w i t h t h e e q u i l i b r i u m

c o r r e s p o n d i n g t o KQ . They ack nowl edge t h a t t h e y can not

4 5

d i s t i n g u i s h between t h e v a r i o u s p o s s i b l e b r i d g i n g groups .

3 -1A v a l u e o f 2 . 2 ( ± 0 . 5 ) x 10 mol 1 was c a l c u l a t e d f o r

under t he c o n d i t i o n s

[FeTMPyP] = 0 . 5 x 1o“ * - A . 3 x 10~* M , 0 .1 M KC1

T hi s v a l u e i s more r e l i a b l e t han t he v a l u e d e t e r m i n e d

by P a s t e r n a c k ( 23 ) and i s o f t h e same o r d e r o f m a g n i t u d e as

t h e v a l u e d e t e r m i n e d her e a t I = 0 . 0 M . They c o n c lu d ed

t h a t t h e r e were no d i m e r i c F e ^ T M P y P s p e c i e s and t h a t above

pH 6 t h e Fe * * * TMPyP monomer was s l ow t o d i m e r i s e , compared- 1

t o t h e sweep r a t e o f t h e i r r e d ox e x p e r i m e n t ( 0 . 1 Vs ) .- 5

I n c r e m e n t a l r edox c y c l i n g o f 10 M aqueous FeTMPyP

a t pH 1 ( 0 . 1 N H SO ) and pH 8 . 3 ( 0 . 1 N c a r b o n a t e ) showed2 4

i s o b e s t i c p o i n t s , s u g g e s t i n g o n l y one s p e c i e s per

o x i d a t i o n s t a t e . They a t t r i b u t e t h e l a c k o f d i m e r i s a t i o n

a t t h e h i g h e r pH t o a s l ow r a t e o f a t t a i n m e n t o f

e q u i l i b r i u i m . However t h e c o n c e n t r a t i o n o f c a r b o n a t e i s

such as to s t a b i l i s e a c a r b o n a t e bound monomer and s h i f t

t h e e q u i l i b r i u m t o g i v e a p r e d o m i n a n t l y monomer ic s p e c i e s .

K u r i h a r a e t a l ( 3 5 ) presumed two d i m e r i c s p e c i e s f rom

- 5 - 4t h e i r e l e c t r o c h e m i c a l d a t a ( [FeTMPyP] = 1 0 - 10 M ,

pH 1 - 13) . However o n l y one d i m e r i c s p e c i e s needs t o be

i n v o k e d t o e x p l a i n t h e i r r e s u l t s .

In t h i s work some s p e c t r o p h o t o m e t r i c and m a g n e t i c

moment measurements wer e made t o i n v e s t i g a t e t h e e x t e n t and

t y p e o f d i m e r i s a t i o n o f FeTMPyP .

The v i s i b l e s p e c t r a and m a g n e t i c moment o f two

s o l u t i o n s o f 0 . 01 M Fe * * * T MPy P , w i t h i o n i c s t r e n g t h s o f 0

and 0 . 2 5 M (KC1) , were d e t e r m i n e d . These s p e c t r a t o g e t h e r

- 4w i t h a n o t h e r sp e c t ru m a t pH 1 0 . 5 and 3 x 1 0 M a r e

46

ABSO

RBAN

CE

FIGURE 1.3 V isible absorption sfectra of Fe p - t m py p

3 x 10"1* M FeP. 20°C

0.01 M FeP, 20°C path length = 1mm

path length = 0.1 mm [ = 0

^ PH I

A.2 7.90 0

— — 2.5 9.15 0.25

t 35°C

A 7

r e p r o d u c e d i n F i g u r e 1 . 3 . W i t h o u t added KC1 t h e

s pe ct rum (pH 7 . 9 ) i s more n e a r l y l i k e t he one obser ved a t

pH 10 . 5 f o r a more d i l u t e s o l u t i o n and t h e m a g n e t i c moment

o f 4 . 2 shows t h a t some monomer ic p o r p h y r i n i s p r e s e n t .

W it h an i o n i c s t r e n g t h o f 0 . 2 5 M (pH 9 . 1 5 ) t h e r e i s a l e s s

pronounced s h o u l d e r and a s h i f t t o s h o r t e r w a v e l e n g t h . The

m a g n e t i c moment was d e t e r m i n e d t o be 2 . 5 which i n d i c a t e s a

g r e a t e r p r o p o r t i o n o f d i m e r w i t h i n c r e a s e d i o n i c s t r e n g t h .

1 . 1 . 4 . 2 . 1 . D e t e r m i n a t i o n o f t h e FeTMPvP d i m e r i s a t i o n

c o n s t a n t JK

V a l u e s o f w er e d e t e r m i n e d by f o l l o w i n g e x t i n c t i o n

c o e f f i c i e n t changes w i t h c o n c e n t r a t i o n ( F i g u r e 1 . 4 ) . No

b u f f e r s wer e used , s i n c e t h e y a f f e c t t h e r e s u l t s . T h i s

e f f e c t i s d i s c u s s e d i n more d e t a i l l a t e r i n t h i s c h a p t e r

and i n a p p e n d i x 1 . The a bs o r b a n c e measurements were

c a r r i e d o u t a t t h r e e d i f f e r e n t i o n i c s t r e n g t h s and two

d i f f e r e n t w a v e l e n g t h s .

A computer p r ogram , d e s c r i b e d i n a p p e n d i x 1 . 3 , was

used t o v a r y eM • e dand K t o g e t a b e s t f i t o f c a l c u l a t e d

a nd e x p e r i m e n t a l abs or ba nc e s . V a r y i n g a l l t h r e e p a r a m e t e r s

f o r t h e I = 0 . 5 0 M d a t a gave t h e f o l l o w i n g r e s u l t s f o r :

5 9 . 0 x 1 o3 ( 423 nm)

3 . 6 0 x 1 0 3 ( 600 nm)

S i n ce t h i s d a t a g i v e s e x t i n c t i o n c o e f f i c i e n t s c l o s e s t

t o t h e l i m i t i n g v a l u e o f e D , t h e s e v a l u e s o *+» cn o a r e used

t h r o u g h o u t .

48

F IG U R E S p e c TROPHOTOMETRIC DETERMINATION of K0 FOR FeTMPyP

CO

423 nm

e / 1 0 e / i o 3

600 nm

20 ± 2°C

1 . 1 . 4 . 2 . 2 . R e s u l t s

Path Ab sorbance T o t a l e / 1 0Length / cm Concn

I o n i c s t r e n g t h = 0 . 0 M , 4 23 nm

- 40 . 0 1 7 4 0 . 7 9 3 5 . 7 8 x 1 0 7 8 . 70 . 0 1 7 4 0 . 2 8 3 1 . 8 5 x 10 c 8 7 . 90 . 1 0 0 0 . 6 8 7 7 . 5 2 x 1 0 9 1. 40 . 1 0 0 0 . 2 0 9 2 . 0 8 x 1 0 1 0 01 . 0 0 0 . 8 7 9 8 . 6 8 x 1 0 1 0 1

I o n i c s t r e n g t h = 0 . 0 M , 6 0 0 nm

- 40 . 1 0 0 . 3 6 5 5 . 7 8 x 1 0 6. 311 . 0 0 1 . 3 5 0 1 . 8 5 x 10 1 7. 311 . 0 0 0 . 629 7 . 5 2 x 1 0 _ 8 . 375 . 0 0 0 . 9 2 0 2 . 0 8 x 1 0 _ 8 . 8 45 . 0 0 0 . 4 1 0 8 . 6 8 x 1 0 9 . 4 5

I o n i c s t r e n g t h = 0 . 3 0 M , 423 nm- 4

0 . 0 1 7 4 1. 071 8 . 6 1 x 1 0 7 1 . 30 . 0 1 7 4 0 . 371 2 . 7 6 x 1 0 , 7 7 . 00 . 1 0 0 0 . 9 4 5 1 . 1 2 x 1 0 _ 8 4 . 40 . 1 0 0 0 . 2 5 9 2 . 7 6 x 1 0 'l 9 3 . 71 . 0 0 1 . 104 1 . 1 2 x 1 0 9 8 . 6

I o n i c s t r e n g t h = 0 . 3 0 M , 600 nm

- 40 . 1 0 0 0 . 4 5 8 8.61 x 10 , 5.320 . 100 0 . 1 6 5 2 . 7 6 x 10 ; 5.971 .00 0.7 8 7 1.12 x 10 7.031 . 00 0.221 2 . 7 6 X 10 1 8.005.00 0 . 4 9 5 1.12 x 10 8.84

I o n i c s t r e n g t h = 0 . 5 0 M , 423 nm-4

0 . 0 1 7 4 0 . 969 8 . 3 0 x 10 . 67.00 . 0 1 7 4 0 . 3 1 5 2.61 x 10 , 69.40 . 100 0 . 8 4 2 1.08 x 10 _- b 7 8 . 00 . 100 0 . 2 3 0 2 . 6 6 x 10 _ 86.61 .00 1.013 1.08 x 10 9 3.9

I o n i c s t r e n g t h = 0 . 5 0 M , 600 nm- 4

0 . 1 0 0 0 . 3 8 6 8 . 3 0 x 10 , 4 .651.00 1.376 2.61 x 10 , 5.281 .00 0 . 6 5 0 1.08 x 10 c 8.025.00 0 . 9 6 4 2 . 6 6 x 10 7 . 265.00 0 . 4 3 4 1.08 X 10 8.04

50

V a r y i n g e.. and K.. f o r t h e I = 0 . 0 M da t a gave t h e M Df o l l o w i n g r e s u l t s f o r e.. :M

1 03 x 1 0 3 ( 423 nm)

9 . 4 0 x 1 0 3 ( 600 nm)

S i m i l a r l y t h e s e v a l u e s o f were used t h r o u g h o u t .

V a r y i n g « D f o r a l l t h r e e se t s o f d a t a gave t h e

f o l l o w i n g r e s u l t s . The c u r v e s on t h e graphs i n F i g u r e 1 . 4

c or r es p on d t o t h e b e s t f i t .

T a b l e 1 . 3 D i m e r i s a t i o n c o n s t a n t f o r Fe p-TMPyP

I o n i c S t r e n g t h / M * * * * * * * * *

4 23 nm

k d '

600

1 0

nm

3 - 1mol 1 t * * * * * * * * *

Aver age ± 1 S . D.

0 . 0 2 . 59 2 . 32 2 . 4 6 ± 0 . 1 30 . 3 0 5 . 58 5 . 2 0 5 . 3 9 ± 0 . 1 90 . 5 0 1 5 . 1 1 6 . 5 1 5 . 8 ± 0 . 6 7

t 20 ± 2 °C

The e v a l u a t i o n o f e..M and eo a s sumes t h a t t h e s e

p a r a m e t e r s do not v a r y w i t h i o n i c s t r e n g t h . The

c o n s i s t e n c y o f t h e r e s u l t s between t h e two w a v e l e n g t h s

suggest s t h a t t h i s i s a r e a s o n a b l e a ss umpt ion . As

e x p e c t e d , t h e v a l u e o f KQ i n c r e a s e s w i t h i n c r e a s i n g i o n i c

s t r e n g t h .

1 . 1 . 5 . S o l u t i o n s u s c e p t i b i l i t y mea s uremen t s

1 . 1 . 5 . 1 . X n t r o d u c t i o n

M a g n e t i c s u s c e p t i b i l i t y measurements have been used

to d e t e r m i n e t h e v a l u e o f t h e d i m e r i s a t i o n c o n s t a n t Qp and

to d e t e r m i n e t he m a g n e t i c p r o p e r t i e s o f t he i n d i v i d u a l

p o r p h y r i n s p e c i e s . The r e s u l t s o f o t h e r w o r k e r s i s

d i s c u s s e d and compared t o t h i s work . The work done h e r e i s

t hen p r e s e n t e d i n d e t a i l .

1 . 1 . 5 . 2 . M a g n e t i c moment o f d i m e r i c Fe * * *TMPvP

G o f f and Morgans * s ( 1 9 ) a s s ig n me n t o f a m a g n e t i c

moment t o t h e d i m e r assumed t h a t F e * * * p - T M P y P was f u l l y

d i m e r i s e d a t 0 . 01 M above pH 7 . From t h e d e t e r m i n a t i o n o f

Kd h e r e , i t i s seen t h a t under t h e s e c o n d i t i o n s a m i x t u r e

o f d i m er and monomer i s p r e s e n t . Knowing t h e m a g n e t i c

moment o f t h e monomer and t h e d i m e r i s a t i o n c o n s t a n t ( f r o m

s p e c t r o p h o t o m e t r i c d a t a ) , a m a g n e t i c moment o f 1 . 8 3 was

c a l c u l a t e d f o r t h e d i m e r ( d e t a i l s i n a pp e n d i x 1 . 4 ) . O t he r

p oxo b r i d g e d f e r r i c p o r p h y r i n d i m e rs have been shown ( 46)

t o have m a g n e t i c moments i n t h e r a n ge 1 . 4 5 t o 1 . 79 a t room

t e m p e r a t u r e . F l e i s c h e r e t a l ( 47 ) r e p o r t t h a t t he

c a r e f u l l y d r i e d p oxo d i m e r i c FeTPP has a m a g n e t i c moment

o f 1 . 7 4 ( 2 5 ° C) but when t h e r e was w a t e r o f h y d r a t i o n t h e

m a g n e t i c moment was 2 . 6 8 ( 2 5 ° C) .

G o f f and Morgan ( 1 9 ) c o n s i d e r e d p y r r o l e s u b s t i t u t e d

f e r r i c p o r p h y r i n d i m e r s , such as hemin C , FeDeut and

FeDSS . I n aqueous s o l u t i o n t h e s e have m a g n e t i c moments

o n l y s l i g h t l y d i m i n i s h e d f rom t h e h i g h s p i n v a l u e o f 5 . 9 .

They a r e t hus no t t h o u g h t t o be p oxo d i me r s . This

52

s i t u a t i o n changes i n h i g h i o n i c s t r e n g t h , where F e P r o t and

FeDeut show d i m i n i s h e d m a g n e t i c moments c o n s i s t e n t w i t h a

p oxo d i m er .

1 . 1 . 5 . 3 . 1 . S o l u t i o n s u s c e p t i b i l i t y o f FeTMPvP and Fe_TPPS.

Go f f and Morgan ( 19 ) have used s u s c e p t i b i l i t y

measurements t o f o l l o w a c i d / base t i t r a t i o n s o f FeTMPyP

oand FeTPPS. t o g i v e t h e f o l l o w i n g v a l u e s f o r Q_ a t 35 C .4 D

C o n d i t i o n s V M

0 . 01 M F e I I X p-TMPyP , 0 . 2 5 M NaCl - 81 .4 x 1 0

0 . 01 M F e 1 1 I TPPS, ,4 4 x 10 ~ 7

0 . 0 5 M a c e t a t e , 0 . 0 7 5 M NaCIO,4

For FeTMPyP t h e e q u i l i b r i u m was v e r y dependent on

i o n i c s t r e n g t h . The t e m p e r a t u r e dependence o f t h e a v e r a g e

m a g n e t i c moment o f FeTMPyP between pH 7 and 9 was

a t t r i b u t e d t o a n t i f e r r o m a g n e t i c c o u p l i n g o f t h e two F e * 1 1

i on s i n t h e d i m e r . However t h e p o s i t i o n o f t he

monomer /d i mer e q u i l i b r i u m and hence t h e a p p a r e n t m a g n e t i c

moment w i l l i n any case change w i t h t e m p e r a t u r e .

Us ing t h e e q u a t i o n

Q _ = K . K 2 D D A1

and u s i n g t h e v a l u e s

p K. . = 5 . 5 9 (31 ° C ) and K.. = 5390 mol 11 ( 2 0 ° C) d e t e r m i n e dA 1 D— 8 — 1h e r e , a v a l u e o f 3 . 5 6 x 10 m o l l was c a l c u l a t e d f o r

- 8 oQD . G o f f and Morgan s ( 1 9 ) v a l u e o f 1 . 4 x 10 M (35 C) i s

not d i r e c t l y c o m pa r a b l e because o f t h e i r e r r one ous

53

MAG

NETI

C HO

HENT

FIGURE 1.5 VARIAnON OF Fep-TMPyP MAGNETIC MOMENT WITH pH

PH

trt~u = 2.51>DPKA1 = 12.0

Kq = Uxio16 morU Q0 = U x 10* mol l"1

(PFe 1 = 0.01 moll'1

u = 5.95

u = l. 83■dpKa1 = 5.59

K0 = 5390 mol“1l

Q0 = 3.56x 10~® moll"1

[PFel = 0.01 moll'1

ass umpt ion t h a t F e ^ ^ p - T M P y P was f u l l y d i m e r i s e d a t 0 . 0 1 M

above pH 7 . Us ing a computer program , d e s c r i b e d i n t he

a p p en d i x 1 . 5 , t he v a r i a t i o n o f t he m a g n e t i c moment w i t h pH

was c a l c u l a t e d f rom b ot h s e t s o f p a r a m e t e r s . To r e p r o d u c e

G o f f and M o r g a n ’ s g r aph , P <A 1 was s e t t o 12 . 0 and pQ t o

2 . 51 , t h i s i s e q u i v a l e n t t o presumming o n l y t h e

e q u i l i b r i u m

QD

2 PFe ( OH^ ) £ * ... PFe-O-FeP + 2 H +

The two graphs ( F i g u r e 1 . 5 ) a r e o f t h e same shape but

d i s p l a c e d by 0 . 2 4 pH u n i t s . I t o n l y r e q u i r e s a s m a l l

d i f f e r e n c e i n e i t h e r p K ^ o r Kq t o cause t h i s s h i f t . The

l o w e r t e m p e r a t u r e used i n t h i s work f o r t h e d e t e r m i n a t i o n

o f K0 , i s enough t o a c c o u n t f o r t h i s missmatch .

H a r r i s and Toppen ( 4 8 ) used s p e c t r o p h o t o m e t r y t o

f o l l o w t h e d i s s o c i a t i o n o f d i m e r i c FeTMPyP . The s p e c t r a

r e c o r d e d , c o r r e s p o n d t o t h e monomer / d i mer s p e c t r a o bs er ved

i n t h i s work . Below pH 6 . 3 2 t h e r a t e was d i r e c t l y_ +

p r o p o r t i o n a l t o [H ] and above pH 6 . 3 2 t h e r a t e dropped o f f

r a p i d l y . The f o l l o w i n g mechanism was proposed

+ KPFe-O-FeP + H m ---------- PFe -O- FeP r a p i d---------^

H kH20 + PFe-O- FeP ------ P F e ( 0 H 2 ) + PFe(OH) r . d . s .

KAiA 1 i .P Fe ( OH 2 ) * ...^ PFe( OH) + H

5 5

The d a t a was e v a l u a t e d t o g i v e

5 , 8 - 1Kd a = 7 . 51 x 1 0 and 3 . 0 6 x 1 0 mol 1

km = 0 . 1 5 5 and 2 . 6 9 s' 1

f o r FeTMPyP and FeTPPS r e s p e c t i v e l y .4

From t he se v a l u e s o f , t h e two proposed f o r m s o f

d i m e r a r e i n e q u a l p r o p o r t i o n s a t pH 5 . 9 f o r FeTMPyP and a t

pH 8 . 5 f o r FeTPPS. . A p oxo d i m er i s e xp e c t e d t o have a*s i g n i f i c a n t l y l o w e r m a g n e t i c moment than t he c o r r e s p o n d i n g

p hydroxo d i me r . So t h e proposed e q u i l i b r i u m between

d i m e rs , i s p r e d i c t e d to g i v e r i s e t o a s i g n i f i c a n t change

i n s u s c e p t i b i l i t y o v e r t h e pH r an ge 5 t o 7 f o r FeTMPyP and

7 . 5 t o 9 . 5 f o r FeTPPS. . I t has been d e m o n s t r a t e d by Go f f4

and Morgan ( 19) , t h a t a t c o n s t a n t t e m p e r a t u r e , t h e

m a g n e t i c moment does not s i g n i f i c a n t l y change f rom pH 6 t o

7 f o r 0 . 01 M FeTMPyP or f rom pH 7 . 5 to 9 . 5 f o r 0 . 01 M

FeTPPS. . A n o t h e r i n t e r p r e t a t i o n o f H a r r i s and Toppens

k i n e t i c d a t a i s c a l l e d f o r .

1 . 1 . 5 . 3 . 2 . FeTPPS . _l t h e v a l u e o f Q_4 0F l e i s c h e r e t a l ( 47 ) r e p o r t t h a t FeTPPS, obeys B e e r ’ s4

- 9 - 4Law i n t h e r e g i o n 1 x 10 M t o 1 x 10 M ( I = 0 . 1 0 ,

NaCIO, ) , which i s c o n s i s t e n t w i t h non a g g r e g a t i o n under

t h e s e c o n d i t i o n s . They f o l l o w e d a pH t i t r a t i o n o f FeTPPS,4

by s p e c t r o p h o t o m e t r y , under t h e f o l l o w i n g c o n d i t i o n s

10~4M FeTPPS, , 0 . 1 M NaNO (1 1, 25, 50 ° C)H 3

— 8The r e s u l t s were e v a l u a t e d t o g i v e = 0 . 7 9 10 M

a t 25°C , wh ich i s o f t h e same o r d e r o f m a gn i t ud e as t he

v a l u e d e t e r m i n e d by G o f f and Morgan ( 19 ) . The v a l u e s o f QD

56

w e r e d e p e n d e n t on i o n i c s t r e n g t h . I t w a s a s s u m e d t h a t

FeTPPS was c o m p l e t e l y d i m e r i s e d above pH 8 , which i s not4

n e c e s s a r i l y t h e case .

H a mb r i gh t e t a l ( 4 9 ) used s p e c t r o p h o t o m e t r y to f o l l o w

pH t i t r a t i o n s and t e m p e r a t u r e jump e x p e r i m e n t s on aqueous

oFeTPPS. . The c o n d i t i o n s were 20 C , 0 . 0 5 M NaNO and i n4 J

p a r t i c u l a r f o r t he k i n e t i c measurements

[ F e T P P S . ] = 8 . 2 x 1 0 " ? - 1 . 7 x 10~ 5 M

390 - 430 nm , pH 6 . 0 9 - 7 . 5 0

The s p e c t r a r e ma i ned unchanged and no r e l a x a t i o n s

were obser ved i n t h e r e g i o n s o f pH 1 t o 5 and 8 t o 12 . I t

was i n f e r r e d t h a t PF e ( 0 H2 ) and PFe-O-FeP r e s p e c t i v e l y ,

p r e d o m i n a t e i n t h e s e r anges o f pH .

An i s o b e s t i c p o i n t was obser ved a t 406 nm f o r t he

s p e c t r a i n t h e pH 5 t o 8 r e g i o n . The d a t a was e v a l u a t e d to

f o l l o w i n g mechanism was

++ H

+ H O 2

1 . 1 . 5 , 3 . 3 . C o n c l u s i o n s

Compar isons o f t h e l i t e r a t u r e v a l u e s o f w i t h t he

v a l u e de r mi ned he r e a r e not m e a n i n g f u l s i n c e t h e c o n d i t i o n s

d i f f e r too much .

g i v e Q0 = 0 . 2 5 1 x 1 0

proposed

The

PFe ( 0 H2 ) i z i-1 P F e ( OH)

2 PFe ( OH ) - 2 PFe-O-FePk

The d a t a was e v a l u a t e d t o g i v e

-11

-2

3 . 3 7 ± 0 . 1 7 s

0 . 9 0 ± 0 . 0 5 s - 1

57

For e i t h e r FeTMPyP or FeTPPS. t he l i t e r a t u r e v a l u e s

o f Q show some c o n s i s t e n c y . However due t o t h e e r r o r s

d e s c r i b e d i n e v a l u a t i n g t h e d a t a t h e s e v a l u e s can not be

- 8a p p l i e d . The v a l u e o f 3 . 5 6 x 10 M f o r , c a l c u l a t e d

f rom the K and K .„ v a l u e s d e t e r m i n e d h er e i s used l a t e r D A 1

f o r f u r t h e r c a l c u l a t i o n s .

1 . 1 . 5 . 4 . S o l u t i o n s u s c e p t i b i l i t y o f t h r e e F e 1 1 * T ( M. E t ) PvP

These s t u d i e s were f u r t h e r e d he r e , by i n v e s t i g a t i n g

t h e e f f e c t o f c o n c e n t r a t i o n , pH and t e m p e r a t u r e on t he

I I Is o l u t i o n s u s c e p t i b i l i t y o f t h r e e Fe T ( M, E t ) P y P .

The m a g n e t i c moments f o r a c i d s o l u t i o n , measured

u s i n g a P e r k i n Elmer R32 , a r e s l i g h t l y h i g h e r t han t h o se

d e t e r m i n e d us i ng t h e B r u k e r WM250 , The R32 r e s u l t s a r e

l e s s a c c u r a t e but s c a l i n g t h e s e s u s c e p t i b i l i t y v a l u e s does

not i mprove t h e d e v i a t i o n o f t h e c a l c u l a t e d f rom

e x p e r i m e n t a l v a l u e s However t h e s e r e s u l t s ( F i g u r e 1 . 6 )

i l l u s t r a t e t he d i f f e r e n c e s i n b e h a v i o u r o f t he

F e 1 1 XT ( M . E t ) PyP s t u d i e d . The f i n a l m a g n e t i c

moments ( 35 ° C , 0 . 2 5 M KC1) v a r y i n t h e o r d e r

F e 1 1 Xp-TMPyP < F e I I ] t m-TMPyP < F e 1 1 ^ - T E t P y P

T hi s can be u n d e r s t o o d i f t h e d e g re e o f d i m e r i s a t i o n

o f t h e F e 1 1 * m - T ( M, E t ) PyP a r e much s m a l l e r o r i f t h e

m a g n e t i c moments o f t h e i r d i m e r i c forms a r e h i g h e r or i f

both o f t h e s e t h i n g s a r e t r u e . The t e m p e r a t u r e dependence

o f t h e f i n a l m a g n e t i c moment o f F e 1 1 I m-TEtPyP i s c o n s i s t e n t

w i t h t h e s e i d e a s . The v a r i a t i o n o f m a g n e t i c moment w i t h

c o n c e n t r a t i o n a t pH 1 0 . 5 f o r Fe* * *m-TMPyP ( F i g u r e 1 . 6 )

suggest s t h a t , a t l e a s t b e l o w 0 . 01 M , t h e r e i s i n c o m p l e t e

58

FIGURE 1 .6 T it r a t io n of F e t m Py p w i t h NaOH

C 4*

• ♦

jjI of 1M NaOH added

k Fe m-TEtPyP

■ Fe m-TMPyP

• Fe p-THPyP

feo-c

38*Ci8*C

Temperature = 35°C unless otherwise stated

0.0 1M PFe . 0 .25M KCl

5.6-cOJEoE ' 5.2-

cucCTIro 4.8

Fe m-TMPyP

4.4 1 ' 1 ' 1 ' ■ ' • •0 2 4 6 8 10

(Fe m-TMPyP]/10*3M

0 .25M KCl . pH 10.5 . 35°C

59

F I GURE 1 .6 C o n t i n u e d

Fe m-T MPyP

pH

0.01m Fe m-TMPyP , 0.2SM KCl , 35°C

60

d i m e r i s a t i o n .

The cur v e f i t t e d t o t h e m a g n e t i c moment v e r s u s pH

d a t a f o r F e ^ I I m-TMPyP ( F i g u r e 1 . 6 ) shows a d e v i a t i o n f ro m

t h e da t a p o i n t s . Th i s may be due t o t he u n c e r t a i n t i e s i n

t h e v a l u e s o f t h e m a g n e t i c moment o f t he d i mer and t h e

d i m e r i s a t i o n c o n s t a n t .

A l l o f t h e s e r e s u l t s p o i n t t o a m a r k e d l y l o w e r

t e n de n c y o f F e * * * m - T ( M, E t ) PyP t o d i m e r i s e compared t o

F e I I I p-TMPyP . A l t h o u g h t h i s i s p r e d i c t e d on e l e c t r o n i c

grounds , t he marked d i f f e r e n c e can not be t o t a l l y

e x p l a i n e d i n t h i s way . The e l e c t r o n i c e f f e c t amounted t o

abo ut a f a c t o r o f 2 i n t h e FeTMPyP K or TMPyP v a l u e s .

The d i f f e r e n c e i s most p r o b a b l y a s t e r i c one . The meso

p y r i d y l s u b s t i t u e n t s must o f f e r some s t e r i c h i n d e r a n c e t o

t h e c l o s e approach o f two F e T ( M , E t ) P y P m o l e c u l e s . The meta

s u b s t i t u e n t s on t h e p y r i d i n e s a r e :

C-H N+- CH 3 N+ -CH 2 -CH 3

F e 1 1 1 p-TMPyP F e I I Z m-TMPyP Fe 1 1 1 m-TEtPyP

So f rom l e f t t o r i g h t t h e d e g r e e o f s t e r i c h i n d r a n c e

i s e x p e c t e d t o i n c r e a s e and t h e d e g r e e o f d i m e r i s a t i o n+

d e c r e a s e . The l a r g e d i f f e r e n c e o f N -CH3 / C - H compared t o

N+ - CH 3 / N + - CH 2 “ CH3 e x p l a i n s t h e s i m i l a r i t y o f t h e meta

i somer s r e l a t i v e t o t h e pa r a i so me r , w i t h r e s p e c t t o

d i m e r i s a t i o n .

1 . 1 . 6 . S u m m a r y o f e q u i l i b r i u m c o n s t a n t e v a l u a t i o n s

The v a l u e o f Q be l ow was c a l c u l a t e d us i ng

equa t i o n

QD A 12

[ PFe(OH ) (OH) ] [H + ]K = -------------------------------- = 2.57 x 10"B mol l " 1 (31°C , 1 = 0.

CPFe( OH ) ]

CPFe(OH) 3CH 3K = ------------------------- = 2.17 x 10 mol 1 (35°C , 1M NaOHJ

[PFe(OH ) (OH)]

[PFe-O-FeP][Hf ] 2Q_ = -------------------------— = 3.56 x 10 mol 1

[PFe(OH2)2lZ

[PFe-0-FeP3K = ------------------------- r = 5.39 x 1 03 mol_1l (20°C , I = 0.30 M)

[PFe(OH) ( 0H2) ] ^

t h e

30 M)

62

1 . 1 . 7 . E x p e r i m e n t a l

1 . 1 , 7. 1 . E v a l u a t i o n o f pK^^ v a l u e s

The f i r s t s e t o f r e s u l t s were o b t a i n e d a t a m b i e n t— 6t e m p e r a t u r e . A p p r o x i m a t e l y 1 x 10 M ( 100 ml ) s o l u t i o n s

o f Fe* * * TMPyP were t i t r a t e d w i t h c a r b o n a t e f r e e

0 . 6 NaOH ( aq) i n an a rgon f l u s h e d f l a s k . At t h e s e

c o n c e n t r a t i o n s t h e p r o p o r t i o n o f d i m e r i c FeTMPyP i s

n e g l i g i b l e . The p o s i t i o n o f e q u i l i b r i u m was f o l l o w e d by

abs or b an ce measurements , a t a w a v e l e n g t h i n t h e S o r e t

r e g i o n , u s i n g a 5 cm pa t h l e n g t h c e l l . For t h e second s e t

o f r e s u l t s an i m p r o v i s e d f l o w a p p a r a t u s , i l l u s t r a t e d

be l ow , was used w i t h a 5 mm p a t h l e n g t h c e l l . An o i l b a t h

owas used t o keep t h e RB f l a s k a t about 30 C . I n each case

2 0 0 ml o f d i s t i l l e d w a t e r and an a p p r o p r i a t e amount o f KNO^

were p l a c e d i n a 500 ml R. B. f l a s k . FeTMPyP was added

u n t i l a c o n v e n i e n t a bs o r b a n c e was obs er ved . The pH o f t h e

argon f l u s h e d s o l u t i o n was a d j u s t e d us i ng c a r b o n a t e f r e e

NaOH .

The r e s u l t s o b t a i n e d u s i n g t h e f l o w c e l l g i v e a

b e t t e r f i t t o a s t r a i g h t l i n e , i n d i c a t i n g t h a t t h e

t e m p e r a t u r e s t a b i l i s a t i o n and improved s a mp l i n g a r e an

a d v a n t a g e .

63

F low apparatus for spectrophotometric titration

The cell was flushed wi1h fresh sample by alternately pinching the tubing at X and Y whilst withdrawing and compressing the syringe Plunger.

64

1 . 1 . 7 . 2 . D e t e r m i n a t i o n o f t h e FeTMPvP d i m e r i s a t i o n

c o n s t a n t J<

250 ml o f d i s t i l l e d w a t e r and t h e a p p r o p r i a t e amount

o f NaCl were p l a c e d i n a 500 ml R. B. f l a s k . The f l a s k was

f l u s h e d w i t h a rgon and t h e pH was a d j u s t e d t o 7 . 5 u s i n g

c a r b o n a t e f r e e NaOH .

A l l v o l u m e t r i c f l a s k s were f l u s h e d w i t h argon b e f o r e

s o l u t i o n s were t r a n s f e r r e d t o them and volumes were made up

w i t h t h e NaCl s o l u t i o n . 1 .3 p i and 5 . 0 p i o f cone NaOH

were i n j e c t e d i n t o two 5 ml f l a s k s c o n t a i n i n g 1 . 3 mg and

4 . 0 mg o f FeTMPyP r e s p e c t i v e l y . A f t e r making up t o

volume , samples o f t h e s e two s o l u t i o n s were d i l u t e d i n

o t h e r f l a s k s .

A l l FeTMPyP s o l u t i o n s were l e f t f o r one hour t o

a s s u r e e q u i l i b r i u m o f monomer and d i m er . At pH 7 . 5

-6e q u i l i b r i u m i s r e a c he d i n a f ew m i n ut e s , whereas a 10 M

pH 10 s o l u t i o n t a k e s hours .

The 0 . 1 7 4 mm p at h l e n g t h c e l l c o n s i s t e d o f two s i l i c a

p l a t e s s e p a r a t e d by PTFE spa cer s . The p a t h l e n g t h was

c a l c u l a t e d f rom t h e r a t i o o f t h e a bs or bance o f a d i c h r o m a t e

s o l u t i o n i n t h i s c e l l t o t h a t i n a 1 mm p a t h l e n g t h c e l l .

S p e c i a l mounts wer e made f rom expanded p o l y s t y r e n e t o

p o s i t i o n t he 0 . 1 7 4 mm and 5 cm pa t h l e n g t h c e l l s i n t he

l i g h t beam o f t h e P e r k i n E l mer 551 s p e c t r o p h o t o m e t e r .

The sample c e l l s were s t o p p e r e d w i t h r u b b e r septum

caps and f l u s h e d w i t h a r gon . The FeTMPyP s o l u t i o n and t h e

NaCl s o l u t i o n were t r a n s f e r r e d i n t o t h e sample c e l l s us i ng

s t e e l t u b i n g and a back p r e s s u r e o f a few p . s . i . o f argon .

65

1 . 1 , 7 . 3 . S o l u t i o n s u s c e p t i b i l i t y o f t h r e e F e * * * T ( M . E t ) P v P

400 p i o f a 0 . 0 1 M s o l u t i o n o f t he f e r r i c p o r p h y r i n

was made up i n an NMR t u b e u s i ng - 4 - 5 mg f e r r i c

p o r p h y r i n and pH 2 (HC1) 0 . 2 5 M KC1 i n aqueous 2 7 t - b u t y l

a l c o h o l . A c o a x i a l l y mounted c a p i l i a r y was added and t h e

NMR t ube was s e a l e d w i t h a r u b b e r septum cap .

The pH wa s a d j u s t e d by i n j e c t i n g p o r t i o n s o f

c a r b o n a t e f r e e 1 M NaOH ( aq) . A f t e r each a d d i t i o n t h e

s e p a r a t i o n o f t h e two t - b u t y l a l c o h o l r es on anc es wa s

measured . The f i n a l m a g n e t i c moment f o r F e * * *m-TEtPyP wa s

d e t e r m i n e d a t t h r e e t e m p e r a t u r e s .

The e x p e r i m e n t was r e p e a t e d f o r Fe* * *m-TMPyP u s i n g

850 p i o f s o l u t i o n i n an NMR t u b e . A f t e r each a d d i t i o n o f

NaOH(aq) t h e pH was d e t e r m i n e d by i n s e r t i n g a t h i n pH

e l e c t r o d e i n t o t h e NMR t u b e .

400 p i o f t h e f i n a l s o l u t i o n was i n j e c t e d i n t o

a n o t h e r NMR t u b e and d i l u t e d by s u c c e s s i v e a d d i t i o n s o f

0 . 2 5 M KC1 i n pH 1 0 . 5 2 7 aqueous t - b u t y l a l c o h o l . A f t e r

each a d d i t i o n t h e t - b u t y l a l c o h o l s e p a r a t i o n was measured .

The f i n a l pH o f t h e d i l u t e d s o l u t i o n was checked and found

to be 1 0 . 5 .

66

1 . 2 . Complexes w i t h o t h e r l i g a n d s

1 . 2 . 1 . I n t r o d u c t i o n

In t h i s s e c t i o n t h e r e a c t i o n o f aqueous FeTMPyP w i t h

v a r i o u s l i g a n d s has been f o l l o w e d u s i ng s p e c t r o p h o t o m e t r y ,

1H NMR , ESR and s u s c e p t i b i l i t y measurements . The sp i n

s t a t e s o f t he p r o d u c t s v a r y f rom h i g h sp i n f o r f l u o r i d e

complexes , t o i n t e r m e d i a t e s p i n f o r an a z i d e complex , t o

l ow sp i n f o r c y a n i d e complexes . The e f f e c t o f b u f f e r

c o o r d i n a t i o n t o FeTMPyP has been t a k e n i n t o a c c ou nt i n

d e t e r m i n i n g e q u i l i b r i u m c o n s t a n t s .

1 . 2 . 2 . V i s i b l e a b s o r p t i o n s p e c t r a

The r e s u l t s o f t h e measurement o f t h e v i s i b l e

a b s o r p t i o n s p e c t r a o f seven F e * * * p - TMPy P s p e c i e s are

r e c o r d e d i n T a b le 1 . 4 A 1 cm pa t h l e n g t h c e l l was used

f o r 700 - 500 nm and a 1 mm p at h l e n g t h c e l l was used f o r

500 - 314 nm . The p o r p h y r i n c o n c e n t r a t i o n i s

-69 6 . 0 3 x 10 M . The pH was a d j u s t e d w i t h aqueous HC1 . The

c o n c e n t r a t i o n s o f t h e l i g a n d s were chosen t o g i v e c om p l e t e

f o r m a t i o n o f t h e complex . T h i s was checked f o r f l u o r i d e

and c y a n i d e by us i ng l o w e r c o n c e n t r a t i o n s o f l i g a n d and 2 l

was t h e g r e a t e s t change i n e x t i n c t i o n c o e f f i c i e n t between

d e t e r m i n a t i o n s . However i n t h e case o f DMAP a t pH 7 . 2

t h e r e a r e s i g n i f i c a n t d i f f e r e n c e s between d e t e r m i n a t i o n s ,

showing t h a t even a t 0 . 6 5 M t h e complex has no t f u l l y

formed . Thr e e p a i r s o f s p e c t r a can be i d e n t i f i e d : t h e two

h e t e r o c y c l i c l i g a n d s , pH 10 KOH / f l u o r i d e and 0 . 01 M HC1

/ a z i d e . W i t h i n each p a i r s i m i l a r i t i e s a r e a p p a r e n t .

67

FIG U R E 1.7 V is ible absorption spectra o f some FeTMPyP c o m p l e x e s

0.67M Imidazole DMAP

WAVELENGTH/nm

0.01M HO 1.0M NaN3

WAVELENGTH/nm

60

FIGURE 1.7 CONTINUED

pH 10 KOH 1.33 M KF

WAVELENGTH/nm

0.0082 M KCN

Path length 1mm ( 3 H - 500nm)

1 cm (500 * 700 nm)

(PFeJ = 96.0 x 10"6 M

20 ♦ 2 °C

69

T a b l e 1 . 4 E x t i n c t i o n c o e f f i c i e n t s o f Fe p - T M P y P c o m p l e x e s

pH , L i gand W a v e l e n g t h / n m e / 1 0 M cm ** ma x

pH 7 . 2 3 3 1 . 5 2 . 540 . 6 7 M I m i d a z o l e 424 13 . 7

5 5 4 . 5 1 . 14

pH 7 . 2 334 2 . 9 80 . 3 4 M DMAP 4 1 9 7 . 78

5 6 9 . 5 0 . 9210 . 6 5 M DMAP 334 3 . 27

422 8 . 4 05 6 9 . 5 0 . 8 4 8

0 . 01 M HC1 33 5 3 . 1 740 1 10 . 95 1 5 1 . 2 1635 0 . 4 0 3

pH 7 . 2 3 4 2 . 5 3 . 841 . 0 M NaN 434 10 . 73 533 . 5 1 . 19

pH 10 KOH 3 4 1 . 5 4 . 0 2423 1 0 . 6597 1 . 0 163 1 0 . 6 4 0

pH 7 . 5 KF 3 3 5 . 5 3 . 4 21 . 33 M 3 6 2 . 5 3 . 5 2

4 2 1 . 5 10 . 95 9 4 . 5 1 . 05

pH 7 . 2 KCN 336 3 . 1 3- 3 4 3 6 . 5 11 . 48 . 2 x 1 0 M 57 1 0 . 8 7 4

The e v a l u e o f 10 . 9 x 10^ i n 0 . 01 M HC1 s hou l d be

compared to Paste rnack ' s ( 2 3 ) v a l u e o f 1 0 . 2 x 10^ f o r a

pH 2 . 1 s o l u t i o n a t 403 nm .

7 0

1 . 2 . 3 . M a g n e t i c t i t r a t i o n s

1 . 2 . 3 . 1 . G e n e r a l c o n s i d e r a t i o n s

FeTPP has been shown ( 50 ) by ESR and

s p e c t r o p h o t o m e t r i c mesurements t o r e a c t w i t h 1 m e t h y l

i m i d a z o l e , i n o r g a n i c s o l v e n t s , t o g i v e a h i gh s p i n 1 : 1

complex and a l ow s p i n 2:1 complex . C o n s e q u e n t l y >> K1

f o r FeTPP and 1 m e t h y l i m i d a z o l e , due to t he e x t r a

s t a b i l i s a t i o n a s s o c i a t e d w i t h t h e change o f sp i n s t a t e .

T hi s r e s u l t i s c o n s i s t e n t w i t h most o f t h e m a g n e t i c

t i t r a t i o n d a t a f o r F e I I I TMPyP w i t h i m i d a z o l e s , i n t h i s

work .

For t h e s o l u t i o n s u s c e p t i b i l i t y measurements made i n

t h i s work , t h e Fe * * * TMPy P makes a s i g n i f i c a n t c o n t r i b u t i o n

t o t h e i o n i c s t r e n g t h . S i n c e t h e p o r p h y r i n m o l e c u l e i s not

a p o i n t cha r ge i t i s n o t a p p r o p r i a t e t o s u b s t i t u t e t he

t o t a l charge i n t o t h e e q u a t i o n f o r i o n i c s t r e n g t h . K o l s k i

and P l ane ( 51 ) a l s o p o i n t ou t t h i s p rob l em i n t h e use o f

O e by e - H u c ke l t h e o r y . However we know t h a t each Fe* * * TMPyP

m o l e c u l e c o n t r i b u t e s f i v e a n i o n s t o t he s o l u t i o n . Assuming

t h a t t h e p o r p h y r i n has an e q u a l e f f e c t , t h en a 0 . 01 M

s o l u t i o n o f F e I I I TMPyP w i l l c o n t r i b u t e 0 . 0 5 M t o t h e i o n i c

s t r e n g t h . The t o t a l i o n i c s t r e n g t h i n t h e m a g n e t i c

t i t r a t i o n s i s t hus e s t i m a t e d as 0 . 2 5 + 0 . 0 5 = 0 . 3 0 M .

I t has been shown i n a p p e n d i x 1 . 7 t h a t t h e c a l c u l a t e d

(3 v a l u e can be c o r r e c t e d f o r t h e c o o r d i n a t i o n o f b u f f e r t o

F e I I I TMPyP , by m u l t i p l y i n g by t h e f a c t o r /Q_ / K 7T" . i s\ / D e f f D

t h e a c t u a l d i m e r i s a t i o n c o n s t a n t and i s t h e a p p a r e n t

d i m e r i s a t i o n c o n s t a n t i n t h e p r e s e nc e o f b u f f e r . The

r a t i o s o f v a l u e s f o r d i f f e r e n t complexes a r e i n s e n s i t i v e

t o t h e v a l u e o f Qg . Hence i n f e r e n c e s made by compar ing (32

v a l u e s a r e i n d e p e n d e n t o f t h e a c c u r a c y o f t he v a l u e o f .

A P e r k i n Elmer R32 NMR s p e c t r o m e t e r was used f o r a l l

o f t he m a g n e t i c t i t r a t i o n s d e s c r i b e d i n t h i s c h a p t e r .

1 . 2 . 3 . 2. 1 . B i o l o g i c a l b u f f e r s

Four t i t r a t i o n s o f Fe * * * TMPyP w i t h i m i d a z o l e were

c a r r i e d out u s i ng 0 . 1 M b i o l o g i c a l b u f f e r s . A computer

program , d e s c r i b e d i n a p p e n d i x 1 . 7 , was used t o v a r y t h e

v a l u e o f so as t o m i n i m i s e t h e d e v i a t i o n s o f t h e

c a l c u l a t e d and e x p e r i m e n t a l m a g n e t i c moments . Graphs o f

m a g n e t i c moment v e r s us t i t r e a r e shown i n F i g u r e 1 . 0 . The

c i r c l e s a r e t h e e x p e r i m e n t a l measurements and t he s o l i d

l i n e i s t h e computer b e s t f i t . The r e s u l t s a r e t a b u l a t e d

below .

1 . 2 . 3 . 2 . 2 . R e s u l t s

pH 6 . 0 0 MES , T i t r a n t = 1 . 0 0 M I m i d a z o l e

I n i t i a l [FeTMPyP] = 9 . 5 7 0 x 10 ~ 3 M

0 2 = 2 . 5 7 x 10 6 m o l " 2 l 2 , 35°C

One s t a n d a r d d e v i a t i o n i n m a g n e t i c moment = 0 . 0 7 2

T i t r e A f M a g n e t i c moment [ l i g a n d ]p i Hz Exp Ca l c [ p o r p h y r i n ]

1 0 1 0 .47 3 .78 3 .78 02 5 ,. 0 9 .69 3 . 6 6 3 . 7 1 1 . 3 13 1 2 . 0 8 . 37 3 .43 3 .47 3 . 1 34 1 6 ., 0 7 ,. 62 3 ,. 29 3 ,. 29 4 ,. 1 85 2 0 ,. 0 6 ,.39 3 ,. 03 3 ,. 1 0 5 . 2 26 25 ,. 0 5 .. 53 2 ,. 83 2 ,, 87 6 ,. 537 30 .. 0 4 ,. 08 2 . 6 8 2 . 67 7 . 848 35 ., 0 4 ., 63 2 ,, 62 2 ., 5 1 9 ,. 1 49 40 .. 0 4 .. 1 7 2 .. 50 2 ..38 1 0 .. 45

1 0 50 ., 0 3 ., 4 1 2 ., 29 2 ., 2 2 1 3 .,061 1 60 ., 0 2 .,70 2 ,. 06 2 .. 1 2 1 5 ,, 671 2 80 . 0 2 .,30 1 .,94 2 ., 0 2 2 0 .,901 3 1 0 0 2 . 0 2 1 ., 8 6 1 ., 97 26 ., 1 21 4 — 2 . 58 1 . 87 1 . 87 1 03 . 52

72

- 3I n i t i a l [FeTMPyP] = 9 . 9 8 5 x 10 M

6 2 2 CD= 2 . 1 5 x 10 mol 1 , 35 C 2


pH 7 . 0 0 P I P E S , T i t r a n t = 0 . 9 9 3 M I m i d a z o l e

T i t r e $epn AfMl Hz Hz

1 0 9 . 0 3 5 . 2 02 5 . 0 8 . 83 4 . 9 03 1 0 . 0 8 . 33 4 . 314 15 . 0 7 . 9 2 3 . 8 05 2 0 . 0 7 . 4 4 3 . 2 36 2 5 . 0 7 . 22 2 . 917 3 1 . 0 6 . 8 3 2 . 4 08 3 6 . 0 7 . 1 2 2 . 6 09 4 0 . 0 6 . 8 6 2 . 2 6

1 0 5 0 . 0 7 . 1 7 2 . 3 81 1 6 0 . 0 7 . 1 7 2 . 1 91 2 8 0 . 0 7 . 39 2 . 0 21 3 1 0 0 7 . 4 6 1. 711 4 * 2 . 3 4

M a g n e t i c moment [ l i g a n d ] Exp C a l c [ p o r p h y r i n ]

2 . 6 1 2 ,. 6 1 02 . 55 2 ,.54 1 ,. 242 .40 2 ,.42 2 ,. 492 ,. 27 2 ., 27 3 .. 732 . 1 1 2 ,. 1 1 4 ,. 972 ,. 0 1 1 ., 99 6 .. 2 21 . 84 1 ,.90 7 ,. 7 11 ,,93 1 ., 8 6 8 .,951 ,. 80 1 .. 84 9 .. 941 ,. 87 1 ., 80 1 2 ., 431 ,. 82 1 ..79 1 4 ,. 921 ,. 78 1 ., 77 1 9 ., 891 ,. 67 1 ,. 76 24 .. 8 61 ,.75 1 .,75 1 0 0 ., 1 5

* FeTMPyP , 1 . 0 0 M I m i d a z o l e* 1 M I m i d a z o l e o n l y

No FeTMPyP+ 100 p i

12 . 67 Hz 10 . 33 Hz

3 . 8 3 Hz 5 . 7 5 Hz

73

pH 7 . 41 HEPES , T i t r a n t = 1 . 1 5 9 M I m i d a z o l e

I n i t i a l CFeTMPyP] = 9 . 9 7 0 x 1 0 ~ 3 M

P2 = 2 . 6 2 x 1 0 6 m o l ~ 2 l 2 , 3 5°C


T i t r e Seen Af M a g n e t i c moment [ l i q a n d ]Ml Hz Hz Exp Ca lc [ p o r p h y r i n ]

1 0 11 . 83 7 . 7 2 3 . 1 8 3 . 1 8 02 5 . 0 1 1 . 1 1 6 . 91 3 . 0 3 3 . 0 7 1 . 453 1 0 . 0 9 . 7 8 5 . 4 8 2 . 71 2 . 8 6 2. 914 15 . 0 9 . 2 2 4 . 8 3 2 . 5 6 2 . 61 4 . 3 65 2 0 . 0 8 . 7 2 4 . 2 3 2 . 41 2 . 3 7 5 . 816 2 6 . 0 8 . 1 4 3 . 5 4 2 . 2 2 2 . 1 9 7 . 5 67 3 0 . 0 8 . 1 1 3 . 4 3 2 . 2 0 2 . 1 1 8 . 7 2B 3 5 . 0 8 . 0 3 3 . 2 6 2 . 1 6 2 . 0 5 1 0 . 1 79 4 0 . 0 7 . 8 6 2 . 9 9 2 . 0 8 2 . 0 1 1 1 . 6 2

1 0 5 0 . 0 8 . 0 0 2 . 9 5 2 . 0 9 1 . 97 14 . 5 31 1 6 0 . 0 7 . 9 7 2 . 7 3 2 . 0 3 1 . 95 1 7 . 4 41 2 8 0 . 0 7 . 8 3 2 . 2 1 1 . 8 6 1 . 92 2 3 . 2 51 3 1 0 0 8 . 2 2 2 . 2 2 1. 91 1. 91 2 9 . 0 61 4 * 2 . 7 5 1 . 89 1 . 89 9 5 . 7 1

FeTMPyP , 0.. 959 M I m i d a z o l e 1 3 . 5 6 Hz1 M I m i d a z o l e o n l y 10 . 81 HzNo FeTMPyP 4 . 1 1 Hz+ 1 0 0 p i 6 . 0 0 Hz

- 3I n i t i a l [FeTMPyP] = 9 . 9 9 6 x 10 M

6 —2 2 o(3 = 2 . 8 6 x 10 mol 1 , 35 C 2One s t a n d a r d d e v i a t i o n i n m a g n e t i c moment = 0 . 0 5 3

pH 8 . 3 2 T r i s , T i t r a n t = 0 . 9 9 2 M I m i d a z o l e

T i t r e Sepn Af M a g n e t i c moment [ l i q a n d ]Ml Hz Hz Exp Ca lc [ p o r p h y r i n ]

1 0 12 . 9 2 7 . 81 3 . 1 9 3 . 1 9 02 5 . 0 12 . 92 7 . 7 3 3 . 20 3 . 1 7 1 . 243 15 . 0 12 . 25 6 . 91 3 . 0 6 3 . 01 3 . 7 24 2 0 . 0 11 . 19 5 . 7 7 2. 81 2 . 9 0 4 . 9 65 2 5 . 0 10 . 78 5 . 2 9 2. 71 2 . 7 7 6 . 2 06 3 0 . 0 10 . 58 5 . 01 2 . 6 5 2 . 6 5 7 . 4 47 3 5 . 0 10 . 33 4 . 6 8 2 . 58 2 . 5 3 8 . 6 88 4 1 . 0 9 . 7 2 3 . 9 8 2 . 3 9 2 . 41 10 . 179 4 5 . 0 9 . 7 8 3 . 9 8 2. 41 2 . 3 4 1 1 . 1 6

1 0 5 0 . 0 9 . 5 3 3 . 6 5 2 . 3 2 2 . 27 1 2 . 4 01 1 5 5 . 0 9 . 2 5 3 . 3 0 2 . 2 1 2 . 2 1 13 . 6 41 2 6 5 . 0 9 . 0 6 2 . 9 5 2 . 1 2 2 . 1 3 1 6 . 1 21 3 85 . 0 9 . 0 0 2 . 5 9 2 . 0 3 2 . 03 2 1 . 081 4 1 0 5 . 0 8 . 8 3 2 . 1 1 1. 87 1 . 98 26 . 051 5 * 2 . 5 3 1 . 82 1 . 87 9 9 . 2 7

* FeTMPyP , 0 . 9918 M I m i d a z o l e 14 . 70 Hz* 1 M I m i d a z o l e o n l y 12 . 17 Hz

No FeTMPyP 5. 11 Hz+ 105 p i 6 . 7 2 Hz

7 5

FIGURE 1.8 T itration of FeTMPyP w i t h i m id a z o l e in o.im buffer

ILigandl /[F e P l

IL ig a n d l/ [FePI

[FePl = 0.01 M, 35°C

7 6

-J-g

IBX)IIpO

UjLnon

Magnetic moment

pH 8.32 Trjs

iLigand 1/ [FePl

Magnetic moment- r. I - 'juO O 4 c t - M

FIGURE 1.8 c

on

tin

ue

d

T a b l e 1 . 5 C o r r e c t i o n f o r b u f f e r c o o r d i n a t i o n

B u f f e r

- 2 2P2/mol 1K . . u n c o r r e c t e d c o r r e c t e de f f

PH 6 . 0 MES 2 . 9 6 X 1 o" 1 0 2 . 3 4 X 105 2 . 57 X , o 6

pH 7 . 0 PIPES 3 . 8 4 X 1 0 “ 1 1 7 . 08 X 104 2 . 1 5 X 10s

pH 7. 41 HEPES 1 .35 X 1 o “ 1 2 1 .. 6 1 X 104 2 . 62 X 10G

PH 8 . 3 2 Tr i s 1 . 97 X 1 0 ~ 1 4 2 ., 1 3 X 103 2 . 8 6 X 10s

Both s e t s o f v a l u e s o f a r e c o r r e c t e d f o r

p r o t o n a t i o n o f the i m i d a z o l e . The r i g h t hand column has

been c o r r e c t e d f o r b u f f e r c o o r d i n a t i o n a l s o . B e f o r e

c o r r e c t i o n t h e v a l u e s d e c r e a s e w i t h i n c r e a s i n g b u f f e r pK^ .

Th i s s ug ges t s t h a t t h e h i g h e r t h e b u f f e r pK, t h e moreA

s t r o n g l y i t i s c o o r d i n a t e d . I t i s seen t h a t a f t e r

c o r r e c t i o n , much more c o n s i s t e n t r e s u l t s a r e o b t a i n e d .

Th i s i l l u s t r a t e s t h e v a l i d i t y o f t h e c o r r e c t i o n . B u f f e r

c o o r d i n a t i o n can not be e l i m i n a t e d by u s i ng b i o l o g i c a l

b u f f e r s . I t was t h e r e f o r e d e c i d e d t h a t f o r f u r t h e r s t u d i e s

w i t h o t h e r l i g a n d s a p h o s ph a t e b u f f e r would be used and i t s

c o o r d i n a t i o n c o r r e c t e d f o r . Fe * * * TMPyP i n 0 . 1 2 5 M

phospha t e has a h i g h e r i n i t i a l m a g n e t i c moment t han t hose

obser ved above due t o s t r o n g e r c o o r d i n a t i o n . T h i s makes

m a g n e t i c moment changes l a r g e r and hence more a c c u r a t e l y

d e t e r m i n e d .

78

1 . 2 . 4 . C o m p l e x e s w i t h i m i d a z o l e s

1 . 2 . 4 . 1 . I n t r o d u c t i o n

H i s t i d i n e i s i m p o r t a n t n a t u r a l l y s i n c e i t i s

c o o r d i n a t e d t o one o f t h e a x i a l p o s i t i o n s o f F e I I P r o t i n

m y og l ob i n and hemog lob i n . The e q u i l i b r i u m c o n s t a n t s f o r

t h e c o o r d i n a t i o n o f i m i d a z o l e and some s u b s t i t u t e d

i m i d a z o l e s to Fe * * * TMPyP have been d e t e r m i n e d by m a g n e t i c

t i t r a t i o n .

The graphs i n F i g u r e 1 . 9 show t h e r e s u l t s o f f i v e

such t i t r a t i o n s . For t h e h i s t i d i n e t i t r a t i o n and l a t e r f o r

t h e DMAP t i t r a t i o n , t h e f i n a l c o n c e n t r a t i o n o f l i g a n d was

r e q u i r e d t o be c o m p a r a t i v e l y h i gh . These t i t r a t i o n s were

thus done i n two s t a g e s . Two p a r a m a g n e t i c s o l u t i o n s were

made w i t h e q u a l c o n c e n t r a t i o n s o f FeTMPyP and b u f f e r . One

s o l u t i o n c o n t a i n e d t h e maximum c o n c e n t r a t i o n o f l i g a n d

r e q u i r e d . 400 p i o f one p a r a m a g n e t i c s o l u t i o n was i n j e c t e d

i n t o an NMR t u b e and t i t r a t e d s t e p w i s e w i t h 400 p i o f t he

o t h e r p a r a m a g n e t i c s o l u t i o n . The t i t r a t i o n was then

r e p e a t e d w i t h t h e p a r a m a g n e t i c s o l u t i o n s r e v e r s e d , so as

to c ov er a n o t h e r r ange o f l i g a n d c o n c e n t r a t i o n s .

T a b l e 1 . 6 |32 v a l u e s f o r c o o r d i n a t i o n o f i m i d a z o l e s

L i gand l i g a n d pK^ P2 / 1 0 6 m ' 2 1 o9 1 0 P 2

1 - H i s t i d i n e 6 . 0 4 0 . 6 0 0 5 . 7 8

I m i d a z o l e 6 . 9 5 2 . 6 5 6 . 4 2

1 m e t h y l i m i d a z o l e 7 . 3 3 5 . 1 2 6 . 71

4 m e t h y l i m i d a z o l e 7 . 5 2 7 . 8 8 6 . 9 0

2 m e t h y l i m i d a z o l e 7 . 8 6 v* 0 . 4 4 ^ 5 . 6 5

7 9

1 . 2 . 4 . 2 . R e s u l t s

T i t r a n t = 0 . 2 5 M 1 - H i s t i d i n e

I n i t i a l [FeTMPyP] = 1 . 0 1 6 x 1 0 “ 2 M

P2 = 6 . 0 0 x 1 0 5 m o l ~ 2 l 2 , 3 5° C


T i t r e Sepn Af M a g n e t i c moment [ l i a a n d ]Hi Hz Hz Exp Ca lc [ p o r p h y r i n ]

1 0 10 . 33 1 3 . 8 4 4 . 2 2 4 . 22 02 15 . 0 18 . 17 1 3 . 6 5 4 . 1 9 4 . 1 7 0 . 893 3 5 . 0 1 7 . 2 8 12 . 73 4 . 0 5 4 . 01 1 . 974 5 5 . 0 15 . 67 1 1 . 0 9 3 . 7 8 3 . 82 2 . 9 75 7 5 . 0 14 . 67 1 0 . 0 7 3 . 6 0 3 . 6 3 3 . 8 86 1 0 0 . 13 . 5 6 8 . 9 3 3 . 3 9 3 . 3 9 4 . 9 27 125. 1 2 . 4 2 7 . 7 6 3 . 1 6 3 . 1 9 5 . 8 68 155 . 1 1 . 7 2 7 . 0 4 3 . 01 2 . 9 9 6 . 8 79 165 . 11 . 53 6 . 8 4 2 . 9 7 2 . 9 4 7 . 1 9

1 0 2 15. 1 0 . 5 0 5 . 7 7 2 . 7 2 2 . 74 8 . 6 01 1 400 . 9 . 6 4 4 . 7 8 2 . 4 8 2 . 4 6 1 2 . 3 01 2 370 . 9 . 8 3 4 . 9 9 2 . 5 3 2 . 4 4 12 . 791 3 3 15. 9 . 4 2 4 . 5 5 2 . 4 2 2 . 4 0 13 . 771 4 265 . 9 . 3 3 4 . 4 3 2 . 3 9 2 . 3 7 1 4 . 8 01 5 170. 9 . 3 9 4 . 4 2 2 . 3 8 2 . 3 2 1 7 . 2 61 6 1 0 0 . 9 . 3 3 4 . 3 0 2 . 3 5 2 . 2 8 1 9 . 6 91 7 4 5 . 0 9 . 11 4 . 01 2 . 2 7 2 . 26 2 2 . 1 21 8 0 8 . 6 9 3 . 5 4 2 . 1 3 2 . 2 4 24 . 61

No FeTMPyPT i t r a n t = 0 . 2 5 M 1 - H i s t i d i n e

T i t r e / p i 0 1 0 0 2 0 0 300 400 400 2 0 0 0[ H i s t i d i n e ] / M 0 0 . 0 5 0 0 . 8 3 0 . 1 0 7 0 . 1 2 5 0 . 1 2 5 0 . 1 6 7 0 . 2 5 0Sepn/Hz 4 . 33 CD 4 . 6 1 4 . 9 2 4 . 94 CMcn 4 . 9 4 5 . 0 6

A graph o f b l a n k s e p a r a t i o n v e r s u s [ h i s t i d i n e ] was used t o c o r r e c t t h e s e p a r a t i o n t o g i v e Af

80

T i t r a n t = 1 . 0 0 M I m i d a z o l e

I n i t i a l [FeTMPyP] = 1 . 0 0 7 x 1 0 ~ 2 M

(3 = 2 . 6 5 x 1 0 6 m o l “ 2 l 2 , 35°C


T i t r e SeDn AfMl Hz Hz

1 0 1 9 . 55 1 4 ,.362 5 . 0 1 8 . 06 1 2 ,.783 1 0 . 0 1 6 . 39 1 1 ,. 0 14 1 5 . 0 1 3 . 8 6 8 ,.395 2 0 . 0 1 2 . 33 6 ..776 25 . 0 1 1 . 04 5 .,387 30 . 0 1 0 . 33 4 ,.588 35 . 0 9 . 85 4 ., 0 19 40 . 0 9 . 65 3 ,. 7 1

1 0 50 . 0 9 . 26 3 .. 1 41 1 60 . 0 9 . 1 9 2 .. 8 81 2 80 . 0 8 . 99 2 ..301 3 1 0 0 . 0 9 . 28 2 .. 2 2

No FeTMPyP 5 . 1 9 Hz+ 1 0 0 p i 7 . 06 Hz

M a g n e t i c moment C l i q a n d ]Exp Ca lc [ p o r p h y r i n ]

4 . 3 2 4 . 32 04 . 1 0 4 . 1 5 1 . 243 . 83 3 . 82 2 . 4 83 . 3 6 3 . 4 2 3 . 7 23 . 0 4 3 . 0 3 4 . 972 . 7 2 2 . 7 2 6 . 2 12 . 5 3 2 . 4 9 7 . 4 52 . 3 8 2 . 3 4 8 . 692 . 3 0 2 . 24 9 . 9 32 . 1 4 2 . 1 1 12. 412 . 0 7 2 . 0 4 1 4 . 9 01 . 89 1 . 98 1 9 . 8 61 . 90 1 . 95 2 4 . 8 3

T i t r a n t = 1 . 0 1 3 M 1 - M e t h y l i m i d a z o l e- 2

I n i t i a l [FeTMPyP] = 1 . 001 x 10 M

= 5 . 1 2 x 10 6 mol 2 l 2 , 35°C


T i t r e Seen AfMl Hz Hz

1 0 1 8 . 94 1 5 ,. 0 02 5 . 0 1 7 . 1 1 1 3 ..083 1 0 . 0 1 5 . 33 1 1 ,. 2 24 1 5 . 0 1 3 . 06 8 ,. 8 65 2 0 . 0 1 1 . 53 7 ,. 246 25 . 0 1 0 . 1 1 5 ,.737 30 . 0 9 . 3 1 4 ,. 858 35 . 0 9 . 08 4 ,. 539 40 . 0 8 . 6 1 3 .. 97

1 0 45 . 0 8 . 36 3 .. 631 1

oin 0 8 . 28 3 ,. 471 2 60 . 0 8 . 1 7 3 ,. 1 81 3 80 . 0 8 . 1 4 2 . 801 4 1 0 0 . 0 8 . 2 2 2 ,. 53

No FeTMPyP 3 . 94 Hz+ 1 0 0 p i 5 . 69 Hz

M a g n e t i c moment [ l i q a nd]Exp Ca lc [ p o r p h y r i n ]

4 . 4 2 4 . 4 2 04 . 1 6 4 . 26 1 . 263 . 87 3 . 9 3 2 . 533 . 4 6 3 . 5 4 3 . 7 93 . 1 5 3 . 1 5 5 . 062 . 8 2 2 . 8 2 6 . 3 22 . 61 2 . 5 9 7 . 592 . 54 2 . 4 2 8 . 852 . 3 9 2 . 3 0 1 0 . 1 22 . 3 0 2 . 2 2 11 . 3 82 . 2 6 2 . 1 6 1 2 . 6 52 . 1 8 2 . 0 8 15 . 1 82 . 09 2 . 0 0 20 . 242 . 0 3 1 . 96 2 5 . 3 0

82

T i t r a n t = 1 . 0 4 6 M 4 - M e t h y l i m i d a z o l e

I n i t i a l [FeTMPyP] = 1 . 0 0 4 x 1 0 ~ 2 M

(32 = 7 . 8 8 x 1 0 6 m o l “ 2 l 2 , 35°C


T i t r e Seen Af M a g n e t i c moment C l i o a nd ]Ml H z Hz Exp Ca lc [ p o r p h y r i n ]

1 0 1 8 ,. 6 1 1 3 ,. 89 4 ,. 25 4 ,. 25 02 5 . 0 1 7 ,. 69 1 2 ., 89 4 ., 1 2 4 ,. 1 0 1 . 303 1 0 . 0 1 6 ,. 1 4 1 1 ., 26 3 .. 8 8 3 ,. 80 2 . 604 1 5 . 0 1 3 ,. 53 8 ., 56 3 ., 40 3 ,. 43 3 . 9 15 2 0 . 0 1 2 ,. 03 6 .. 98 3 .. 09 3 .. 06 5 . 2 16 25 . 0 1 0 ., 44 5 . 3 1 2 ., 7 1 2 .,76 6 . 5 17 30 . 0 9 .. 8 1 4 .. 60 2 ,. 54 2 ,. 53 7 . 8 18 35 . 0 9 ,, 06 3 . 77 2 ., 3 1 2 ..38 9 . 1 29 40 . 0 8 .. 94 3 ., 56 2 .. 26 2 ,. 27 1 0 . 42

1 0 50 . 0 8 ., 64 3 . 1 0 2 ., 1 3 2 ., 1 3 1 3 . 0 21 1 60 . 0 8 ..78 3 ., 08 2 .. 1 5 2 .. 06 1 5 . 631 2 80 . 0 8 ., 44 2 . 4 1 1 .,94 1 .,99 2 0 . 841 3 1 0 0 . 0 8 .. 64 2 . 28 1 .,93 1 ..95 26 . 05

No FeTMPyP 4 ., 72 Hz+ 1 0 0 Ml 6 ..36 Hz

83

T i t r a n t = 3 . 0 0 8 M 2 - M e t h y l i m i d a z o l e

I n i t i a l [FeTMPyP] = 1 . 0 0 6 x 1 0 ~ 2 Mc -• O O r\

4 . 4 x 10 mol 1 , 35 C


T i t r e Seen Af M a g n e t i c moment [ l i g a n d ]Ml Hz H z Exp Ca lc [ p o r p h y r i n ]

1 0 18 . 94 1 4 . 8 0 4 . 38 4 . 3 8 02 5 . 0 17 . 39 13 . 0 8 4 . 1 5 4 . 3 5 3 . 7 43 1 0 . 0 1 6 . 0 8 11. 61 3 . 9 3 4 . 26 7 . 4 84 15 . 0 15 . 0 8 1 0 . 4 4 3 . 7 5 4 . 1 2 1 1 . 2 15 2 0 . 0 1 4 . 7 8 9 . 97 3 . 69 3 . 9 4 1 4 . 9 56 2 5 . 0 13 . 86 8 . 89 3 . 50 3 . 7 5 1 8 . 6 97 3 0 . 0 1 3 . 5 8 8 . 44 3 . 43 3 . 5 6 2 2 . 4 38 3 5 . 0 1 3 . 2 5 7 . 9 4 3 . 3 5 3 . 3 8 2 6 . 1 69 4 0 . 0 1 3 . 1 9 7 . 72 3 . 3 2 3 . 2 2 2 9 . 9 0

1 0 4 5 . 0 12. 81 7 . 1 7 3 . 2 2 3 . 0 7 3 3 . 6 41 1 5 0 . 0 12 . 64 6 . 8 4 3 . 1 6 2 . 9 4 3 7 . 3 81 2 6 0 . 0 1 2 . 3 9 6 . 2 5 3 . 0 6 2 . 7 3 4 4 . 8 51 3 8 0 . 0 12 . 3 9 5 . 59 2 . 9 5 2 . 4 7 5 9 . 8 01 4 1 0 0 . 0 11 . 8 9 4 . 4 2 2 . 6 8 2. 31 7 4 . 7 5

No FeTMPyP 4 . 1 4 Hz+ 1 0 0 Ml 7 . 47 Hz a

84

FIGURE 1. 9 T i t r a t i o n of FeTMPyP w i t h i m i d a z o l e s

iLigandl / lFePl

I l ig and ) / l FeP)pH 7.20 (0.125 M phosphate), 35°C

85

FIGURE 1.9 CONTINUED

t L i g a n d ] / 1 FePl

pH 7.20 (0.125M phosphate), 35°C

7.0

pKA Ligand

1 . 2 . 4 . 3 . D i s c u s s i o n o f r e s u l t s

For t h e f i r s t f o u r i m i d a z o l e s t h e r e i s an i n c r e a s e i n

(3 w i t h an i n c r e a s e i n t h e l i g a n d pK . The l a s t graph i n2 AF i g u r e 1 .9 shows the l i n e a r r e l a t i o n s h i p between l o g p 2 and

t he l i g a n d pKt . T h i s r e l a t i o n s h i p has a l s o beenA

obser ved ( 52 ) f o r t he r e a c t i o n o f s u b s t i t u t e d p y r i d i n e s

w i t h m e t a l l o p o r p h y r i n s . The l i g a n d pl<A v a l u e s a r e t aken

f rom s e v e r a l sources ( 5 3 a , 5 4 , 5 5 ) .

6The v a l u e o f 2 . 6 5 x 10 d e t e r m i n e d her e f o r i m i d a z o l eg

compares w e l l w i t h t h e a v e r a g e o f 2 . 5 5 x 10 f o r the

p r e v i o u s d e t e r m i n a t i o n s i n b i o l o g i c a l b u f f e r s .

For F eT P P( C l ) i n c h l o r o f o r m , James ( 34 ) has

d i s c u s s e d t h e a no m a l o u s l y h i g h r a t i o (^ 1 0 0 0 ) o f t h e |3

v a l u e s f o r i m i d a z o l e compared t o 1 m e t h y l i m i d a z o l e . Th i s

was r e l a t e d t o t h e a b i l i t y o f c o o r d i n a t e d i m i d a z o l e t o

promote d i s s o c i a t i o n o f t h e c o o r d i n a t e d c h l o r i d e . In t h i s

work , t h e c o r r e s p o n d i n g r a t i o (^ 2) i s much s m a l l e r . Th i s

i s because no c h l o r i d e or t o s y l a t e i o n was c o o r d i n a t e d t o

FeTMPyP .

The v a l u e o f |3 f o r t h e 2 m e t h y l i m i d a z o l e complex i s

l o w e r t han e x p e c t e d f rom t h e l i g a n d pK^ . The a m e t h y l

group o f 2 m e t h y l i m i d a z o l e w i l l impose s t e r i c h i n d r a n c e t o

c o o r d i n a t i o n t o Fe* * * TMPyP , t hus weaken ing t h e bond . The

4 m e t h y l i m i d a z o l e l i g a n d a l s o has an a m e t h y l group .

However i n w a t e r t h e p o s i t i o n o f t h e N-H bond i s known ( 56)

t o i s o m e r i s e t o g i v e 5 m e t h y l i m i d a z o l e w i t h a f3 m e t h y l

group .

07

N<# S'''N-H + H * *" ■■■■ ^ N - H ^ Z ^ H - N ' "'N + H

w w w

4 m e t h y l I m i d a z o l e 5 m e t h y l i m i d a z o l e

The c u r ve s produced by t h e computer

program ( F i g u r e 1 . 9 ) , f o r t h e model employed , do no t

f o l l o w t h e g e n e r a l shape o f t h e d a t a p o i n t s on t he 2 - m e t h y l

i m i d a z o l e g raph . I t i s known ( 57 ) t h a t f o r t h e s e

s t e r i c a l l y h i n d e r e d l i g a n d s and a r e o f s i m i l a r s i z e ,

d e s p i t e t he n e c e s s i t y o f two l i g a n d s to g i v e a low s p i n

complex . However when t h i s was t a k e n i n t o acc o un t , t h e

computer g e n e r a t e d c u r v e s were f u r t h e r f rom t he shape

o u t l i n e d by t h e d a t a p o i n t s .

The f i n a l c o n c e n t r a t i o n o f l i g a n d r e p r e s e n t s a

s i g n i f i c a n t change i n s o l v e n t c o m p o s i t i o n . T h i s may be t h e

cause o f t h e s e d e v i a t i o n s . B u i l d i n g t h i s i n t o t h e model

would be q u i t e d i f f i c u l t .

I t i s p o s s i b l e t o o p t i m i s e t h e f i t o f t he computer

c a l c u l a t e d r e s u l t s t o t h e e x p e r i m e n t a l d a t a , by v a r y i n g

both and t h e m a g n e t i c moment o f t h e f i n a l complex .

However v a r y i n g two p a r a m e t e r s l e a d s t o u n r e a l i s t i c

r e s u l t s .

An i n d i c a t i o n o f t h e m a g n e t i c moment o f t h e f i n a l

complex i s g i v e n by t h e l i m i t i n g m a g n e t i c moment w i t h

i n c r e a s i n g t i t r e . I m i d a z o l e or i t s 1 m e t h y l or 4 m e t h y l

d e r i v a t i v e s gave complexes w i t h v e r y s i m i l a r m a g n e t i c

moments . So an a v e r a g e o f 1 . 8 8 was used . S i n c e t h e

8 8

m a g n e t i c moments o f t h e 2 m e t h y l i m i d a z o l e , SCN or DMAP

complexes a r e unknown , a v a l u e o f 1 . 08 was a l s o used .

The h i s t i d i n e complex o b v i o u s l y has a m a g n e t i c moment

h i g h e r t han 1 . 0 0 . The v a l u e o f 2 . 1 8 * 0 . 0 4 ( 34 ° C) r e p o r t e d

by Ox l ey and Toppen ( 58 ) was used .

1 . 2 . 4 . 4 . Compar isons w i t h o t h e r s t u d i e s

Ox l ey and Toppen ( 58 ) c a r r i e d ou t s p e c t r o p h o t o m e t r i c

t i t r a t i o n s o f Fe* * * TMPyP w i t h h i s t i d i n e , under t h e

f o l l o w i n g c o n d i t i o n s :

0 . 0 1 0 M p ho spha t e pH 6 . 9 7 - pH 7 . 5 6

I = 0 . 1 0 M ( N a C l ) , 2 5 °C

[FeTMPyP] = 1 . 68 - 2 . 11 X 10 ~ 5 M

The a u t h o r s c o r r e c t l y presume t h a t t h e FeTMPyP i s

p r e d o m i n a n t l y monomer ic under t h e s e c o n d i t i o n s . The

e v a l u a t i o n showed t h a t two h i s t i d i n e m o l e c u l e s c o o r d i n a t e

and t h a t >> . T h e i r e v a l u a t i o n o f an e q u i l i b r i u m

c o n s t a n t d i d no t i n c l u d e any c o r r e c t i o n f o r b u f f e r

3 - 2 2c o o r d i n a t i o n or pH . The v a l u e o f 4 . 0 x 10 mol 1 must be

c o r r e c t e d b e f o r e i t can be compared t o t h e r e s u l t o b t a i n e d

h e r e . I t i s d i f f i c u l t t o e s t i m a t e t h e e f f e c t o f t h e b u f f e r

f rom t h e s e r e s u l t s , however t o a good a p p r o x i m a t i o n

0 . 0 1 0 M pho spha t e w i l l no t a f f e c t t h e r e s u l t a p p r e c i a b l y .

So i f b u f f e r c o o r d i n a t i o n i s i g n o r e d t hen e q u a t i o n { 1 }

( a p p e n d i x 1 . 8 ) can be used .

CH + ] * k a i ~

£ H + J

89

A v a l u e ofpl <A 1 a t I = 0 . 1 M i s not a v a i l a b l e , so a s

a rough e s t i m a te 5 . 2 wa s t a k e n , be i ng t h e av e ra ge o f two

v a l u e s ( I = 0 . 0 , 0 . 2 5 M) d e t e r m i n e d her e . Ta k in g t h e two

l i m i t i n g v a l u e s o f pH , t h e r e s u l t s f o r (32 3 r e :

2 . 4 5 - 2 2 x 1 0 mol L c ( pH 6 . 9 7 )

9 . 2 , „ 5 - 2 . 2 x 1 0 mol 1 ( pH 7 . 5 6 )

The v a l u e o f 6 . 0 0 x 1 0 3 mol - 2 i 2 d e t e r m i n e d h e r e by

m a g n e t i c t i t r a t i o n i s i n t h i s range •

F a r a g g l e t a l ( 59 ) used s p e c t r o p h o t o m e t r y t o

d e t e r m i n e t h e e q u i l i b r u i m c o n s t a n t s f o r i m i d a z o l e and

h i s t i d i n e c o o r d i n a t i o n . T h e c o n d i t i o n s were :

2 x 10 3 M p ho spha t e or c a r b o n a t e , 25°C , I = 0 . 11

The i n i t i a l s pe c t r u m o f t h e i r t i t r a t i o n (pH 5 . 6 1 )

does not match t h a t o b t a i n e d h e r e under s i m i l a r

c o n d i t i o n s , i n t h e absence o f a b u f f e r . T h i s i s

p r esu ma bl y due t o c o o r d i n a t i o n o f b u f f e r t o t h e FeTMPyP .

In each t i t r a t i o n i s o b e s t i c p o i n t s were o bs er ved

t h r o u g h o u t . I t was c o n c l u d ed t h a t >> K.j . The

f o l l o w i n g r e s u l t s were o b t a i n e d

E q u i l i b r i u m c o n s t a n t pH s l o pe

I m i d a z o l eK = 3 . 2 x 1 0 - 8 5 . 6 1 . 99K ~ = 2 x5 1 0 8 .3 3 . 9 8

H i s t i d i n eK = 2 - 5 X 10- 9 6 . 0 —

K = 1 . 5 x5 1 0 8 . 0

90

i s e q u i v a l e n t t o p^ • Us ing t h e same p r o c e d u r e as

f o r t he p r e v i o u s c o r r e c t i o n , v a l u e s o f p can Ue

o b t a i n e d . Aga in an e x a c t v a l u e i s not a v a i l a b l e f o r

t he c o n d i t i o n s o f t h e i r t i t r a t i o n , so t h e e s t i m a t e o f 5 . 2

6 5i s used . T h i s l e a d s t o v a l u e s o f 1.1 x 10 and 1 . 8 x 10

f o r i m i d a z o l e and h i s t i d i n e r e s p e c t i v e l y . C o n s i d e r i n g the

a p p r o x i m a t i o n s made i n t h e c o r r e c t i o n t h e agr ee ment w i t h

t h e v a l u e s o b t a i n e d i n t h i s work i s c l o s e . F a r a g g l e t a l

i m p l y t h e f o l l o w i n g d e f i n i t i o n f o r

C P F e ( L ) ] COH" ] 2

= ---------------------------- I[ P F e - O - F e P ] C L ]

From t h e d e f i n i t i o n s o f p and K_ i t can be shownZ 5t h a t

Q0 = ^ 2 ' KW * K5

Using t h e s e v a l u e s o f p_ and K_ t h e f o l l o w i n g v a l u e sZ b

were c a l c u l a t e d f o r •-9

I m i d a z o l e d a t a Qp = 6 . 5 x 10

. . -9H i s t i d i n e d a t a Q = 2 . 3 x 10

The i n c o n s i s t e n c y between t h e above two v a l u e s f o r Qp

i s p r es u ma b ly because F a r a g g l e t a l have o v e r l o o k e d t h e pH

dependence o f p^ . These a r e l o w e r t h an t he

— 83 . 5 6 x 10 ( I = 0 . 3 0 M) d e t e r m i n e d i n t h i s work . T h i s i s

c o n s i s t e n t w i t h t h e l o w e r i o n i c s t r e n g t h used by

F a r a g g l e t a l .

P a s t e r n a c k and S p i r o ( 60 ) qu o te a v a l u e o f

= 2 . 5 x 107mol 2 l 2 f o r FeTMPyP and i m i d a z o l e , a t pH 4 . 5

and 2 5 °C . T h i s i s h i g h e r t h a n t h e v a l u e d e t e r m i n e d i n t h i s

work , p o s s i b l y due t o a d i f f e r e n c e i n i o n i c s t r e n g t h .

Summary o f e v a l u a t i o n s

FeTMPyP complex condit ions 5 -2 2 0 2 / 1 0 mol 1 Ref

PFe( h i s t ) 2 25°C . 1 = 0 . 1 M 2.4 - 9.2 58

PFe(hist ) 2 25°C , I = 0 . 1 1 M 1 . 8 59

PFe(h i s t ) 2 35°C , I = 0.30 M 6 . 0 This work

PFe( Im) 2 25°C , I = 0 . 1 1 M 1 1 59

PFe( Im) 2 25°C 250 60

PFe( Im)_ 35°C , I = 0.30 M 26.5 This work2

F l e i s c h e r e t a l ( 6 1 ) have s p e c t r o p h o t o m e t r i c a l l y

6 5d e t e r m i n e d |3 v a l u e s o f 1 . 7 x 10 and 1 . 8 x 10 (pH 6 ) ,

f o r t he r e a c t i o n o f monomer ic FeTPPS. w i t h i m i d a z o l e andA*h i s t i d i n e , r e s p e c t i v e l y . These v a l u e s a r e o f t h e same

o r d e r o f m a g n i t u d e as t h o s e d e t e r m i n e d i n t h i s work f o r

FeTMPyP . However t h e r a t i o s o f i m i d a z o l e / h i s t i d i n e

v a l u e s a r e d i f f e r e n t .

F l e i s c h e r e t a l ( 6 1 ) have d e t e r m i n e d an e q u i l i b r i u m

c o n s t a n t f o r t h e r e a c t i o n o f p oxo d i m e r i c FeTPPS^ w i t h

i m i d a z o l e or h i s t i d i n e .

CPFe( L) ] 2 C0h " ] 2

K2 = ---------------- 4[ P F e - O - F e P ] . CL]

92

T h o m p s o n and K r i s h n a m u r t h y (62) h a v e s i m i l a r l y

d e t e r m i n e d a r e l a t e d e q u i l i b r i u m c o n s t a n t K , for r e a c t i o n

of p oxo d i m e r i c F e T P P S ^ or F e T A P P w i t h i m i d a z o l e .

C P F e (L ) ] 2K a --------------------— —

[ P F e - O - F e P ] . CL] CH ]2By i n s p e c t i o n K = K.K

Cm W

A l s o f r o m the d e f i n i t i o n s of (3 ,

for K^ (as d e f i n e d by F l e i s c h e r )2 2 0 . K /Q p 2 W D

Q and K,, it is s e e n t h a t D W

I m i d a z o l e

p oxo d i me r K2 C o n d i t i o n s R e f e r e n c e

FeTPPS,A 2 . 8 X 1 o" 7 pH 9 . 5 - 9 . 8 61

FeTPPS, A 1 X 1 0 ~ 7 pH 9 . 1 , I = 0 . 1 M 62

FeTMPyP 5 . 3 X 1 o” 9 pH 7 . 2 , I = 0 . 3 0 M T hi s work

FeTAPP 3 . 6 X 1 o“ 1 3 pH 9 . 1 . I = 0 .1 M 62

H i s t i d i n e

|j oxo d i m e r K 2 C o n d i t i o n s R e f e r e n c e

F e T M P y P 2.7 x 1 o"1 0 pH 7.2 . I = 0 .30 M T his w o r k

FeTPPS, 4.6 4 x 1 0"1 0 pH 9.5 - 9 . 8 6 1

The Kg v a l u e s f o r h i s t i d i n e c o m p l e x e s are of s i m i l a r

m a g n i t u d e . T his is c o n s i s t e n t s i n c e the |3g v a l u e s for the

h i s t i d i n e c o m p l e x e s w e r e s i m i l a r The K 2 v a l u e s for

F e T P P S and i m i d a z o l e are l a r g e r t h a n t h e v a l u e s for

F e T M P y P and i m i d a z o l e . T h i s is not e x p e c t e d s i n c e the

93

c o r r e s p o n d i n g v a l u e s w e r e s i m i l a r . The v a l u e for F e T A P P

is c o n s i d e r a b l y l o w e r t h a n the o t h e r v a l u e s .

T h o m p s o n and K r i s h n a m u r t h y (62) p r o p o s e a m e c h a n i s m

for the b r e a k up of the d i m e r i n v o l v i n g an i n t e r m e d i a t e

g o x o / p i m i d a z o l e b r i d g e d d i m e r .

c o o r d i n a t i o n of i m i d a z o l e to F e T C P P . The pH d e p e n d e n c e of

this c o o r d i n a t i o n w a s f o l l o w e d by ESR s p e c t r o s c o p y and the

f o l l o w i n g e q u i l i b r i u m w a s p r o p o s e d

log K; = 7 . 0 5 ± 0.272

H o w e v e r this pH d e p e n d e n c e can a l s o be e x p l a i n e d by

the p r o t o n a t i o n of i m i d a z o l e w h i c h has a pK of 6.95 .

A t i t r a t i o n of F e T C P P w i t h i m i d a z o l e at pH 8.4 (44)

w a s f o l l o w e d s p e c t r o p h o t o m e t r i c a l l y and f r o m the r e s u l t s

the f o l l o w i n g e q u l i b r i u m w a s p r o p o s e d

V * 3 VP F e - O - F e P + 2 Im ^ I m - P F e - 0 - F e P - Im

A p l o t of 2 l o g [ I m ] v e r s u s l o g { [ P r o d u c t ] / [ R e a c t a n t ] }

had a s l o p e of 0 . 9 6 and an i n t e r c e p t of 1.22 ,

-3c o r r e s p o n d i n g to - l o g . H o w e v e r 10 M w a s u sed i n s t e a d

of M for [Im] so 6 m u s t be s u b t r a c t e d to g i v e

- log K 3 = 4 . 2 2 - 6

ie log K = 4.783

A f u r t h e r c h e c k on t h i s c o r r e c t i o n can be m a d e . It

is r e p o r t e d t h a t for [P r o d u c t ] / [ R e a c t a n t ] = 1 . 0 ,

H a r t z e l l et al (44) h a v e i n v e s t i g a t e d the

rI m - P F e - O - F e P - I m +

94

[ I m ] / [ F e ] = 43.3 . A l s o [Fe] = 5 - 12 x 1 0 “ 5 M . So u s i n g

[ Fe] = 10 x 1 0 " 5 M

l 1 (43.4 x 10 x 1 0 “ 5 ) 2 >53 x 10

So log K 4.73

T h i s a g r e e s w i t h the p r e v i o u s c o r r e c t i o n

N o n a d h e r e n c e to the C o w g i l l - C l a r k d i l u t i o n

t e s t (5) , r u l e s out the r e a c t i o n

d i m e r + n . l i g a n d ^ 2 . m o n o m e r i c c o m p l e x

It d o e s not d i s t i n g u i s h b e t w e e n the f o l l o w i n g e q u i l i b r i a

d i m e r + n . l i g a n d ^ ~ d i m e r i c c o m p l e x

m o n o m e r + n . l i g a n d .^ m o n o m e r i c c o m p l e x

An e q u i v a l e n t i n t e r p r e t a t i o n is thus

+ K / [ H + 3P R e ( O H ) (OH) + 2 Im + H J i______ P F e ( I m ) 0 + H „ 0Z ^ z z

So P 2 = K 3 / ( K 2 . C H + ]) = 2.9 x 1 0 6 m o l ” 2 l 2

NB: log l<2 = p K ^i = 6 . 7 2 ( s e c t i o n 1.1 . 3 . )

T his v a l u e of (3 c o m p a r e s c l o s e l y to the v a l u e

o b t a i n e d h e r e for F e T M P y P and i m i d a z o l e .

T h e a u t h o r s p r o p o s e t h a t d e p r o t o n a t i o n of c o o r d i n a t e d

i m i d a z o l e a n d / o r a c h a n g e in b r i d g i n g l i g a n d c a u s e s the

l o w e r a f f i n i t y for i m i d a z o l e w i t h i n c r e a s i n g pH . T h i s can

a l s o be e x p l a i n e d by t h e displacement of the e q u i l i b r i u m

b e l o w to the r i g h t w i t h i n c r e a s i n g pH .

P Fe (OH ^ P F e ( 0 H 2 )(0H) + H +

95

Two f u r t h e r m a g n e t i c t i t r a t i o n s o f FeTMPyP wer e

c a r r i e d out w i t h DMAP and KSCN . A s i m i l a r d e v i a t i o n o f

e x p e r i m e n t a l and c a l c u l a t e d m a g n e t i c moments i s seen f o r

DMAP as compared to 2 - m e t h y l i m i d a z o l e . A v a l u e o f

10 - 2^ 4 x 1 0 M was d e t e r m i n e d f o r . For t h i s l i g a n d

t h e r e should be no s t e r i c h i n d r a n c e to c o o r d i n a t i o n . Aga in

i t i s p r e su ma b ly t h e h i g h c o n c e n t r a t i o n o f l i g a n d t h a t i s

c a u s i n g t h e d e v i a t i o n s .

1 . 2 . 5 . C o m p l e x e s w i t h DMAP a n d SCN

R e s u l t s

T i t r a n t = 0 . 5 0 3 M DMAPI n i t i a l [ FeTMPyP] = 9 . 9 4 2 x 10~ M

0 2 ~ 4 x 1 0 1 0 m o l " 2 l 2 , 3 5 °COne s t a n d a r d d e v i a t i o n i n m a g n e t i c moment = 0 . 1 9 6

T i t r e Sepn Af M a g n e t i c moment C l i q a n d ]Ml Hz Hz Exp C a l c [ p o r p h y r i n ]

1 0 1 7 . 0 8 1 2 . 6 9 4 . 0 8 4 . 0 8 02 1 0 . 0 1 6 . 1 5 1 1 . 6 9 3 . 9 2 4 . 0 6 1 . 2 43 15 . 0 1 6 . 4 4 1 1 . 8 8 3 . 9 5 4 . 0 3 1 . 834 2 5 . 0 15 . 3 7 10 . 71 3 . 75 3 . 9 5 2 . 9 85 4 5 . 0 1 4 . 0 2 9 . 1 2 3 . 4 6 3 . 7 4 5 . 1 26 6 5 . 0 13 . 91 8 . 79 3 . 4 0 3 . 5 0 7 . 0 87 9 0 . 0 1 2 . 4 6 7 . 0 9 3 . 0 5 3 . 2 2 9 . 3 08 125 . 1 2 . 6 4 7 . 0 2 3 . 0 4 2 . 9 0 1 2 . 0 69 170. 1 1 . 5 9 5 . 6 9 2 . 7 3 2 . 6 3 1 5 . 1 0

1 0 265 . 1 1 . 7 2 5 . 4 3 2 . 67 2 . 3 4 2 0 . 1 81 1 400 . 1 1 . 0 9 4 . 47 2 . 4 2 2 . 1 9 2 5 . 3 21 2 290 . 11 . 2 8 4 . 3 9 2 . 4 0 2 . 1 1 2 9 . 3 51 3 205 . 1 0 . 8 6 3 . 7 3 2 . 2 1 2 . 0 6 3 3 . 4 71 4 140 . 1 1 . 2 6 3 . 9 3 2 . 2 7 2 . 0 2 3 7 . 5 11 5 9 0 . 0 1 0 . 8 9 3 . 3 7 2 . 1 0 2 . 0 0 4 1 . 3 31 6 4 5 . 0 1 1 . 36 3 . 6 8 2 . 2 0 1 . 9 8 4 5 . 5 11 7 0 1 1 . 1 1 3 . 23 2 . 07 1 . 9 6 5 0 . 6 3

No FeTMPyPT i t r a n t = 0. 503 M DMAPT i t r e / p l 0 400 400 0Sepn/Hz 4 . 3 9 6 .. 67 6 . 57 7 . 8 8A graph o f b l a n k s e p a r a t i o n ver sus [DMAP] was used t oc o r r e c t t h e s e p a r a t i o n t o g i v e Af

96

FI GURE 1.10 T i t r a t i o n of FeTMPyP wi th dmap and kscn

DMAP

KSCN

Uigandl/ lFeP]

pH 7. 20 (0.125 M phosphate), 35°C

iFeP) = 0.01 M

97

T i t r a t i o n o f 0 . 0 1 M F e T M P y P w i t h a q u e o u s KSCN c a u s e d

p r e c i p i t a t i o n , f o r c o n c e n t r a t i o n s o f KSCN i n excess o f- 2

3 x 1 0 M . Computer e v a l u a t i o n o f t h e a v a i l a b l e d a t a ,

assuming a m a g n e t i c moment o f 1 . 8 8 f o r t h e complex , gave a

6 *"2v a l u e o f 1 . 2 x 10 M f o r • T h i s i s o f t h e same o r d e r

as t he v a l u e s f o r t h e i m i d a z o l e s .

R e s u l t s

T i t r a n t = 0 . 1 4 8 M KSCNI n i t i a l [FeTMPyP] = 9 . 9 1 4 x 10 M

C o O —P 2 = 1 . 2 x 10 mol 1 , 35 COne s t a n d a r d d e v i a t i o n i n m a g n e t i c moment = 0 . 0 4 7

T i t r e Seen Af M a g n e t i c moment [ l i a a n d 1p i Hz Hz Exp C a l c [ p o r p h y r i n ]

1 0 18 . 33 14 . 01 4 . 3 0 4 . 3 0 02 5 . 0 1 8 . 3 5 1 4 . 0 3 4 . 33 4 . 3 0 0 . 1 93 1 0 . 0 17. 71 1 3 . 3 9 4 . 25 4 . 29 0 . 3 74 15 . 0 17 . 67 1 3 . 3 5 4 . 27 4 . 2 7 0 . 5 65 2 0 . 0 17. 31 1 2 . 9 9 4 . 24 4 . 25 0 . 7 56 2 5 . 0 17 . 14 1 2 . 8 2 4 . 2 4 4 . 2 2 0 . 9 37 3 0 . 0 16 . 59 1 2 . 2 7 4 . 1 7 4 . 1 9 1 . 1 28 3 5 . 0 16 . 39 1 2 . 0 7 4 . 1 6 4 . 1 5 1 . 319 4 0 . 0 15 . 69 1 1 . 3 7 4 . 0 6 4 . 1 2 1 . 49

1 0 4 5 . 0 15 . 53 1 1 . 2 1 4 . 0 5 4 . 0 8 1 . 6 81 1 5 0 . 0 14 . 94 1 0 . 6 2 3 . 9 7 4 . 0 4 1 . 871 2 6 0 . 0 14 . 58 1 0 . 2 6 3 . 9 4 3 . 9 5 2 . 2 41 3 7 0 . 0 13 . 67 9 . 3 5 3 . 8 0 3 . 8 5 2 . 6 21 4 8 0 . 0 12 . 83 8 . 5 1 3 . 6 7 3 . 7 6 2 . 9 91 5 9 0 . 0 12 . 83 8 . 5 1 3 . 71 3 . 6 6 3 . 3 61 6 1 0 0 . 1 2 . 2 2 7 . 9 0 3 . 61 3 . 56 3 . 7 41 7 1 1 0 . 11 . 83 7 . 5 1 3 . 5 5 3 . 4 6 4 . 11

No FeTMPyP 4 . 3 2 Hz+ 1 1 0 p i 4 . 3 2 Hz

9 8

1 . 2 , 6 . A z i d e c o m p l e x

1 . 2 . 6 . 1 . I n t r o d u c t i o n

I t i s p o s s i b l e f o r l i g a n d s o f i n t e r m e d i a t e s t r e n g t h

I I Ito g i v e Fe p o r p h y r i n complexes w i t h an i n t e r m e d i a t e

(S = 3 / 2 ) sp i n s t a t e or w i t h a s p i n s t a t e e q u i l i b r i u m

( 6 3 - 6 5 ) . The r e a c t i o n o f a z i d e i o n w i t h Fe* * * TMPyP gave a

complex which s a t i s f i e s t h e l a t t e r c o n d i t i o n . The complex

i s i n v e s t i g a t e d u s i n g v a r i o u s t e c h n i q u e s .

1 . 2 . 6 . 2 . M a g n e t i c t i t r a t i o n s

T i t r a t i o n w i t h aqueous a z i d e a t pH 4 . 7 5 ( 0 . 2 5 M

a c e t a t e ) or a t pH 7 . 2 0 ( 0 . 1 2 5 M p ho s p h a t e ) gave m a g n e t i c

moments a p p r o a c h i n g 4 . 6 5 w i t h i n c r e a s i n g a z i d e

c o n c e n t r a t i o n ( F i g u r e 1 . 1 1 ) . T h i s m a g n e t i c moment sug gest s

t h a t an azi de . compl ex in spi n equi l ibr ium i s formed . No

computer e v a l u a t i o n o f e q u i l i b r i u m c o n s t a n t s was made .

A 200 p i g r a d u a t e d g l a s s p i p e t t e was used f o r t he

pH 4 . 5 a z i d e t i t r a n t , i n p l a c e o f t h e u s u a l m i c r o s y r i n g e .

The s t a i n l e s s s t e e l p l u n g e r t u r n e d t h e a z i d e s o l u t i o n red .

1 . 2 . 6 . 3 . S p e c t r o p h o t o m e t r y

S p e c r o p h o t o m e t r i c t i t r a t i o n s were c a r r i e d ou t t o ga i n

i n f o r m a t i o n abo ut t h e r e l a t i v e s t r e n g t h o f c o o r d i n a t i o n o f

h y d r o x i d e , a z i d e and p h o s ph a t e t o FeTMPyP .

I t was seen t h a t as t h e pH 7 . 2 p ho spha t e b u f f e r

c o n c e n t r a t i o n ( 0 . 1 2 5 M, 0 . 5 0 M and 2 . 0 M) i n c r e a s e d , so

t h e c o n c e n t r a t i o n o f a z i d e needed t o g i v e t h e f i n a l

spect r um i n c r e a s e d f rom a p p r o x i m a t e l y 0 . 3 M t o 0 . 5 5 M .

9 9

Mag

neti

c m

omen

t

F I G U R E . 1.11 M a g n e t i c t i t r a t i o n of FeTMPyP w i t h n3 n3

5.6i

5.2-

• pH 4.75 0.25M acetate buf fer

■ pH 7-20 0.125M phosphate buffer

4.8-

4-4-

n

4.00 4 8 12 16 20 24 28 32 36 40 44 48 52

[FePl = 0.01 M. 3 5°C [ L i g a n d ] / (FePI

R e s u l t s

pH = 7 . 2 0 ( 0 . 1 2 5 M p o t a s s i u m p ho s ph a t e ) , 35°C

T i t r a n t = 1 . 941 M NaN3

I n i t i a l [FeTMPyP] = 9 . 9 2 6 x 10 ~ 3 M

T i t r e S e p a r a t i o n Af M [ A z i d e ]Ml Hz Hz [ p o r p h y r i n ]

1 0 17 . 39 1 3 . 4 2 4 . 20 02 5 . 0 17. 81 1 3 . 8 7 4 . 3 0 2 . 4 43 1 0 . 0 17 . 94 1 4 . 0 3 4 . 3 5 4 . 894 15 . 0 17. 81 1 3 . 9 3 4 . 3 6 7 . 3 35 2 0 . 0 1 7 . 7 8 1 3 . 9 4 4 . 3 9 9 . 7 86 2 5 . 0 17 . 67 1 3 . 8 6 4 . 4 0 1 2 . 2 27 3 0 . 0 17. 71 1 3 . 9 3 4 . 44 14 . 668 3 5 . 0 17. 61 1 3 . 8 6 4 . 4 5 17. 119 4 0 . 0 1 7 . 6 9 1 3 . 9 7 4 . 5 0 19 . 5 61 0 4 5 . 0 1 7 . 3 6 1 3 . 6 7 4 . 4 7 2 2 . 0 01 1 5 0 . 0 1 7 . 3 2 1 3 . 6 7 4 . 50 2 4 . 4 51 2 6 0 . 0 1 7 . 1 2 1 3 . 5 3 4 . 53 2 9 . 3 41 3 8 0 . 0 16. 61 1 3 . 1 4 4 . 56 39 . 111 4 1 0 0 . 0 16. 21 1 2 . 8 7 4 . 6 0 4 8 . 8 9

No FeTMPyP 3 . 9 7 Hz+ 1 0 0 p i 3 . 3 4 Hz

pH = 4 . 7 5 (0 . 25 M sodium a c e t a t e ) , 3 5 °C

T i t r a n t = 2 . 023 M NaN

I n i t i a l [FeTMPyP] = 9 . 8 3 4 x 10 ” 3 M

T i t r e S e p a r a t i o n A f M [ A z i d e ]Ml Hz Hz [ p o r p h y r i n ]

1 0 2 8 . 1 5 2 3 . 2 3 5 . 5 6 02 2 0 . 0 2 3 . 5 8 1 8 . 9 0 5 . 1 3 1 0 . 2 93 4 0 . 0 2 0 . 7 7 1 6 . 3 2 4 . 8 8 2 0 . 5 74 6 2 . 0 1 9 . 1 0 14 . 91 4 . 7 8 3 1 . 895 82 . 0 1 8 . 0 7 14 . 11 4 . 7 5 4 2 . 1 86 1 0 2 . 1 7 . 2 8 1 3 . 5 6 4 . 7 5 5 2 . 4 57 1 2 2 . 1 6 . 5 7 1 3 . 0 8 4 . 7 6 6 2 . 7 48 142. 1 5 . 2 7 1 2 . 0 2 4 . 6 5 7 3 . 0 3

No FeTMPyP 4 . 9 2 Hz+ 142 p i 3 . 2 5 Hz

1 0 1

T h i s i s c o n s i s t e n t w i t h o n e o r t w o a z i d e i o n s d i s p l a c i n g

c o o r d i n a t e d pho spha t e i on s .

The spe ct r um o f a FeTMPyP / 1 M NaN^ s o l u t i o n was

measured a t v a r i o u s pH v a l u e s . The same s pe ct rum was

obs e rv ed a t pH 5 and pH 7 as was obser ved i n pho spha t e

b u f f e r . At pH 12 t h e s pe c t r u m was t h a t o f t h e d i m e r i c

FeTMPyP and a t pH 9 . 5 t h e sp e c t ru m was i n t e r m e d i a t e between

t h e two s p e c t r a . These o b s e r v a t i o n s a r e c o n s i s t e n t w i t h

t h e d i s p l a c e m e n t o f c o o r d i n a t e d a z i d e by h y d r o x i d e f o l l o w e d

by d i m e r i s a t i o n , w i t h i n c r e a s i n g pH .

S e v e r a l t e c h n i q u e s w er e used t o f o l l o w t h e b e h a v i o u r

o f t h e complex w i t h r e s p e c t t o t e m p e r a t u r e change .

1 . 2 . 6 . 4 . S u s c e p t i b i l i t y measurements

A l l s e p a r a t i o n s were measured w i t h a B r u k e r WM250 NMR

s p e c t r o m e t e r . An oven d r i e d c o a x i a l NMR t u b e was used ,

I I Iw i t h t h e Fe TMPyP s o l u t i o n i n t h e c e n t r a l t u b e . A l l

s o l u t i o n s were made i n D2 0 and t h e i n t e r n a l r e f e r e n c e was

t e t r a m e t h y l ammonium c h l o r i d e . Such s o l u t i o n s s l o w l y

p r e c i p i t a t e d a c o l o u r e d s u b s t a n c e which r e d i s s o l v e d i n

d i s t i l l e d w a t e r .

A s o l u t i o n 1M i n NaN0 , 0 . 0 2 3 M i n ( CH. , ) #NC1 and

0 . 0 1 M i n FeTMPyP had a pH o f 9 ( e s t i m a t e d f rom t h e pK^ o f

oKN^) . The c h e m i c a l s h i f t s e p a r a t i o n (5 - 90 C) was s m a l l

and c or r es p on de d t o a m a g n e t i c moment o f a bo ut 2 .- 3The m a g n e t i c moment o f a pH 6 ( 2 . 3 x 10 M MES)

s o l u t i o n o f 2 M NaN , 4 . 8 x 10~2 M ( CH„ ) , NC1 and

8 x 10 3 M FeTMPyP , was measured up t o 60°C . At h i g h e r

102

t e m p e r a t u r e s no NMR s i g n a l was obser ved due t o c o n s i d e r a b l e

p r e c i p i t a t i o n .

T e m p e r a t u r e / ° C | 2 15 30 45 60p | 3 . 0 0 3 . 3 5 4 . 4 6 4 . 5 9 4 . 6 8

I t i s seen t h a t m a g n e t i c moment i n c r e a s e s w i t h

i n c r e a s i n g t e m p e r a t u r e . T h i s i s c o n s i s t e n t w i t h a

complex in spin st a t e equi l ibr ium . The complex was

s t a b i l i s e d by t h e d e c r e a s e i n pH f rom 9 t o 6 .

1 . 2 . 6 . 5 . V a r i a b l e t e m p e r a t u r e s p e c t r o p h o t o m e t r y

The s pe c t r u m o f an FeTMPyP / 2 M NaN^

s o l u t i o n ( F i g u r e 1 . 1 2 ) was scanned u s i n g a v a r i a b l e- 3

t e m p e r a t u r e sample h o l d e r . At pH 6 . 0 (10 M MES) t h e

i n t e r s e c t i o n s o f t h e s p e c t r a were an a p p r o x i m a t e i s o b e s t i c

p o i n t on d e c r e a s i n g or i n c r e a s i n g t h e t e m p e r a t u r e . At _ 3

pH 7 . 4 (10 M p h o s p h a t e ) a r ange o f i n t e r s e c t i o n s was

obs er ved . The e x i s t e n c e o f an i s o b e s t i c p o i n t i s

c o n s i s t e n t w i t h a s i n g l e a z i d e complex ch a ng i ng s p i n s t a t e

and hence chromophore w i t h t e m p e r a t u r e . Ac id c o n d i t i o n s

may be c r i t i c a l i n s t a b i l i s i n g t h e a z i d e complex a t h i g h e r

t e m p e r a t u r e s f rom s u b s t i t u t i o n by h y d r o x i d e . However i f

t h e pH i s l o w e r e d b e l ow 6 t h e c o o r d i n a t e d as w e l l as

u n c o o r d i n a t e d a z i d e may be p r o t o n a t e d ( 6 6 ) mak ing

i n t e r p r e t a t i o n more c o m p l i c a t e d . I t i s no t p o s s i b l e t o say

w h e t h e r one or two a z i d e i o n s a r e c o o r d i n a t e d .

1 0 3

FIGURE 1.12 V i s i b l e a b s o r p t i o n a n d e s r s p e c t r a of the FeTMPypVisible AZIDE COMPLEX

0.20 0.24 0.28 0.32 0 36 0 40

Field strength / Tesla

Both samplesTemp = 77K Freq * 9 217 GHz

pH 6 0.001M MES ; 2 m NaN3

1 0 4

1 . 2 . 6 . 6 .■ ES R s p e e r a

The ESR s p e c t r u m o f t h e a z i d e complex ( 3 . 7 x 10 M

FeTMPyP , 1 . 0 x 10_3 M pH 6 MES , 2 M NaN^ and 10 l v / v

aqueous e t h y l e n e g l y c o l ) was scanned a t t e m p e r a t u r e s f rom

- 1 7 0 t o - 40°C ( F i g u r e 1 . 1 2 ) . A l ow sp i n F e * * * r e s o n a n c e

was o b s e rv ed , wh ich b r oadened w i t h t e m p e r a t u r e . At - 7 0 ° C

a v e r y s m a l l p r o p o r t i o n o f h i g h s p i n s i g n a l was obs er ved .

From t h e s o l u t i o n s u s c e p t i b i l i t y measurements a rough

e s t i m a t e o f 0 . 1 t o f h i g h s p i n form a t - 7 0 ° C was made .

Th i s i s c o n s i s t e n t w i t h t h e s e ESR o b s e r v a t i o n s .

Neya and M o r i s h i m a ( 63 ) obs er ved a c o m b i n a t i o n o f

h i g h and low s p i n ESR r e s o n an ce s f rom t h e i r hemin - a z i d e -

d i m e t h y l s u l p h o x i d e complex between 77 and 163 K .

- 3

1 0 5

1 . 2 . 7 . F l u o r i d e c o m p l e x

1 . 2 . 7 . 1 . I n t r o d u c t i o n

The f l u o r i d e i o n i s known ( 6 7 - 6 9 ) t o g i v e h i g h s p i n

I I IFe p o r p h y r i n complexes and i s shown h er e t o c o o r d i n a t e

w e a k l y t o F e H I TMPyP .

1 . 2 . 7 . 2 . S p e c t r o p h o t o m e t r i e t i t r a t i o n

S p e c t r o p h o t o m e t r i c t i t r a t i o n o f F e I I I p-TMPyP w i t h

aqueous KF ( F i g u r e 1 . 1 3 ) showed t h a t a s m a l l bu t m e a s u r a b l e

change i n t h e v i s i b l e a b s o r p t i o n spe ct rum t a k e s p l a c e .

1 . 2 . 7 . 3 . T i t r a t i o n f o l l o w e d bv ESR s p e c t r o s c o p y

No s p l i t t i n g o f t h e g = 6 r e s o n an ce was obser ved w i t h

a d d i t i o n o f F . However t h e s i n g l e g = 2 r e s o n a n c e

g e n e r a l l y changed o v e r t o a t r i p l e t r e s o n a n c e as t h e F~

c o n c e n t r a t i o n was i n c r e a s e d f rom 0 t o 0 . 1 M ( F i g u r e 1 . 1 4 ) .

The t r i p l e t s t r u c t u r e was due t o c o u p l i n g o f two F

1 9nuc le i . s i n c e F i s 100 l abundant w i t h s p i n 1 / 2 . No

i n t e r m e d i a t e d o u b l e t , a s s i g n e d to c o o r d i n a t i o n by a s i n g l e

F i o n , was o bs er ved .

The d a t a be l ow shows t h a t t h e s p l i t t i n g o f t h e g = 2

r es on a nc e i s o f t h e same o r d e r as t h a t o bs er ved by o t h e r

a u t h o r s .

Complex S p l i t t i n g (g = 2 ) / 1 0 3 T R e f e r e n c e

FeTMPyP( F ) 4 . 4 T h i s work

FeTPP( F ) 3 . 5 67

M y og l o b i n f l u o r i d e 4 . 3 ± 0 . 2 68

Hemin f l u o r i d e 4 . 4 69

1 06

F I G U R E ‘ 1 . 1 3 S p e CTROPHOTOMETRIC TITRATION OF FeTMPyP WITH KF

pH = 7.6 (no bu f f e r )

Path' length = 1cm

---------------[KF1 = 0.0M , Amax = 597. 5 nm

-------------- iKFl = 0.242 m , Amax = 595 nm

[PFel = 7 x 10~5 M

1 0 7

FIGURE 1.14. TITRATION OF FeTMPyP WITH KF FOLLOWED BY ESR

Field stre ngth / Tesl a

0.24 0.28 0.32 0.36

0.24 0.28 0.32 0.36

Temp = 77K Freq = 9.215 GHz pH 7.20 (0.125 M phosphate)

[KF) in lett hand margin [PFe] = 5.0 x 10-3 M 10% v/v. HO-..l'OH

108

1 . 2 . 7 . 4 . M a g n e t i c t i t r a t i o n

The m a g n e t i c moment i s seen ( F i g u r e 1 . 1 5 ) to i n c r e a s e

w i t h i n c r e a s i n g f l u o r i d e c o n c e n t r a t i o n and t o approach t h e

h i g h sp i n v a l u e . Both t he mono and d i f l u o r o complexes

must be h i gh s p i n . The m a g n e t i c moment o f F e T P P ( F ) 2 has

been d e t e r m i n e d by t h e Evans' method as 6 . 0 ( 67 ) and by t h e

F a r ad a y method as 5 . 9 5 ( 7 0 ) . As w e l l as o p t i m i s i n g t h e

v a l u e o f K ^ / K 2 t h e l i m i t i n g c o n d i t i o n s r e p r e s e n t e d by

K* << and K^>> w er e a l s o c o n s i d e r e d . A

s i g n i f i c a n t l y b e t t e r f i t i s o b t a i n e d by a l l o w i n g t h e v a l u e

o f K. j / K2 to v a r y . The r e s u l t s a r e t hus

„ 3 - 2 2P2 = 19 . 3 x 10 mol 1

K^/ K' = 1 . 43

R e s u l t s

T i t r an t = 1 . 855 M KF

Conditions

Standard deviat ion in p

I n i t i a l C FeTMPyP] = 1 .002 x 1 0

A Bk;<< k; k * = 1.43 k '1 2 1 2

0.111 0.043

Ki» K20 . 101

T i t r eMl

SeDnHz

AfHz

Magnetic Exp A

momentB

CL]C

T/ [ F e ] T

1 0 17.68 12.77 4.08 4.08 4.08 4.08 02 5.0 19.51 14.67 4.40 4.20 4.38 4.52 2.313 10.0 21.36 16.58 4.71 4.47 4.67 4.83 4.634 15.0 22.68 17.97 4.93 4.78 4.92 5.05 6.945 20.0 24.20 19.55 5.17 5.07 5.14 5.22 9.266 25.0 24.13 19.55 5.20 5.31 5.31 5.34 11.577 30.0 25.38 20.86 5.41 5.49 5.45 5.44 13.888 35.0 26.38 21 .93 5.58 5.62 5.55 5.51 16.209 40.0 26.52 22.13 5.63 5.71 5.63 5.57 18.51

10 45.0 26.94 22.62 5.73 5.77 5.69 5.62 20.8311 50.0 26.50 22.25 5.71 5.81 5.74 5.66 23.1412 60.0 26.67 22.55 5.81 5.86 5.80 5.72 27.7713 70.0 26.70 22.71 5.90 5.88 5.84 5.76 32.4014 80.0 26.25 22.39 5.92 5.89 5.86 5.78 37.0315 100. 25.02 21 .42 5.91 5.91 5.89 5.82 46.28

No FeTMPyP 4.91 Hz100 pi 3.60 Hz

109

Mag

neti

c m

omen

t

F I G U R E U 5 M agnetic titration of FeTMPyP w i t h kf

pH = 7.20 l 0.125 M phosphate) , 35°C

1 1 0

1 . 2 . 7 . 5 . D i s c u s s i o n

Program FEP4 and t h e v a l u e s o f (3 2 and K^/K^ were

used to p r e d i c t t he mole f r a c t i o n s o f t h e f o u r FeTMPyP

s p e c i e s . Two i n c o n s i s t e n c i e s a r e a p p a r e n t f rom t h e mole

f r a c t i o n s d i a g r a m ( F i g u r e 1 . 1 5 ) . The ESR t i t r a t i o n s do not

a t any s t a g e show e v i d e n c e o f t h e mono f l u o r o complex and

i n d i c a t e t h a t t h e r e a c t i o n i s v i r t u a l l y c o mp l e t e a t KF

c o n c e n t r a t i o n s above 0. 1M .

These d i f f e r e n c e s may be due t o t h e 10 I. o f e t h y l e n e

g l y c o l used i n t h e s o l v e n t f o r t h e ESR t i t r a t i o n but not

t h e m a g n e t i c t i t r a t i o n . A l so t h e ' s o l u t i o n w i l l have c o o le d

w h i l s t s t i l l f l u i d , t h e p o s i t i o n o f e q u i l i b r i u m b e i n g t h a t

as t h e s o l u t i o n f r o z e . These t h i n g s may a l t e r t h e v a l u e s

o f and K* /Kg compared t o t h e i r v a l u e s a t 35°C .

The s o l u t i o n s w er e c o o l e d s l o w l y t o a v o i d c r a c k i n g

t h e s i l i c a t u b e used i n t h e ESR t i t r a t i o n . I f a t h i c k

w a l l e d s i l i c a t u b e wer e used i t co u ld be warmed t o 35°C and

c oo led by p l u n g i n g i n t o l i q u i d n i t r o g e n . T h i s may f r e e z e

out t h e p o s i t i o n o f e q u i l i b r i u m a t t h e h i g h e r t e m p e r a t u r e .

1 1 1

1 . 2 . 8 . C y a n i d e c o m p l e x e s

1 . 2 . 8 . 1 . I n t r o d u c t i o n

The c o o r d i n a t i o n o f c y a n i d e to FeTMPyP has been

f o l l o w e d by s p e c t r o p h o t o m e t r y , NMR and s u s c e p t i b i l i t y

measurements . D e s p i t e t h e pK^ v a l u e o f 9 . 31 , c y a n i d e

c o o r d i n a t i o n was o bs er ved i n s o l u t i o n s as a c i d i c as

pH 3 . 7 5 . A v a r i e t y o f c o n d i t i o n s were used and t h e e f f e c t

o f b u f f e r c o o r d i n a t i o n and pH on t h e v a l u e s o f K ^ / K ' and

P2 i s i l l u s t r a t e d . D i s c r e p a n c i e s a r i s e between t h e v a l u e s

o f e v a l u a t e d i n a l k a l i n e and a c i d s o l u t i o n s .

1 . 2 . 8 . 2 . 1 . S p e c t r o p h o t o m e t r i c t i t r a t i o n . pH 3 . 7 5 t o 7 . 2

To i n v e s t i g a t e t h e s p e c i e s i n s o l u t i o n an i n i t i a l

rough t i t r a t i o n was c a r r i e d o u t a t pH 3 . 8 us i ng no b u f f e r .

The o n l y s p e c i e s t o be p r e s e n t under t h e s e c o n d i t i o n s a r e

t h e aqua monomer and any c y a n i d e complexes . No c l e a r

i s o b e s t i c p o i n t s w er e seen , i n d i c a t i n g t h a t t h e

c o n c e n t r a t i o n s o f mono and d i cyano complexes a r e both

s i g n i f i c a n t . The s p e c t r a i n d i c a t e t h a t t h e a bs o r b a n c e o f

t h e mono and d i cyano complexes does not d i f f e r

s i g n i f i c a n t l y i n t h e r ange 500 t o 570 nm , t h e main

d i f f e r e n c e b e i ng a s h o u l d e r a t about 600 nm f o r t h e d i

cyano complex . I t wa s not p o s s i b l e t o a s s i g n one sp e c t ru m

as r e p r e s e n t i n g s o l e l y t h e a b s o r p t i o n o f t h e mono cyano

complex .

The t i t r a t i o n was r e p e a t e d us i ng s m a l l amounts o f

pH 3 . 7 5 f o r m a t e b u f f e r i n t h e t i t r a n t s o l u t i o n . The

i n i t i a l s p e c t r a show i s o b e s t i c p o i n t s , i n d i c a t i n g t h e

p r es e n c e o f two s p e c i e s , PFe( OH2 ) 2 and PFe( OH2 ) ( CN) .

1 1 2

However when an excess o f t i t r a n t was added t o o b t a i n t h e

f i n a l s pe c t r u m t he t r a c e d e v i a t e d f rom t h i s i s o b e s t i c p o i n t

even i f d i l u t i o n was t a k e n i n t o acc ount . T h i s i s due t o

t he p r es e n c e o f PFe f CN) ^ i n s o l u t i o n . The graph o f

l o g l ( A - A ) / (A - A) } v e r s e s logCCN ] ( F i g u r e 1 . 1 6 ) gave 0 10 0a s t r a i g h t l i n e o f s l o p e 0 . 9 9 7 , f o r l og [ CN ] < - 8 . 3 . T h i s

i s c l o s e t o t h e t h e o r e t i c a l v a l u e o f 1 .0 ( a p p e n d i x 1 . 8 ) and

shows t h a t t h e a p p r o x i m a t i o n s made a r e v a l i d i n t h i s

r e g i o n . At h i g h e r c o n c e n t r a t i o n s d e v i a t i o n s f rom t h i s

s t r a i g h t l i n e a r e c o n s i s t e n t w i t h t h e p r e s e n c e o f a

s i g n i f i c a n t amount o f t h e d i cyano complex . I t i s because

t h e e x t i n c t i o n c o e f f i c i e n t s o f t h e mono and d i cyano

complexs do no t s i g n i f i c a n t l y d i f f e r a t 560 nm , t h a t t he

v a l u e o f A10Q i s v a l i d .

F u r t h e r s p e c t r o p h o t o m e t r i c t i t r a t i o n s were c a r r i e d

out a t o t h e r v a l u e s o f pH , w i t h and w i t h o u t s i g n i f i c a n t

c o n c e n t r a t i o n s o f b u f f e r p r e s e n t . I f a h i g h c o n c e n t r a t i o n

o f b u f f e r was p r e s e n t no a t t e m p t was made t o c o r r e c t f o r

b u f f e r c o o r d i n a t i o n . I n a c i d i c s o l u t i o n t h e c o n d i t i o n

K ’ £ K ' i s s a t i s f i e d , w her eas a l k a l i n e s o l u t i o n s a n d / o r

b u f f e r c o o r d i n a t i o n l e a d s t o t h e c o n d i t i o n

I<1 << ^2 ( a PPe n d i x 1 - 6 ) . The s p ec t r o p h o t o m e t r i c d a t a

o b t a i n e d h e r e under a c i d c o n d i t i o n s was e v a l u a t e d

g r a p h i c a l l y t o g i v e K.j . For pH 3 . 7 5 and 4 . 5 0 , t h e s l op es

a r e n ea r t o t h e t h e o r e r i c a l v a l u e o f 1 . 0 . T h e pH 7 . 2 0 da t a

i s not v e r y a c c u r a t e , bu t rough v a l u e s o f l o g K.j were

e s t i m a t e d . The o n l y a t t e m p t t o draw a b e s t s t r a i g h t l i n e

gave a s l o p e o f 1 . 7 . T h i s shows t h a t t h e c o n d i t i o n

K ’ >> K ' i s no t a t any s t a g e s a t i s f i e d , a t pH 7 . 2 0 .

1 1 3

FIGURE-1.16 SPEC TRO PHOTO ME TR.IC TITRATION of FeTMPy P w i t h

CYANIDE , pH 3.75

log ICN") 3io

[ fo rm ate ] = 5— 9x 10~4M

1 1 A

1 . 2 . 8 . 2 . 2 . R e s u l t s ± t i t r a t i o n s w i t h m o r e t h a n t h e m i n i m u m

o f b u f f e r

pH 3 . 7 5 ( 0 . 2 5 M f o r m a t e ) , 34 ± 2°C

CFe ] T = 0 . 9 6 x 1 0 " 5 M

T i t r a n t = 3 . 7 4 3 M KCN

^100 c o r r e c t e c * ^or d i l u t i o n = 0 . 0 6 4

560 nm , s l o p e = 0 . 0 7 , i n t e r c e p t = 7 . 1 5

K ‘ = 1 . 4 x 10 7 m o l " 11

T i t r e / p l Absorbance l o g { ( A - A q ) / ( A 10Q- A ) } logCCN]

0 0 . 4 8 61 . 0 0 . 5 2 3 - 0 . 9 6 5 - 8 . 2 92 . 5 0 . 5 4 9 - 0 . 6 9 9 - 7 . 895 . 0 0 . 5 0 9 - 0 . 4 2 6 - 7 . 5 9

10 . 0 0 . 6 5 2 - 0 . 1 0 6 - 7 . 2915 . 0 0 . 6 9 3 0 . 0 0 3 - 7 . 1 22 0 . 0 0 . 7 2 0 0 . 2 5 0 - 6 . 9 94 0 . 0 0 . 7 9 2 0 . 6 2 8 - 6 . 7 0

1 0 0 . 0 0 . 0 2 2

pH 4 . 5 0 ( 0 . 2 5 M a c e t a t e ) , 32 - 3 6 . 0 ° C

[ F e ] T = 9 . 6 7 x 1 o " 5 M

T i t r a n t = 3 . 5 2 9 M KCN

565 nm , A ^ ^ c o r r e c t e d f o r d i l u t i o n = 0 . 0 5 3

s l o p e = 1 . 0 2 , i n t e r c e p t = 7 . 0 0

K ’ = 1 . 0 x 10 7 m o l " 11

T i t r e / p l Absorbance l o g { ( A - A Q) / ( A^ - A ) } logCCN]

0 0 . 4 6 80 . 2 0 . 4 8 8 - 1 . 2 6 1 - 8 . 2 70 . 4 0 . 5 0 4 - 0 . 9 8 6 - 7 . 9 70 . 6 0 . 5 2 2 - 0 . 7 8 7 - 7 . 790 . 8 0 . 5 3 2 - 0 . 7 0 0 - 7 . 6 61 . 0 0 . 5 4 8 - 0 . 5 8 1 - 7 . 5 7

2 0 . 0 0 . 8 4 4

1 1 5

pH 7 . 2 ( 0 . 1 2 5 P h o s p h a t e )

CFe] = 9 . 0 7 3 x 10" 5 M

T i t ra n t = 0 . 1 3 7 7 M KCN

570 nm , s l o p e = 1 .7 , i n t e r c e p t = 5 . 6

K ' * 4 x <n5 - 1, 1 0 mol 1

T i t r e / p l Absorbance l o g { ( A - A 0 ) / ( A 1 00 - A) > l o g [ CN]

0 0 . 5 3 91 . 0 0 . 5 5 9 - 1 . 068 - 6 . 3 12 . 0 0 . 5 8 7 - 0 . 6 3 3 - 6 . 0 23 . 0 0 . 6 1 3 - 0 . 3 8 6 - 5 . 8 54 . 0 0 . 6 4 0 - 0 . 1 8 0 - 5 . 7 2

* 0 . 7 9 3

* Excess s o l i d KCN

T a b l e 1 . 7 D e t e r m i n a t i o n o f k ; f o r c y a n i d e c o o r d i n a t i o n

pH Slope A/nm pk; k;*

1 Conditions

3.75 0.87 560 7.15 1 .4 X 107 0.25 M formate , 34±2°C

4.50 1 .02 565 7.0 1.0 X , o7 0.25 M acetate , 34°C

7.20 1 .70 570 *5 .6 4 X 105 0.125 M phosphate , 33±2°C

* K! r e f e r s t o K„ u n c o r r e c t e d f o r b u f f e r 1 1c o o r d i n a t i o n .

1 1 6

1 . 2 . 8 . 2 . 3 . R e s u l t s : t i t r a t i o n s w i t h t h e m i n i m u m o f b u f f e r

pH 3 . 7 5 (5 x 1 0 " 4 M f o r m a t e ) , I = 0 . 3 0 M ( KN03 ) , 30°C

CFe] = 1 0 . 2 7 x 1 o " 5 M

T i t r a n t = 0 . 4 6 9 6 M KCN ( 0 . 1 M f o r m a t e )

5 6 5 . 5 nm , S l o pe = 0 . 9 9 7 , i n t e r c e p t = 7 . 6 5

K = 4 . 5 3 x 10? m o l " 1l

T i t r e / p l*

Absorbance l o g { ( A - A q ) / ( A1 0 0 - A ) } l o g [ CN]

0 0 . 4 4 61 . 0 0 . 4 5 9 - 1 . 534 - 9 . 1 92 . 0 0 . 4 7 0 - 1 . 257 - 8 . 8 93 . 0 0 . 4 8 3 - 1 . 056 - 8 . 7 24 . 0 0 . 4 9 4 - 0 . 9 3 2 - 8 . 5 96 . 0 0 . 5 1 4 - 0 . 7 5 9 - 8 . 4 28 . 0

113.0 . 5 3 50 . 9 0 4

- 0 . 6 1 8 - 8 . 2 9

* c o r r e c t e d f o r d i l u t i o n

pH 3 . 7 5 (No b u f f e r ) , I = 0 . 0 M , 34 . 8° C

C F e ] T = 8 . 7 1 3 x 10" 5 M

T i t r a n t = 0 . 4 4 1 2 M KCN ( 0 . 1 M f o r m a t e )

560 nm , A1Q0 c o r r e c t e d f o r d i l u t i o n = 0 . 8 2 5

s l o p e = 1. 01 , i n t e r c e p t = 8 . 5 5

K . = 3 . 5 5 x 1 0 8 m o l " 1 1 1

T i t r e / p l Absorbance l o g { ( A- Ag ) / (A-j qq- A) } l o g [ CN]

0 0 . 4 5 80 . 5 0 . 4 9 3 - 0 . 9 7 7 - 9 . 551 . 0 0 . 5 1 7 - 0 . 7 1 8 - 9 . 2 41 . 5 0 . 5 4 2 - 0 . 5 2 7 - 9 . 0 72 . 0 0 . 5 6 2 - 0 . 4 0 3 - 8 . 9 42 . 5 0 . 5 7 9 - 0 . 3 0 8 - 8 . 8 43 . 0 0 . 5 9 8 - 0 . 2 1 0 - 8 . 7 63 . 5 0 . 6 0 8 - 0 . 1 6 0 - 8 . 6 94 . 0 0 . 6 2 4 - 0 . 0 8 3 - 8 . 6 35 . 0

6 0 . 00 . 6 4 60 . 8 0 2

0 . 021 - 8 . 5 4

1 1 7

pH 4 . 5 0 (No b u f f e r ) , I = 0 . 0 M , ^ 30°C

[ F e ] T = 8 . 2 2 7 x 10~5 M

T i t r a n t = 0 . 1 M KCN

560 nm , s l o p e = 1 . 0 9 , i n t e r c e p t = 8 . 34

K = 2 . 4 x 108 mol ^1

T i t r e / p l Absorbance l o g { ( A - A Q) / ( A - A ) } l o g [ C N ]

0 0 . 4 9 40 . 5 0 . 5 1 41 . 0 0 . 5 3 32 . 0 0 . 5 6 75 . 0 0 . 5 9 17 . 0 0 . 6 2 9

7 0 . 0 0 . 7 4 8

pH 7 . 2 , 1 = 0 . 0 M , 35 ± 0 . 1 ° C

[ Fe 3 T = 8 . 6 0 4 x 1 0 ~ 5 M

T i t r a n t = 0 . 0 2 0 1 4 M KCN

635 nm , i n t e r c e p t = 6 . 9 ± 0 . 2

K = 3 . 3 x 108 m o l ~ 1l

T i t r e / p l Absorbance l o g { ( A - A 0 ) / ( A 100- A) > l o g [ CN 3

0 0 . 6 0 21 . 0 0 . 5 7 8 - 0 . 9 8 1 -j CD PO

2 . 0 0 . 551 - 0 . 6 0 0 - 7 . 7 92 . 5 0 . 5 4 5 - 0 . 5 3 9 - 7 . 4 23 . 0 0 . 5 3 9 - 0 . 4 8 2 - 7 . 224 . 0 0 . 5 3 0 - 0 . 4 0 3 - 6 . 9 65 . 0 0 . 511 - 0 . 2 5 3 - 6 . 8 7

* 0 . 3 4 8

- 1 . 068 - 0 . 741 - 0 . 3 9 4 - 0 . 2 0 9

0 . 0 5 5

- 9 . 3 3- 9 . 0 3- 8 . 7 2- 8 . 5 3- 8 . 2 6

* 10 p i 0 . 1 M KCN

1 1 8

pH 7 . 2 ( 0 . 0 1 M PI PES) , 33 ± 2°C

[ F e ] T = 8 . 41 x 10” 5 M

T i t r a n t = 0 . 1 5 1 M KCN

564 nm , i n t e r c e p t = 6 . 3 ± 0 . 2

K = 0 . 3 x 107 m o l " 11

T i t r e / p l Absorbance l o g ( ( a - a q ) / ( a 1oq- a ) } l o g [ CN]

0 0 . 5710 . 5 0 . 6 0 5 - 0 . 4 9 8 - 6 . 8 71 . 0 0 . 6 2 6 - 0 . 1 9 4 - 6 . 4 82 . 0 0 . 6 7 0 0 . 3 7 2 - 6 . 1 53 . 0 5 . 0

0 . 6 9 60 . 7 1 2

0 . 8 9 3 - 5 . 9 3

1 1 9

T a b l e 1 . 8 D e t e r m i n a t i o n o f K1 f o r c y a n i d e c o o r d i n a t i o n

pH Slope A/ nm p k ; * K1 / 1 0 7 M C o n d i t i o n s

3 . 7 5 0 . 9 9 7 5 6 5 . 5 7 . 65 4 . 53 1 = 0 . 3 0 M 9 x 10 ” 4

, 30°C up t o M f o r m a t e

3 . 7 5 1. 01 560 8 . 5 5 3 5 . 5 1=0 . 0 M , 5 x 1 0 “ ^

, 33°C up to M f o r m a t e

4 . 5 0 1 . 09 560 8 . 3 4 24 1=0 . 0 M ,, - 3 0 °C

7 . 2 0 — 635 ~ 6 .9 33 1=0 . 0 M ,, 3 5 ± 0 . 1 °C

7 . 2 0 __________ 564 ~ 6 .3 8 . 3 0 . 01 M PIPES , 3 3 ± 2 °C

* K,j r e f e r s t o K1 u n c o r r e c t e d f o r h y d r o l y s i s of

c o o r d i n a t e d w a t e r .

The K1 v a l u e s f o r 0 . 0 M i o n i c s t r e n g t h a r e

8 -1c o n s i s t e n t l y c l o s e t o 3 . 0 x 10 mol 1 . The two t i t r a t i o n s

a t pH 3 . 7 5 show t h a t K d e c r e a s e s w i t h an i n c r e a s e i n i o n i c

s t r e n g t h . T h i s i s c o n s i s t e n t w i t h t h e more h i g h l y charged

non c y a n i d e complex , b e i n g r e l a t i v e l y s t a b i l i s e d by

i n c r e a s e d i o n i c s t r e n g t h . Even 0 . 01 M PIPES b u f f e r r educes

t h e v a l u e o f K.j .

1 2 0

1 . 2 . 8 . 3 . 1 . S o e c t r o p h o t o m e t r i e t i t r a t i o n ^ joH 7 . 9 t o 1 0 . 0

In a l k a l i n e s o l u t i o n i t should be p o s s i b l e t o make a

d e t e r m i n a t i o n o f p 2 , s i n c e K' >> under t h e s e

c o n d i t i o n s . A t t e m p t s were made us i ng t he minimum

c o n c e n t r a t i o n s o f t h e b u f f e r s T r i s and CHES .

1 . 2 . 8 . 3 . 2 . R e s u l t s

pH = 7 . 9 0 (1 - 6 x 1 0 " 3 M T r i s ) [FeTMPyP] = 6 . 5 5 9 x 10~4 M

T i t r a n t c o n c e n t r a t i o n = 0 . 1 4 0 2 M

Wav e l e ng th = 533 nm

3 -1E x t i n c t i o n c o e f f i c i e n t s / 10 mol 1cm

Monomer

8 . 3 2

Dimer

1 . 79

Complex

7 . 5 4

Computer c a l c u l a t e d cur v es

1 2 - 2„K2 >> K1

oCMiiCMCD. x 1 0

7

mol 1

- 1K1 >> K2 K1 = 2 . 2 x 10 mol 1

* * * * * * * * * * *E x p e r i m e n t a l

Absorbance

K2> >K1

* * * * * * * * *k , >> k 2

T i t r e Ml

[ U t / i o " 3 m

1 0 . 251 0 . 251 0 . 251 0 02 0 . 2 7 3 0 . 2 6 2 0 . 2 7 9 0 . 3 0 0 . 1 43 0 . 2 9 0 0 . 279 0 . 3 0 4 0 . 6 0 0 . 2 84 0 . 3 0 8 0 . 2 9 8 0 . 3 2 7 0 . 9 0 0 . 4 25 0 . 3 2 7 0 . 3 1 8 0 . 3 4 7 1 . 20 0 . 5 66 0 . 3 4 4 0 . 3 3 9 0 . 3 6 5 1 . 50 0 . 7 07 0 . 3 7 4 0 . 3 7 2 0 . 391 2 . 0 0 0 . 9 3

.8 0 . 3 9 9 0 . 4 0 2 0 . 411 2 . 5 0 1 . 169 0 . 4 2 5 0 . 4 2 9 0 . 4 2 7 3 . 0 0 1 . 39

1 0 0 . 4 4 6 0 . 4 5 1 0 . 4 3 9 3 . 5 0 1 . 621 1 0 . 4 6 4 0 . 4 6 7 0 . 4 4 8 4 . 00 1 . 841 2 0 . 4 7 5 0 . 4 7 7 0 . 4 5 5 4 . 50 2 . 0 71 3 0 . 4 8 2 0 . 481 0 . 4 6 0 5 . 0 0 2 . 3 01 4 0 . 4 8 5 0 . 4 8 4 0 . 4 6 7 6 . 0 0 2 . 7 5

1 2 1

pH = 0 . 0 0 (1 - 15 x 10~3 M T r i s ) [FeTMPyP] = 8 . 1 5 5 x 10~4 M


Wave l eng th = 540 nm

3 -1E x t i n c t i o n c o e f f i c i e n t s / 10 mol 1cm

Monomer 0 i mer Complex

7. 71 2 . 1 7 7 . 5 5

Computer c a l c u l a t e d c u r ve s :

k 2 >> Kl f>2 « 1 . 51 2x 10 mol 2 !

K . >> K„ 7C II ro o « 7 - 1 x 10 mol 11 2 1

* * * * * * * * * * * Absorbance * * * * * * * * * T i t r e [ L ] / 1 0 " 3 ME x p e r i m e n t a l k 2>> k 1 K 1>>K2 Ml

1

1 0 . 3 0 6 0 . 3 0 6 0 . 3 0 6 0 02 0 . 3 2 7 0 . 3 1 5 0 . 331 0 . 3 0 0 . 1 33 0 . 3 3 8 0 . 3 3 0 0 . 3 5 4 0 . 6 0 0 . 2 54 0 . 3 5 7 0 . 3 4 7 0 . 3 7 6 0 . 9 0 0 . 3 85 0 . 3 7 3 0 . 3 6 5 0 . 3 9 6 1 . 20 0 . 5 06 0 . 3 9 0 0 . 3 8 4 0 . 4 1 5 1 . 50 0 . 6 37 0 . 4 1 8 0 . 4 1 5 0 . 4 4 3 2 . 0 0 0 . 8 38 0 . 4 4 4 0 . 4 4 6 0 . 4 6 8 2 . 5 0 1 . 049 0 . 4 7 2 0 . 4 7 5 0 . 4 8 9 3 . 0 0 1 . 25

1 0 0 . 4 9 7 0 . 5 0 2 0 . 5 0 6 3 . 5 0 1 . 451 1 0 . 5 1 7 0 . 5 2 7 0 . 521 4 . 00 1 . 661 2 0 . 5 3 8 0 . 5 4 9 0 . 5 3 2 4 . 5 0 1 . 861 3 0 . 5 5 9 0 . 5 6 7 0 . 5 4 2 5 . 0 0 2 . 061 4 0 . 5 8 4 0 . 5 8 9 0 . 5 5 7 6 . 0 0 2 . 4 71 5 0 . 5 9 8 0 . 5 9 7 0 . 5 7 6 9 . 00 3 . 6 7

122

pH = 9 . 0 0 (1 - 8 x 10 " 3 M CHES) CFeTMPyP] = 9 . 4 5 8 x 10~4 M



E x t i n c t i o n c o e f f i c i e n t s 1 0 mol ^lcm ^

Monomer Dimer Complex

8 . 02 2 . 3 4 7 . 6 8

Computer c a l c u l a t e d cur v es J

K2 >> K 1 0 2 = 1 . 0 X 1 0 11 mol 2 J.2

K 1 » K 2 K = 2 . 2 X 1 o7 mol 11

* * * * * * * * * * * Absorbance * * * * * * * * * T i t r e C L ] / 1 0“ 3 ME x p e r i m e n t a l K2> > K1 K > > K 1 2 Ml

1

1 0 . 3 6 5 0 . 3 6 5 0 . 3 6 5 0 02 0 . 3 8 5 0 . 3 7 2 0 . 3 9 2 0 . 3 0 0 . 1 53 0 . 4 0 4 0 . 3 8 5 0 . 4 1 8 0 . 6 0 0 . 3 04 0 . 4 2 3 0 . 401 0 . 4 4 2 0 . 9 0 0 . 455 0 . 4 4 0 0 . 4 1 9 0 . 4 6 4 1 . 20 0 . 616 0 . 4 5 8 0 . 4 3 8 0 . 4 8 5 1 . 50 0 . 767 0 . 4 8 8 0 . 4 6 9 0 . 5 1 6 2 . 0 0 1. 018 0 . 5 1 9 0 . 501 0 . 5 4 4 2 . 5 0 1 . 269 0 . 5 4 5 0 . 5 3 3 0 . 5 6 8 3 . 0 0 1 . 50

1 0 0 . 571 0 . 5 6 3 0 . 5 8 8 3 . 5 0 1 . 751 1 0 . 5 9 3 0 . 591 0 . 6 0 5 4 . 0 0 2 . 0 01 2 0 . 6 1 4 0 . 6 1 7 0 . 6 1 9 4 . 50 2 . 241 3 0 . 6 3 4 0 . 6 3 9 0 . 631 5 . 0 0 2 . 491 4 0 . 6 5 5 0 . 6 7 3 0 . 6 4 9 6 . 0 0 2 . 9 81 5 0 . 6 7 6 0 . 691 0 . 661 7 . 0 0 3 . 4 61 6 0 . 6 9 0 0 . 6 9 8 0 . 6 6 9 8 . 0 0 3 . 9 41 7 0 . 7 0 0 0 . 701 0 . 6 7 4 9 . 0 0 4 . 4 21 8 0 . 7 0 3 0 . 7 0 0 0 . 6 7 8 1 0 . 0 0 4 . 9 0

1 23

pH = 10 . 02 (1 - 17 x 10“ 3 M CHES) [FeTMPyP] = 9 . 3 5 3 x 10~4 M



3 - 1E x t i n c t i o n c o e f f i c i e n t s / 10 mol 1cm

Monomer Dimer Complex

0. 21 1 . 80 7 . 4 2

Computer c a l c u l a t e d cur v es :

AACM e 2 = 3 . 61 0x 1 0 mol 2 !

K >> K K . = 4 . 5 , n7 - 1 x 10 mol 11 2 1

* * * * * * * * * * *E x p e r i m e n t a l

Absorbance

K2>>K1

* * * * * * * * *

V >K2

T i t r e p i

C L ] T / 1 o" 3 M

1 0 . 3 3 0 0 . 3 3 0 0 . 3 3 0 0 02 0 . 3 3 7 0 . 331 0 . 3 4 2 0 . 3 0 0 . 113 0 . 3 4 3 0 . 3 3 4 0 . 3 5 5 0 . 6 0 0 . 2 24 0 . 351 0 . 3 4 2 0 . 3 7 4 1 . 1 0 0 . 4 05 0 . 3 7 3 0 . 3 6 2 0 . 4 0 6 2 . 0 0 0 . 7 26 0 . 3 9 3 0 . 3 9 0 0 . 4 3 8 3 . 00 1 . 077 0 . 4 1 7 0 . 4 2 0 0 . 4 6 5 4 . 0 0 1 . 42 .8 0 . 4 4 5 0 . 4 5 2 0 . 4 9 0 5 . 0 0 1 . 779 0 . 4 8 4 0 . 4 8 3 0 . 511 6 . 00 2 . 1 2

1 0 0 . 5 1 4 0 . 5 1 3 0 . 5 2 9 7 . 0 0 2 . 481 1 0 . 5 4 5 0 . 541 0 . 5 4 4 8 . 0 0 2 . 811 2 0 . 582 0 . 5 8 6 0 . 5 6 8 10 . 0 0 3 . 4 91 3 0 . 6 1 4 0 . 6 1 8 0 . 5 8 5 1 2 . 0 0 4 . 1 61 4 0 . 6 3 9 0 . 641 0 . 6 0 2 1 5 . 0 0 5 . 1 51 5 0 . 6 4 9 0 . 6 4 7 0 . 611 1 8 . 0 0 6 . 1 21 6 0 . 6 4 9 0 . 6 4 6 0 . 6 1 5 2 1 . 00 7 . 08

1 2 4

12

5

FIG U R E 1.17 S pectrophotometric titration with cyanide . pH 7.9-10.0

K, « K2 K, » K2

0 1 2 3 4 5 6 7i k cn j t / 10~3M

[PFe] = 1 x 10~3M Path length = 1 mm

1 . 2 . 8 . 3 . 3 . D i s c u s s i o n

The graphs i n F i g u r e 1 . 17 show t he e x p e r i m e n t a l

r e s u l t s ( d o t s ) and some computer ( a p p e n d i x 1 . 8 ) c a l c u l a t e d

l i n e s f o r p a r t i c u l a r v a l u e s o f 0 2 and K . I t i s assumed

t h a t e i t h e r K >> or t h a t >> , r e s p e c t i v e l y . T h a t

i s to say o n l y the two e x t r em e s a r e c o n s i d e r e d . The l i n e s

ar e not b e s t f i t t e d by t h e computer program , but t h e 0 2 o r

K v a l u e s wer e chosen t o g i v e a r e a s o n a b l e f i t .

The >> K. c u r v e more c l o s e l y f o l l o w s t h e d a t a f o r 2 1

pH 7 . 9 , pH 8 . 0 or pH 1 0 . 0 t han t he K >> K cu r v e . A

cur ve i n t e r m e d i a t e between t h e e x t r em es i s needed t o f i t

t he pH 9 . 0 d a t a . The v a l u e s o f 0 2 a r e c o n s i d e r a b l y l o w e r

than t he v a l u e s o b t a i n e d by m a g n e t i c t i t r a t i o n i n t he r ange

pH 7 . 2 t o pH 3 . 7 5 . The v a l u e s o f f?2 evaluated h e r e ,

12 10 - 2 2d e c r e a s e f rom 3 x 10 t o 3 . 6 x 10 mol 1 w i t h an

i n c r e a s e i n pH f rom 7 . 9 t o 10 . One p o s s i b l e e x p l a n a t i o n ,

i s t h a t w i t h i n c r e a s i n g pH , t h e s p e c i e s PFe(CNMOH)

becomes s i g n i f i c a n t . T h i s would a l t e r t he pH dependence o f

K' .

The s i t u a t i o n c ou ld be checked out by f o l l o w i n g t he

t i t r a t i o n u s i n g d i r e c t 1H NMR measurements . The i n t e g r a l s

o f t he v a r i o u s NMR s i g n a l s can be used to c a l c u l a t e t he

v a l u e o f P2 .

1 . 2 . 8 . 3 . A . Compar ison w i t h o t h e r work

F a r a g g y l e t a l ( 5 9 ) have c a r r i e d ou t s i m i l a r

s p e c t r o p h o t o m e t r i c t i t r a t i o n s under t h e f o l l o w i n g

c o n d i t i o n s- 3

pH 8 . 6 - pH 1 0 . 5 ( 2 x 1 0 M phosphat e or c a r b o n a t e )

[FeTMPyP] = 1 0 ~ 5 - 1 0 ~ 4 m o l l " 1

1 2 6

F a r a g g y l e t a l obser ved good i s o b e s t i c p o i n t s and

presumed t h a t a t l e a s t 95 l o f d i m er was p r e s e n t . Us ing

t he v a l u e o f d e t e r m i n e d h er e a t I = 0 . 3 0 m o l l 1 , l e s s

- 4 - 1t han 35 l d i m er i s c a l c u l a t e d f o r a 2 x 1 0 m o l l

s o l u t i o n o f FeTMPyP . An e q u i l i b r i u m c o n s t a n t K_ was5

d e f i n e d :

KgPFe-O-FeP + 4 CN ^ — j . 2 P F e ( CN) 2 + m OH

CPFe(CN) ] 2 . COH" ] mK = -----------------------------------7“ m = 2

C P F e - O - F e P ] . CCN]

F a r a g g y l e t a l do not mass b a l a n c e t h e i r e q u i l i b r i u m

e q u a t i o n f o r K_ , o m i t t i n g t h e t e r m "m OH " . T h i s means

t h a t K , as t h e y d e f i n e i t w i t h no COH ] m t e r m , i s pOH 5

dependent . T h e i r a n a l y s i s o f t h e v a r i a t i o n o f K_ w i t h

pOH , showed t h a t m = 2 . Th i s i s c o n s i s t e n t w i t h H^O or

n o t h i n g b e i ng c o o r d i n a t e d t o t he o u t e r a x i a l p o s i t i o n s o f

t h e d i m er . The v a l u e s o f K_ t a b u l a t e d a r e f o rDpOH = 0 ( t h a t i s COH ] = 1 . 0 ) , t h i s i s a l s o t h e pOH

i n d e p e n d e n t v a l u e o f K_ (as d e f i n e d h e r e ) .5G r a p h i c a l a n a l y s i s o f t h e i r r e s u l t s gave s l opes o f

4 . 2 ± 0 . 2 c o r r e s p o n d i n g f a i r l y w e l l w i t h t h e t h e o r e t i c a l

v a l u e o f 4 . 0 , f o r K ' >> . They t a k e t h i s t o i n d i c a t e

t h a t t he mono cyano complex i s h i gh s p i n , however t he

a u t h o r s do not c o n s i d e r t h a t a t t h e c o n d i t i o n s o f t h e i r

t i t r a t i o n t h e s t a b l e monomeric FeTMPyP i s PFe ( OH ) ('OH) .

The c o n d i t i o n >> K ’ i s c o n s i s t e n t w i t h t h e i n i t i a l

I = 0 . 1 1 m o l l - 1 , 2 5 ± 1 ° C

1 2 7

c y a n i d e i o n d i s p l a c i n g h y d r o x i d e and t he second c y a n i d e i o n

d i s p l a c i n g w a t e r , w i t h bot h p r o d u c t s be i ng low sp i n .

I t can be shown f rom t h e d e f i n i t i o n s o f QD and

t h a t

*2 " v / V Q0 / K W

- 8 - 1Using t h e v a l u e o f 3 . 5 6 x 10 m o l l ( I = 0 . 3 0 M)

f o r Qp d e t e r m i n e d h e r e and F a r a g g l ' s v a l u e o f

4 . 6 x 105 mol 11 f o r K_ , a v a l u e o f 1 . 3 x 1 0 13 mol 2 1 2 was5

c a l c u l a t e d f o r P2 . T h i s i s a b o ut a f a c t o r o f 10 l o w e r t han

t h e v a l u e s d e t e r m i n e d h e r e i n m a g n e t i c t i t r a t i o n s .

Under t h e c o n d i t i o n s o f t he s p e c t r o p h o t o m e t r i c

t i t r a t i o n s i n t h i s work a b o ut 60 l o f t h e FeTMPyP i s

c a l c u l a t e d t o be i n t h e d i m e r i c form . T h e r e f o r e t h e

g r a p h i c a l e v a l u a t i o n i s no t s t r i c t l y a p p r o p r i a t e , but i t

was a p p l i e d as a compa r i son t o F a r a g g l ' s e v a l u a t i o n . The

pH 7 . 9 and pH 8 . 0 d a t a gave c u r v e s w i t h s l o p e s r a n g i n g f rom

2 t o 4 . The pH 9 d a t a gave a s t r a i g h t l i n e o f s l o p e 2 . 3

and t he pH 10 . 0 d a t a gave a s t r a i g h t l i n e o f s l o pe 4 . 0 5 .

Thus o n l y t h e e v a l u a t i o n o f t h e pH 10 d a t a gave a s l o pe

c l o s e t o t h e t h e o r e t i c a l v a l u e o f 4 . 0 .

I t has been proposed ( 7 1 ) t h a t c y a n i d e b i nds t o

( F e T P P S ^ O i n a f a s t f i r s t s t e p , f o r m i n g a cyano p oxo

d i m e r which t hen d i s s o c i a t e s i n t o d i c y a n o monomers . Th i s

mechanism i s c o n s i s t e n t w i t h t h e b e h a v i o u r o f ( FeTMPyP^ O

obser ved h er e .

128

1 . 2 . 8 . 4 . T i t r a t i o n f o l l o w e d by H NMR

In o r d e r to g a i n more i n f o r m a t i o n about t h e s p i n

s t a t e s o f t h e FeTMPyP c y a n i d e complexes , a t i t r a t i o n was

f o l l o w e d by sca nn i ng t h e 1H NMR spec t rum . I n t h i s way

i n d i v i d u a l s p e c i e s wer e i d e n t i f i e d . The r e s u l t s were a l s o

e v a l u a t e d t o g i v e v a l u e s o f (3 and K * / K • An aqueous

FeTMPyP sample i n an NMR t ub e was t i t r a t e d w i t h a c y a n i d e

s o l u t i o n , u s i n g a m i c r o s y r i n g e .

NMR s p e c t r a l a s s i g n m e n t s can be made by r e f e r e n c e t o

t h e d a t a r e c o r d e d by G o f f and Morgan ( 72 ) .

Sample P y r r o l e H 2 3 CH3

0. 01 M FeTMPyP 0 . 1 M DC1

- 3

6 8 . 5 13 . 3 10 . 85 5 . 57

5 . 0 x 10 0 . 0 5 M KCN

- 3

M FeTPPS. ( CN ) „h 2 - 6 . 0 0 5 . 9 5 8 . 9 0

5 . 0 x 10 0 . 0 5 M KCN

M FeTCPP( CN) - 4 . 4 7 5 . 7 8 9 . 2 8

The 6 8 . 5 ppm r e s o n a n c e obser ved by G o f f and Morgan i s

h er e s h i f t e d d o w n f i e l d t o 74 ppm ( F i g u r e 1 . 1 8 ) . T h i s i s

p r esumably due to t h e c o o r d i n a t i o n o f f o r m a t e t o FeTMPyP i n

t h i s e x p e r i m e n t .

On a d d i t i o n o f c y a n i d e two new r es on anc es appear ed ,

a t - 1 8 . 9 5 and - 1 4 . 3 3 ppm 5 . G o f f amd Morgan r e c o r d e d no

spect r um f o r FeTMPyP(CN)_ . T h e i r F e T P P S . ( CN) 0 and2 4 2

FeTCPP( CN) s p e c t r a bot h show p y r r o l e p r o t o n resonances

u p f i e l d o f TMS a t - 6 . 0 0 and - 4 . 4 7 r e s p e c t i v e l y . By

compar i son , t h e u p f i e l d r e son ances o bs er ved h e r e are

129

FIGURE 1.18 T it r a t i o n of FeTMPyP w i t h pH3.75 c y a n i d e ,FOLLOWED BY 1H NMR

0.03M KCN

B » formate

Conditions: 9.72x10"3M FeTMPyP, pH 3-7 5 { 0.25m formate) , 35°C

1 3 0

a s s i g n e d t o t h e p y r r o l e p r o t o n s . S i nce t h e - 1 8 . 9 5 ppm

reson ance appear ed f i r s t i t i s a s s ig n ed to t he mono cyano

complex and t hus t h e - 1 4 . 3 3 ppm r es on anc e t o t h e d i cyano

complex .

The p y r r o l e p r o t o n s h i f t s f o r t h e mono and d i 'cyano

complexes a r e both sha rp compared to t he non c y a n i d e

complex and both a r e i n t h e same r e g i o n . T h i s i s

c o n s i s t e n t w i t h t h e e a r l i e r c o n c l u s i o n t h a t both complexes

ar e l ow s p i n .

The i n t e g r a l s o f t h e 74 , - 1 8 . 9 5 and - 1 4 . 3 3 ppm

r e son ances were used t o c a l c u l a t e t h e mole f r a c t i o n o f each

s p e c i e s .

7 4 ppmMole F r a c t i o n s

- 1 8 . 9 5 ppm 14 . 3 3 ppmCKCN]T / m o l l " 1

0 . 7 6 5 7 0 . 2 3 4 3 0 0 . 0 1 1 0 40 . 4 6 8 4 0 . 4 3 8 7 0 . 0 9 2 9 0 . 0 2 9 8 40 . 2 4 5 5 0 . 5 2 7 1 0 . 2 2 7 4 0 . 0 7 2 2 90. 1949 0 . 4 7 6 9 0 . 3 2 8 2 0 . 0 9 0 5 80 0 . 3 5 1 9 0 . 6481 0 . 2 3 3 2

A computer program ( a p p e n d i x 1 . 9 ) , was used t o

o b t a i n b e s t f i t t e d v a l u e s o f K ’ / K^ = 4 . 41 and

13 - 2 2(3 = 3 . 9 x 10 mol 1 f rom t h i s d a t a . I t i s not

p o s s i b l e f rom t h i s e x p e r i m e n t t o c o r r e c t e i t h e r o f t h e s e

r e s u l t s f o r b u f f e r c o o r d i n a t i o n t o FeTMPyP . The c u r v e s on

t h e graph i n F i g u r e 1 . 1 8 a r e t h e mole f r a c t i o n s c a l c u l a t e d

f rom t h e b e s t f i t p a r a m e t e r s .

1 3 1

D i s c u s s i o n

C o n s i d e r i n g t he i n a c c u r a c i e s i n meas ur ing t he

i n t e g r a l s , t h e f i t i s good . The i n t e g r a l s a r e

i n c r e a s i n g l y l e s s a c c u r a t e w i t h i n c r e a s i n g c y a n i d e

c o n c e n t r a t i o n . Th i s i s r e f l e c t e d i n t he graph , however no

s p e c i a l w e i g h t i n g was a t t e m p t e d .

In c o n c l u s i o n i t may be s a i d t h a t

1) c y a n i d e c o m p l e x a t i o n i s a two s t e p p r ocess

2 ) K, > K2

3) c y a n i d e exchange i s s l ow on t h e NMR t i m e s c a l e

Wi t h r e g a r d t o F e P r o t and c y a n i d e i n d DMSO ,6

Ye e t a l ( 7 3 ) a l s o drew t h e s e c o n c l u s i o n s and f rom

s u s c e p t i b i l i t y measurements t h e y showed t h a t t h e mono cyano

complex i s l ow sp i n .

132

1 . 2 . 8 . 5 . 1 . M a g n e t i c T i t r a t i o n s

Samples o f FeTMPyP were t i t r a t e d w i t h c y a n i d e a t

v a r i o u s pH us i ng d i f f e r e n t b u f f e r systems . The r e a c t i o n

was f o l l o w e d by m e a s u r i n g t he s u s c e p t i b i l t y u s i n g t he

Evans' method on a P e r k i n Elmer R32 NMR s p e c t r o m e t e r .

Va l ue s o f were d e t e r m i n e d and t h e e v a l u a t i o n s a r e

d i s c u s s e d .

1 . 2 . 8 . 5 . 2 . R e s u l t s

pH = 7 . 2 0 ( 0 . 1 2 5 M p h o s p h a t e )

T i t r a n t = 0 . 1 1 5 1 M KCN

I n i t i a l [FeTMPyP] = 10 . 01 x 10~3 M

IICMCO. 2 . 5 4 x 1 0 1 * mol 2 1 2

One s t a n d a r d d e v i a t i o n i n m a g n e t i c moment = 0 . 044

T i t r e Seon Af M a g n e t i c moment [ l i a a n d ]p i Hz Hz Emp C a l c [ p o r p h y r i n ]

1 0 17 . 43 12 . 8 4 4 . 09 4 . 0 9 02 5 . 0 16. 91 1 2 . 3 3 4 . 0 4 4 . 03 0 . 1 43 10 . 0 1 6 . 5 8 12 . 01 4 . 01 3 . 9 7 0 . 2 94 15 . 0 15 . 83 1 1 . 2 7 3 . 91 3 . 9 0 0 . 4 35 2 0 . 0 15 . 53 1 0 . 9 8 3 . 8 8 3 . 8 4 0 . 5 76 2 5 . 0 14 . 58 9 . 9 4 3 . 71 3 . 7 6 0 . 7 27 3 0 . 0 1 4 . 3 2 9 . 7 9 3 . 71 3 . 6 8 0 . 8 68 3 5 . 0 13. 41 8 . 8 9 3 . 5 5 3 . 5 9 1. 019 4 0 . 0 12 . 97 8 . 4 6 3 . 4 9 3 . 4 8 1 . 1 5

1 0 4 5 . 0 1 2 . 6 8 8 . 1 8 3 . 4 5 3 . 3 7 1 . 291 1 5 0 . 0 1 1 . 3 0 6 . 81 3 . 1 6 3 . 2 4 1 . 4 41 2 5 5 . 0 1 1 . 0 8 6 . 60 3 . 1 3 3 . 1 0 1 . 5 81 3 6 0 . 0 1 0 . 0 2 5 . 55 2 . 8 9 2 . 9 4 1 . 7 21 4 6 5 . 0 9 . 71 5 . 2 5 2 . 8 2 2 . 7 9 1 . 8 71 5 7 0 . 0 9 . 2 2 4 . 7 7 2 . 7 0 2 . 6 8 2 . 011 6 7 5 . 0 8 . 7 6 4 . 3 2 2 . 5 9 2 . 6 4 2 . 1 61 7 8 0 . 0 8 . 8 8 4 . 4 5 2 . 64 2 . 6 2 2 . 3 01 8 8 5 . 0 8 . 8 6 4 . 4 4 2 . 6 5 2 . 6 2 2 . 4 41 9 9 0 . 0 8 . 4 5 4 . 04 2 . 5 4 2 . 61 2 . 5 920 9 5 . 0 8 . 81 4 . 41 2 . 6 7 2 . 61 2 . 7 32 1 100 . 0 8 . 6 7 4 . 28 2 . 6 4 2 . 61 2 . 8 7

No FeTMPyP 4 . 59 Hz+ 100 p i 4 . 39 Hz

1 3 3

T i t r a n t = 0 . 1 0 6 0 M KCN

I n i t i a l [FeTMPyP] = 1 0 . 0 5 x 10~3 M

14 - 2 2P2 = 2 . 0 9 x 10 mol 1

pH = 4 . 5 0 ( 0 . 2 5 M a c e t a t e )


T i t r e Seon & £ M a g n e t i c moment [ l i a a n d 1p i H z H z Emp Ca lc C p o r p h y r i n ]

1 0 3 1 . 65 2 6 . 6 6 5 . 89 5 . 8 9 02 5 . 0 3 1 . 38 2 6 . 3 7 5 . 89 5 . 7 6 0 . 1 33 10. 0 2 9 . 4 8 2 4 . 4 6 5 . 71 5 . 64 0 . 264 15 . 0 2 7 . 4 8 2 2 . 4 4 5 . 5 0 5. 51 0 . 4 05 20 . 0 2 6 . 6 2 2 1 . 57 5 . 4 3 5 . 4 0 0 . 5 36 3 0 . 0 2 3 . 9 2 18 . 84 5 . 1 3 5 . 17 0 . 7 97 4 0 . 0 2 1 . 62 16 . 51 4 . 86 4 . 9 5 1 . 0 58 50 . 0 2 0 . 5 8 15 . 44 4 . 7 5 4 . 74 1 . 3 29 6 0 . 0 19 . 28 1 4 . 1 0 4 . 59 4 . 5 5 1 . 5 8

1 0 60 . 0 18 . 87 1 3 . 6 9 4 . 52 4 . 5 5 1 . 5 81 1 7 0 . 0 17 . 77 1 2 . 5 6 4 . 3 8 4 . 3 7 1 . 8 51 2 8 0 . 0 16 . 34 1 1 . 1 0 4 . 1 6 4. 21 2 . 1 11 3 9 0 . 0 15 . 58 10 . 31 4 . 0 5 4 . 0 6 2 . 3 71 4 100 . 0 14 . 89 9 . 5 9 3 . 9 5 3 . 9 2 2 . 6 41 5 120 . 0 13 . 35 8 . 0 2 3 . 6 8 3 . 69 3 . 1 61 6 140 . 0 12 . 58 7 . 2 2 3 . 5 6 3 . 51 3 . 691 7 160 . 0 11 . 69 6 . 3 0 3 . 3 9 3 . 37 4 . 2 21 8 180 . 0 11 . 17 5 . 7 5 3 . 2 9 3 . 2 6 4 . 7 51 9 2 0 0 . 0 10 . 37 4 . 9 2 3 . 1 0 3 . 1 7 5 . 2 7

No FeTMPyP 4 . 9 9 Hz+ 100 p i 5 . 3 0 Hz+ 200 Ml 5 . 4 5 Hz

1 3 4

T i t r a n t = 0 . 4 5 6 4 M KCN

I n i t i a l [FeTMPyP] = 9 . 9 9 9 x 10“ 3 M

pH = 3 . 7 5 ( 0 . 2 5 M p o t a s s i u m f o r m a t e )

14 - 2 2P2 = 1 . 6 x 10 mol 1


T i t r e S eon Af M a g n e t i c moment [ l i a a n d ]p i Hz Hz Emp Ca lc C p o r p h y r i n ]

1 0 3 3 . 5 5 2 7 . 7 6 6 . 0 2 5 . 9 5 02 5 . 0 3 0 . 8 7 2 5 . 0 9 5 . 7 6 5 . 6 4 0 . 5 73 10 . 0 27 . 50 2 1 . 74 5 . 4 0 5 . 3 7 1 . 144 15 . 0 2 5 . 5 7 1 9 . 8 2 5 . 1 8 5 . 1 4 1. 715 2 0 . 0 2 3 . 9 7 18 . 23 5 . 0 0 4 . 9 3 2 . 2 86 2 5 . 0 2 2 . 4 0 1 6 . 6 8 4 . 81 4 . 7 5 2 . 857 3 0 . 0 20 . 55 14 . 84 4 . 57 4 . 5 9 3 . 4 28 4 0 . 0 1 8 . 5 0 12 . 8 2 4 . 29 4 . 3 3 4 . 569 5 0 . 0 1 6 . 9 5 1 1 . 3 0 4 . 08 4 . 1 2 5 . 71

1 0 6 0 . 0 1 5 . 5 8 9 . 9 5 3 . 8 7 3 . 9 4 6 . 8 51 1 8 0 . 0 1 4 . 2 0 8 . 6 3 3 . 6 8 3 . 69 9 . 1 31 2 100 . 0 12 . 69 7 . 1 7 3 . 42 3 . 51 11 . 41

No FeTMPyP 5 . 7 9 Hz+ 200 p i 5 . 5 2 Hz

1 3 5

Mag

neti

c m

omen

tpH 7.20(0.125M phosphate)

F I G U R E 1 . 19 Ma g n e t i c t i t r a t i o n of FeTMpy p w i t h

tFeP) = 0.01 M # 3 5°C

1.5

IKC N ) / l FePl

Mag

neti

c m

omen

t

CYANIDE . pH 7 -20- 3.75

2.5

pH^ .5 0 (0.25M acetate)

= 2.09 x 10u mol-212

2 3

i K C N l / lF e P ]

137

FIGURE 1.19 Co n t i n u e d

pH 3.75 (0.25 M formate)

iFeP) = 0.01 M. 3 5°CSt

anda

rd

Dev

iati

on

0- 08 5

0 . 0 8 0 -

0.075-

0. 0 7 0 -

0 .065-

0.06 0+- *13

6X*9

logi0Keff*11 *9 *7

1 . 2 . 8 . 5 . 3 . D i s c u s s i o n

Using a computer program ( a p p e n d i x 1 . 7 ) t h e v a l u e s o f

(3 and K^/ l<2 were v a r i e d t o g i v e t h e f o l l o w i n g b e s t

f i t t e d r e s u l t s f o r t he pH 7 . 2 0 and pH 4 . 5 0 d a t a . Only t he

v a l u e o f was v a r i e d f o r t h e pH 3 . 7 5 d a t a , t h i s i s

e x p l a i n e d be l ow .

T a b l e 1 . 9 0 2 v a l u e s f o r c o o r d i n a t e d c y a n i d e

C o n d i t i o n s Ki / K 2 P2 / mo l 2 i 2

pH 3 . 7 5 , 0 . 25 M 4. 41 1 . 6 X 1 0 1 4pota s s ium f o r m a t e

pH 4 . 5 0 , 0 . 2 5 M a c e t a t e 0 . 591 2 . 0 9 X 1 0 U

pH 7 . 2 0 , 0 . 1 2 5 M 0 . 5 5 4 2 . 5 4 X 1 0 14pot a s s ium phospha t e

The e f f e c t o f b u f f e r c o o r d i n a t i o n i s c o r r e c t e d f o r

us i ng t h e e x p r e s s i o n P2 = 0 2 * \ /QD Ke f f ( a p p e n d i x 1 . 7 ) .

The v a l u e o f K „ „ can be c a l c u l a t e d f rom t h e d i f f e r e n c e o fe f f

t he i n i t i a l m a g n e t i c moment and t h e e f f e c t i v e h i gh sp i n

v a l u e o f 5 . 9 5 ( a p p e n d i x 1 . 7 ) . However f o r pH 3 . 7 5 ( 0 . 2 5 M

f o r m a t e ) b u f f e r t h e two m a g n e t i c moment v a l u e s a r e v e r y

c l o s e t o g e t h e r and so K _ „ can not be e v a l u a t e d i n t h i se f f

w a y .

B u f f e r c o o r d i n a t i o n a l wa y s d e c r e a s e s K be low QD , - 8so K „„ < 3 . 5 6 x 10 M . The v a r i a t i o n i n s t r e n g t h o f e f f

b u f f e r c o o r d i n a t i o n i s e x p e c t e d t o g i v e t h e f o l l o w i n g

v a r i a t i o n i n K :e f f

phospha t e << a c e t a t e f o r m a t e

1 3 8

The r e q u i r e d v a l u e o f K „ „ i s thus above the v a l u e i ne f t-9a c e t a t e b u f f e r , l e K 1. 31 x 10 M

In o r d e r to r educ e t he number o f v a r i a b l e s to two a

v a l u e o f 4 . 41 was t a k e n f o r K^/Kg . Th i s v a l u e was

d e t e r m i n e d under t he same c o n d i t i o n s us i ng d i r e c t 1H NMR

measurements . The two d e t e r m i n a t i o n s o f |3 a t

pH 3 . 7 5 ( m a g n e t i c moment d a t a and 1H NMR d a t a ) a r e not

e q u a l l y s e n s i t i v e to t h e v a l u e o f K ’ / K^ * Th i s i s

d i s c u s s e d l a t e r .

The pH 3 . 7 5 m a g n e t i c moment d a t a was e v a l u a t e d a t

v a r i o u s v a l u e s o f K . The r ange o f K „ used i s f rom t h ee f f e f f

v a l u e a p p r o p r i a t e f o r pH 7 . 2 0 , 0 . 1 2 5 M phospha t e b u f f e r t o

t h e maximum v a l u e .

T a b l e 1 . 10 E v a l u a t i o n O f ^ 2 as a f u n c t i o n o f Ke f f

Ke f f /M 109 Ke f f Std De vn

10 13m o l " 2 l 2

6 . 6 3 x I Q ’ 131 ° ' ] n

- 1 2 . 1 8 3 . 0 5 0 0 . 06481 . 0 X - 1 1 . 0 3 . 0 4 3 0 . 06501 . 0 X o01 3 . 0 3 8 0 . 065 11. 31 X 10 .®

COCOCO1 3 . 0 3 9 0 . 06565 . 0 X

o o

o o

1 1

1 1

CD C

O CD

a - 8 . 3 0 3 . 0 2 6 0 . 06781 . 0 X - 8 . 0 3 . 0 1 5 0 . 07041 . 8 X - 7 . 7 5 2 . 9 9 3 0 . 07503 . 56 X - 7 . 4 5 2 . 9 3 6 0 . 0852

3I t can be seen t h a t f o r t h e 50 x 10 range o f K „e f f

chosen , t h e b e s t f i t t e d v a l u e o f (3 o n l y v a r i e s by

3 . 7 X . T h i s i s because under t h e s e c o n d i t i o n s t h e r e i s

v e r y l i t t l e d i m er p r e s e n t . Even w i t h o u t s p e c i f y i n g we

13 - 2 2may c on c l u d e t h a t {3 = 3 . 0 x 10 mol 1 . C o n s i d e r i n g

t h e e q u a t i o n (3. = 0 ' • / q" / K 7 7 , t h e v a l u e o f 0O2 2 v D e f f 2

139

c a l c u l a t e d w i l l v a r y m a r k e d l y o ve r t h i s r ange o f K . . .e f f

The s t a n d a r d d e v i a t i o n o f t he c a l c u l a t e d f rom t he

e x p e r i m e n t a l m a g n e t i c moments i s a measure o f t he c l o s e n e s s

o f f i t and hence i n d i c a t e s t he a c c u r a c y o f t he (3* and K2 e f f

v a l u e s used . The graph o f s t a n d a r d d e v i a t i o n ve r s us l o g

K „ . ( F i g u r e 1 . 1 9 ) shows no minimum . T h i s means t h a t a e f f

b e s t f i t t e d v a l u e o f P2 can not be o b t a i n e d by v a r y i n g

Ke f f * Us ing t h e v a l u e o f ^e f f a PPr ° P r i a t e f o r a c e t a t e

b u f f e r , a v a l u e o f 5 . 2 i s c a l c u l a t e d f o r J Q ^/K „ _ . Th i se f f

g i v e s p^ = 1 . 6 x 1 0 1 mol ^ 1 ^ .

I t i s p o s s i b l e t o o b t a i n a check on t h e v a l u e o f t he

correction factor /Q_/K 77 :V D e f f

From t h e d e f i n i t i o n s o f p 2 and p^

K K1 2

K 1 K '- 1. L 2j

. p2

From t h e s p e c t r o p h o t o m e t r i c d a t a o b t a i n e d under t h e

same c o n d i t i o n s

> 1

3 . 2

T h i s i s c o n s i s t e n t w i t h t h e v a l u e o f 5 . 2 used i n t h e

above e v a l u a t i o n .

No c o n s i s t e n c y i s e x p e c t e d between t h e K ‘ / v a l u e s

f o r t h e d i f f e r e n t c o n d i t i o n s . The p^ v a l u e s show

r e a s o n a b l e agr ee ment , t h e v a l u e f o r pH 3 . 7 5 p resu ma bl y

K1 / K = 3 . 2

We know t h a t K „ / K ’ 2 2

So P2 > 3 . 2 x P2

Hence / Q / K 77 > V D e f f

140

b e i n g t he l e a s t a c c u r a t e . For pH 7 . 2 0 t he graph c l e a r l y

shows t h a t i t r e q u i r e s two e q u i v a l e n t s o f c y a n i d e t o

c om p l e t e t h e r e a c t i o n .

The m a g n e t i c t i t r a t i o n d a t a i s f u r t h e r e v i d e n c e f o r

t he low sp i n n a t u r e o f t h e FeTMPyP mono cyano complex . I t

i s n e c e s s a r y t o presume both l ow sp i n mono and d i cyano

FeTMPyP i n o r d e r t o f i t an a de q u a t e cur ve t h r o u gh t he

d a t a .

The f i n a l m a g n e t i c moment o f 2 . 61 i s s i g n i f i c a n t l y

h i g h e r than t he v a l u e s f o r t h e complexes w i t h n i t r o g e n o u s

l i g a n d s . Bis cyano F e I r i p r o t o has a m a g n e t i c moment o f

2 .1 (73 ) .

1 4 1

The r e s u l t s o b t a i n e d f rom NMR measurements and

some r e s u l t s o b t a i n e d f rom a bs o rb an ce measurements can no t

be c o r r e c t e d f o r b u f f e r c o o r d i n a t i o n , so K ' v a l u e s ar e

compared .

1) Absorbance measurements

1 . 2 . 8 . G . C o m p a r i s o n o f c v a n o c o m p l e x f o r m a t i o n c o n s t a n t s

PH A / nm k ; C o n d i t i o n s

3 . 7 5 560 1 . 4 X 1 o7 0 . 2 5 M of o r m a t e , 3 4 ± 2 C

oin 565 1 . 0 x 1 o 7 0 . 2 5 M oa c e t a t e , 34 C

7 . 2 0 570 lA If X 1 o 5 0 . 1 2 5 M phosphat e , 33±2 ° c

2) S u s c e p t i b i l i t y mea s u r ement s

pH / m° l - 2 i 2 K ‘ / m o l" 1i C o n d i t i o n s

3 . 7 5 3 . 0 4 x 1 0 13 1 . 1 9 x 1 o7 * 0 . 2 5 M f o r m a t e , 3 5 ° C

4 . 5 0 4 . 0 0 x 1 0 13 4 . 8 6 x 1 o6 0 . 2 5 M a c e t a t e , 3 5° C

7 . 2 0 1 . 1 0 X 1 0 12 7 . 8 0 x 1 o5 0 . 1 2 5 M phosphat e , 3 5° C

* The v a l u e o f /K^ used t o c a l c u l a t e t h i s v a l u e was

d e r i v e d f rom t h e d i r e c t 1H NMR d a t a .

3 ) 1 H NMR measurements

pH = 3 . 7 5 , 0 . 25 M f o r m a t e , 3 5 °C

P2 = 3 . 9 0 x 1 0 13 " 2 2 mol 1 = 1. 31 x 10 7 m o l " 11

For a g i v e n s e t o f c o n d i t i o n s , t he v a l u e s o f K * are

a l l o f t h e same o r d e r o f m a gn i t ude . Th i s c o n s i s t e n c y

between t h e d i f f e r e n t t e c h n i q u e s used backs up t h e v a l i d i t y

o f t h e r e s u l t s .

1 4 2

Both s e t s o f Kj v a l u e s show t h e same v a r i a t i o n w i t h

b u f f e r . The more 3 t r o n g l y t h e b u f f e r c o o r d i n a t e s t he l o w e r

t h e v a l u e o f K ’ .

The v a l u e o f K^/K^ has a marked e f f e c t on t h e f i t

o f t h e c a l c u l a t e d to t h e e x p e r i m e n t a l d a t a f o r t h e d i r e c t

1H NMR measuremets . T h i s i s because t he c o n c e n t r a t i o n s o f

both c y a n i d e complexes a r e measured d i r e c t l y . The

e v a l u a t i o n o f t h e s u s c e p t i b i l i t y measurements made under

t h e same c o n d i t i o n s i s r e l a t i v e l y i n s e n s i t i v e t o t h e v a l u e

o f K^/K^ t a k e n . T h i s i s because an o v e r a l l

s u s c e p t i b i l i t y i s measured and t h e c y a n i d e complexes a r e

r e a s o n a b l y assumed t o have t h e same m a g n e t i c moment .

The most r e l i a b l e d e t e r m i n a t i o n o f K.. i s1

4 . 5 x 10 7 mol 1 1 ( s p e c t r o p h o t o m e t r i c ) and t h e most r e l i a b l e

14 - 2 2d e t e r m i n a t i o n o f i s 2 . 3 x 10 mol 1 , be i ng t he

a v e r a g e o f t h e pH 4 . 5 and pH 7 . 2 0 m a g n e t i c t i t r a t i o n

r e s u l t s .

The c y a n i d e c o o r d i n a t e s v e r y much more s t r o n g l y t han

t h e n i t r o g e n l i g a n d s s t u d i e d h e r e . Th i s i s c o n s i s t e n t w i t h

t h e t o x i c i t y o f c y a n i d e t o b i o l o g i c a l systems c o n t a i n i n g

i r o n p o r p h y r i n s .

The e v i d e n c e f o r bot h mono and d i c y a n o complexes o f

Fe* * * TMPyP , b e i n g l ow s p i n i s :

1 ) s i m i l a r i t y o f t h e i r v i s i b l e a b s o r p t i o n s p e c t r a

2) s i m i l a r i t y o f t h e i r 1H NMR s p e c t r a

3) f i t o f t h e c a l c u l a t e d c u r v e t o t h e m a g n e t i c t i t r a t i o n

d a t a

4) K ' > K ' a t l ow pH

1 4 3

The v a l u e s o f f rom t h e l i t e r a t u r e d i f f e r i n t h e

c o n d i t i o n s under which t h e y w e re d e t e r m i n e d and t h e y a r e

u n c o r r e c t e d f o r t h e e f f e c t o f b u f f e r c o o r d i n a t i o n . The

v a l u e s d e t e r m i n e d her e by m a g n e t i c t i t r a t i o n were made

under c o n s i s t e n t c o n d i t i o n s and have been c o r r e c t e d f o r

b u f f e r c o o r d i n a t i o n . I t i s a measure o f t h e v e r s a t i l i t y o f

t h e m a g n e t i c t i t r a t i o n i n aqueous s o l u t i o n t h a t t h e p^

v a l u e s range o v e r a f a c t o r o f 1 0 1 0 .

1 . 2 . 9 . S u m m a r y o f J3.2 v a l u e s

T a b l e 1. 11 p^ v a l u e s by m a g n e t i c t i t r a t i o n

L i gand - 2 2P2 /mol 1 *

KF 1 .93 x 1 0 4

1 - H i s t i d i n e 6 . 0 0

inoX

I m i d a z o l e 2 . 6 5 X o CD

1 m e t h y l i m i d a z o l e 5 . 1 2 x 1 0 6

4 m e t h y l i m i d a z o l e 7 . 8 8 X o CD

2 m e t h y l i m i d a z o l e v* 4 . 4

inoX t

KSCN 1 . 2 x 1 o 6

DMAP XCNJ-J-s 1 0 1 0 t

KCN 2 . 3 X 1 0 1 4 *

* I = 0 . 3 0 M , 0 . 1 2 5 M p h o s p h a t e , 35°C

t Poor computer f i t t o d a t a

$ Average o f two v a l u e s a t pH 4 . 5 0 and pH 7 . 2 0

1 4 4

1 . 2 . 1 0 . F e 1 I m-TMPvP

1 . 2 . 1 0 . 1 . S y n t h e s i s

The f o r m a t i o n o f Fe**TMPyP was f o l l o w e d

s p e c t r o p h o t o m e t r i c a l l y . H e a t i n g TMPyP w i t h a f e r r o u s s a l t

was done a t pH 3 ( t a r t r a t e b u f f e r ) t o avo id p r e c i p i t a t i o n

o f f e r r o u s h y d r o x i d e . I f t h e pH i s reduced to be l ow 2 . 5

t h en a p p r e c i a b l e amounts o f t h e d i p r o t o n a t e d TMPyP ( w i t h+

a l l p y r r o l e s c o o r d i n a t e d to H ) w i l l form . T h i s w i l l s lowI I - 3down t h e f o r m a t i o n o f Fe TMPyP . A 10 M TMPyP s o l u t i o n

i n a 1 mm pa t h l e n g t h c e l l was purged w i t h argon and an

oxygen f r e e f e r r o u s s o l u t i o n was i n j e c t e d . The c e l l was

h e a t ed f o r a t o t a l o f t h r e e hours and t h e spec t rum was

scanned ( 700 - 500 nm) a t v a r i o u s s t ages . The f i r s t few

s p e c t r a showed i s o b e s t i c p o i n t s . but sub sequent s p e c t r a

d e v i a t e d f rom t h e s e . T h i s i n d i c a t e d d e c o m p o s i t i o n o f t he

F e I I TMPyP .

A d d i t i o n o f a s c o r b i c a c i d g e n e r a t e d t h e Fe ^ T MPy P

spe ct r um ( 4 5 , 7 4 ) , w i t h a A o f 562 nm . H a r r i s andmax

Toppen ( 74 ) have s t u d i e d t h e k i n e t i c s and mechanism o f the

a s c o r b i c a c i d r e d u c t i o n . B u b b l i n g oxygen t h r o u g h t he

s o l u t i o n a t t h i s s t a g e caused an a b s o r p t i o n t a i l i n g s t e e p l y

i n t o t h e UV , i n d i c a t i n g d e c o m p o s i t i o n .

A t t e m p t s t o produce samples o f F e I I m-TMPyP i n an NMR

t ube were made by two a pp ro aches .

A n a e r o b i c h e a t i n g o f TMPyP w i t h a f e r r o u s s a l t a t

pH 2 . 5 ( s u l p h a t e b u f f e r ) d i d no t work , p r esu ma bl y because

t h e Fe**TMPyP so produced decomposes a t e l e v a t e d

t e m p e r a t u r e s .

1 4 5

Reducing t he f e r r i c p o r p h y r i n by add ing s o l i d Na S.O.Z 2to an argon purged NMR t u b e was more p r o m i s i n g but i t was

not p o s s i b l e t o g e t r e p r o d u c i b l e r e s u l t s . T h i s i s p r o b a b l y

due t o oxygen l e a k i n g i n as t h e d i t h i o n i t e was added . One

o f t he b e t t e r r e s u l t s i s r e p r o d u c e d be low . The i n i t i a l

m a g n e t i c moment o f 4 . 61 i s s l i g h t l y l o we r than the e x p e c t e d

sp i n o n l y v a l u e o f 4 . 9 f o r h i g h sp i n f e r r o u s i o n . The

f i n a l m a g n e t i c moment o f about 1 .3 i s more than can be

account ed f o r by t e m p e r a t u r e i n d e p e n d e n t pa r ama gne t i sm i n a

spi n p a i r e d Fe * * complex . These d e v i a t i o n s a r e c o n s i s t e n t

w i t h t h e p r e s e n c e o f some f e r r i c i o n .

1 . 2 . 1 0 . 2 . R e s u l t s : t i t r a t i o n w i t h i m i d a z o l e

pH = 6 .5 ( 0 . 1 M P I P E S )

T i t r a n t = 1 . 4 6 9 M I m i d a z o l e

I n i t i a l [FeTMPyP] = 10 . 7 x 1 0 ~ 3 M

I n i t i a l m a g n e t i c moment ( F e * * * ) = 4 . 7 7

T i t r e Ml

S h i f tHz

AfHz

M a g n e t i cmoment

[ I m i d a z o l e 1 [ P o r p h y r i n ]

1 0 2 0 ,. 67 1 7 ,. 42 4 ,. 6 1 02 1 1 7 . 49 1 4 ,. 2 1 4 . 1 7 0 .343 2 1 4 . 58 1 1 ,.27 3 ,. 72 0 ,. 694 3 1 3 . 50 1 0 ,. 1 6 3 . 54 1 ,. 035 4 1 0 ,. 89 7 ..52 3 ,. 05 1 ,.376 5 8 ,. 67 5 ,. 27 2 .55 1 ,.727 6 7 .. 6 1 4 ., 1 8 2 ,. 28 2 ., 068 7 6 ,.94 3 ,.48 2 . 08 2 ,.409 8 6 ,.36 2 ., 87 1 ,, 89 2 ., 75

1 0 9 6 ,. 25 2 ,. 7 3 1 ,. 85 3 .. 091 1 1 0 6 .. 1 4 2 ., 59 1 ., 80 3 ., 431 2 1 5 5 ,.44 1 ..74 1 ..48 5 .. 1 51 3 2 0 5 .,36 1 ., 5 1 1 .,39 6 ., 8 61 4 25 5 .. 2 2 1 .. 2 2 1 ,. 26 8 ..581 5 30 5 .,33 1 .,38 1 .,35 1 0 .,30

No FeTMPyP 3 . 25 Hz30 p i 4 . 1 5 Hz

1 4 6

FIGURE 1.20 Magnetic titration of • Fe11 TMPyP with imioazole

5-On

A. 0-

Z 3.0-<Dccn

2 . 0 -

1. 0-0 1 2 3 4 5 6 7 8 9

(Imidazolel/lFeP)10 11

pH = 6.5 (0.1 M PIPES)

I n i t i a l magnetic moment (Fe1” ) = 4.77

[FePl = 0.01 M. 35°C

1 47

1 . 2 . 1 0 . 3 . O t h e r w o r k

F l e i s c h e r and F e r r a ( 7 5 ) have used hydrogen and a

p a l l a d i u m c a t a l y s t to r e d uc e F e I I I TMPyP . U n f o r t u n a t e l y i t

i s not d e s i r a b l e to have f i n e l y d i v i d e d p a l l a d i u m i n an NMR

sample .

F a r a g g l e t a l ( 7 6 ) have r educed F e* * * p - T MP y P w i t h

f a s t e l e c t r o n s f rom a p u l s e r a d i o l y s i s system . Pu lses o f

50 t o 1500 ns gave r a d i c a l c o n c e n t r a t i o n s o f 5 x 10 t o

- 52 . 4 x 10 M . The e f f e c t o f a b s o r b i n g f a s t e l e c t r o n s i n

w a t e r i s d e s c r i b e d by

H2 0y\/v/^-~.e~ ( aq) , H* , * OH . , H3 0 +

In argon s a t u r a t e d n e u t r a l s o l u t i o n s o f Fe* * * TMPyP

and h i gh c o n c e n t r a t i o n s o f t - b u t y l a l c o h o l t h e ’ OH and H*

r e a c t w i t h t h e t - b u t y l a l c o h o l t o y i e l d t h e r e l a t i v e l y

u n r e a c t i v e h y d r a t e d e l e c t r o n e ( aq) . The e ( aq) i s thus

t h e o n l y r e m a i n i n g s p e c i e s , wh ich r educes t h e Fe* * * TMPyP .

F e I I TMPyP has been produced e l e c t r o l y t i c a l l y

( 4 5 , 7 7 - 8 0 ) i n low c o n c e n t r a t i o n s and has been shown ( 7 7 ) to

r e du c e oxygen t o w a t e r v i a a m u l t i s t e p mechanism . i s

produced as an i n t e r m e d i a t e , wh ich a l s o s l o w l y

i r r e v e r s i b l y o x i d i s e s Fe* *TMPyP . The r e a c t i o n k i n e t i c s o f

11Fe TMPyP w i t h 0 2 have been i n t e r p r e t e d ( 7 6 ) as i n d i c a t i n g

t h e f o r m a t i o n o f a p pe r oxo f e r r i c d i m e r . A t o l u e n e

s o l u b l e f e r r o u s p o r p h y r i n ( 0 1 ) gave r i s e t o a p per oxo

f e r r i c d i m e r on r e a c t i o n w i t h C>2 a t - 8 0 ° C .

1 48

1 . 2 . 1 1 . E x p e r i m e n t a l

1 . 2 . 1 1 . 1 . F l u o r i d e t i t r a t i o n f o l l o w e d bv ESR

S u c c e s s i v e amounts o f e t h y l e n e g l y c o l were added to a

- 3 I I I1 . 0 x 10 M Fe TMPyP / 1 M KF aqueous s o l u t i o n . The ESR

spect r um showed improvement s i n r e s o l u t i o n up to 20 l

e t h y l e n e g l y c o l . T h i s i s due t o t h e i mproved g l a s s f o r mi n g

p r o p e r t i e s i n t h e p r e s e n c e o f p o l y a l c o h o l s .

- 3 I I IA 5 . 0 x 10 M Fe TMPyP ( 400 p i ) s o l u t i o n i n an ESR

t ube was t i t r a t e d w i t h aqueous KF v i a a m i c r o l i t r e

s y r i n g e . Both s o l u t i o n s were 0 . 1 2 5 M i n pH 7 . 2 phopsphate

and 10 l ( v / v ) i n e t h y l e n e g l y c o l . A f t e r each a d d i t i o n the

s o l u t i o n was co o le d i n l i q u i d n i t r o g e n and t h e ESR spect rum

was r e c o r d e d .

T i t r a n t 1 M KF , [FeTMPyP] = 5 . 0 0 x 1 0 " 3 m o l l 1

T i t r e / p l ~ | 0 1 3 6 1 0 2 0C KF ] / 1 0 " 3 M | 0 2 . 4 9 7 . 4 4 14 . 8 2 4 . 4 47 . 6

T i t r a n t 5 M KF , [FeTMPyP] = 4 . 91 x 10~ m o l l "

T i t r e / M-3 J 0 2 4 8 20[ KF] / 10 3 M | 0 2 4 . 9 4 9 . 5 9 8 . 0 238

1 . 2 . 1 1 . 2 . S o e c t r o p h o t o m e t r i e c y a n i d e t i t r a t i o n

p H 3 . 7 5 ^ 7 . 2

2 ml o f s o l v e n t s o l u t i o n was p i p e t t e d i n t o a 1 cm

pat h l e n g t h c e l l . S o l i d FeTMPyP was added and t he c e l l was

s e a l e d w i t h a S u b a - s e a l . T h i s s o l u t i o n was t i t r a t e d w i t h a

KCN s o l u t i o n u s i n g a m i c r o s y r i n g e . The a bs or bance was

measured a f t e r each such a d d i t i o n .

1 4 9

The c o n c e n t r a t i o n o f FeTMPyP was c a l c u l a t e d f rom t h e

f i n a l abs or bance a t 571 nm . A P e r k i n Elmer 551

s p e c t r o p h o t o m e t e r was used i n a l l bu t t h e pH 7 . 2 t i t r a t i o n

a t G 3 5 nm , where a H i t a c h i P e r k i n Elmer 124

s p e c t r o p h o t o m e t e r was used .

The KCN t i t r a n t s o l u t i o n was a d j u s t e d t o t he r e q u i r e d

pH by add ing aqueous n i t r i c a c i d w h i l s t s t i r r i n g . S i n ce

a d j u s t i n g h i gh c o n c e n t r a t i o n KCN s o l u t i o n s to pH 3 . 7 5

causes much e v o l u t i o n o f HCN , an i n i t i a l excess o f KCN was

used . Th i s a l s o n e c e s s i t a t e s t h e use o f a good fume

cupboard .

1 . 2 . 1 1 . 3 . S p e c t r o p h o t o m e t r i c c y a n i d e t i t r a t i o n

p H 7 . 9 10 . 0

For each t i t r a t i o n two s o l u t i o n s , A and B , were

made . For s o l u t i o n A , KNO^ and t h e b u f f e r were p l a c e d i n

an argon f l u s h e d 500 ml t h r e e necked RB f l a s k . 200 ml o f

d i s t i l l e d w a t e r was added and t h e pH was a d j u s t e d t o t he

d e s i r e d v a l u e u s i ng n i t r i c a c i d or c a r b o n a t e f r e e aqueous

1 M NaOH . S o l u t i o n B was made i n a s i m i l a r way us i ng KCN ,

t he b u f f e r and 100 ml o f d i s t i l l e d w a t e r . The pH o f

s o l u t i o n B was a d j u s t e d so t h a t when 1 ml o f s o l u t i o n B was

i n j e c t e d i n t o 30 ml o f s o l u t i o n A t h e r e was no change i n

pH . The d i f f e r e n c e i n pH o f s o l u t i o n s A and B was not more

than 0 .1 . S o l u t i o n B was a n a l y s e d f o r c y a n i d e by t i t r a t i o n

w i t h s t a n d a r d AgNO^ .

500 p i o f s o l u t i o n A was i n j e c t e d ont o 0 . 5 mg o f

FeTMPyP and 300 p i o f t h e r e s u l t i n g s o l u t i o n was i n j e c t e d

i n t o a 1 mm pat h l e n g t h c e l l . These t r a n s f e r s were c a r r i e d

1 5 0

out i n an argon f i l l e d g l o v e bag , to a v o i d CO

a b s o r p t i o n . The pH 10 FeTMPyP s o l u t i o n was l e f t f o r 2 . 5

hours t o ens u re e q u i l i b r a t i o n o f t he monomer and d i m er .

Us ing a 5 p i g r a d u a t e d s y r i n g e s o l u t i o n B was

t i t r a t e d i n t o t h e FeTMPyP s o l u t i o n and t he spec t r um ( 500 -

700 nm) was scanned a f t e r each such a d d i t i o n . In none o f

t h e s e d e t e r m i n a t i o n s were i s o b e s t i c p o i n t s obs er ved ,

because t h e a bs o rb an ce i n c r e a s e d over t h e whole scan

r an ge . The c o n c e n t r a t i o n o f FeTMPyP was c a l c u l a t e d f rom

t h e f i n a l abs or b an ce a t 571 nm . A l a r g e excess o f b u f f e r

o v e r c y a n i d e was a v o i d e d by i n c l u d i n g most o f t h e b u f f e r i n

t h e t i t r a n t s o l u t i o n .

C o n d i t i o n s

Solution A Solution B pH A/nm [Buffer]

1 0,.25 M KN°3 0.. 1402 M KCN 7.9 533 1 - 6 x 10 M

+ 10-3 M Tris + 0.25 M Tris

2 0,.25 M kno3 0..1230 M KCN 0.0 540 1 - 15 x 10’ 3 M

+ 10-3 M Tris + 0.50 H Tris

3 0,.25 M KN03 0.,1519 H KCN 9.0 536 1 - 8 x 10"3 M

+ 10 -3 M CHES + 0.25 M CHES

4 0.,25 M KN0_3 0., 1082 M KCN 10.02 534 1 - 17 x 10"3 M

+ 10 -3 H CHES + 0.25 M CHES

1 5 1

1 . 2 . 1 1 . 4 . Cyan i de t i t r a t i o n f o l l o w e d bv 1H NMR

The NMR t ube c o n t a i n e d 400 p i o f D^O , 0 . 2 5 M i n- 3

sodium f o r m a t e , 9 . 7 2 x 10 M i n FeTMPyP and 0 . 1 5 l v / v i n

t - b u t y l a l c o h o l . The pD was a d j u s t e d to 3 . 7 5 w i t h DC1 ,

us i ng a t h i n pH e l e c t r o d e t o measure pD .

A s o l u t i o n o f 10 g KCN and 0 . 8 5 g sodium f o r m a t e i n

30 ml H^O was a d j u s t e d t o pH 3 . 7 5 us i ng about 15 ml o f cone

H C l ( a q ) . The c o n c e n t r a t i o n o f c y a n i d e was found t o be

1 . 1 1 5 M , by t i t r a t i o n w i t h s i l v e r n i t r a t e .

152

1 , 3 . S y n t h e s i s a n d a n a l y s i s

1 . 3 . 1 . P r e p a r a t i o n o f F e T ( M, E t ) PyP

I r o n i n s e r t i o n was a cc o mp l i s he d by l i t e r a t u r e- 3

methods ( 2 3 , 4 8 , 8 2 ) . A s o l u t i o n 28 x 10 M i n f e r r o u s

- 3ammonium s u l p h a t e and 9 x 1 0 M i n T ( M , E t ) P y P was r e f l u x e d

f o r two hours . The s o l u t i o n was c oo led , f i l t e r e d , b o i l e d

and one f i f t h o f a volume o f 20 l aqueous NaClO. was added4

d r o p w i s e . The s o l u t i o n was co o le d s l o w l y o v e r n i g h t . The

p r e c i p i t a t e was f i l t e r e d , washed w i t h pH 2 p e r c h l o r i c a c i d

and e t h a n o l and d r i e d i n vacuum o v e r n i g h t .

Fe p-TMPyP

C a l c u l a t e d f o r C . . H__ Cl _ F e N_ 0 _ _4 4 J o S 8 2 0

C , 4 2 . 9 7 H . 2 . 9 5 N . 9 . 1 1

FoundC , 4 3 . 8 2 H , 2 . 9 5 N , 9 . 2 5

M o l e c u l a r r a t i o s C H N44 3 8 . 1 7 7 . 9 6

C o n v e r s i o n t o t h e c h l o r i d e s a l t was a c c o m p l i s h e d by

s t i r r i n g w i t h 10 t o 20 e q u i v a l e n t s o f D owex - 1X 8 - 100

exchange r e s i n f o r 2 hours . The r e s u l t i n g m i x t u r e was

poured ont o a n o t h e r 1 0 t o 2 0 e q u i v a l e n t s o f exchange r e s i n

and e l u t e d w i t h w a t e r . The w a t e r was e v a p o r a t e d and t he

s o l i d was p r e c i p i t a t e d f rom m e t h a n o l / a c e t o n e or

m e t h a n o l / bu t anone and d r i e d i n vacuum .

1 5 3

Fe TMPyP

C a l c u l a t e d f o r C, . H__ FeNrtCl _4 4 3 b o 5

C . 5 8 . 0 8 H . 3 . 9 9 N . 1 2 . 3 1

Found f o r Fe m-TMPyP C . 5 1 . 2 9 H . 3 . 9 0 N . 1 0 . 5 7


Found f o r Fe p-TMPyP C . 5 1 . 6 2 H . 4 . 0 6 N , 1 0 . 8 7


Fe m-TEtPyP

C a l c u l a t e d f o r C48 H4 4 FeN8 C

C , 59 . 68 H , 4 . 5 9 N . 1 1 . 60

FoundC , 4 0 . 4 9 H , 4 . 6 5 N , 9 . 3 5

M o l e c u l a r r a t i o sC H N48 54 . 85 7 . 9 4

The a n a l y s i s r e s u l t s f o r t he h i g h l y charged

T ( M, E t ) P y P and t h e i r i r o n d e r i v a t i v e s a r e g e n e r a l l y l ow i n

car bon , hydrogen and n i t r o g e n . T h i s i s q u i t e u s u a l f o r

t h e s e compounds , as o bs er ved by P a s t e r n a c k e t a l ( 23 ) .

The C, H, N r a t i o s a r e however c l o s e t o t h e t h e o r e t i c a l

v a l u e s . Th i s s ug ges t s t h a t t h e o r g a n i c p r o d u c t i s

e s s e n t i a l l y pure and t h a t s ome i n o r g a n i c i m p u r i t y i s

p r e s e n t . The i r o n a n a l y s i s showed t h a t t h e r e i s no excess

o f i r o n .

1 5 4

The p e r c h l o r a t e samples g e n e r a l l y a r e c r y s t a l i n e and

g i v e good a n a l y s i s r e s u l t s . These a r e u n f o r t u n a t e l y

i n s u f f i c i e n t l y s o l u b l e i n w a t e r t o be o f d i r e c t use and

must be c o n v e r t e d to t h e more s o l u b l e c h l o r i d e .

The p o t e n t i a l l y e x p l o s i v e n a t u r e o f t he p e r c h l o r a t e

s a l t s o f TMPyP and some o f i t s complexes has been p o i n t e d

out ( 4 8 , 7 4 , 8 3 , 8 4 ) . To a v o i d t h i s p o s s i b i l t y , t h e

p e r c h l o r a t e s were not a l l o w e d to d r y a t t h e s i n t e r and were

t r a n s f e r r e d u s i n g a p l a s t i c s p a t u l a .

Sephadex LH 20 ( P h a r m a c i a F i n e C h e m i c a l s ) can be used

f o r s i z e e x c l u s i o n c hr o m a t o g r a p h y ( l a r g e s t m o l e c u l e s f i r s t )

and w i t h some p o l y a r o m a t i c m o l e c u l e s f o r a d s o r p t i o n

chr om at o gr a ph y ( l a r g e s t m o l e c u l e s l a s t ) .

250 mg o f p r e s w o l l e n Sephadex LH 20 was packed i n t o

a 5 x 40 mm g l a s s column . An aqueous s o l u t i o n o f 15 mg o f

Fe m-TMPyP was run ont o t he column and e l u t e d a t a r a t e o f

15 ml hr 1 w i t h w a t e r . The e l u e n t was e v a p o r a t e d t o

dr y ne s s and t h e r e s i d u e was d r i e d i n vacuum . The a n a l y s i s

was m a r g i n a l l y worse . R e p e a t i n g t h e e x p e r i m e n t u s i n g a

f l o w r a t e o f 1 .4 ml hr d i d no t i mprove t h e r e s u l t s .

1 5 5

A g l a s s tube ( d i a m e t e r : 5 mm i n t e r n a l , 7 mm

e x t e r n a l ) was s e a l e d a t one end and a s m a l l b u l b was

blown . A sample o f a few mg o f i r o n p o r p h y r i n was washed

i n t o t h e t ub e u s i n g a v o l a t i l e s o l v e n t . The s o l v e n t was

e v a p o r a t e d to d r y ne s s i n an oven .

One g l a s s a n t i b u m p i n g g r a n u l e and t h r e e drops o f 60 l

A n a l a r p e r c h l o r i c a c i d were added t o the t u be . The t ube

was hea ted g e n t l y i n a Bunsen f l a m e u n t i l t h e s o l i d was

d i g e s t e d . Then t he s o l u t i o n was hea ted more s t r o n g l y . Up

t o 90 m i n u t e s o f h e a t i n g were n e c e s s a r y t o g i v e a

c o l o u r l e s s s o l u t i o n on c o o l i n g . The f i n a l ho t s o l u t i o n i s

y e l l o w .

A f t e r d i l u t i o n t h e i r o n was d e t e r m i n e d

c o l o u r m e t r i c a l l y u s i ng D r a b k i n ' s ( 85) o - p h e n a n t h r o l i n e

method . A s t a n d a r d i r o n s o l u t i n was made by warming i r o n

w i r e i n aqueous s u l p h u r i c a c i d .

The abs or b an ce o f t h e sample s o l u t i o n and t he

s t a n d a r d F e I I o - phen s o l u t i o n were d e t e r m i n e d a t 485 , 511

and 535 nm , u s i ng 1 cm pa t h l e n g t h c e l l s .

Samples o f ( F e ^ ^ T P P J ^ O , k i n d l y s u p p l i e d by

T. A. James , gave t h e f o l l o w i n g r e s u l t s .

1 . 3 , 2 . A n a l y s i s o f F e T M P v P f o r i r o n

Mass ( F e 1 1 JTP P) 20/mg l i r o n

5 . 9 1 5 8 . 235 . 9 8 0 8 . 216 . 0 7 0 8 . 216 . 0 4 2 8 . 1 9

The a v e r a ge v a l u e i s 8 . 2 1 l

1 5 6

The I. mass v a l u e s c a l c u l a t e d f rom C„„H,. , .Fe N„0 a r e :88 56 2 8

c . 7 8 . 1 1 H , 4 . 17 Fe , 8 . 2 5 N . 8 . 2 5

The m i c r o a n a l y s i s o f t h e ( F e ^ ^ T P P J ^ O sample was

C , 77 . 48 H , 4 . 1 3 N , 8 . 2 1

Combining t h e i r o n a n a l y s i s w i t h t h e s e r e s u l t s g i v e s

t he f o l l o w i n g e m p i r i c a l f o r m u l a

C8 8 H5 5 . 8 9 Fe2 . 0 0 5 N7 . 9 9 6 ° ?

The agr eement i s good and i l l u s t r a t e s t h e v a l i d t y o f

t he method . The f o i l o w n g r e s u l t s were o b t a i n e d f o r two

samples o f Fe* * * TMPyP t o s y l a t e .

Ma s s/mg 7. i r o n

8 . 0 0 3 . 2 08 . 1 8 3 . 2 2

The a v e r a g e v a l u e = 3 . 2 1 l

The 7 mass v a l u e s c a l c u l a t e d f rom C , _ H, . FeN„0,_S, . a r e7 9 7 1 8 1 5 5C . 5 9 . 7 3 H . 4 . 5 1 N . 7 . 0 5 F e . 3 . 5 2

The m i c r o a n a l y s i s f o r t h i s FeTMPyP sample gave

C . 5 4 . 9 9 H . 4 . 4 1 N . 6 . 4 8

Combining t h e two s e t s o f a n a l y s i s r e s u l t s g i v e s the

f o l l o w i n g e m p i r i c a l f o r m u l a

C H N Fe79 7 5 . 4 9 7 . 9 8 3 0 . 9 9 2

1 5 7

The i r o n c o n t e n t i s c o n s i s t e n t w i t h t h e carbon and

n i t r o g e n c o n t e n t . The hydrogen c o n t e n t i s r e l a t i v e l y

h i gh , due t o w a t e r a b s o r p t i o n f rom t he a i r . The d r i e d

sample g a i n e d w e i g h t i n i t i a l l y on exposur e to a i r . A l l

samples wer e l e f t t o e q u i l i b r a t e i n a i r b e f e r e use .

1 . 3 . 3 . A n a l y s i s o f c y a n i d e s o l u t i o n s

Cyan i de s o l u t i o n s were a n a l y s e d by t i t r a t i n g w i t h

AgNO^ s t a n d a r d i s e d a g a i n s t NaCl us i ng t h e p r o c e d u r e

d e s c r i b e d by V o g e l (86 a , b ) .

158

CHAPTER 2

Some r e a c t i o n s o f MnTMPyP and NiTMPyP

159

2 . 1 . I n t r o d u c t i o n

The work on t h e r e a c t i o n s o f MnTMPyP and NiTMPyP has

been drawn t o g e t h e r i n one c h a p t e r f o r c o n v e n i e n c e .

S e c t i o n s 2 . 2 and 2 . 3 o f t h i s c h a p t e r c or r es p on d t o MnTMPyP

and NiTMPyP r e s p e c t i v e l y .

2 . 2 . MnTMPvP

2 . 2 . 1 . I n t r o d u c t i o n

H a r r i ma n and P o r t e r ( 87 ) have i n v e s t i g a t e d t h e

aqueous s o l u t i o n b e h a v i o u r o f MnTMPyP i n i t s v a r i o u s

o x i d a t i o n s t a t e s . The h i g h e s t o x i d a t i o n s t a t e was a s c r i b e d

t o a M n * 1 * p o r p h y r i n tt r a d i c a l c a t i o n . Th i s s p e c i e s d i d

IVnot e x h i b i t an ESR s p e c t r u m . Mn p o r p h y r i n s a r e however

known ( 88 ) and have ESR s p e c t r a .

The p«A v a l u e s f o r t h e v a r i o u s o x i d a t i o n s t a t e s were

r e p o r t e d ( 87 ) :

T a b l e 2 .1 pK v a l u e s f o r MnTMPyP

O x i d a t i o n s t a t e pKA1 PKA2

" n m? 12. 4

n I I IMn it r a d i c a l c a t i o n8 . 0 10 . 77 . 5 10 . 6

2 . 2 . 2 . 1H NMR o f Mn1 1 *TMPvP

Using a 0 . 01 M Mn** *TMPyP s o l u t i o n (pD 6 . 4 0 . 0 3 M

phospha t e , 2 . 5 7. v / v t - b u t y l a l c o h o l ) and a B r u k e r WM 250

s p e c t r o m e t e r , t h e 1H NMR was measured as a f u n c t i o n o f

t e m p e r a t u r e . C u r i e Law p l o t s have been drawn .

The most broadened and s h i f t e d peak i n t h e NMR

s pe ct rum ( F i g u r e 2 . 1 ) i s a s s i g n e d t o t he p y r r o l e p r o t o n s .

Two r es on a nc es were seen a t about 9 ppm 6 , p r es uma b ly the

s h a r p e r peak i s due t o t h e more remote o f t h e p y r i d y l

160

p r o t o n s . T h e r a t i o o f t h e i n t e g r a l s f o r t h e p y r i d y l t o

p y r r o l e peaks i s 2 . 4 : 1 , compared to the t h e o r e t i c a l

r a t i o o f 2 : 1 f o r t h e s e a s s i g n m e n t s . The d i f f e r e n c e may

be due to o v e r l a p f rom t h e HOD r esonance . These

ass ig n me n ts a r e c o n s i s t e n t w i t h t h o s e made f o r Mn* * * t e t r a

t o l y l p o r p h y r i n i n C D C1 ( 8 9 ) .

T a b l e 2 . 2 H NMR c h e m i c a l s h i f t s o f Mn***TMPyP

C hemi ca lA

s h i f t / p p m 6 C

T emp/K 1 0 ^ / T emp

- 3 3 . 6 6 8 . 8 3 3 7 283 3 . 53- 3 1 . 72 8 . 8 7 3 5 294 3 . 4 0- 2 8 . 8 4 8 . 8 9 3 3 3 1 3 3 . 20- 2 6 . 5 7 8 . 9 2 8 3 333 3 . 0 0- 2 3 . 9 9 8 . 9 6 3 0 353 2 . 8 3- 2 3 . 0 1 8 . 9781 363 2 . 7 6

The p a r a m a g n e t i c s h i f t s a r e u p f i e l d f o r t h e A and C

p r o t o n s and d o w n f i e l d f o r t h e B p r o t o n s . T h i s a l t e r n a t i o n

i n d i r e c t i o n around t h e p y r i d y l r i n g i s c o n s i s t e n t w i t h a

p r e d o m i n a n t l y c o n t a c t s h i f t mechanism , as noted by o t h e r

w o r k e r s ( 8 9 , 9 0 ) f o r o t h e r Mn * * * p o r p h y r i n s .

Graphs o f A and C p r o t o n c h e m i c a l s h i f t ve r s us

r e c i p r o c a l t e m p e r a t u r e ( F i g u r e 2 . 1 ) a r e l i n e a r t o w i t h i n

t h e e x p e r i m e n t a l e r r o r , i n d i c a t i n g C u r i e Law b e h a v i o u r .

E x t r a p o l a t i o n t o 1 / T = 0 g i v e s c h e m i c a l s h i f t s o f 14 . 14

and 9 . 4 9 ppm 5 f o r A and C p r o t o n s . These a r e both

d o w n f i e l d o f t h e c o r r e s p o n d i n g c h e m i c a l s h i f t s o f 8 . 9 7 and

9 . 2 0 / 9 . 0 0 ppm f o r d i a m a g n e t i c ZnTMPyP . T h i s non

c o i n c i d e n c e was n o t i c e d by o t h e r w o r k e r s ( 8 9 , 9 0 ) f o r o t h e r

m 111Mn p o r p h y r i n s .

162

FIGURE 2.1 250 MHz ’h NMR OF MnmTMPyP

o

10 5 0Chemical shift / p p m &

-20 -25

Slope = - 13 5 x 103 ppm

K-1

FIGU

RE 2

.1

Co

nt

inu

ed

2 . 2 . 3 . 1 . R e a c t i o n o f M n ^ p o r p h y r i n s w i t h d i o xvge n

Hoffman e t a l ( 9 1 ) have shown t h a t Mn* * T PP( py ) r e a c t s

r e v e r s i b l y w i t h d i o x y g e n i n t o l u e n e a t - 7 9 ° C . 14 hours o f

e x p o su r e t o 1 a t mosphe re o f d i o xy g e n f o l l o w e d by

d e o x y g e n a t i o n o f t h e s o l u t i o n r e s u l t e d i n 70 l r e c o n v e r s i o n

I I ot o Mn TPP( py ) . At - 4 5 C t h e complex was r a p i d l y

i r r e v e r s i b l y o x i d i s e d and i n m e t h y l e n e c h l o r i d e s o l u t i o n

i r r e v e r s i b l e o x i d a t i o n i s more r a p i d . The o x i d a t i o n

p r o d u c t was t h o u g h t t o be t h e p o x o d i m e r i c Mn* * * TPP .

F o r m a t i o n c o n s t a n t s f o r d i o x y g e n complexes o f t o l u e n e

s o l u b l e meso s u b s t i t u t e d Mn11 p o r p h y r i n s have been

d e t e r m i n e d ( 92 ) s p e c t r o p h o t o m e t r i c a l l y a t - 7 8 ° C .

The Mn**TPP d i o x y g e n complex ( 91 ) has an S = 3 / 2 sp in

IVs t a t e and i s f o r m u l a t e d as a Mn - p e r o x i d e w i t h no sp i n

d e n s i t y on t h e p e r o x i d e . Edge on c o o r d i n a t i o n o f p e r o x i d e

i s presumed , end on c o o r d i n a t i o n h a v i ng been r u l e d out .

The g ** 5 . 5 r e g i o n o f t h e ESR spec t r um o f t he Mn**TPP

d i o x y g e n complex c o n s i s t s o f two o v e r l a p p i n g s e t s o f

s e x t e t s . The d i o x y g e n complex o f a manganese I I

p h t h a l o c y a n i n e ( 9 3 ) gave a q u i t e d i f f e r e n t ESR spe ct r um and

was f o r m u l a t e d as a M n * * 1 - s u p e r o x i d e complex .

2 . 2 . 3 . 2 . Mn1 1 TMPvP

I n t h i s work ESR measurements ( F i g u r e 2 . 2 ) have been

used t o f o l l o w t h e r e a c t i o n o f d i o x y g e n w i t h Mn^TMPyP i n

aqueous and i n m e t h a n o l s o l u t i o n .

Aqueous s o l u t i o n

- 2A 400 p i aqueous s o l u t i o n , 5 x 1 0 M i n pH 9 . 5

- 3 -3CHES , 1 8 x 1 0 M i n TMPyP and 2 x 1 0 M i n manganese I I

1 64

a c e t a t e was h e a t ed o v e r n i g h t .

The ESR spe ct rum r e s e mb l es t h a t f o r M n ^ T P P f p y ) .

B u b b l i n g d i o x y g e n b r i e f l y a t amb i en t t e m p e r a t u r e d i m i n i s h e d

t h e i n t e n s i t y o f t h i s r e s o n an ce d r a s t i c a l l y . P ur g i ng w i t h

argon a t a mb i en t t e m p e r a t u r e made no s i g n i f i c a n t d i f f e r e n c e

obut p u r g i n g a t 70 C r e p r o d u c e d about 30 l o f t he o r i g i n a l

i n t e n s i t y .

M e t h a n o l s o l u t i o n

25 p i o f NaOCH^ i n m e t h a n o l (75 mg Na i n 100 ml

m e t h a n o l ) was added t o a 400 p i m e t h a n o l s o l u t i o n

- 3 - 317 x 10 M i n TMPyP and 2 x 1 0 M i n manganese I I a c e t a t e

and h e a t e d o v e r n i g h t .

Aga in t h e ESR s pe c t r u m c l o s e l y rese mbl ed t h a t f o r

MnI I TPP i n t o l u e n e . B u b b l i n g d i o x y g e n f o r 13 m i n u t e s a t

o- 9 6 C gave a spec t r um which r e se m b l e d a c o m b i n a t i o n o f t h a t

obs er ved f o r MnI I TPP and i t s d i o x y g e n complex . A t t e m p t s to

r e s t o r e t h e o r i g i n a l s pe c t rum by p u r g i n g w i t h a rgon f o r

s e v e r a l hours , s u c c e s s i v e l y a t - 9 6 , - 6 5 ,, - 2 2 and o o o

made l i t t l e d i f f e r e n c e .

T a b l e 2 . 3 ESR p a r a m e t e r s f o r Mn11TMPyP and Mn1 1TPP

Compound 9.L W 10'- 3 t R e f e r e n c e

Mn* *TMPyP Mn j J P P ( p y )

5 . 9 8 7 . 3 T h i s work5 . 9 6 7 . 4 9 1 b

Mn | 1TMPy P :0Mn1 iPP : 0 2 2

^ 5 . 8 8 — T hi s work5 . 4 - 5 . 5 5 . 7 and 8 . 8 9 1 b

A l l ESR s p e c t r a were r e c o r d e d us i ng f r o z e n s o l u t i o n s

a t - 19 6 °C .

1 65

FIGURE 2.2 R e a c t i o n of MnnTtiPyP a n d d i o x y g e n f o l l o w e d by esr

Aqueous solution (pH 9.5 0.0 5m CHES)

Field strength /Tesla

Temp = 77 K . Freq = 9.220 GHz

(MnTMPyPl = 2x 10"3M

166

FIGURE 2.2. Continued

MeOH/MeONa solution

0.08 0.16 0.24 0.32 0.40> i i _________ i_____________ i

Purged with argon at f*5°C

0.08 0.16 0.24 0.32 0.40


Temp * 77K , Freq - 9.219 GHz

[MnTMPyPl = 2 x 10“3M

1 6 7

B u b b l i n g d i o xy g en a t a mb i en t t e m p e r a t u r e f o r s e v e r a l

seconds gave an ESR s pe ct rum which resembled t h a t due t o

t he M n ^T PP d i o x y g e n complex . P u r g in g t h i s s o l u t i o n a t

45°C w i t h argon f o r s e v e r a l hours produced t h e Mn**TMPyP

spect rum w i t h about 30 1. o f i t s o r i g i n a l i n t e n s i t y .

2 . 2 . 3 . 3 . D i s c u s s i o n

The ESR p a r a m e t e r s f o r Mn**TMPyP c l o s e l y r e s e mb l e

t hose f o r Mn**TPP . I t i s d i f f i c u l t t o a s s i g n g v a l u e s f rom

t he m u l t i l i n e ESR s p e c t r u m o f t he Mn**TMPyP d i o xy g e n

complex . So a s i n g l e g v a l u e c o r r e s p o n d i n g t o t h e mid

p o i n t o f t h e 0 .1 T r es on a nc e i s quo ted .

On r e a c t i o n w i t h d i o x y g e n t he aqueous s o l u t i o n o f

Mn**TMPyP showed no ESR e v i d e n c e f o r a d i o x y g e n complex .

S i nce some o f t he Mn11TMPyP was r e g e n e r a t e d t h e r e i s

pr esuma bl y an ESR s i l e n t s p e c i e s o t h e r t han t h e p oxo

d i m e r i c Mn***TMPyP i n aqueous s o l u t i o n .

In m e t h a n o l s o l u t i o n t h e Mn^TMPyP d i o x y g e n complex

cou ld be d e t e c t e d even a t room t e m p e r a t u r e . This

o x y g e n a t i o n r e a c t i o n c ou l d be r e v e r s e d t o t h e same d e g re e

as i n aqueous s o l u t i o n . The obs e rv anc e o f a d i ox yg e n

complex i n m e t h a n o l may be due t o t h e non e x i s t e n c e o f the

ESR s i l e n t i n t e r m e d i a t e proposed f o r t h e aqueous s o l u t i o n .

As f o r t h e Co**TMPyP sys tem d i s c u s s e d i n C h a p t e r 3 ,

ESR has proven t o be a u s e f u l t o o l i n f o l l o w i n g the

r e a c t i o n w i t h d i o x y g e n . I t i s a p p a r e n t t h a t Mn^TMPyP

forms a more s t a b l e d i o x y g e n adduct t han Co**TMPyP . The

d i f f e r e n c e s obser ved between aqueous and m e t h a n o l s o l u t i o n

f o r Mn**TMPyP a r e not a p p a r e n t f o r Co**TMPyP .

168

Mn**TMPyP i n w a t e r or m e t h a n o l seems t o be more

s t a b l e to i r r e v e r s i b l e o x i d a t i o n t han Mn* *TPP i n t o l u e n e ,

which was r e p o r t e d by Hof fman e t a l ( 91 ) to be u n s t a b l e a t

- 4 5° C .

The k i n e t i c s o f t h e r e a c t i o n o f d i o x y g e n w i t h

Mn^TMPyP ( 94 ) and Mn* *TPPS. ( 75 ) have been s t u d i e d . The

r e a c t i o n i s f i r s t o r d e r i n d i o x y g e n i n both cases . The

d i t h i o n i t e r e d u c t i o n k i n e t i c s o f Mn***TMPyP have been

s t u d i e d ( 94 ) .

2 . 2 . 4 . S y n t h e s i s

2 . 2 . 4 . 1 . Mn1 1 TTMPv P

A s o l u t i o n o f 100 mg TMPyP and 80 mg manganese I I

a c e t a t e i n 10 ml o f pH 3 aqueous a c e t i c a c i d was r e f l u x e d

f o r one hour . C o n c e n t r a t e d NaClO, was added d r o p w i s e , the

r e a c t i o n s o l u t i o n was c oo l ed s l o w l y and r e f r i g e r a t e d

o v e r n i g h t . The p r e c i p i t a t e was f i l t e r e d and washed a t the

s i n t e r w i t h d i l u t e NaClO, ( a q ) and e t h a n o l . The sample was4

d r i e d i n vacuum .

Cald f o r C4 4 H3 6 C15 MnN 0 8 20

C , 4 3 . 0 0 H , 2 . 9 5 N , 9 . 1 2

Found C , 4 1 . 55 H . 3 . 1 4 N , 8 . 7 6

Empi r i c a l f o r m u l aC 44 H 3 9 . 6 2 N 7 . 9 5

A s l u r r y o f t h i s sample i n w a t e r was s t i r r e d f o r

s e v e r a l hours w i t h 1 . 3 5 g o f A m b e r l i t e I RA- 4 0 0 c h l o r i d e

exchange r e s i n . The m i x t u r e was t r a n s f e r r e d to a column of

a n o t h e r 1 . 35 g o f exchange r e s i n and e l u t e d w i t h w a t e r .

The f i l t r a t e was e v a p o r a t e d t o d r y ne s s . The r e s i d u e was

1 6 9

od r i e d i n a vacuum a t 70 C and l e f t t o e q u i l i b r a t e i n a i r

f o r one week .

Ca ld f o r C. , H__Cl _MnN0 H J b b o

C , 58 . 1 4 H . 3 . 9 9 N, 1 2 . 3 3

FoundC , 4 8 . 6 1 H , 4 . 4 1 N , 1 0 . 0 1

Empi r i c a l f o r m u l a C 44 H 4 7 . 5 6 N 7 . 7 7

The Mn***TMPyP had a v i s i b l e spec t r um i d e n t i c a l t o

t h a t r e p o r t e d by P o r t e r e t a l ( 87 ) w i t h a maximum

abs or bance a t 463 nm (pH 7) .

2 . 2 . 4 . 2 . Mn11TMPvP

P r o d u c t i o n o f Mn**TMPyP was a t t e m p t e d i n pH 9 . 5

aqueous CHES or NaOCH^ i n m e t h a n o l s o l v e n t i n an argon

purged ESR t u be by d i t h i o n i t e r e d u c t i o n o f MnI I I TMPyP .

A t t e m p t s t o produce MnI I TMPyP i n non b u f f e r e d aqueous

s o l u t i o n or pure m e t h a n o l gave s o l u t i o n s w i t h a g = 2

ESR s i g n a l c h a r a c t e r i s t i c o f s o l v a t e d Mn11 i o n .

P o r t e r e t a l ( 94 ) r e p o r t t h a t i n d eo x ge na t ed aqueous

s o l u t i o n above pH 6 r e d u c t i o n o f Mn* * * TPPS, w i t h d i t h i o n i t e

l e a d s q u a n t i t a t i v e l y to MnI I TPPS. . O x y g e n a t i o n o f t h i s4

s o l u t i o n r e g e n e r a t e d MnI I TPPS, w i t h o u t l o s s . I f pH < 64

t hen Mn* * TPPS. under went r a p i d d e c h e l a t i o n . The k i n e t i c s 4o f t h i s r e a c t i o n have been s t u d i e d ( 9 5 , 9 6 ) . In t h i s work

some s o l v a t e d Mn11 ESR r e s o n a n c e was a l ways n o t i c e d i f

d i t h i o n i t e was used . I f t h e s o l u t i o n was opened t o the

a i r , t h i s ESR s i g n a l grew a t t h e expense o f any o t h e r

s i g n a l s . The d i t h i o n i t e p r e su ma b ly caused d e c o m p o s i t i o n o f

t h e Mn^TMPyP i n t h e p r e s e n c e o f d i o x y g e n t o produce f r e e

1 7 0

M n *1 . T h i s t y p e o f d e c o m p o s i t i o n was a l s o n o t i c e d when

F e ^T M Py P was produced by d i t h i o n i t e r e d u c t i o n .

Samples o f Mn**TMPyP were s u c c e s s f u l l y produced by

h e a t i n g Mn11 a c e t a t e w i t h an 8 f o l d excess o f TMPyP . The

c o n d i t i o n s have been o u t l i n e d above .

1 7 1

2 . 3 . NiTMPvP

2 . 3 . 1 . I n t r o d u c t i o n

P a s t e r n a c k e t a l ( 9 7 ) have r e p o r t e d an e q u i l i b r i u m

between h i gh and l ow s p i n forms o f Ni * *TMPyP i n aqueous

s o l u t i o n . In t h i s work t he aqueous s o l u t i o n e q u i l i b r i a a r e

f u r t h e r i n v e s t i g a t e d by a v a r i e t y o f t e c h n i q u e s .

Thermodynamic and k i n e t i c p a r a m e t e r s a r e r e p o r t e d .

2 . 3 . 2 . S p e c t r o o h o t o m e t r i c pH t i t r a t i o n

The i m p r o v i s e d f l o w a p p a r a t u s d e s c r i b e d i n c h a p t e r 1

was used f o r a s p e c t r o p h o t o m e t r i c t i t r a t i o n o f NiTMPyP .

The spec t r um was scanned f rom 300 - 400 nm , and t h e pH was

a d j u s t e d f rom 6 . 1 t o 1 3 . 2 u s i n g aqueous NaOH .

S ma l l random changes i n s p e c t r a were obs er ved f o r

s u c c e s s i v e changes i n pH . A b s o r p t i o n maxima were a t 418

and 543 nm . T h i s i s c o n s i s t e n t w i t h s m a l l t e m p e r a t u r e

f l u c t u a t i o n s and no e v i d e n c e f o r a x i a l w a t e r h y d r o l y s i s was

t h e r e f o r e obs er ved . The spe ct r um i s s e n s i t i v e t o

t e m p e r a t u r e changes because o f t h e e q u i l i b r i u m be l ow .

Coates e t a l ( 3 1 ) have shown t h a t a n o t h e r N i 11 non

r i g i d t e t r a d e n t a t e amine complex has a pK o f 1 0 . 2 f o r

c o o r d i n a t e d w a t e r .

2 . 3 . 3 . L a b i l i t y o f a x i a l w a t e r

The e q u i l i b r i u m b e l ow has been f o l l o w e d by

s u s c e p t i b i l i t y measurements and by d i r e c t l y o b s e r v i n g t he

1H NMR .

172

KPNi ♦ 2 H20 PNi ( OH2 ) 2

d i a m a g n e t i c p a r a m a g n e t i c

[ p a r a m a g n e t i c ]K = ------------------------------

[ d i a m a g n e t i c ]

The absence o f a p o s s i b l e f i v e c o o r d i n a t e complex has

been d i s c u s s e d by o t h e r a u t h o r s ( 3 1 , 9 7 ) .

/2 . 3 . 4 . S u s c e p t i b i l i t y measurements

The Evans' Method was used to d e t e r m i n e the

s u s c e p t i b i l i t y o f aqueous NiTMPyP a t v a r i o u s t e m p e r a t u r e s .

I n i t i a l measurements u s i n g t - b u t y l a l c o h o l , e t h y l e n e

g l y c o l and ( C H - ) . NCI d i d not g i v e c o n s i s t e n t r e s u l t sJ 4

between t h e d i f f e r e n t r e f e r e n c e s . The l a t t e r two

r e f e r e n c e s gave t h e c l o s e s t match .

A d i a m a g n e t i c r e f e r e n c e s o l u t i o n was made by

d i s s o l v i n g 1 mg o f ( CH_ ) , NC1 and 1 mg o f p e n t a e r y t h r i t o l i nj •*2ml D20 . The p a r a m a g n e t i c s o l u t i o n c o n t a i n e d an a d d i t i o n a l

- 315 . 34 x 10 M o f NiTMPyP . 200 p i samples o f t h e two

s o l u t i o n s were t r a n s f e r r e d t o t h e s e p a r a t e p a r t s o f a

c o a x i a l NMR t u b e . The c h e m i c a l s h i f t s e p a r a t i o n s o f the

r e f e r e n c e s ub s t a n c e s were measured us i ng a B r u k e r WM250 NMR

s p e c t r o m e t e r .

The r e s u l t s b e l ow show t h a t t h e s e p a r a t i o n and hence

t he a p p a r e n t m a g n e t i c moment i n c r e a s e w i t h i n c r e a s i n g

t e m p e r a t u r e f o r p e n t a e r y r t h r i t o l as r e f e r e n c e . T h i s data

i s t h e r e f o r e no t c o n s i d e r e d f u r t h e r .

173

Temp/ °C S e p a r a t i o n / HzP e n t a e r y r i t o l ( CH ) NCI

J 4

1 0 2 0 . 3 9 820 9 . 9 9 2 15 . 53 630 1 3 . 9 78 11 . 32 940 1 6 . 6 1 0 7 . 8 3 360 1 7 . 953 4 . 7 4 490 1 8 . 4 77

D e n s i t y d a t a ( 5 3b ) f o r 0^0 was used to c o r r e c t f o r

changes i n NiTMPyP c o n c e n t r a t i o n w i t h t e m p e r a t u r e .

Temperature/°C 10 20 30 40 60 90

[NiTMPyP]/ 1 0~3 M 15.35 15.34 15.31 15.26 15.13 14.86

A computer program ( a p p e n d i x 2 . 1 ) was used t o v a r y AH and

AS so as t o m i n i m i s e t h e d e v i a t i o n s o f e x p e r i m e n t a l and

c a l c u l a t e d m a g n e t i c moments . For t h e (CH0 ) .NC1 s e p a r a t i o n sJ 4

t h e r e s u l t s a r e :

AH = - 2 3 . 9 KJ mol ^

AS - - 9 2 . 4 JK 1 mol

The f i t o f t h e c a l c u l a t e d t o t he e x p e r i m e n t a l

s u s c e p t i b i l i t i e s i s good as shown by t h e g r a ph i n

F i g u r e 2 . 3 . P a s t e r n a c k ( 97 ) made rough e s t i m a t e s o f

AH = - 3 9 . 3 KJmol and AS = - 130J K ^mol . The m a g n e t i c

moment v a l u e s d e t e r m i n e d h e r e a r e a t v a r i a n c e w i t h the

om a g n e t i c moment o f 2 . 1 ( 35 C , I = 0 . 1 M) d e t e r m i n e d by

P a s t e r n a c k ( 97 ) . However t h e i o n i c s t r e n g t h i n t h i s work

i s v i r t u a l l y z e r o and t h e s e e q u i l i b r i a a r e known t o be

s e n s i t i v e t o i o n i c s t r e n g t h ( 3 0 , 3 1 , 9 8 ) .

174

F I G U R E 2 . 3 Te m p e r a t u r e d e p e n d e n t m a g n e t i c s u s c e p t i b i l i t y

OF NiTMPyP

The best f i t t e d l ine cor responds to

AH = - 23.9 KJ mol"1

AS = - 92.4 JK'1mol*1

p = 3.2■H

[NiTMPyP] * 0.015 M

Magnetic moments determined by the Evan s' Method using (CH3)4NCl as reference

1 7 5

T a b l e 2 . 4 M a g n e t i c m o m e n t o f N i T M P y P

T emp/ ° C M a g n e t i cE x p e r i m e n t a l

moment C a l c u l a ted

1 0 1 . 6 9 5 1 . 69720 1 . 5 0 6 1 . 49030 1 . 309 1 . 30740 1 . 1 0 8 1 . 14860 0 . 8 9 3 0 . 8 9 6

P a s t e r n a c k ( 97 ) d e t e r m i n e d m a g n e t i c moments o f 3.1

and 3 . 3 f o r t h e b i s p y r i d i n e and b i s i m i d a z o l e complexes o f

NiTMPyP . The a v e r a g e o f t h e s e two v a l u e s was used h e r e f o r

b i s aqua NiTMPyP . A z e r o m a g n e t i c moment was a s s i g n e d t o

t h e f o u r c o o r d i n a t e NiTMPyP . K i n e r e t a l ( 99 ) d e t e r m i n e d a

m a g n e t i c moment o f 2 . 8 3 f o r a s o l i d sample o f b i s i m i d a z o l e

NiTMPyP . Th i s v a l u e seems u n u s u a l l y low . K i n e r a l s o

d e t e r m i n e d t h e s t r u c t u r e o f t h i s complex , c o n f i r m i n g i t s

s i x c o o r d i n a t e n a t u r e .

2 . 3 . 5 . D i r e c t o b s e r v a t i o n o f 1H NMR

2 . 3 . 5 . 1 . Ch e mi ca l s h i f t s

The NMR o f NiTMPyP i n t h e t e m p e r a t u r e range

0 - 90°C showed peaks s i m i l a r t o t h e p a t t e r n d i s p l a y e d by

t h e f r e e base TMPyP . A l l o f t h e p a r a m a g n e t i c s h i f t s were

d o w n f i e l d and t h e p y r r o l e peak i s s h i f t e d most . The p a i r

o f d o u b l e t s e x h i b i t e d by t h e p y r i d i n e p r o t o n s c o l l a p s e d to

a p a i r o f s i n g l e t s a t l o w e r t e m p e r a t u r e due t o l i n e

b r o a d e n i n g . The t h e o r y i s e x p l a i n e d i n ap p en d i x 2 . 2 . An

i n t e r n a l r e f e r e n c e o f t - b u t y l a l c o h o l was used . The

p y r r o l e p r o t o n p a r a m a g n e t i c s h i f t s were c a l c u l a t e d by

s u b t r a c t i n g t h e s h i f t f o r d i a m a g n e t i c ZnTMPyP , d e t e r m i n e d

1 7 6

F I G U R E 2 . 4 . 250 M Hz 1H NMR OF NiTMPyP

Chemical shift / ppm

[NiTMPyP] = 0.022 M , reference: t - but y l alcohol

1 77

h e r e t o be 0 . 9 7 5 ppm 5 .

I t i s n e c e s s a r y t o know t h e v a l u e o f t h e C u r i e

Co n st a n t , wh i ch r e l a t e s t h e c h e m i c a l s h i f t o f the

p a r a m a g n e t i c b i s aqua NiTMPyP t o t h e t e m p e r a t u r e . S i nce

o n l y t im e a v e r ag ed r es on anc es f o r m i x t u r e s were seen no

d i r e c t measurement o f t he C u r i e C o n s t a n t wa s p o s s i b l e . The

NMR spec t r um o f 12 x 10 ‘3 H NiTMPyP i n aqueous 1,. 5 M

i m i d a z o l e , gave peaks a t 7 . 5 0 and 8 . 0 3 ppm 5 .

a t t r i b u t a b l e t o p y r i d y l and N- CH3 . No peaks a t t r i b u t a b l e

to p y r r o l e p r o t o n s were seen i n t he r e g i o n 150 to

- 2 3 0 ppm 5 and hence no C u r i e C o n s t a n t v a l u e c o u ld be

c a l c u l a t e d f o r compar i son .3

For Ni m - T T P ( p i p ) 2 ( 2b) a v a l u e o f 1 2 . 5 x 10 ppm K

can be c a l c u l a t e d f o r t h e p y r r o l e p r o t o n s f rom t he p l o t o f

i s o t r o p i c s h i f t v e r s u s r e c i p r o c a l t e m p e r a t u r e .

Us ing d a t a f rom t h e s u s c e p t i b i l i t y measurements and

1t h e d i r e c t H NMR measurements , a v a l u e o f

32 2 . 8 ( ± 1 . 7 ) x 10 ppm K was c a l c u l a t e d f o r NiTMPyP .

D e t a i l s o f t h e c a l c u l a t i o n a r e i n a p p e n d i x 2 . 2 . Th i s v a l u e

was used i n t h e e v a l u a t i o n o f t h e d i r e c t NMR d a t a .

A computer program d e s c r i b e d i n a pp e n d i x 2 . 2 was

w r i t t e n t o e v a l u a t e t h e c h e m i c a l s h i f t d a t a . The

d i f f e r e n c e s o f t h e c a l c u l a t e d and e x p e r i m e n t a l c h e m i c a l

s h i f t s were m i n i m i s e d by v a r y i n g AH and AS t o g i v e :

AH = - 2 1 . 4 KJmol” 1

AS = - 8 3 . 8 J K ~ 1m o l ~ 1

The f i t o f t h e c a l c u l a t e d t o t h e e x p e r i m e n t a l

c h e m i c a l s h i f t s i s shown i n T a b l e 2.5. and F i g u r e 2 . 5 .

1 7 8

179

F I G U R E 2 . 5 NiTMPyP PYRROLE PROTON NMR DATA

Best f i t t e d line assumes C = 22.83 * 103 ppm K

= 261 HzAH = ” 21.4 K J mol*AS - - 83.8 JK_1 mol*

Results :A = 24 8Ea = 26 0 KJ mol*

1.0 4-

0 To 40 60 80Temperature / °C

o

0 20 40 60 80Temperature / °C

T a b l e 2 . 5 H NMR NiTMPyP c h e m i c a l s h i f t s

T emp/ °CP y r r o l e 1H c h e m i c a l s h i f t

E x p e r i m e n t a l C a l c u l a t e d

0 37 . 556 3 7 . 2 1 25 3 3 . 5 7 3 3 . 6 8 9

1 0 3 0 . 4 3 1 3 0 . 5 7 720 2 5 . 1 8 0 2 5 . 4 6 030 21 . 370 2 1 . 5 8 340 18 . 841 1 8 . 6 7 050 1 6 . 7 1 0 1 6 . 48770 1 3 . 7 3 3 1 3 . 60790 1 2 . 0 3 6 11 . 942

The v a l u e o f AH. and t h e f i t o f t h i s d a t a i s

i n s e n s i t i v e to t h e v a l u e o f t h e C u r i e C o n s t a n t i n t h e r ange 3

(20 - 70) x 10 ppm K . The u n c e r t a i n t y i n AH i s thus

s m a l l e r t h a n f o r AS . These v a l u e s f o r AH and AS compare

w e l l t o t h o s e o b t a i n e d f ro m s u s c e p t i b i l i t y measurements .

2 . 3 . 5 . 2 . Peak h a l f w i d t h s

E v a l u a t i o n o f t h e p y r r o l e peak h a l f w i d t h s showed

t h a t t h e r e a r e two c o n t r i b u t i n g f a c t o r s :

1) t h e p r o p o r t i o n o f p a r a m a g n e t i c NiTMPyP

2) t he r a t e o f exchange between t h e two forms o f NiTMPyP

Ap pend i x 2 . 3 d e s c r i b e s how t h e p r e e x p o n e n t i a l

f a c t o r A and t h e a c t i v a t i o n e n e rg y , f rom t h e A r r h e n i u s

E q u a t i o n , a r e e v a l u a t e d f o r t h e f o r w a r d r e a c t i o n

k-iPNi * 2 H O ___PNi lOH )

k1Using t h e v a l u e s o f AH and AS above and a c a l c u l a t e d

peak h a l f w i d t h o f 2 6 1 . 0 Hz f o r p a r a m a g n e t i c NiTMPyP , t he

e x p r e s s i o n ( l - W /W \ was m i n i m i s e d by v a r y i n g the \ ©xp c a l /

1 8 0

v a l u e s o f A and E, t o g i v e t h e f o l l o w i n g r e s u l t sA

A = 248 x 1 0 9 s~ 1

E a = 2 6 . 0 KJ mol "1A

The c o r r e s p o n d i n g v a l u e s o f A and E^ f o r t h e back

r e a c t i o n a r e r e l a t e d i n a s i m p l e manner by t h e v a l u e s o f AH

and AS .

T a b l e 2 . 6 and F i g u r e 2 . 5 i l l u s t r a t e t h e f i t o f

c a l c u l a t e d t o e x p e r i m e n t a l peak h a l f w i d t h s .

T a b l e 2 . 6 P y r r o l e peak h a l f w i d t h d a t a

T emp/°C Peak h a l f E x p e r i m e n t a l

w i d t h / H z C a l c u l a t e d

Log h a l f E x p e r i m e n t a l

w i d t hC a l c u l a t e d

0 1 288 1 659 3 . 11 3 . 2 25 1 102 1112 3 . 0 4 3 . 0 5

1 0 8 4 7 . 8 7 4 8 . 2 2 . 9 3 2 . 8 720 4 0 6 . 8 3 4 7 . 0 2. 61 2 . 5 430 1 3 5 . 6 1 7 0 . 4 2 . 1 3 2 . 2340 9 1 . 9 7 9 0 . 8 1 1 . 96 1 . 9670 2 2 . 1 5 2 3 . 9 1 1 . 35 1 . 3890 1 2 . 3 2 1 3 . 7 8 1 . 09 1 . 14

2 . 3 . 5 . 3 . E f f e c t o f a ce t o n e

A sample o f NiTMPyP i n 0 20 was t i t r a t e d w i t h

1d a c e t o n e and t h e H NMR was r e c o r d e d a t each s t a g e us i ng 6a P e r k i n E l mer R32 s p e c t r o m e t e r . At 35°C t h e p y r r o l e peak

s h i f t e d f rom 2 0 . 4 t o 9 . 9 t o 9 . 3 ppm 5 on i n c r e a s i n g the

a c e t o n e c o n c e n t r a t i o n f r o m 0 t o 20 t o 50 7 ( v / v ) .

P a s t e r n a c k ( 9 7 ) a l s o o b s e r v e d f rom s p e c t r o p h o t o m e t r i e

measurements t h a t 30 7. a c e t o n e was s u f f i c i e n t t o produce

t h e maximum i n t e n s i t y a t 420 nm . Ace tone promotes the

f o r m a t i o n o f t h e d i a m a g n e t i c NiTMPyP .

1 8 1

2 . 3 . 6 . O t h e r systems

Coates e t a l ( 3 1 ) have used s p e c t r o p h o t o m e t r i c

measurements to d e t e r m i n e t her modynami c p a r a m e t e r s f o r a

N i * 1 non r i g i d t e t r a d e n t a t e amine complex . The l ow s p i n -

h i gh s p i n e q u i l i b r i a a r e c o n s i s t e n t w i t h t h e l o s s o f

c o o r d i n a t e d w a t e r w i t h i n c r e a s i n g t e m p e r a t u r e t o g i v e a

d i a m a g n e t i c f o u r c o o r d i n a t e n i c k e l complex . The

e q u i l i b r i u m was found t o be i o n i c s t r e n g t h dependent .

C L i C I O . ] AH/KJmol 1 AS / J K~ 1mol 1

0 . 0 7 . 2 0 . 4 2 3 . 6 ± 1 . 30 . 2 5 4 . 7 ± 0 . 3 18. 1 ± 0 . 80 . 5 0 3 . 3 0 . 1 15 . 3 ± 1 . 2

Rusnack and Jordan ( 2 9 ) used s o l u t i o n s u s c e p t i b i l i t y and

d i r e c t 1H NMR measurement s t o d e t e r m i n e ther modynami c

p a r a m e t e r s f o r a N i * 1 r i g i d t e t r a d e n t a t e amine complex .

For aqueous s o l u t i o n t h e r e s u l t s wer e .

T ec hn i que A H / K Jm o l ” 1 AS/ J K” 1mol 1

1 H NMR - 2 6 . 7 - 74 . 9S u s c e p t i b i l i t y - 2 9 . 2 - 7 6 . 6

The a u t h o r s had a s i m i l a r p r o b l e m i n not be i ng a b l e to

d i r e c t l y measure t h e c h e m i c a l s h i f t or m a g n e t i c moment o f

t he h i gh s p i n complex The a gr ee ment between t e c h n i q u e s i s

about t h e same as o b s e r v e d i n t h i s work .

2 . 3 . 7 . Summary o f r e s u l t s f o r NiTMPvP

The two d e t e r m i n a t i o n s o f AH and AS f rom

s u s c e p t i b i l i t y and 1H NMR measurements , show r e a s o n a b l e

182

agreement . Both e v a l u a t i o n s i n v o l v e u n c e r t a i n t i e s ,

however t he 1H NMR d e t e r m i n a t i o n o f AH i s n o t v e r y

s e n s i t i v e to t he C u r i e C o n s t a n t and i s t h e r e f o r e a more

r e l i a b l e v a l u e . The a v e r a g e v a l u e s ,, between t h e two

d e t e r m i n a t i o n s ,, a r e qu o te d be l ow . The AH v a l u e i s

w e i g h t e d i n f a v o u r o f t h e more r e l i a b l e v a l u e .

AH = - 2 2 K J m o l " 1

AS = - 88 J K ~1m o l " 1

For r e f e r e n c e , t h e k i n e t i c p a r a m e t e r s were

d e t e r m i n e d t o be :

A = 250 x 109 s ~ 1

E a = 26 K J mo l " 1A

2 . 3 . 8 . S y n t h e s i s

A s o l u t i o n o f 200 mg o f TMPyP and 512 mg o f n i c k e l

n i t r a t e i n 15 ml o f w a t e r was r e f l u x e d f o r 24 hours . The

s o l u t i o n was c o o l e d , f i l t e r e d , made up t o 100 ml and

r e b o i l e d . 10 ml o f 20 l aqueous NaCIO was added d r o p w i s e4

and t h e m i x t u r e was c o o l e d s l o w l y . The n e e d l e l i k e c r y s t a l s

were f i l t e r e d o f f and washed w i t h 20 ml 0 . 1 / . NaCIO, and

2 ml e t h a n o l . The c r y s t a l s wer e washed i n t o a n o t h e r f l a s k

w i t h 5 0 / 5 0 a c e t o n e / w a t e r and t h e s o l v e n t was e v a p o r a t e d

o f f on a vacuum l i n e . The p r e c i p i t a t i o n p r o c e d u r e was

r e p e a t e d .

The 24 hour r e a c t i o n t i m e i s n e c e s s a r y , o t h e r

a u t h o r s have no t ed t h a t N i i n c o r p o r a t i o n i s s l o w e r t h a n f o r

t h e Cu , Zn , Mn , Co or Fe d i v a l e n t i o n s ( 1 0 0 , 1 0 1 ) .

P a s t e r n a c k e t a l ( 9 7 ) p o i n t o u t t h a t t h e i r p e r c h l o r a t e

sample e x p l od e d . I t i s b e s t t o a v o i d s c r a t c h i n g t h e d r i e d

1 83

samples on a g l a s s s u r f a c e w i t h a m e t a l s p a t u l a .

C a l c u l a t e d f 0 r C44 H3BC14 N

C , 46 . 63 H , 3 . 2 0 N , 9 . 89

Found C , 46 . 1 3 H . 3 . 1 7 N , 9 . 7 8

The e m p i r i c a l f o r m u l a i sC H N44 3 6 . 0 3 8 . 0 0

T h i s sample was washed i n t o a n o t h e r f l a s k w i t h

a c e t o n e / w a t e r and e v a p o r a t e d t o d r yn e ss . 3 g o f Dowex

1X8- 100 exchange r e s i n was added , t h e t o t a l volume was

made up t o 20 ml and t h e m i x t u r e was s t i r r e d f o r t h r e e

hours . The m i x t u r e was t r a n s f e r r e d t o a column o f a n o t h e r

3 g o f exchange r e s i n and e l u t e d w i t h w a t e r . The f i l t r a t e

was e v a p o r a t e d t o d r y n e s s on a vacuum l i n e . The d r i e d

s o l i d was l e f t t o e q u i l i b r a t e i n a i r f o r 10 days .

C a l c u l a t e d f o r C , . H0 _ C l , N 0 Ni7 7 J b H O

C , 6 0 . 2 4 H ,4 . 14 N, 1 2 . 7 7

FoundC , 5 0 . 0 6 H , 4 . 0 3 N , 1 0 . 6 0

The e m p i r i c a l f o r m u l a i s C H N44 4 2 . 2 1 7 . 9 9

As f o r t h e Fe * * * TMPyP c h l o r i d e samples t h e r e seems t o

be some i n o r g a n i c i m p u r i t y . M i x t u r e s o f w a t e r w i t h a c e t o n e

or e t h a n o l a r e good s o l v e n t s f o r d i s s o l v i n g TMPyP

p e r c h l o r a t e s . However t h e s o l u b i l i t y i n t h e n e a t s o l v e n t s

i s poor . P a s t e r n a c k e t a l ( 9 7 ) d i s c u s s t h i s p o i n t .

1 8 4

CHAPTER 3

R e a c t i o n o f CoTMPyP w i t h d i o x y g e n and o t h e r l i g a n d s

1 8 5

3 . 1 . I n t r o d u c t i o n

C o b a l t p o r p h y r i n s a r e r e l a t e d t o t h e n a t u r a l l y

o c c u r r i n g c o b a l t c o r r i n , v i t a m i n and have been

used ( 1 0 2 , 1 0 3 ) t o c a t a l y t i c a l l y r ed uc e d i o x y g e n . A l so ,

squar e Co** complexes w i t h one a x i a l l y c o o r d i n a t e d base a r e

known to be d i o x y g e n c a r r i e r s ( 1 0 4 - 1 0 9 ) . Hemoglobin has

been s t u d i e d by ESR (1 c . d ) by s u b s t i t u t i n g Co** f o r Fe * * ,

t h i s " c o l b o g l o b i n " shows a c o o p e r a t i v e e f f e c t i n i t s d i o x y g e n

b i n d i n g .

Few s t u d i e s have been done on Co* * p o r p h y r i n s i n

aqueous s o l u t i o n . P i l b r o w e t a l ( 26 ) d i d not o b s e r v e an

ESR s pe ct rum f o r aqueous Co* * TPPS. u n t i l DMF , DMSO or

e t h a n o l was added t o d i s a g g r e g a t e t h e p o r p h y r i n . Co**TCPP

i s i n s o l u b l e i n a c i d i c s o l u t i o n . I n t h e work done h e r e ,

Co**TMPyP was found t o be w e l l behaved i n aqueous

s o l u t i o n , b e i n g s o l u b l e and non a g g r e g a t e d o v e r an

e x t e n s i v e pH r a nge .

S e v e r a l r e p o r t s have appear ed on Co** *TMPyP ,

c o n c e r n i n g i t s r e d u c t i o n ( 1 1 0 - 1 1 2 ) and a x i a l l i g a n d

s u b s t i t u t i o n ( 4 0 , 1 1 3 - 1 1 5 ) . I n t h i s work , q u a l i t a t i v e ESR1

and H NMR measurements have been made t o i n v e s t i g a t e t h e

c o o r d i n a t i o n c h e m i s t r y o f Co**TMPyP . I n p a r t i c u l a r t he

r e a c t i o n w i t h d i o x y g e n was s t u d i e d . ESR s u p e r h y p e r f i n e

s t r u c t u r e a l l o w s a d i r e c t i n d i c a t i o n o f t h e t y p e o f a x i a l

l i g a n d . S i g n i f i c a n t d i f f e r e n c e s a r e ob s er v e d compa r ed t o

t h e r e p o r t e d ( 2 6 ) b e h a v i o u r o f Co* * TPPS. , f o r both aqueous4-

or a l c o h o l s o l u t i o n s . Some u n p r e d i c t e d r e s u l t s have been

o b t a i n e d , such as t h e ease o f c o o r d i n a t i o n o f PIPES t o

Co**TMPyP . ESR g and A v a l u e s a r e c om p i l e d f o r some

1 8 6

Co^TMPyP complexes . A t e c h n i q u e f o r p r o d u c i n g CoI I TMPyP

samples , i n s i t u , f o r ESR and NMR measurements i s

d e s c r i b e d .

3 . 2 . S u s c e p t i b i l i t y mea s uremen t s

Co**TMPyP was produced a n a e r o b i c a l l y i n an NMR tube ,

i n o r d e r to s t u dy i t s r a t e o f f o r m a t i o n f rom c o b a l t n i t r a t e

and TMPyP and t o s t udy i t s r e a c t i o n w i t h d i o x y g e n . The

-3s o l u t i o n was 2 0 . 2 x 10 M i n c o b a l t n i t r a t e and

2 2 . 4 x 10~3 M i n TMPyP i n 0 . 1 M pH 6 . 8 PIPES b u f f e r .

C o n d i t i o n s M a g n e t i c moment

Heated f o r 15 m i n u t e s 4 . 22Heated f o r 40 hours 2 . 11Oxygen bubb led f o r 30 s 1 . 73Oxygen bubb led f o r 1 hour 1 . 14Oxygen bubb led f o r a f u r t h e r 0hour w h i l s t h e a t i n g

A f t e r h e a t i n g f o r 27 hours t h e m a g n e t i c moment had

l e v e l l e d a t 2 .1 wh ich i n d i c a t e s c om pl e t e f o r m a t i o n o f

CoI I TMPyP . B u b b l i n g oxygen t h r o u g h t h e s o l u t i o n f o r 30

seconds gave a s i g n i f i c a n t r e d u c t i o n i n t h e m a g n e t i c

moment , however i t r e q u i r e s h e a t i n g t o obta i n a

d i a m a g n e t i c s o l u t i o n .

3 . 3 . ESR s p e c t r a

3 . 3 . 1 . A b b r e v i a t i o n s and n o t e s

PCo(O) Co**TMPyP w i t h one a x i a l oxygen donor

PCo( N ) CoI I TMPyP w i t h one a x i a l n i t r o g e n donor

P Co(0 2 ) •

PCo( 0 ) ( 0 2 ) d i o x y g e n a d d u c t s

P C o ( N ) ( 0 2 ) .

1 8 7

The s u b s c r i p t s II and -1- r e f e r to t he o r i e n t a t i o n o f

t he m a g n e t i c f i e l d w i t h r e s p e c t to t he un i que a x i s ( z ) o f

t h e p o r p h y r i n m o l e c u l e .

3 . 3 . 2 . Main f e a t u r e s

The re a r e two c o m p l i c a t i o n s t o t h e ESR s p e c t r a . A

f r e e r a d i c a l s p e c i e s ( F i g u r e 3 . 1 ) , as d e s c r i b e d by o t h e r

a u t h o r s ( 1 1 6 - 1 1 8 ) , g i v e s a r esonance a t g = 2 . 0 0 . The

resonance can be found even f o r t h e f r e e base p o r p h y r i n and

can be d i s t i n g u i s h e d f rom t h e r esonance f o r t h e d i o x y g e n

adduct which i s b r o a d e r and has h y p e r f i n e s t r u c t u r e .

At h i g h g a i n a m u l t i l i n e r eson ance i s seen i n t h e

0 . 3 3 T r e g i o n As sour ( 1 1 9 ) has a l s o obser ved t h i s and

a s s igned i t t o Cu* * i m p u r i t y . A Cu**TMPyP sample made by

s u b s t i t u t i n g Cu* * f o r Co* * matches t h e se l i n e s seen a t h igh

g a i n ( F i g u r e 3 . 1 ) .

Two t y p e s o f ESR s p e c t r a have been obser ved f o r

Co**TMPyP ( F i g u r e 3 . 2 ) . I f a n i t r o g e n donor , such as

i m i d a z o l e , was p r e s e n t t hen t h e e i g h t peaks o f t h e g

r e g i o n were s p l i t i n t o t r i p l e t s . The t r i p l e t s p l i t t i n g

1 4a r i s e s because N i s 9 9 . 6 3 1 abundant and has a n u c l e a r

sp i n o f 1 . I f an oxygen donor i s c o o r d i n a t e d a x i a l l y ,

which i s t h e s i t u a t i o n i n n e a t w a t e r , t hen no

s u p e r h y p e r f i n e s t r u c t u r e i s seen i n t h e g^ r e g i o n and an

e x t r a peak a t about 0 . 2 6 T i s e v i d e n t . I n d i v i d u a l examples

o f t h e s e complexes a r e d i s c u s s e d l a t e r . ESR s p e c t r a o f

d i o xy g en a d d uc t s were some t i m e s observed when d i o x y g e n was

bubbled t h r o u g h s o l u t i o n s o f Co**TMPyP w i t h v a r i o u s

l i g a n d s . The s pe ct rum f o r t he P C o ( N ) ( 0 2 ) adduct i s

188

189

F I G U R E 3. 1 ESR SPECTRUM OF CunTMPyP AND A FREE RADICAL IMPURITY

0.20 0.24 0.2 8 0.32 0.36 0.40


FIGURE 3.2 PCo(O) AND PCo(N) TYPE e s r s p e c t r a

Field strength l Tesla

0.24 0.28 0.32 0.3 6___i_____________________ i_____________________ i_____________________ i---------------------------------1-------------------------------- 1------------------------------ 1—

0.24 0.28 0.32 0.36

Temp = 77K, neat water (no bu f fe r)

190

FIGURE 3.2 C o n t i n u e d

Field strength / Tesla0.24 0.28 0.32 0.36

0.24 0.28 0.32 0.36Temp = 77K , 0.10M Diethanolamine

d i f f e r e n t f rom t h e P C o ( 0 ) ( 0 2 ) s p e c t r a

r e c o r d e d ( F i g u r e 3 . 2 ) . These d i o x y g e n adduct s p e c t r a a r e

s i m i l a r t o t h o s e r e c o r d e d f o r o t h e r Co1 *

p o r p h y r i n s ( 2 6 , 1 1 8 , 1 2 0 ) .

More e x t e n s i v e d i s c u s s i o n s o f t h e p o s s i b l e t y p e s o f

Co* * p o r p h y r i n ESR s p e c t r a a r e a v a i l a b l e ( 1d) .

3 . 3 . 3 . P h y s i c a l s o l v e n t e f f e c t s

A s i n g l e sample o f Co**TMPyP i n d r y

m et h a n o l ( F i g u r e 3 . 3 ) gave an ESR spect r um d i f f e r e n t to

t h a t o b t a i n e d f o r Co * * TMPyP i n aqueous s o l u t i o n . The

a d d i t i o n o f w a t e r t o t h i s sample caused a peak a t 0 . 2 8 T t o

i n c r e a s e . These d i f f e r e n c e s may be due t o non c o o r d i n a t i o n

o f s o l v e n t i n m e t h a n o l s o l u t i o n or t h e y may be due t o

d i f f e r e n c e s i n s o l v e n t s t r u c t u r e on f r e e z i n g .

Four aqueous samples o f Co**TMPyP were i n i t i a l l y

f r o z e n w i t h l i q u i d n i t r o g e n and s t o r e d f o r s e v e r a l days a t

o- 1 8 C i n a r e f r i g e r a t o r . The ESR s p e c t r a o f t h e s e samples

were q u i t e d i f f e r e n t t o t h e u s u a l PCo(O) t y p e s p e c t r a . On

m e l t i n g , p u r g i n g w i t h a rgon and r e f r e e z i n g i n l i q u i d

n i t r o g e n , t h e u s u a l PCo( O) t y p e spe ct rum was seen . Th is

e f f e c t cou ld be due t o p h y s i c a l changes , such as

c r y s t a l l i s a t i o n f rom s o l i d s o l u t i o n o v e r a p e r i o d o f days

a t - 1 8 ° C but not a t - 1 9 6 ° C .

A d d i t i o n o f e t h y l e n e g l y c o l t o two aqueous Co**TMPyP

s o l u t i o n s gave d i f f e r e n t s p e c t r a t o t h e i n i t i a l PCo(O) t ype

s p e c t r a ( F i g u r e 3 . 3 ) . The most s i g n i f i c a n t d i f f e r e n c e

be i ng an i n c r e a s e d i n f l e x i o n a t 0 . 2 8 T . M e l t i n g and

r e f r e e z i n g made no d i f f e r e n c e t o t h i s . Po l y a l c o h o l s are

192

FIGURE 3.3 • EFFECT OF SOLVENT ON THE ESR SPECTRUM of ConTMPyP


i___ ________________ i____________________ i____________________ i____________________ i____________________i____________________i____________________i ___

(L24 ' 028 ' 032 ' ^ 3 6

Temp = 77K . Freq = 9.212 GHz

1 9 3

known t o i mp ro ve t h e g l a s s i n g p r o p e r t i e s o f f r o z e n aqueous

s o l u t i o n s and so t h i s i s a l s o pr esuma bl y a p h y s i c a l

e f f e c t .

W a l k e r e t a l ( 1 1 8 ) have noted t h a t t h e r e s o l u t i o n o f

t he spe c t rum o f Co * * ( p - OCH^ ) TPP i s d ep enden t on t h e s o l v e n t

and on t he r a t e o f f r e e z i n g o f t he sample .

- 3 I IA 16 x 10 M Co TMPyP s o l u t i o n i n 0 . 0 5 M aqueous

1 4q u i n u c l i d i n e showed a PCo( N) t y p e ESR spe ct rum but no N

s u p e r h y p e r f i n e s t r u c t u r e c o u ld be r e s o l v e d ( F i g u r e 3 . 4 ) .

Improvements i n r e s o l u t i o n were obser ved up t o 15 7 g y c e r o l

but a 0 . 2 6 T peak a l s o a pp e a r e d . At 50 7 g l y c e r o l t h e g

r e g i o n r e se mb l ed t h e s u p e r p o s i t i o n o f PCo(O) and PCo( N)

t y p e s p e c t r a . B u b b l i n g d i o x y g e n though t h i s s o l u t i o n f o r

10 m i n u t e s r educed t h e i n t e n s i t y by 50 7 . S i m i l a r e f f e c t s

- 3 I Iwere n o t i c e d f o r t i t r a t i o n o f 1 5 x 1 0 M Co TMPyP i n

0 . 0 6 5 M aqueous e t h a n o l a m i n e w i t h e t h l e n e g l y c o l , e x c e p t

t h a t i t r e q u i r e d abo ut 20 l e t h y l e n e g l y c o l t o o p t i m i s e

r e s o l u t i o n . A f t e r one m i n u t e o f d i o x y g e n b u b b l i n g t h r o u g h

a s o l u t i o n 50 7 i n e t h y l e n e g l y c o l a d i o x y g e n add u c t was

observed . Reduc i ng t h e c o n c e n t r a t i o n o f Co**TMPyP t o - 3

1 .4 x 10 M i n t h e i n i t i a l s o l u t i o n gave a b e t t e r r e s o l v e d

spe ct r um .

I t seems t h a t p o l y a l c o h o l s d e s t a b i l i s e t he

c o o r d i n a t i o n o f amines t o Co I I TMPyP . More e t h y l e n e g l y c o l

t han g l c e r o l was needed t o g i v e t he same e f f e c t . S i nce

p o l y a l c o h o l s a f f e c t t h e s o l u t i o n e q u i l i b r i a t h e y were not

used t o i mprove r e s o l u t i o n . I f s u p e r h y p e r f i n e s t r u c t u r e

needed t o be b e t t e r r e s o l v e d t h e n t h e c o n c e n t r a t i o n o f

I I - 3Co TMPyP was r ed uc e d t o a b o ut 2 x 1 0 M .

194

FIGURE 3~4EFFECT OF GLYCEROL ON CoIITMPyP ESR SPECTRA


0.24 0.28 0.32 0.36

2.40/0

8.3 0/ 0

i i

0.24 0.36

0.05 H Cuinuclidine , 0/0 of" aqueous glycerol in right margin

Temp = 77K, Freq = 9.215 GHz

195

3 . 4 . R e a c t i o n w i t h d i o x v o e n f o l l o w e d bv ESR s p e c t r o s c o p y

For s o l u t i o n s o f Co**TMPyP c o n t a i n i n g s u c c i n a t e

b u f f e r or no b u f f e r , 2 t o 3 m i n u t e s o f b u b b l i n g w i t h

d i o x y g e n was r e q u i r e d to c o n v e r t t h e PCo(O) t y p e spec t rum

to a PCo f OMO^ ) t y p e sp e c t ru m ( F i g u r e 3 . 5 ) . P u r g i n g t he

s o l u t i o n a t t h i s s t a g e w i t h a rgon o v e r n i g h t r e p r o d u c e s t he

PCo(O) t y p e s pe ct rum w i t h abo ut 20 t o 30 J o f t h e o r i g i n a l

i n t e n s i t y . I f d i o x y g e n was bub b l ed t h ro u g h t h e s o l u t i o n

f o r one hour o n l y a s m a l l amount o f PCo(O) or PCoCOMO^)

cou ld be d e t e c t e d . P u r g i n g w i t h argon o v e r n i g h t a t t h i s

s t a g e r e p r o d u c e d o n l y a v e r y s m a l l p r o p o r t i o n o f PCo(O) .

However i f t h e s o l u t i o n was h e a t ed to 80°C f o r one hour

w h i l s t p u r g i n g w i t h a rgon t h e PCo(O) spe c t rum was

r e p r o d u c e d w i t h most o f i t s o r i g i n a l i n t e n s i t y . These

e v e n t s co u ld be r e p e a t e d o v e r more than one O^/ Ar c y c l e .

S i n c e CoI I I TMPyP i s n o t e x p e c t e d t o be reduc ed t o

I I oCo TMPyP on p u r g i n g w i t h a r gon a t 80 C a n o t h e r ESR s i l e n t

s p e c i e s i s proposed wh i ch forms f rom t he d e c o m p o s i t i o n o f

t h e P C o ( 0 ) ( 0 2 ) . O t h e r a u t h o r s ( 1 2 1 - 1 2 3 ) have proposed a

p pe r oxo d i m e r f o r s i m i l a r systems . A mechanism o f t he

t y p e be l ow i s e n v i s a g e d :

PCo1 1 ( 0 ) + 0 P Co1 1 1 ( 0 ) ( 0~)

+ P Co 11 - PCo 11

1 / 2 PCo1 1 1- 0 - 0 - P C o I 11 ---------=»- PCo111 + 0 ( - 1 )

0 ( - 1 ) r e p r e s e n t s oxygen i n t h e f o r m a l o x i d a t i o n s t a t e -1 ,

t h i s i s t h e case f o r e i t h e r H2°2 p r o d u c t i o n or

a l t e r n a t i v e l y d i s p r o p o r t i o n a t i o n t o 0^ and H^O .

1 9 6

FIGURE 3.5 R e a c t i o n of conTMPy p w i t h o2 f o l l o w e d by e s r

Field strength / Tesla0.2 4 0.28 0.32 0.36

» I________________ > I ___i_ _ ___ I _I 1

Temp = 77K , pH 6 (0.05m succinate)

1 9 7


Field strength / Tesla0-2U 0.28 0.32 0.36

X

Temp = 77 k . pH6{Q.05M succinate)

The p per oxo d i m e r i c Co* * d i m e t h y l g l y o x i m a t e

r e p o r t e d by S i mand i e t a l ( 1 2 1 ) i s s a i d t o d i s p r o p o r t i o n a t e

t o d i o x y g e n , t h e p sup er oxo d i m e r and s t a b l e

c o b a l o x i m e ( I I I ) .

I f PCo** i s more r e a c t i v e w i t h d i o xy g e n t hen i t i s

e x p e c t e d t h a t P C o * * ( 0 ) w i l l be more r e a c t i v e w i t h PCo* * t o

g i v e a p peroxo d i m e r . So i n c r e a s e d a f f i n i t y w i t h d i o x y g e n

I Ii s e x p e c t e d t o d e c r e a s e t h e c o n c e n t r a t i o n s o f bot h PCo

and P C o * * ( 0 2 ) more r a p i d l y t o g i v e s p e c i e s w i t h no ESR

s i g n a l .

Un less o t h e r w i s e s t a t e d t h e word r e v e r s i b i l i t y i s

used t o mean t h e p r o p o r t i o n o f o r i g i n a l i n t e n s i t y

r e p r o d u c e d f rom an ESR s i l e n t s o l u t i o n , by p u r g i n g w i t h

argon a t an e l e v a t e d t e m p e r a t u r e .

The one e l e c t r o n o x i d a t i o n o f a p peroxo d i m e r should

y i e l d an ESR s i g n a l f rom a p superoxo d i m e r o f t h e t ype

d e s c r i b e d by M o r i e t a l ( 1 2 4 ) . O t h e r a u t h o r s ( 1 2 5 ) have

used a v a r i e t y o f o x i d a n t s . A d d i t i o n o f c o l d a l k a l i n e

NaOBr t o s o l u t i o n s o f Co**TMPyP i n aqueous PIPES o r aqueous

n - b u t y l a m i n e t h r o u g h which d i o x y g e n has been b u b b le d d id

not y i e l d any ESR s i g n a l s .

Even w i t h o u t an e x t r a o x i d a n t , o t h e r

a u t h o r s ( 1 2 6 , 1 2 7 ) have obs e rv ed 15 l i n e ESR s p e c t r a , which

t h e y a t t r i b u t e t o p sup er oxo complexes .

199

3 . 5 . R e a c t i o n w i t h i n d i v i d u a l l i g a n d s

3 . 5 . 1 . Amine complexes

Ammonia

Two samples o f Co**TMPyP were made i n 0 .1 M pH 9 . 2

14 15aqueous ammonia , u s i n g NH^ and NH^ . I t was n e c e s s a r y

t o m e l t and f r e e z e t h e s e s o l u t i o n s s e v e r a l t im es t o g e t

s u i t a b l y w e l l d e f i n e d N s u p e r h y p e r f i n e s t r u c t u r e . The

f i r s t two l ow f i e l d g components a r e r e s o l v e d i n t o

1 4t r i p l e t s m t h e case o f NH^ and i n t o d o u b l e t s i n t h e case

15 14o f NH^ ( F i g u r e 3 . 6 ) . T h i s i s c o n s i s t e n t w i t h t h e N and

1 5 N n u c l e a r sp i ns o f 1 and 1 / 2 r e s p e c t i v e l y . The r a t i o o f

15 14Akl v a l u e s f o r N : N i s p r e d i c t e d t o be 1 . 4 : 1 . 0 f romN

t h e r e l a t i v e m a g n e t o g y r i c r a t i o s . The r a t i o o f 1 . 5 : 1

d e t e r m i n e d h e r e i s w i t h i n t h e e x p e r i m e n t a l e r r o r . These

r e s u l t s c o n f i r m t h a t t h e t r i p l e t and d o u b l e t s p l i t t i n g o f

t h e g r e g i o n i s N s u p e r h y p e r f i n e s t r u c t u r e .

I n c r e a s i n g t h e ammonia c o n c e n t r a t i o n f rom 0 . 0 5 t o

0 . 5 0 M d i d not change t h e shape o f t h e s p e c t r u m .

i n d i c a t i n g t h a t a b i s ammonia complex i s no t formed under

t h e s e c o n d i t i o n s . The ammonia complexes r e a c t e d r a p i d l y

and i r r e v e r s i b l y w i t h d i o x y g e n , t o g i v e an ESR s i l e n t

s p e c i e s .

n - B u t v l a m i n e

A PCo( N) t y p e s p e c t r u m was obs er ved , t h e complex

r e a c t e d r a p i d l y w i t h d i o x y g e n , t o g i v e an ESR s i l e n t

s p e c i e s .

G l y c i n e

At pH 9 . 8 a PCo( N) t y p e spe ct r um was obs e rv ed .

A d d i t i o n o f a c i d and t h e n base changed t h e s p e c t r u m to

2 0 0

FIGURE 3.6 e sr s p e c t r a of t h e u n h 3 a n d 15n h3 c o m p l e x e s

OF Co” TMPyP


0.28 0.30 0.32 0.34 0.36

Temp = 7 7 K . pH 9.2 0.10 M NH3

20 1

PCo(O) t y p e and back t o PCo( N) t y p e a g a i n . Th i s r e f l e c t s

t he p r o t o n a t i o n o f t h e amine i n a c i d s o l u t i o n . The complex

was v e r y r e a c t i v e w i t h d i o x y g e n . No d i o xy g e n adduct

spe ct rum was obs e rv ed bu t t h e r e a c t i o n was 25 l

r e v e r s i b l e .

E t h a n o l a m i n e

0 . 0 7 M o f t h e l i g a n d was s u f f i c i e n t t o produce a

PCo( N) t y p e spe ct rum . A d i o x y g e n adduct spe c t rum cou ld

j u s t be d e t e c t e d on r e a c t i o n w i t h d i o x y g e n . The r e a c t i o n

was 15 t r e v e r s i b l e .

D i e t h a n o l a m i n e

0 . 2 0 M l i g a n d gave m a i n l y a PCo(N) t y p e spe ct r um ,

but even 1 . 4 M l i g a n d produced a s m a l l PCo(O) component .

The r e a c t i o n w i t h d i o x y g e n was 50 l r e v e r s i b l e and t h e ESR

spe ct rum o f t h e d i o x y g e n a d d u c t was obs er ved .

T r i e t h a n o l a m i n e

Even w i t h 4 . 8 M l i g a n d a s i g n i f i c a n t PCo(O) component

was obs er ved .

T r i e t h v l a m i n e

A s a t u r a t e d s o l u t i o n o f l i g a n d produced a c o m b i n a t i o n

o f PCo(O) and PCo( N) t y p e s p e c t r a ( F i g u r e 3 . 7 ) . A f t e r 30

m i n u t e s o f d i o x y g e n b u b b l i n g a s u p e r i m p o s i t i o n o f t he

d i o x y g e n add u c t s pe c t r u m and t h e i n i t i a l spe c t rum was s t i l l

seen . The r e a c t i o n was a bo ut 80 l r e v e r s i b l e , f rom t h i s

s t a g e .

Q u i n u c l i d i n e

0 . 0 5 M l i g a n d was s u f f i c i e n t t o produce a PCo( N) t yp e

s pe ct rum ( F i g u r e 3 . 7 ) b u t w i t h an i n f l e x i o n i n t h e gx

peak . B u b b l i n g d i o x y g e n f o r 1 m i n u t e produced an i n i t i a l

20 2

FIGURE 3.7 ESR SPECTRA OF SOME ConTMPyP TERTIARY AMINE COMPLEXES

Field strength /Tesla

0.24 0.28 0.32 0.36•--------------------------- 1----------------------------1----------------------------1---------------------------- 1___________________i__________________ i___________________i

Temp = 7 7 k

2 0 3

PCo( 0 2 ) t y pe spe ct rum bu t a f t e r 10 mi n ut e s o f b u b b l i n g

l i t t l e o f t h i s s p e c i e s was l e f t . The r e a c t i o n was 100 l


S i m i l a r l y W a l k e r ( 1 1 0 ) no t ed t h a t t h e 1:1

q u i n u c l i d i n e : Co1 1 ( p-OCH^) TPP complex i n t o l u e n e d i f f e r e d

f rom o t h e r PCo * * ( N ) complexes i n t h a t t he gx peak was s p l i t

i n t o two .

Q u i n u c l i d i n e shows a g r e a t e r deg re e o f c o m p l e x a t i o n

to Co^TMPyP a t 0 . 0 5 M t han t r i e t h y l a m i n e d i d i n s a t u r a t e d

aqueous s o l u t i o n . C o n s i s t e n t w i t h t h i s t he q u i n u c l i d i n e

complex r e a c t s more r e a d i l y w i t h d i o xy g e n . Both amines

have s i m i l a r p r o t o n b a s i c i t y , bu t q u i n u c l i d i n e i s known to

be a l e s s s t e r i c a l l y h i n d e r e d l i g a n d .

3 . 5 . 2 . B i o l o g i c a l b u f f e r s

These b u f f e r s a r e p r i m a r y ( T r i s ) and t e r t i a r y (MES

and PIPES) amines .

Thr ee s o l u t i o n s 0 . 0 5 M i n b u f f e r gave a PCo(O) t yp e

s pe c t r u m f o r T r i s or MES and a PCo( N) t y p e s pe ct rum w i t h

t r i p l e t s u p e r h y p e r f i n e s t r u c t u r e f o r PIPES ( F i g u r e 3 . 7 ) .

The PC o* 1 r e a c t e d r e v e r s i b l y w i t h d i o xg e n t o p r od u ce a

P C o ( 0 2 ) t y p e spe ct rum i n a l l cases . The r e a c t i o n i s 80 l

r e v e r s i b l e f o r PIPES b u f f e r .

Even a f t e r s e v e r a l hours o f d i o xy g e n b u b b l i n g the

s o l u t i o n s c o n t a i n i n g MES or T r i s b u f f e r s s t i l l showed the

p r e s e n c e o f s i g n i f i c a n t amounts o f d i o x y g e n add uc t .

Aqueous s o l u t i o n s o f Co**TMPyP , w i t h or w i t h o u t f o r m a t e or

s u c c i n a t e b u f f e r s , showed no ESR spec t r um a f t e r a few

m i n u t e s o f d i o x y g e n b u b b l i n g . S u l p h o n a t e s have a l r e a d y

2 0 4

been obs er ved t o a s s o c i a t e w i t h m-TMPyP and Fe p-TMPyP .

Such a s s o c i a t i o n w i t h t he monomer ic d i o xy g e n add uc t would

d e s t a b i l i s e t h e f o r m a t i o n o f a d i m e r . Po l y a l c o h o l s have

a l s o been o bs er ved t o r e du c e t he r e a c t i v i t y o f Co^I TMPyP

w i t h d i o x y g e n , p o s s i b l y a l s o by an a s s o c i a t i o n pr oce ss .

PIPES (pK^ = 6 . 8 ) has a much l o w e r p r o t o n b a s i c i t y

t han say t r i e t h y l amine (pl<A = 1 1 . 0 ) which c o o r d i n a t e s o n l y

w e a k l y . The a b i l i t y o f t h e PIPES m o l e c u l e t o c o o r d i n a t e

t h r o u g h one i t s n i t r o g e n atoms i s thus u ne x pe c t e d . The

3 - 4 f o l d excess c o n c e n t r a t i o n o f PIPES o ve r Co**TMPyP i s

i n s u f f i c i e n t f o r any i m p u r i t i e s i n t h e b u f f e r t o cause t h i s

r e s u l t .

3 . 5 . 3 . C o n c l u s i o n s

The a l i p h a t i c amines s t u d i e d complexed w i t h

Co^TMPyP . The h i g h e r t h e d e g r e e o f s u b s t i t u t i o n t he

h i g h e r t h e c o n c e n t r a t i o n o f amine needed t o approach f u l l

c o m p l e x a t i o n . I t would seem t h a t f o r s t e r i c r e a s o n s t h e

o r d e r o f s t a b i l i t y o f t h e s e complexes i s :

o o o 1 > 2 > 3

A l l o f t h e s e complexes r e a c t e d w i t h d i o x y g e n ,

however d i o x y g e n add u c t s wer e d i f f i c u l t t o o b s e r v e f o r

p r i m a r y amine complexes . The r e a c t i v i t y t o wa r d d i o x y g e n

d e c r e a s e s and t h e r e v e r s i b i l i t y o f r e a c t i o n i n c r e a s e d i n

t h e o r d e r :

o o o 3 > 2 > 1

2 0 5

3 . 5 . 4 . I m i d a z o l e

0 . 0 5 M i m i d a z o l e produced a t y p i c a l PCo(N) t ype

spe ct rum but 0 . 5 M i m i d a z o l e gave r i s e t o a s e r i e s o f 8

i n f l e x i o n s i n t h e 0 . 3 T r e g i o n ( F i g u r e 3 . 8 ) . As the

c o n c e n t r a t i o n o f i m i d a z o l e was i n c r e a s e d above 0 . 5 M

t owa rds 8 M t h e 0 . 2 8 T peak i n c r e a s e d a t t h e expense o f the

o t h e r peaks . T h i s i s i n d i c a t i v e o f t he f o r m a t i o n o f a 2:1

complex . B u b b l i n g d i o x g e n f o r even a few seconds th r ough

t h e s e s o l u t i o n s caused a l o s s o f ESR s i g n a l . P u r g i n g w i t h

o . . . .argon a t 80 C r e p r o d u c e d an i n s i g n i f i c a n t amount o f the

Co 11TMPyP ESR s i g n a l .

I t i s a measure o f t h e d i o x y g e n a f f i n i t y o f the

Co**TMPyP i m i d a z o l e complex t h a t t h e p a r t i a l f o r m a t i o n o f

t h e b i s i m i d a z o l e complex d i d no t s low t h e r e a c t i o n r a t e

n o t i c e a b l y .

O t h e r a u t h o r s ( 1 1 8 , 1 2 8 ) have n o t i c e d t h a t the

s t r e n g t h o f c o o r d i n a t i o n o f i m i d a z o l e to Co* * p o r p h y r i n s i s

h i g h e r t han t h a t f o r more b a s i c amines . T h i s has been

l i n k e d t o t h e a b i l i t y o f i m i d a z o l e as a tr donor .

W a l k e r ( 1 1 8 ) n o t i c e d a s i m i l a r s e r i e s o f changes f o r

Co**TMPP i n p y r i d i n e / t o l u e n e m i x t u r e s . These changes

were a s c r i b e d t o t h e pr ocess

PCo* * ( Py ) + Py < — PCo* * ( P y ) 2

L i n and Lau ( 1 1 6 ) o b s e rv ed an ESR sp e c t ru m w i t h

c o m p l i c a t e d s u p e r h y p e r f i n e s t r u c t u r e f o r Co**TCPP i n

p y r i d i n e . The s p e c t r u m was a s s i g n e d t o a b i s p y r i d i n e

complex .

2 0 6

FIGURE 3.8 Formation of the pco^dmij complex followed by esr


I________________ I_________________I_________________l_________________ I_________________ I_________________ 1_________________ i_________________ L

Temp = 7 7K . pH 7 , ( Imidazole) indicated in le f t margin

2 0 7



0.24 0.28 0.32 0.36—i-------------1---------------■— ■ ________ i________ i________ i

Temp = 77K . pH 7 . ( Imidazole! indicated in l e f t margin

20 8

3 . 5 . 5 . S u b s t i t u t e d p y r i d i n e s

P y r i d i n e

0 . 0 5 M l i g a n d gave a PCo( N) t y p e spec t r um . B u b b l i n g

d i o x y g e n f o r 30 s caused d e c o m p o s i t i o n to an ESR s i l e n t

s p e c i e s .

DMAP

0 . 0 5 M l i g a n d was s u f f i c i e n t t o g i v e a PCo( N) t y p e

s pe ct rum . The complex r e a c t e d r a p i d l y w i t h d i o x y g e n b u t no

d i o x y g e n add uc t was d e t e c t e d . T h i s r e a c t i o n was 32 l


a P i c o l i n e

0 . 0 5 M a P i c o l i n e was s u f f i c i e n t t o g i v e a

p r e d o m i n a n t l y PCo(N) t y p e s pe c t r u m w i t h a s m a l l peak a t

0 . 2 6 T . A f t e r b u b b l i n g d i o x y g e n f o r 2 . 3 hours a l l o f t he

d i o x y g e n add uc t had decomposed . The r e a c t i o n was 30 /.


C o l l i d i n e

0 . 0 5 M c o l l i d i n e gave a PCo(O) t y p e spe ct rum . The

d i o x y g e n adduct had no t c o m p l e t e l y decomposed a f t e r s e v e r a l

hours o f d i o x y g e n b u b b l i n g .

U n l i k e c o l l i d i n e , a p i c o l i n e w i t h one a m e t h y l group

11does c o o r d i n a t e t o Co TMPyP i n aqueous s o l u t i o n . The

o b s e r v a n c e o f a s m a l l peak a t 0 . 2 6 T sug ges t s no t q u i t e

1 00 7. f o r m a t i o n o f t h e a P i c o l i n e complex . T h i s , t o g e t h e r

w i t h t he s l ow r e a c t i o n w i t h d i o x y g e n and t h e d e g r e e o f

r e v e r s i b i l i t y , sug ges t s t h a t t h e complex i s weak . The

a m e t h y l group p r e su m a b l y i m p a r t s some s t e r i c h i n d r a n c e

compared t o p y r i d i n e .

2 0 9

The c o l l i d i n e m o l e c u l e d i d not complex t h r o u gh i t s N

atom and does not have an 0 atom to c o o r d i n a t e t h r o u gh .

The two a m e t h y l groups i m p a r t s u f f i e n t s t e r i c h i n d r a n c e t o

s t op c o o r d i n a t i o n . The s t a b i l i s a t i o n o f t h e d i o x y g e n

adduct may be due t o a s s o c i a t i o n o f t h e c o l l i d i n e m o l e c u l e s

w i t h t h e p o r p h y r i n by tt o v e r l a p , i n the manner d e s c r i b e d

by Kabbami ( 24 ) . The a s s o c i a t i o n o f any m o l e c u l e s w i t h t he

monomer ic superoxo complex w i l l i n h i b i t t he f o r m a t i o n o f

d i m e r i c s p e c i e s wh ich would s t a b i l i s e t he monomer i f i t

decomposes t o a p peroxo d i m e r .

3 . 5 . 6 . Anions

HaN3

A t y p i c a l PCo( N) t y p e spe ct r um was obs er ved . The

complex r e a c t e d 1 0 0 l r e v e r s i b l y w i t h d i o x y g e n , but no

PCofO^) ESR sp e c t ru m was o b s e r v e d .

KF

- 3 I IT i t r a t i o n o f 23 x 10 M aqueous Co TMPyP up to a

t o t a l c o n c e n t r a t i o n o f 1 . 3 M KF i n c r e a s e d t h e 0 . 2 8 T peak

r e l a t i v e t o t h e 0 . 2 6 T peak . However t h e spe c t rum was

e s s e n t i a l l y PCo(O) t y p e and t h e r e a c t i v i t y w i t h d i o xy g en

was not i n c r e a s e d compared t o n e a t aqueous s o l u t i o n . The

r e a c t i o n was 50 l r e v e r s i b l e . T h i s b e h a v i o u r i s ve r y

s i m i l a r t o t h a t i n t h e absence o f KF , hence l i t t l e

e v i d e n c e i s seen f o r f l u o r i d e c o o r d i n a t i o n .

KSCN

A d d i t i o n o f KSCN t o Co**TMPyP caused p r e c i p i t a t i o n

and so i t was d i f f i c u l t t o a s c e r t a i n i f t h e s p e c t r a

o b t a i n e d were due t o t h e p h y s i c a l changes or p o s s i b l e

2 1 0

c h e m i c a l changes . T h i s l i g a n d can p o t e n t i a l l y b ind v i a

s u l p h u r or n i t r o g e n .

3 . 5 . 7 . M er c a p t o e t h a n o l

V a r i o u s amounts o f aqueous pH 10 m er c a p to e t h a n o l

were added to aqueous Co**TMPyP up to a f i n a l c o n c e n t r a t i o n

o f 0 . 4 5 M . A PCo( N) t y p e sp e c t ru m was obser ved . T h i s may

be due t o a n i t r o g e n o u s i m p u r i t y . B u b b l i n g d i o x y g e n d i d

not d e c r e a s e t h e i n t e n s i t y o f t h i s r esonance but t h e shape

o f t h e g r e g i o n changed .

D ickenson and Chien ( 1 2 0 ) observed t h a t C o ^ p r o t

d i m e t h y l e s t e r forms complexes w i t h 2 ( m e t h y l t h i o ) e t h a n o l

and m e r c a p t o e t h a n o l i n t o l u e n e . These s u l p h u r bound

complexes gave ESR s p e c t r a s i m i l a r t o PCo(O) t y p e s p e c t r a

and u n l i k e t h e ESR s pe ct rum obser ved he r e f o r CoI I TMPyP i n

aqueous m e r c a p t o e t h a n o l . Changes t o t he ESR s p e c t r a a t

h i g h l i g a n d c o n c e n t r a t i o n s were a t t r i b u t e d t o s o l v e n t

changes . The 0 . 4 5 M o f m e r c a p t o e t h a n o l used i n t h i s work

i s e x p e c t e d t o produce s o l v e n t e f f e c t s . However t h i s does

not e x p l a i n t h e g ' t r i p l e t s u p e r h y p e r f i n e s t r u c t u r e .

21 1

3 . 6 . Complexes i n m e t h a n o l s o l u t i o n

A sample o f Co**TMPyP i n m e t h a n o l r e a c t e d w i t h

d i o x y g e n o v e r 10 s to g i v e a d i o x y g e n adduct . P u r g i n g w i t h

argon a t am bi e n t t e m p e r a t u r e r e v e r s e d t he r e a c t i o n to g i v e

about 50 l o f t he o r i g i n a l i n t e n s i t y . A f t e r b u b b l i n g

d i o x y g e n f o r 10 m i n u t e s t h e d i o x y g e n adduct ESR s i g n a l had

been reduced to a l o w l e v e l . P u rg i ng w i t h argon f o r one

hour a t a mb i en t t e m p e r a t u r e r e p r o d u c e d v e r y l i t t l e s i g n a l .

oHowever p u r g i n g w i t h a rgon a t 60 C f o r 3 hours r e v e r s e d t he

r e a c t i o n and r e p r o d u c e d a bo ut 50 l o f t he non d i o x g e n

adduct ESR s i g n a l .

I t i s a p p a r e n t t h a t t h e r e a c t i v i t y and r e v e r s i b i l i t y

o f t h e r e a c t i o n w i t h d i o x y g e n i s v e r y s i m i l a r to t h a t

obser ved i n aqueous s o l u t i o n i n t h e absence o f e x t r a

l i g a n d s or b u f f e r s .

P i l b r o w e t a l ( 2 6 ) f ound q u i t e d i f f e r e n t b e h a v i o u r

f o r Co**TPPS i n e t h a n o l s o l u t i o n . They o bs er ved a r educed

r e a c t i v i t y w i t h d i o x y g e n compared t o mixed

aqueous / e t h a n o l s o l v e n t . I t was i n f e r r e d f rom t h e ESR

spect r um t h a t a b i s e t h a n o l complex was p r e s e n t i n m i x t u r e s

o f more t h an 50 l e t h a n o l . T h i s means t h a t d i o x y g e n would

have to compete w i t h e t h a n o l f o r t he s i x t h c o o r d i n a t i o n

s i t e .

A s o l u t i o n o f Co ^T MP yP i n 0 . 0 5 3 M m e t h a n o l i c

b e n z i m i d a z o l e gave a PCo( N) t y p e s pe ct rum . A f t e r one

second o f d i o x y g e n b u b b l i n g a d i o xy g e n add u c t spe c t rum was

observed . The r e a c t i o n c o u l d be 100 l r e v e r s e d f rom t h i s

s t a g e . I f d i o x g e n was bu b b l ed f o r a l o n g e r p e r i o d , t he

d i ox ge n add uc t decomposed and t h e r e a c t i o n was 80 I.

21 2


Th i s complex behaved l i k e t he aqueous d i e t h a n o l a m i n e

complex , w i t h r e s p e c t to r e v e r s i b i l i t y and r e a c t i v i t y

toward d i o x y g e n . The s t e r i c b u l k o f t h e b e n z i m i d a z o l e may

account f o r t h e g r e a t e r s t a b i l i t y o f t he d i o x y g e n add u c t

compared t o t h a t i n aqueous i m i d a z o l e s o l u t i o n .

C o n c l u s i o n s

In summary , t h e r e a r e t h r e e f a c t o r s a f f e c t i n g t h e

a b i l i t y o f n i t r o g e n donors t o c o o r d i n a t e to Co**TMPyP :

i ) t y p e o f n i t r o g e n ( ami ne , p y r i d i n e , i m i d a z o l e )

i i ) s t e r i c b u l k

i i i ) p r o t o n b a s i c i t y ( p K v a l u e )

The scheme proposed i n t h i s work f o r t h e r e a c t i o n

w i t h d i o x y g e n i s c o n s i s t e n t w i t h e x p e r i m e n t a l r e s u l t s which

show t h a t t h e more s t a b l e t h e i n i t i a l complex t h e more

r a p i d t he r e a c t i o n w i t h d i o x y g e n to produce s p e c i e s which

g i v e no ESR s i g n a l . PCo( N) complexes a r e s i g n i f i c a n t l y

more r e a c t i v e t owa rd s d i o x y g e n t han PCo(O) complexes .

21 3

3 . 7 . ESR p a r a m e t e r s

Ass i gnment s a r e made by compar i son to t ho se made by

11o t h e r a u t h o r s ( 2 6 , 1 1 8 , 1 2 6 ) f o r s i m i l a r Co complexes and

t he r ange o f v a l u e s o f g and A a r e seen to be c o n s i s t e n t

w i t h t h e s e r e p o r t s .

T a b l e 3 ESR p a r a m e t e r s f o r Co 1 I TMPyP complexes

L i gand 9j_ Ax t 9 n a h + an *

Aqueous s o l n 2 . 4 4 3 5 . 4 2 . 0 3 6 9 . 0 —

M e t h a n o l s o l n 2 . 3 ? — 2 . 0 5 0 7 . 8 —

l s NH3NH3

2 . 3 0 5 — 2 . 0 3 4 7 . 6 1 . 42 . 2 9 2 — 2 . 0 3 0 7 . 3 2 . 1

Bu t y I a m i n e 2 . 289 — 2 . 0 3 9 7 . 1 1 .3G l y c i n e 2 . 2 9 4 — 2 . 0 3 8 7 . 0 1 . 3E t h a n o l a m i n e 2 . 2 9 5 — 2 . 0 3 9 7 . 1 1 . 3D i e t h a n o l a m i n eT r i e t h a n o l a m i n e

2 . 3 1 0*

--- 2 . 0 2 8 7 . 7 1 . 7

T r i e t h y l a m i n e 2 . 3 0 5 — 2 . 0 3 7 7 . 4 1 . 7Q u i n u c l i d i n e 2 . 3 1 5 — 2 . 0 3 9 7 . 2 1 . 0

T r i s * 2 . 4 5 4 6 . 0 2 . 0 3 4 9 . 3 —MES * 2 . 4 4 6 5 . 7 2 . 031 9 . 0 —

PIPES 2 . 3 0 6 — 2 . 0 3 3 7 . 6 1 . 5

I m i d a z o l e 2 . 3 0 7 — 2 . 0 5 4 6 . 7 1 . 7B e n z i m i d a z o l e 2 . 3 0 3 — 2 . 0 3 2 7 . 2 1 . 4P y r i d i n e 2 . 3 0 7 — 2 . 0 3 7 7 . 3 1 . 34 -Cyano p y r i d i n e D i m e t h y l amino

2 . 3 1 2 2 . 0 3 5 7 . 5 1 . 5

p y r i d i n e 2 . 3 0 6 — 2 . 0 4 4 6 . 9 1 . 1a - P i c o l i n e 2 . 3 1 0 — 2 . 0 3 8 7 . 4 1 . 6C o l l i d i n e * 2 . 4 4 0 5 . 3 2 . 0 3 7 8 . 8 —

NaN KF ?

2 . 3 0 0 — 2 . 0 3 5 7 . 4 1 . 8? — 2 . 0 3 4 9 . 0 —

t 1 0 cmT m i x t u r e o f PCo(O) and PCo( N)? a s s i g n m e n t d i f f i c u l t* no c o o r d i n a t i o n v i a n i t r o g e n

A v a l u e s a r e ± 0 . 5 x 10 3 cm g v a l u e s a r e ± 0 . 0 0 8

The ESR p a r a m e t e r s f o r Co^TMPyP i n m e t h a n o l s o l u t i o n

a r e s i m i l a r t o t hos e r e p o r t e d by P i l b r o w ( 26 ) e t a l f o r

214

C o ^ T P P S . i n e t h a n o l s o l u t i o n :

9j . = 2 . 3 6 Aj_ = 4 . 5 3 x 10 " 3 cm" 1 ,

9 II = 2 . ii<—ino 9 . 0 x 1 0 3 cm 1

The 9 II v a l u e s a r e i n s e n s i t i v e to t h e d i f f e r e n c e s

between t he l i g a n d s . T h i s c o n s i s t e n c y suggest s t h a t t he

a c c u r a n c y i s b e t t e r t h an t h e e s t i m a t e d ± 0 . 0 0 8 . The

v a l u e s a r e much more s e n s i t i v e . A n i t r o g e n donor g i v e s

-3 -1r i s e t o a v a l u e o f about 7 . 5 x 10 cm and an oxygen

- 3 - 1donor g i v e s a v a l u e o f abo ut 9 . 0 x 10 cm . Wi t h t h e

1 5e x c e p t i o n o f t h e NH^ complex which has a A^ v a l u e o f- 3 -1 - 3 - 12.1 x 10 cm , t he A,, v a l u e s a r e about 1 . 5 x 10 cm

N

The g± v a l u e s show much g r e a t e r v a r i a t i o n , n i t r o g e n

donors g i v e r i s e to a v a l u e o f about 2 . 3 0 and oxygen donors

t o a v a l u e o f about 2 . 4 4 . The A j_ v a l u e s a r e o n l y

d e t e r m i n a b l e f o r PCo(O) t y p e s p e c t r a and a r e l o w e r t h an t he

A || v a l u e s .

These g and A v a l u e s a r e c o n s i s t e n t w i t h t h e

t h e o r e t i c a l a c c ou nt o f and w i t h t he examples g i v e n by

Subramanian ( I d ) .

The d i o x y g e n adduct i n n e a t m et h a n o l gave a spec t r um

s i g n i f i c a n t l y d i f f e r e n t to t h e t r e n d f o r P C o ( 0 ) ( 0 2 ) t ype

s p e c t r a . T h i s , t o g e t h e r w i t h t he d i f f e r e n c e s a l r e a d y

noted f o r Co**TMPyP i n n e a t m et h a n o l , suggest t h a t

d i f f e r e n t t y p e s o f complex a r e p r e s e n t compared t o t h o s e i n

n e a t w a t e r .

S i m i l a r t r e n d s a r e obser ved f o r t h e d i o xy g e n

complexes as have been o bs er ved f o r t h e non d i o xy g e n

complexes .

The P C o ( 0 ) ( 0 ) t y p e s p e c t r a tend t o g i v e g _ v a l u e s o f

2 1 5

about 2 . 0 7 , whereas P C o ( N ) ( 0 2 ) t y p e s p e c t r a tend t o g i v e

v a l u e s o f about 2 . 0 9 . The Ax v a l u e s show no g e n e r a l

- 3 - 1t r e n d s , a l l b e i n g a p p r o x i m a t e l y about 1 . 6 x 1 0 cm

T a b l e 3 . 2 ESR p a r a m e t e r s f o r d i o x y g e n adduct s

L i gand 9jl A JL + 9 ii a h fM e t h a n o l so l n 2 . 0 7 6 2 . 0 1 . 9 9 9 1 . 4

Aqueous so l n 2 . 0 9 0 1 . 6 2 . 0 1 7 1 . 5S u c c i n a t e b u f f e r 2 . 091 1 . 6 2 . 0 1 7 1 . 4T r i s * 2 . 0 0 6 1 . 5 2 . 0 1 6 1 . 4MES * 2 . 0 9 4 1 . 9 2 . 0 1 4 1 . 5C o l l i d i n e * 2 . 0 8 4 1 . 7 2 . 0 1 2 1 . 5

T r i e t h y l a m i n e 2 . 0 7 8 1 . 6 1 . 991 1 . 2D i e t h a n o l a m i n e 2 . 0 7 3 1 . 6 2 . 011 0 . 9PIPES 2 . 0 7 0 1. 4 2 . 0 1 5 1 . 0B e n z i m i d a z o l e 2 . 071 1 . 5 2 . 011 1 . 0

. , - 3 -1t 1 0 cm _ 3A v a l u e s a r e ± 0 . 5 x 10 cm g v a l u e s a r e ± 0 . 0 0 8 * no c o o r d i n a t i o n v i a n i t r o g e n

A p a r t f rom t h e t r i e t h y l amine complex , t h e g v a l u e s

a r e v e r y s i m i l a r . The AJ( v a l u e s seem t o be g e n e r a l l y- 3

h i g h e r ( - 1 . 4 x 10 ) f o r P C o ( 0 ) ( 0 2 ) t y p e s p e c t r a t h a n f o r

PCo ( N ) ( 0 2 ) t y p e s p e c t r a (~ 1 . 0 x 1 0 3 ) .

The d i f f e r e n c e s d i s c u s s e d above a r e a l l o f t h e same

o r d e r o f m a gn i t u d e as t h e e s t i m a t e d e r r o r s i n measurement .

However i t i s f e l t t h a t t h e g e n e r a l t r e n d s o bs er ved a r e

r e a l .

I t i s g e n e r a l l y a c c e p t e d ( 1 2 9 ) t h a t i n t h e d i o x y g e n

adduct s t h e r e i s a l m o s t c o m p l e t e t r a n s f e r o f an e l e c t r o n

f rom t h e c o b a l t i o n t o t h e d i o x y g e n . T h i s r e s u l t s i n spin

d e n s i t y on t h e f o r m a l s u p e r o x i d e i o n and no s p i n d e n s i t y on

t h e f o r m a l C o * 1 * i o n . T h i s ac c ou nt s f o r t h e l o w e r g and A

v a l u e s f o r t h e d i o x y g e n complexes .

2 1 6

3 . 8 . R e a c t i o n w i t h d i o x v g e n f o l l o w e d bv 1H NMR and

ES R s p e c t r o s c o p y

3 . 8 . 1 . I n t r o d u c t i o n

The r e a c t i o n w i t h d i o x y g e n and i t s r e v e r s a l were

f o l l o w e d by ESR and NMR s p e c t r o s c o p y . Thr ee samples a r e

d i s c u s s e d and compa r i son s between t h e v a r i o u s NMR s p e c t r a

o b t a i n e d a r e i m p l i e d i n T a b l e 3 . 3 . There a r e some

s i g n i f i c a n t v a r i a t i o n s i n c h e m i c a l s h i f t between s p e c t r a

f o r t hose peaks a s s i g n e d t o p y r r o l e and p y r i d y l . Th i s i s

pr esuma bl y due t o d i f f e r e n c e s i n am bi e n t t e m p e r a t u r e o f t he

NMR probe on d i f f e r e n t days .

3 . 8 . 2 . Sample J_

The NMR s p e c t r a a r e c o m p l i c a t e d by t h e p r e se n ce o f

t o s y l a t e i on . Peaks f o r t h e t o s y l a t e i ons c o u ld be

i d e n t i f i e d i n t h e d i a m a g n e t i c s o l u t i o n s , bu t not f o r t h e

p a r a m a g n e t i c s o l u t i o n . The i n i t i a l spe c t rum I shows broad

peaks a t 0 . 2 0 , 6 . 21 , 9 . 6 2 and 1 2 . 6 ppm 5 . The two

u p f i e l d peaks do no t c o r r e s p o n d t o a n y t h i n g o bs er ved i n

samples 2 and 3 and a r e p r e su m a b l y f rom a p a r a m g n e t i c

s p e c i e s , such as a d i o x y g e n add uc t . The f o l l o w i n g

a ss ign me nt s a r e made on t h e b a s i s o f t h e i n t e g r a l s .

Ass ignment C h e mi ca l I n t e g r a ls h i f t A c t u a l T h e o r e t i c a l

P Co11P y r i d y l 0 . 2 0 2 . 1 2 . 0P y r r o l e

P Co 1 1 1 ( 0 2 )6 . 21 1 . 0 1 . 0

P y r i d y l 9 . 6 2 2 . 0 2 . 0P y r r o l e 12 . 6 1 . 03 1 . 0

2 1 7

FIGURE 3.9 R e a c t i o n of conTMPyP w i t h o2 f o l lo we d by 1h n m r

14 12 10 8 6 4 2 O

Chemical shif t / ppm S

ICoTMPyP] = 19.7 x 10"3M

2 1 8

F IQURE 3.9 Co nt in u ed

Sample 2 , Spectrum I

d, HOD Ref erence

* b»

a,

V____________ wV.

• Ambient temperature , Freq = 250 MHz for al l spectra

[CoTMPyPl = 1 3.1 x 10“3 M

Subscripts 1 to 4 re fe r to di fferent CoTMPyP species

219

220

Table 3.3 1H NMR chemical sh if ts of CouTMPyP complexes

Assignment *** Sample I

1 ft ft *I I

********I

Sample 2 1 I I I I I I I I

3 *****I I I IV

Pyridy1 b 2 • C 2 0.20

t-butyl alcohol — 1.22 1.22 1 .22 t 1 .22 1.22 1 .22 1.22

n *-c h 3 d 3 4.74

n --c h 3 d 4 4.77

HOD 4.82 4.96 4.80 4.79 4.79 4.82 4.81 4.80 4.80

n +-c h 3 d 1 5.13 — 5.27 — 5.24 5.28 5.28 5.20 5.17

Pyrrole a 2 6.21

Pyridy1 b 3 8.694 t 8.694 8.961 8.966 8.956 8.956 8.977 8.970

Pyridyl \ 8.923 t 9.014 9.005 8.967 8.975 9.027

Pyridyl C 3 9.197 t 9.160 9.222 9.223 9.171 9.202 9.264 9.261

Pyridy1 c4 9.267 9.215 9.364 9.360 9.217 9.219 9.373

Pyrrole a 4 9.28

Pyrrole 3 3 9.38

Pyridyl b 1 C 1 9.62 — 9.7 — 9.5 9.59 9.59 9.74 —

Pyrrole a 1 12.6 — 12.97 — 13.6 12.98 13.00 13.45 13.65

t t-butyl alcohol evaporated , so HOD set to 4.793 ppm 6

$ centre of doublet . not resolved in other specta

Letters a to d refer to the type of 'h in the same molecule arid subscripts 1 to 4 refer to different molecules

3 . 0 . 3 . Samples 2 and 3.

The broad peaks o f t h e i n i t i a l NMR s p e c t r a a r e

a ss i g n e d to P C o * * ( 0 ) . The r e l a t i v e i n t e n s i t y o f t he sharp

peaks i n t he 9 ppm r e g i o n v a r i e s so as to suggest two

s p e c i e s . By a c o n s i d e r a t i o n o f t h e i n t e g r a l s and by

compar i son w i t h t he ZnTMPyP NMR spec t r um , i t i s i n f e r r e d

t h a t t h e s e a r e both p y r i d y l p r o t o n s . Sharp p y r r o l e peaks

a r e a l s o e x p e c t e d f o r t h e s e two s p e c i e s i n t he 9 ppm r e g i o n

but non were i d e n t i f i e d .

3 . 8 . 4 . Sample 2

The i n i t i a l s o l u t i o n gave a PCo(0 ) t y p e ESR

spe ct r um , c e n t r e d a t g = 2 . 3 and NMR spect r um I w i t h

m a i n l y broad peaks and sha rp 9 ppm peaks i n s m a l l

p r o p o r t i o n . The f o l l o w i n g a s s i g n m e n t s were made .

Ass i gnment C h e mi c a l I n t e g r a ls h i f t A c t u a l T h e o r e t i c a l

N-CH 5 . 2 7 3 . 1 9 3 . 0P y r i a y 1 9 . 7 4 . 0 4 . 0P y r r o l e 1 2 . 9 7 2 . 3 0 2 . 0

A f t e r b u b b l i n g d i o x y g e n t h r o u g h t h e s o l u t i o n f o r 2 . 5

hours a t 65°C , some d i o x y g e n add uc t was obs er ved f rom t he

ESR spe ct rum . The NMR s p e c t r u m showed two se t s (3 and 4)

o f sharp peaks i n t h e 9 ppm r e g i o n and no broad peaks . The

f o l l o w i n g i n t e g r a l s wer e r e c o r d e d .

C hemi ca l I n t e g r a ls h i f t A c t u a l T h e o r e t i c a l

8 . 961 1 . 0 0 1 . 09 . 2 2 2 1 . 0 6 1 . 0

2 2 1

The N-CH^ peak f rom t h e p o r p h y r i n s p e c i e s may be

c o i n c i d e n t w i t h t h e HOD peak , as i n o t h e r d i a m a g n e t i c

TMPyP complexes . No e v i d e n c e o f sharp p y r r o l e peaks was

obs er ved .

A f t e r p u r g i n g t h e s o l u t i o n w i t h argon a t 60°C , t h e

broad peaks a r e a g a i n ob s er v e d i n s m a l l p r o p o r t i o n t o t h e

sharp 9 ppm peaks . Some r e g e n e r a t i o n o f t h e o r i g i n a l PCo1 *

i s e v i d e n t l y p o s s i b l e f rom t h e s e d i a m a g n e t i c p o r p h y r i n

s p e c i e s .

3 . 8 . 5 . Sample 3.

The i n i t i a l NMR spe ct rum showed m a i n l y broad peaks

w i t h sharp peaks i n t h e 9 ppm r e g i o n , i n s m a l l

p r o p o r t i o n . A f t e r p u r g i n g t h e s o l u t i o n w i t h argon f o r 2 . 5

hours a t 65°C , no d i f f e r e n c e was obser ved .

Ass ignment s C h e m i c a ls h i f t

I n t e g r a lA c t u a l T h e o r e t i c a l

N - C H 5 . 2 8 3 . 0 0 3 . 0P y r i a y l 9 . 5 9 3 . 4 2 4 . 0P y r r o l e 1 3 . 0 0 2 . 0 6 2 . 0

A f t e r b u b b l i n g d i o x y g e n t h r o u g h t h e s o l u t i o n f o r a

few seconds , t h e b road peaks ( a „ , b , , c „ and d „) i n NMR1 1 1 1spe ct rum I I I became s m a l l i n compar i son t o t he sharp 9 ppm

peaks .

As more d i o x y g e n was bubb led t h r o u g h t h e s o l u t i o n ,

t h e r e l a t i v e i n t e n s i t y o f t h e sharp peaks i n c r e a s e d .

222

3 . Q. G. C o n c l u s i o n s

For sample 1 t he 9 ppm r e g i o n peaks a r e s p l i t i n t o

d o u b l e t s and t he c o r r e l a t i o n between a c t u a l and t h e o r e t i c a l

i n t e g r a l s i s b e t t e r t h a n f o r samples 2 and 3 . T h i s i s

because the NMR s p e c t r a f o r sample 1 a r e b e t t e r r e s o l v e d •

O v e r l a p between t h e sharp and broad peaks i n t h e

9 ppm r e g i o n c o m p l i c a t e s t h e i n t e r p r e t a t i o n o f t he

i n t e g r a l s . C o r r e c t i o n s were a t t e m p t e d where p o s s i b l e .

From t h e t h r e e samples s t u d i e d , some e v i d e n c e i s

seen f o r f o u r s p e c i e s , two p a r a m a g n e t i c (1 and 2) and two

d i a m a g n e t i c (3 and 4) , i n aqueous s o l u t i o n . T h i s i s

c o n s i s t e n t w i t h t h e scheme p r e s e n t e d he r e f o r t h e r e a c t i o n

o f Co**TMPyP w i t h d i o x y g e n .

3 . 9 . O t he r s t u d i e s

LaMar and W a l k e r ( 1 3 0 ) have p u b l i s h e d t h e spe c t rum o f

Co* * TTP and make t h e f o l l o w i n g a ss i gn m en ts . The p a t t e r n o f

s h i f t s i s t h e same as o b s e rv ed h e r e f o r Co**TMPyP .

As s i gnment C h e m i c a l s h i f t / p p m 5

T o l y l m e t h y l 4 . 5P y r i d y l meta 1 0P y r i d y l o r t h o 1 3P y r r o l e 1 6

D o k u z o v i c e t a l ( 1 2 8 ) have s p e c t r o p h o t o m e t r i c a l l y

f o l l o w e d t h e k i n e t i c s o f t h e o x i d a t i o n o f t h e f i v e

c o o r d i n a t e C o * * p r o t o d i m e t h y l e s t e r complex t o g i v e t h e s i x

c o o r d i n a t e C o * * * p r o d u c t . The r e a c t i o n r e q u i r e d a p r o t i c

s o l v e n t and a c i d i f i c a t i o n promoted t h e r e a c t i o n . The r a t e

o f t h e r e a c t i o n changed i n t h e o r d e r :

Im > p i p > 4CH^ Py > Py > 4 CN py > 3 CN py

2 2 3

T h e p r o p o s e d m e c h a n i s m w a s

P Co 11 + ROH ~ PCo1 1 ( ROH )

PCo1 1 ( ROH) PCo1 1 ( L ) + ROH+ L ------^

PCo1 1 ( L ) + o_ ----- - PCo111 (L) (0 ")2 ------7I I I . . , I I I , .PCo A1 ( L ) ( 0 2 ) + L -----=■“ PColL ( L ) 2 + H02

Where ROH i s propan 2 o l , e t h a n o l or m e t h a n o l

Stynes e t a l ( 1 3 1 ) have s p e c t r o p h o t o m e t r i c a l l y

d e t e r m i n e d t h e f o r m a t i o n c o n s t a n t f o r 5 c o o r d i n a t e

C o ^ p r o t o d i m e t h y l e s t e r complexes i n t o l u e n e . The o r d e r

wa s

4 NH^ py > py > Im > 4CN py

Th i s does not i n d i c a t e a s i m p l e c o r r e l a t i o n t o t he

r e a c t i v i t y w i t h d i o x y g e n . The t y p e o f bonding ( it v e r s u s o)

as w e l l as t h e s t r e n g t h o f c o o r d i n a t i o n i s p r esu ma bl y

i m p o r t a n t h e r e .

E l l i s e t a l ( 1 3 2 ) p o i n t ou t a l i n e a r r e l a t i o n s h i p

between t h e l o g o f t h e f o r m a t i o n c o n s t a n t t o l i g a n d pK, ,A

f o r s t r u c t u r a l l y s i m i l a r l i g a n d s .

2 2 4

3 . 1 0 . S y n t h e s i s and p u r i f i c a t i o n

3 . 1 0 . 1 . Co1 I TMPvP

Two s e t s o f c o n d i t i o n s were used . I f o n l y ESR

s p e c t r o s c o p y was t o be a p p l i e d , then an excess o f TMPyP

was used . I f NMR s p e c t r o s c o p y was a l s o t o be a p p l i e d ,

then excess Co* * n i t r a t e was used i n D2 0 s o l u t i o n and t h e

u n r e a c t e d Co* * was l a t e r removed .

Samples f o r ESR s t u d i e s

S i n g l e samples o f Co**TMPyP were made i n s i t u by

t r a n s f e r r i n g 10 mg TMPyP and 300 to 400 p i o f a s o l v e n t ,

w i t h or w i t h o u t a l i g a n d , t o an ESR t u b e . The s o l u t i o n

was purged w i t h a rgon , 2 mg o f C o * * N 0 3 . 6 H 20 was

s i m u l t a n e o u s l y added and t h e t ube was h e a t e d to about 80°C

o v e r n i g h t i n an a rgon a t mos phe r e .

Ba tches o f f i v e samples were made i n a s m a l l

11c e n t r i f u g e t u be . About 10 mg o f Co N 0 ^ . 6 H 20 was added t o

2 ml o f an argon purged aqueous s o l u t i o n c o n t a i n i n g 50 mg

oTMPyP . The c e n t r i f u g e t u b e was h e a te d t o about 90 C i n an

argon a t mosphe re o v e r n i g h t . A f t e r c o o l i n g , samples were

t r a n s f e r r e d t o each o f f i v e ESR t ubes u s i n g s t e e l t r a n s f e r

t u b i n g .

I f m e t h a n o l was used as a s o l v e n t , e i t h e r i n t h e

p r e p a r a t i o n o f s i n g l e or b a t c h samples , t h e c o b a l t was

added as anhydrous CoCl^ d i s s o l v e d i n m e t h a n o l .

The c o n c e n t r a t i o n o f C o * * N 0 ^ . 6 H 20 was reduc ed by a

f a c t o r o f 10 i n l a t e r p r e p a r a t i o n s i n o r d e r t o g i v e b e t t e r

1 4r e s o l v e d N s u p e r h y p e r f i n e s t r u c t u r e i n ESR s p e c t r a .

A t t e m p t s t o r e d u c e Co* * * TMPyP w i t h d i t h i o n i t e or

a s c o r b i c a c i d caused d e c o m p o s i t i o n o f t h e complex .

2 2 5

Samples f o r NMR s t u d i e s

A s m a l l c e n t r i f u g e t u b e c o n t a i n i n g an argon purged

s o l u t i o n o f 12 . 3 mg TMPyP , 3 . 5 mg anhydrous CoCl^ i n 1 ml

D^0 was h e a t ed i n an a r gon a t mosphe re a t 70°C , o v e r n i g h t .

5 p i o f cone NaOD was added t o t he c oo led s o l u t i o n and t he

p r e c i p i t a t e d excess c o b a l t was s e p a r a t e d by s p i n n i n g i n a

c e n t r i f u g e . To each o f two NMR tubes , 300 p i o f the

s u p e r n a t a n t was t r a n s f e r r e d u s i n g s t e e l t u b i n g f o l l o w e d by

an i n j e c t i o n o f 0 . 3 p i o f t - b u t y l a l c o h o l . The pD o f a

s i m i l a r s o l u t i o n was f ound t o be 1 2 . 5 . Sample 1 was made

w i t h 27 mg o f TMPyP and 4 . 3 mg o f anhydrous CoCl^ , the

c o n c e n t r a t i o n s o f CoI I TMPyP pr oduced were

Sample 1 19 . 7 x 10 “ 3 M

- 3Samples 2 and 3 13. 1 x 10 M

3 . 1 0 . 2 . M a t e r i a l s

B e n z i m i d a z o l e (98 l ) o b t a i n e d f rom A l d r i c h was t w i c e

sub l i med i n vacuum o n t o a c o l d f i n g e r t o g i v e w h i t e

. . oc r y s t a l s . The m e l t i n g p o i n t was 170 - 171 C , t he

l i t e r a t u r e ( 53c ) v a l u e i s 1 7 0 . 5°C .

PIPES was o b t a i n e d f ro m Sigma , r e c r y s t a l l i s e d f rom

d i s t i l l e d w a t e r and d r i e d i n vacuum .

C a l c u l a t e d f o r C0 H . 0N 0 _ So8 1 o c o 2

C 3 1 . 7 8 H 6 . 0 0 N 9 . 2 6

Found C 3 1 . 6 5 H 6 . 0 0 N 9 . 1 7

A l l o t h e r l i g a n d s were used as r e c e i v e d . The

c o n c e n t r a t i o n o f t h e aqueous l i g a n d was 0 . 0 5 M u n l e ss

o t h e r w i s e s t a t e d .

2 2 6

1 5NV 0 3 ( 9 9 . 0 atom 7. ) was o b t a i n e d f rom Prochem . A

0 . 5 M aqueous ammonia b u f f e r was made by add ing 40 mg o f

NH. N0._ t o 1 ml o f an argon purged 0 . 2 5 M NaOH s o l u t i o n . 4 J100 p i o f t h i s s o l u t i o n was i n j e c t e d i n t o t h e aqueous

Co**TMPyP sample .

2 2 7

P r e p a r a t i o n , p u r i f i c a t i o n and a n a l y s i s

2 2 8

A . 1 . Ca rbona t e f r e e NaQH

A c a r b o n a t e f r e e s o l u t i o n o f aqueous NaOH was made by

a d ev e lo p me nt o f V o g e l ’ s ( 8 6 c ) t e c h n i q u e . 15 g o f NaOH

p e l l e t s and 15 ml o f d i s t i l l e d w a t e r were p l a c e d i n a PTFE

c e n t r i f u g e t ube , s t o p p e r e d and l e f t o v e r n i g h t . The t ube

was c e n t r i f u g e d a t h i gh speed f o r 15 m i n u t e s . Us ing a

p l a s t i c s y r i n g e w i t h p o l y p r o p y l e n e t u b i n g , 4 ml o f the

s u p e r n a t a n t was t r a n s f e r r e d t o 94 ml o f d i s t i l l e d w a t e r .

The whole t r a n s f e r was done i n a g l o v e bag . A f i n a l

c o n c e n t r a t i o n o f 0 . 6 M was e s t i m a t e d .

4 . 2 . I m i d a z o l e s

1 - h i s t i d i n e h y d r o c h l o r i d e was o b t a i n e d f rom BDH and

used as r e c e i v e d . The o t h e r i m i d a z o l e s were o b t a i n e d f rom

A l d r i c h and p u r i f i e d . 1 m e t h y l i m i d a z o l e was d r i e d over

3 A m o l e c u l a r s i e v e s . 4 m e t h y l i m i d a z o l e was s ub l i med onto

oa co l d f i n g e r a t 0 C i n vacuum . 2 m e t h y l i m i d a z o l e was

r e c r y s t a l l i s e d f rom t o l u e n e i n an a rgon a t mosphe re and

i m i d a z o l e was r e c r y s t a l l i s e d f rom c h l o r o f o r m . 4 m e t h y l

i m i d a z o l e i s d e l i q u e s c e n t and so t h e d r i e d s o l i d was

han d l ed i n an argon f i l l e d g l o v e bag .

4 . 3 . F ree base p o r p h y r i n s

4 . 3 . 1 . TPvP

These compounds were s y n t h e s i s e d a c c o r d i n g t o t he

p r o c e d u r e p u b l i s h e d by Longo e t a l ( 133 ) . The d e t a i l s and

t h e p u r i f i c a t i o n p r o c e d u r e a r e o u t l i n e d h e r e .

229

m-T Pv P

6. 71 g o f p y r r o l e was added to a r e f l u x i n g s o l u t i o n

o f 10 . 7 g o f 3 - p y r i d i n e c a r b o x a l d e h y d e i n 400 ml p r o p i o n i c

a c i d . A f t e r r e f l u x i n g f o r a f u r t h e r 45 m i n u t e s , the

p r o p i o n i c a c i d was e v a p o r a t e d u s i n g a r o t a r y e v a p o r a t e r a t

reduc ed p r e s s u r e . The t a r r y r e s i d u e was h e a te d w i t h 300 ml

o f b o i l i n g aqueous 5 l KOH f o r 35 m i n u t e s . The r e s i d u e was

f i l t e r e d f rom t h e c o o l e d l i q u i d , washed w i t h warm w a t e r

and d r i e d a t t h e f i l t e r .

The r e s i d u e was d i s s o l v e d i n 50 ml o f d i s t i l l e d CHCl^

and poured e v e n l y on t o a 7 x 10 cm a l um in a column . The

m-TPyP was e l u t e d g r a d i e n t w i s e f rom d i s t i l l e d t o 5 0 / 5 0

d i s t i l l e d / non d i s t i l l e d CHCl^ . The m-TPyP e l u t e s as a

red band . 1 g o f 2 , 3 d i c h l o r o - 5 , 6 d i c y a n o - 1 , 4 - b e n z o q u i n o n e

i n 30 ml o f t o l u e n e was added t o 430 ml o f a r e f l u x i n g

s o l u t i o n o f t h e m-TPyP i n d i s t i l l e d CHCl^ . The r e f l u x was

c o n t i n u e d f o r 50 m i n u t e s .

The c o o l e d r e a c t i o n s o l u t i o n was poured o n t o a

6 x 10 cm a l u m i n a column and e l u t e d g r a d i e n t w i s e f rom

d i s t i l l e d t o 6 0 / 4 0 d i s t i l l e d / non d i s t i l l e d CHCl^ . A

m in or y e l l o w band was f o l l o w e d by t h e main r ed m-TPyP

band .

The m-TPyP was r e p r e c i p i t a t e d f rom 250 ml o f

C^ 2 C^2 m e t h a n o l and d r i e d a t 100°C f o r 24 hours i n

vacuum , to y i e l d 2 . 7 5 g .

C a l c u l a t e d f o r C. nH0(.N_H U d o oC , 7 7 . 6 5 H . 4 . 2 4 N , 1 8 . 1 1

Found

C . 7 7 . 7 2 H . 4 . 2 3 N , 1 8 . 0 1

2 3 0

p - T P y P

1 6 . 2 5 g o f p y r r o l e was added to a r e f l u x i n g s o l u t i o n

o f 26 g o f 4 - p y r i d i n e c a r b o x a l d e h y d e and 1 l i t r e o f

p r o p i o n i c a c i d . The r e f l u x i n g was c o n t i n u e d f o r 45 m i n u t e s

and t he p r o p i o n i c a c i d was e v a p o r a t e d us i ng a r o t a r y

e v a p o r a t e r under reduced p r e s s u r e . The r e s i d u e was washed

a t a s i n t e r e d g l a s s f u n n e l w i t h DMF and e t h e r to y i e l d

6 . 6 g .o2 l i t r e o f d i s t i l l e d CHCl^ was warmed t o 40 C w i t h

2 g o f c r ude p-TPyP and f i l t e r e d t h r o u g h a f l u t e d f i l t e r

pap er .

T h i s sample was run onto a 7 x 9 cm column o f

a l u m in a . The column was e l u t e d g r a d i e n t w i s e up t o 5 0 / 5 0

d i s t i l l e d / non d i s t i l l e d CHC13 . The red band was

c o l l e c t e d and t h e volume was reduced t o 70 ml . The s o l i d

was p r e c i p i t a t e d u s i n g m e t h a n o l and d r i e d i n vacuum .

C a l c u l a t e d f o r C, _H N_40 26 8

C , 7 7 . 6 5 H . 4 . 2 4 N . 1 8 . 1 1

Found

C . 7 6 . 7 4 H . 4 . 2 8 N , 17 . 54

Notes

1 . p-TPyP i s s i g n i f i c a n t l y l e s s s o l u b l e t h a n m-TPyP i n

CHCl^ ( 1 3 4 , 1 3 5 ) . An i mp ro ve me nt i n s o l u b i l i t y by

i n c o r p o r a t i n g Fe or Zn a t t h i s s t a g e was no t p o s s i b l e s i n ce

Fe p-TPyP and Zn p-TPyP w e r e both found t o be l e s s s o l u b l e

t han p-TPyP i n CHCl^ .

2. May and Baker l a b g r a d e CHCl^ c o n t a i n s 1 7. e t h a n o l as

a s t a b i l i s e r . Th i s makes t h e CHCl^ more p o l a r t h a n i s

23 1

r e q u i r e d f o r t h i s c h r o m a t o g r a p h y . T h e e t h a n o l ma y b e

removed by d i s t i l l a t i o n f rom P_0_ or by p a s s i n g t h r o u g h az 5column o f 9 DH 5A m o l e c u l a r s i e v e s .

oThe m o l e c u l a r s i e v e s wer e hea ted t o 260 C f o r s e v e r a l

days b e f o r e use . A 3 . 5 x 450 cm column was packed in a

g l a s s t u be spr ayed w i t h y e l l o w l a c q u e r and was s u f f i c i e n t

to t r e a t 3 . 5 l i t r e o f non d i s t i l l e d CHCl^ . NMR was used

t o t e s t f o r e t h a n o l .

4 . 3 , 2 . T ( M. E t ) PvP

An a d a p t a t i o n o f t h e method r e p o r t e d by

P a s t e r n a c k e t a l ( 21 ) was used .

m-TMPvP

160 mg m-TPyP , 960 mg m e t h y l p - t o l u e n e s u l p h o n a t e

and 64 ml DMF were r e f l u x e d under argon f o r 90 m i n u t e s .

The r e a c t i o n s o l u t i o n was f i l t e r e d and 64 ml o f e t h e r was

oadded . A f t e r c o o l i n g t o 10 C f o r 90 m i n u t e s t he

p r e c i p i t a t e was f i l t e r e d and washed w i t h a c e t o n e , CHCl^

and e t h e r . The m-TMPyP was r e p r e c i p i t a t e d f rom about 10 ml

o f m e t h a n o l / a c e t o n e , f i l t e r e d , washed w i t h a c e t o n e and

od r i e d i n vacuum a t 110 C f o r 24 hours t o y i e l d 200 mg .

C a l c u l a t e d f o r C_ _H _ N . 0 „ _ S ,72 66 8 12 4

C . 6 3 . 4 2 H . 4 . 8 8 N . 8 . 2 2 S . 9 . 4 0

Found

C . 6 1 . 3 2 H . 4 . 7 3 N . 8 . 0 2 S . 9 . 2 9

M o l e c u l a r R a t i o s :C H N S

7 2 6 6 . 1 8 8 . 0 8 4 . 0 9

2 3 2

p - T M P v P

1 g p-TPyP , 31 g m e t h y l p - t o l u e n e s u l p h o n a t e and

770 ml DMSO were r e f l u x e d f o r 50 m in u t e s i n an a rgon

a t mosphere . 2230 ml o f e t h e r and 30 ml o f a c e to n e wer e

measured out and t he c o o l e d r e a c t i o n s o l u t i o n was added .

The s us p en s i o n was f i l t e r e d t h r o u g h a 7 cm d i a m e t e r No 3

s i n t e r e d g l a s s f u n n e l . The s o l i d was washed w i t h a c e t o n e

and r e p r e c i p i t a t e d f ro m 100 ml o f m e t h a n o l / b u t a n o n e t o

y i e l d 1 . 67 g .

C a l c u l a t e d f o r C7 2 H6 6 N8 0 1 2 S4

C , 63 . 42 H . 4 . 8 8 N . 8 . 2 2

Found

C . 6 3 . 1 2 H . 4 . 8 4 N . 8 . 2 0

M o l e c u l a r r a t i o sC H N

72 6 5 . 7 9 8 . 0 2

m-TEtPvP

A s o l u t i o n o f 122 mg o f m-TPyP and 1 g o f e t h y l

p - t o l u e n e s u l p h o n a t e i n 50 ml o f d r y OMF was r e f l u x e d f o r

90 m i n u t e s under argon . The DMF was e v a p o r a t e d on a r o t a r y

e v a p o r a t o r under reduc ed p r e s s u r e . An i n i t i a l a t t e m p t t o

p r e c i p i t a t e t h e p r o d u c t f rom m e t h a n o l / a c e t o n e produced an

o i l . T r i e t h y l amine was added to t u r n t h e o i l f rom gr een

t o red and t h e o i l was l e f t t o s t and o v e r n i g h t . The

r e s i d u e was f i l t e r e d and d r i e d i n vacuum t o y i e l d 230 mg .

C a l c u l a t e d f o r C__H_ . NoO. _S.f b ( b o I c

C , 6 4 . 3 0 H , 5 . 2 5 N , 7 . 8 9

Found

C . 5 9 . 1 0 H . 5 . 1 6 N . 7 . 2 3

2 3 3

M o l e c u l a r r a t i o sc H N

76 7 9 . 0 7 7 . 9 7

Notes

1 . To a v o i d t h e f o r m a t i o n o f an o i l when a t t e m p t i n g t o

p r e c i p i t a t e T ( M , E t ) P y P , a l l g l a s s w a r e should be oven d r i e d

and a l l s o l v e n t s should be d r i e d over 3A m o l e c u l a r s i e v e s .

I t i s a d v i s a b l e to use a l a r g e enough r e c e i v e r f l a s k so

t h a t t he r e a c t i o n s o l u t i o n can be f i l t e r e d i n a s i n g l e

s t e p . The t op l a y e r o f t h e s u p e r n a t a n t tends to r e d i s s o l v e

t h e p r e c i p i t a t e , so t h e f i l t e r should be run d r y once

o n l y .

2. p-TPyP i s s i g n i f i c a n t l y l e s s s o l u b l e t han m-TPyP i n

OMF , so DMSO i s used as a s o l v e n t i n s t e a d .

3. An a t t e m p t t o p r e p a r e m-TEtPyP f rom m-TPyP and E t I i n

r e f l u x i n g DMSO gave a w a t e r s o l u b l e p r o d u c t . 1H NMR showed

t he N - a l k y l groups t o be a m i x t u r e o f m e t h y l and e t h y l .

Presumably some i n t e r a c t i o n o f E t I and DMSO t ook p l a c e .

Thi s does not a p p ea r t o be a p r ob l em w i t h DMF and e t h y l

p - t o l u e n e s u l p h o n a t e .

4 . 4 . E t h y l p - t o l u e n e s u l p h o n a t e

E t h y l p - t o l u e n e s u l p h o n a t e was s y n t h e s i s e d by a

v a r i a t i o n o f t h e method r e p o r t e d by Roos e t a l ( 136 ) .

500 ml o f a s o l u t i o n o f 100 g o f t e c h n i c a l p - t o l u e n e

sulphono c h l o r i d e i n t o l u e n e was f i l t e r e d and washed i n a

s e p a r a t i n g f u n n e l w i t h 3 x 80 ml o f 5 /l NaOH ( aq ) . The

t o l u e n e s o l u t i o n was s t i r r e d f o r 30 m i n u t e s w i t h 17 g

powdered K^CO^ ' f i l t e r e d and t h e t o l u e n e was e v a p o r a t e d on

2 3 4

a r o t a r y e v a p o r a t o r . T h e r e s i d u e w a s w a s h e d a t a f i l t e r

w i t h a s m a l l volume o f t o l u e n e and d r i e d under vacuum ,

o v e r n i g h t .

11 . 5 g o f e t h a n o l and 2 6 . 3 g o f p - t o l u e n e su l phono

c h l o r i d e were t r a n s f e r r e d to a 250 ml t h r e e neck f l a s k ,

f i t t e d w i t h a m e c h a n i c a l s t i r r e r , a t h e r mo m e te r and a

100 ml s e p a r a t i n g . f u n n e l . 40 ml o f 5 M NaOH ( a q ) was

s l o w l y run i n . A n o t h e r p o r t i o n o f 2 6 . 3 g o f p - t o l u e n e

sul phono c h l o r i d e was added and then a f u t h e r 40 ml o f 5 M

NaOH ( a q ) was run i n . The NaOH was added a t such a r a t e as

t o keep t h e r e a c t i o n t e m p e r a t u r e between 14 - 2 1 °C . The

whole a d d i t i o n took 45 m i n u t e s .

A f t e r f o u r hours o f f u r t h e r s t i r r i n g t h e aqueous

l a y e r was f i l t e r e d away . The r e s i d u e was added t o pe t

e t h e r and t h e aqeuous l a y e r was s e p a r a t e d . The s o l u t i o n

was washed w i t h 6 ml o f 10 1. aqueous NaOH and d r i e d over

2 . 8 g o f anhydrous K^CO^ .

The p e t e t h e r was d i s t i l l e d o f f and t h e r e s i d u e was

vacuum d i s t i l l e d . An i n i t i a l f r a c t i o n o f u n r e a c t e d

p - t o l u e n e su l phono c h l o r i d e was f o l l o w e d by a f r a c t i o n

between 136 t o 143°C a t 2 . 7 5 mm Hg . The ^H NMR shows t h i s

f r a c t i o n t o be a m i x t u r e o f e t h y l p - t o l u e n e

s u l p h o n a t e (83 I. ) and p - t o l u e n e su lphono c h l o r i d e (17 '/ .) .

The y i e l d was 16 g .

2 3 5

A P P E N D I X 1

FeTMPyP

2 3 6

Appendix J.

Th i s ap p en d i x cover s t h e a l e g b r a and computer programs f o r

t he e v a l u a t i o n o f d a t a f rom e x p e r i m e n t s us i ng Fe I I I TMPyP .

S e c t i o n 1 . 6 and p a r t o f s e c t i o n 1.1 r e f e r to g e n e r a l t h e o r y

and t h e r e m a i n i n g s e c t i o n s r e f e r t o p a r t i c u l a r

e x p e r i m e n t s .

1.1 S p e c t r o p h o t o m e t r i c t i t r a t i o n s

T i t r a t i o n s wh i ch i n v o l v e one a b s o r b i n g r e a g e n t "R" and one

a b s o r b i n g p r o d u c t "P" w i t h a 1:1 s t o i c h i o m e t r y a r e a

s p e c i a l case . I f a bs or bance s a r e c o r r e c t e d f o r d i l u t i o n ,

t he n (CR] + CP] ) may be t a k e n as c o n s t a n t .

A = e R.CR] + e CP]

Where e R and a r e t h e e x t i n c t i o n c o e f f i c i e n t s f o r R and P

r e s p e c t i v e l y .

At t h e b e g i n n i n g o f t h e t i t r a t i o n

e R Aq / ( C R ] + CP] )

At t h e end o f t h e t i t r a t i o n

A 1o Q/ ( C R] + CP])

By s u b s t i t u t i o n f o r e and e and m u l t i p l y i n g by (CR] + CP])K P

A. ( CR] + CP] ) A 0 .CR] ♦ A i o q .CP]

R e a r r a n g i n g g i v e s

CP]

CR]

tA - V

( A 100 - A1{ 1 }

2 3 7

Al so A. ( CR] + CP] ) Aq . ( CR] + C P ] ) - Aq . CP] + A1q o . CP]

So (A - A ) ( CR] + CP]) = ( A 10 q - Aq ) . C P ]

CP]And

( CR] + CP] )

(A - V

, A 100 - Ao>{ 2 }

S p e c t r o p h o t o m e t r i c t i t r a t i o n o f F e T ( M. E t ) PvP

KA1P F e ( OH ^ ) 2 ^ — — PFe(OH2 ) (OH) + H

BASE

C BASE]CH+ ]

CACID]

ACID

A 1

CBASE]So ------------

CACID]

A 1

CH+ ]

T h i s i s a s p e c i a l case o f t h e t y p e d e s c r i b e d above , so

0 <1<

C BASE]

( A 1 0 0 ~ A> CACID]

Hence l og

i-----o<i<i______

l o g ( K ) A 1 + l o g1

A - AL 1 oo J

1—1+Xi_i

______1

= PH PKA1

A p l o t o f l o g { ( A - Aq ^ ^ A 1 0 0 " ve r sus pH has a s l o p e o f

u n i t y and t h e pH i n t e r c e p t i s pK, , .A 1

2 3 8

1 . 2 To c a l c u l a t e oK._ f r o m m a q n e t i c moment d a t aA 2

The e q u i l i b r i u m o f i n t e r e s t between monomers i s :

A 2P F e( OH ^ ) ( OH) ^ ^ P F e ( OH ) + H

We can assume t h a t b o t h monomer ic s p e c i e s have t h e same

m a gn e t i c moment so

M2 .C F e ] T MM ' CM;iT2+ uH0 2CD] C1 }

where C M] = CPFe(OH2 ) (OH) ] + CPFe(OH)2 ]

CF e] = CM]t + 2 C D ]

So 2CD] = C Fe ] T - cm] t

S u b s t i t u t i n g f o r 2 CD] i n e q u a t i o n { 1 } and r e a r r a n g i n g g i v e s

CM] T = C F e ] T .(M

2 2 . PD

{ 2 }(H

2 2 , M - MD ’

CD]We know t h a t K = ------------------------------- -

D CPFe(OH2 ) ( O H ) ] 2

S u b s t i t u t i n g f o r CD] and r e a r r a n g i n g g i v e s

C P F e ( OH 2 ) (OH) ]C F e ] T - CM]t

2k d

S u b s t i t u t i n g f o r

CPFe(0H2 ) (OH) ]

CM]t u s i n g { 2 } and c o l l e c t i n g l i k e te rms

C Fe]T (PM2 - M2 )

2 K D ’ (^ M 2 - ^ D 2 '{ 3 }

From t he d e f i n i t i o n o f CM]^ above

CPFe(OH) ] = CM]t - CPFe(OH2 ) (OH) ] { A}

CPFe(OH) ] CH+ ]We know K = ------------------------------- { 5 }

A 2 CPFe(OH2 ) (OH) ]

239

Using e q u a t i o n s { 2 } t o { 5 } a v a l u e o f K can be

c a l c u l a t e d . The f o l l o w i n g d a t a i s used

mmn 5 . 9 6

m dr 1 . 83

k d= 3 1 . 6 x 1 0 3 mol 1 1

and f rom G o f f and M o r g a n ’ s r e s u l t s ( 1 9 )

M ii ( 1 M NaOH )

CFe] T = 0 . 0 1 M

The v a l u e o f K i s v e r y i o n i c s t r e n g t h dep enden t , and

v a l u e i n 1 M NaOH i s no t a v a i l a b l e . So an e s t i m a t e

t w i c e t h e v a l u e o b t a i n e d i n t h i s work a t I = 0 . 5 0 M ,

made .

C a l c u l a t i o n

cm] t = 5 . 8 2 5 X 1 0 ' 3 M

CP(=g(0H2 ) (OH) ] - 4= 2 . 5 7 0 X 1 0 M

CPFe(OH) ]- 3

= 5 . 5 6 8 X 1 0 M

t h e

o f

wa s

1 .3 S p e c t r o o h o t o m e t r i c d e t e r m i n a t i o n o f d i m e r i s a t i o n c o n s t a n t

The e q u i l i b r i u m o f i n t e r e s t i s

K2 PFe(OH^) (OH) PFe-O- FeP + 3 H2 0

[ P F e - O - F e P ]k - 2 ^1 y

C P F e ( OH ) (OH) ]

S u b s t i t u t i n g ( C F e ] T - [ P F e ( OH ) ( OH) ] ) / 2 f o r [ P F e - O - F e P ]

i n e q u a t i o n { 1 } and e x p a n d i n g g i v e s

2 . K Q. CPFe(OH2 ) (OH ) ] 2 + CPFe( 0H2 ) ( OH ) ] - C F e ] y = 0

Th i s i s a q u a d r a t i c i n CPFe(OH2 ) ( O H ) ] , t h e r o o t s o f wh ich

a r e g i v e n by

1 + 8 .K [ F e ]------------- »---------- L {2}

4 . Kd

Only t h e p o s i t i v e r o o t i s m e a n i n g f u l .

- 1 ± yCPFe(OH ) (OH) ] = ---------- -

From B e e r ' s Law

A = e . CPFe(OH ) ( O H ) ] . 1 + 2 . . [ P F e - O- F e P ] . 1M 2 U { 3 }

S u b s t i t u t i n g ( [ F e ] - [ P F e ( OH ) ( O H ) ] ) / 2 f o r [ P F e - O - F e P ]

i n e q u a t i o n { 3 } and c o l l e c t i n g l i k e terms g i v e s

A = " Gn ) • C P F e ( O H ) ( O H ) ] . 1 + e _ . [ F e ] _ . lM D 2 D T {4 )

By s u b s t i t u t i n g f o r [ P F e ( OH ) ( OH) ] i n { 4 } u s i ng { 2 }

(EM - V •/-1 + / 1 + 8 . K . [ Fe ]

4 . K + eD * CFe3T . 1 {5 }

By d e f i n i t i o n

A

[ Fe ] T . 1

24 1

So f rom { 4 }

e = ---- - ---------— . CPFetOH ) ( OH) ] + e { 6 }C Fe ] T

C o n s i d e r i n g { 6 } , a t h i g h c o n c e n t r a t i o n [ P F e ( 0H2 ) ( OH ) ] = 0

and [ P F e - O - F e P ] = CF e ] T / 2

so e = gD

At low c o n c e n t r a t i o n [ PFe ( OH^) ( OH) ] = [ F e ] ^ and

[ P F e - O - F e P ] = 0

so g = gvj .

Computer Program

The a r i t h m e t i c i n e q u a t i o n { 5 } may be s i m p l i f i e d t o g i v e

[ < e M - e p ) • ( y ° . 0625 ♦ 0 . 5 . K 0 . [ F e ] T - 0 . 2 5 ) / K Q ^ p . C F e ^ J . l

In o r d e r t o w e i g h t t h e e x p e r i m e n t a l r e s u l t s

c o r r e c t l y , t h e computer p r ogram m i n i m i s e s t h e d e v i a t i o n :

D e v i a t i o n = H A - A „ ) ^exp c a l

A l g e b r a i c t e r m Program v a r i a b l e name

A ABSORB(J )exp

k dCNST

C Fe ] T CONC( J )

D e v i a t i o n DEVN

ED EXTD

EM " E D EXT DIFF

eM EXTM

1 PATH( J )

2 4 2

F o r t r a n program

PROGRAM DIMERIS ( INPUT, OUTPUT, TAPE5=INPUT, TAPE6=0UTPUT)CC A PROGRAM TO BEST FIT VALUES OF DIMERISATION CONSTANT AND C EXTINTION COEFFICIENTS TO SPECTROPHOTOMETRIC DATA C

DIMENSION ABSORB( 5 0 ) ,CONC(50).PATH(50)DIMENSION RLGCONC( 5 0 ) ,EXTEXP(50),EXTCALC(50)

C READ IN EXPERIMENTAL DATA AND INFORMATION ON PARAMETERS C TO BE VARIED

READ( 5 . * )IPOINTS,EXTM.IM.EXTD,ID.CNST,IC READ( 5 . * ) ( CONC( J ) , J = 1 . I POINTS)

C ARE THERE ANY VARIABLES?IRESULT =IM +ID+ ICI F ( IRESULT.EQ.0 ) GO TO 1200READ( 5 . * ) (ABSORB( J ) . J =1 . I POINTS)READ( 5 , * ) ( PATH( J ) , J=1, I POINTS)

C FIND FIRST DEVIATION EXTDIFF=EXTM-EXTD DEVN = 0 .0DO 100 J=1, IPOINTSDEVN=DEVN+(ABSORB( J) - (EXTDIFF*( SORT(0.0625+0.5*CNST*CONC( J ) ) -0 .25)

C/CNST+EXTD*CONC(J))* PATH( J ) ) * * 2 100 CONTINUE

C STORE OLD VARIABLES 200 OLDEXTM=EXTM

OLDEXTD=EXTD OLDCNST=CNST

C IS THE MONOMER EXTINCTION TO BE VARIED?I F ( IM. EQ. 0 ) GO TO 500

C INITIALISE STEP STEP = 0 . 1

C VAIRY MONOMER EXTINCTION 300 EXTM=EXTM+STEP*EXTM

C WORK OUT EXTINTION DIFFERENCE EXTDIFF=EXTM-EXTD

C STORE PREVIOUS DEVIATION PREVS=DEVN

C WORK OUT NEW DEVN DEVN = 0.0DO 400 J=1, IPOINTSDEVN=DEVN+(ABSORB(J)-(EXTDIFF*(SQRT(0.0625+0.5*CNST*CONC(J)) -0.25)

C/CNST +EXTD*CONC( J ) )* PATH( J ) ) * * 2 400 CONTINUE

C IS DEVN SMALLER?IF(DEVN.LT.PREVS)GO TO 300

C IF NOT REDUCE STEP AND CHANGE DIRECTION STEP=-STEP/3.1

C ARE STEP AND CHANGES IN DEVN GREATER THAN 100PPM?I F (ABS( DEVN-PREVS) . GT.0.0001*DEVN.OR.ABS(STEP).GT.0.0001)GO TO 300

C IF NOT REGENERATE PENULTIMATE EXTM AND DEVN EXTM=EXTM+3.1*STEP*EXTM DEVN = PREVS

243

C IS THE DIMER EXTINCTION TO BE VARIED?500 I F ( 10 . EQ. 0 ) GO TO 300

C INITIALISE STEP STEP=0.1

C VAIRY DIMER EXTINCTION GOO EXTD=EXTD*STEP*EXTD

C WORK OUT EXTINCTION DIFFERENCE EXTDIFF=EXTM-EXTD

C STORE PREVIOUS DEVIATION PREVS = DEVN

C WORK OUT NEW DEVN DEVN = 0.0DO 700 J=1 , IPOINTSDEVN=DEVN+( ABSORB( 3 ) - (EXTDIFF*( SORT(0.0625+0.5*CNST*CONC(J) ) -0 .25)

C/CNST+EXTD*CONC(J))* PATHCJ) ) * * 2 700 CONTINUE

C IS DEVN SMALLER?IF(DEVN.LT.PREVS)GO TO 600

C IF NOT REDUCE STEP AND CHANGE DIRECTION STEP = -STEP/3.3

C ARE STEP AND CHANGES IN DEVN GREATER THAN 100PPM?IF(ABS(DEVN-PREVS). GT. 0.0001*DEVN. OR. ABS( STEP) . GT. 0.0001)GO TO 600

C IF NOT REGENERATE PENULTIMATE EXTD AND DEVN EXTD=EXTD+3. 3*STEP*EXTD DEVN=PREVS

C IS THE DIMERISATION CONSTANT TO BE VARIED?800 I F ( IC . EQ. 0 ) GO TO 1100

C INITIALISE STEP STEP=0.1

C SET EXTINCTION DIFFERENCE EXTDIFF=EXTM-EXTD

C VAIRY DIMERISATION CONSTANT 900 CNST=CNST+STEP*CNST

C STORE PREVIOUS DEVIATION PREVS = DEVN

C WORK OUT NEW DEVN DEVN = 0 .0DO 1000 J=1, IPOINTSDEVN=DEVN+ (ABSORB!J) - ( EXTDIFF*( SORT(0.0625 + 0 . 5*CNST*C0NC(J ) ) - 0 . 25 )

C/CNST + EXTD*CONC(J))* PATH( J ) ) **2 1000 CONTINUE

C IS DEVIATION SMALLER?IF(DEVN.LT.PREVS)GO TO 900

C IF NOT REDUCE STEP AND CHANGE DIRECTION STEP=-STEP/5.1

C ARE STEP AND CHANGES IN DEVN GREATER THAN 100PPM?IF(ABS(DEVN-PREVS). GT.0.0001*DEVN. OR. ABS( STEP) . GT.0 .0001)GO TO 900

C IF NOT REGENERATE PENULTIMATE DIMERISATION CONSTANT AND DEVN CNST = CNST+ 5 . 1*STEP*CNST OEVN=PREVS

C ARE THE CHANGES IN THE VARIABLES GREATER THAN 500PPM?1100 IF(ABS(EXTM-OLDEXTM) . GT.0 .0005*EXTM)GO TO 200

I F (ABS( EXTD-OLDEXTD) . GT.0 .0005*EXTD)GO TO 200 IF(ABS(CNST-OLDCNST).GT.0.0005*CNST)GO TO 200

244

C WORK OUT LOG OF CONCENTRATIONS AND CALCULATED EXTINCTIONS 1200 EXTDIFF=EXTM-EXTD

DO 1300 J=1, IPOINTS RLGCONC(J)=ALOG10(CONC(J) )EXTCALC(J)=EXTDIFF*(SQRT(0.0625 + 0 . 5*CNST* CONC( J) ) - 0 . 2 5 ) /

C( CNST*CONC( J ) )*EXTD 1300 CONTINUE

C WRITE OUT VARIABLES WRITE ( 6 , HOO)

1400 FORMAT(1H1)WRITE(6,1500)

1500 FORMAT( 63H DIMERISATION CONSTANT MON EXTINCTION DIMER EXTCINCTION)

WRITE(6,1600)CNST. EXTM,EXTD 1 60 0 format: 1X,1PE12.4,14X,1PE12.4,7X,1PE12.4)

IF(IRESULT.NE.0)GO TO 2000 C PROGRAM CARRIES ON IF NO VARIABLES C WRITE OUT CONCENTRATIONS AND EXTINCTIONS

WR ITE( 6 ,1 700)1700 FORMAT( / / 5 5 H PT TOT CONCN LOG CONCN EXTINCTION P

CT)DO 1900 J=1.IPOINTSWRITE!6.1800)J.CONC!J). RLGCONC!J), EXTCALC( J ) . J

1 8 00 FORMAT! I X . ^ ^ X . I P E ^ ^ ^ X . I P E ^ ^ ^ X . I P E ^ ^ ^ X , ^ )1900 CONTINUE

GO TO 2700

C PROGRAM CARRIES ON IF ANY VARIABLES 2000 SUM=0.0

DO 2100 3= 1 , IPOINTSEXTEXP!J)=ABSORB(J)/(CONC!J)*PATH!J))SUM=SUM+( EXTCALC( J)-EXTEXP!J))**2

2100 CONTINUESTNDEVN=SQRT(SUM/FLOAT!IPOINTS-1))WR I TE( 6 .2 2 00 )

2200 FORMAT( / / 6 6 H CEFS/CM-1,M-1 )

WRITE(6,2300)2300 FORMAT( 8 8 H PT ABSORBANCE PATH/CM TOT CONCN

C CALCULATED LOG CONCN PT)DO 2500 J=1.IPOINTSWRITE(6,2400)J.ABSORB!J),PATH(J).CONC(J) , EXTE

CRLGCONC( J ) , J24 0 0 FORMAT!1X.1 2 . 1X .F5 .3 .6X .F6 .4 , 2X,1 PEI 2 . 4 , 4X. 1P

C4X, 1PE12.4.3X.12)2500 CONTINUE

WRITE(6,2600)STNDEVN2600 FORMAT( / / 24H ONE STANDARD DEVIATION=.1PE12.4)2700 CONTINUE

STOP END

EXTINCTION CO

EMPERICAL

P( J).EXTCALC!J),

12.4.4X,1PE12.4,

2 4 5

1 . 4 To c a l c u l a t e t h e m a g n e t i c m o m e n t o f d i m e r i c F e T M P v P

The e q u i l i b r i u m o f i n t e r e s t i s :

K2 PFe(OH 2 ) ( OH) * - - y PFe-O-FeP + 3 H2 0

I t has been shown , i n s e c t i o n 1 . 3 t h a t

[ P F e ( 0 H 2 ) ( OH ) ]-1 ♦ J 1 - 8 . KD . [ F e ] T


XT • C F e ] T = xM- CPFe( OH2 ) ( OH) ] + xQ . CPFe-0 - FeP]

X . CF e l T - x M.CPFelOH ) ( O H ) ]So x = -------------------------------------------------------------

D [ P F e - O - F e P ]

2. ( XT • C F e ] - XM - CPFe(OH ) ( O H ) ] )____ T_____ T____ M_________2______( [ F e ] T - CPFe(0H2 ) (OH) 3 )

M D = 7 9 7 . 6 6 . ^ 3 0 8 x ( XQ/ 2 )

Using t h e v a l u e o f K o f 5392 m o l " 11 ( I = 0 . 3 0 M)

d e t e r m i n e d s p e c t r o p h o t o m e t r i c a l l y , c a l c u l a t i o n s o f Xq a r e

made f rom two s e t s o f e x p e r i m e n t a l r e s u l t s .

Conditions CFe3T / 1 0 ' 3 H CPFe( 0H2 ) ( OH) ] / 1 0~3 M XD/10'8 Mo

0.25 M KC1 10.00 3.189 3.367 1 .82

0.25 M KC1 10.05 3.225 3.454 1 .84

The a v e r a g e r e s u l t s a r e x D -83 . 4 1 0 x 1 0 1 . 83

1 . 5 T h e o r y a n d c o m p u t e r p r o g r a m f o r c a l c u l a t i n g m a g n e t i c

moment v a r i a t i o n w i t h pH

The e q u i l i b r i a under c o n s i d e r a t i o n a r e :

KA. A 1 +P F e ( OH ^ ^ — PFe(OH2 ) ( OH) + H

2 P F e ( OH ) ( OH) PFe-O- FeP + 3 H2 0

l e t CM]t = [ P F e ( 0 H 2 ) 2 ] + [ P F e ( 0 H 2 ) ( O H ) ]

f rom t h e d e f i n i t i o n o f KA1

CPFe( OH2 ) 2 ][ P F e ( OH 2 ) (OH) ] . CH ]

A 1

So CM] [ P F e ( OH 2 ) ( OH ) ]

[ P F e ( OH2 ) (OH) ]

CH + ]

A 1

+ CPFe(OH2 ) (OH) ]

KA1 + CH ]

A 1

So CPFe( OH2 ) (OH) ] c m] t ■ k a i

KA1 + CH+]{ 1 }

C o n s i d e r i n g t h e s p e c i e s p r e s e n t

CD] ( C F e ] T - CM] ) / 2 { 2 }

Using e q u a t i o n s { 1 } and { 2 } t o s u b s t i t u t e i n t h e d e f i n i t i o n

f o r Kd g i v e s :

( C Fe ] T - CM] ). (K + CH + ] ) 2 ------------------------------- x -----

CM]T2 - KA1 2

Expanding t h i s e q u a t i o n and c o l l e c t i n g terms i n CM]^ g i v e s

2 . Kn . KA12 . [ M] _ 2 + (K. +CH+ ] ) 2 . CM] t - ( K a +CH+ ] ) 2 . C F e ] T = 0D A I T A1 T A1 T

Z k l

T h i s i s a q u a d r a t i c i n [ M ] ^ a n d t h e p o s i t i v e r o o t i s :

- ( KA 1 + [ H + ] ) 2 - 7 ( KA1*CH + ] ) 4 ♦ 8 . K D. KA12 . (KA 1 + CH+ ] ) 2 . [ F e ] r

4 . K . K . , D A 1

I t i s r e a s o n a b l e to assume t h a t both monomers have t h e same

m a g n e t i c moment , so

Xy • C F e ] T = x M- CMJt + x D . CPFe-O-FeP]

S u b s t i t u t i n g f o r CPFe-O-FeP] u s i ng {2 } and r e a r r a n g i n g g i v e s

XT = ( CM3T / C F e ] T ) . ( x m - X 0 / 2 ) + XQ/ 2

Mt = 7 9 7 . 6 6 J X j x 3 0 8 . 2

A l g e b r a i c e x p re s s i o n Program e x p r e s s i o n

C F e ] T CONCN( J )

, KA1 + CH+ j ) 2 CONST 1

4 .K .K 2 D A 1 CON ST 2

k dDIMER

pKA1 PEEKAY

pH PEHACH

[M3 T RMONT

PD RMUD

RMUM

°D RQD ( = CONST2/4 )

Xp/2 SUSEPT1

x„ - X d / 2 SUSEPT2

2 4 8

F o r t r a n p r o g r a m

PROGRAM FEPPH( INPUT,OUTPUT,TAPE5=INPUT,TAPE6 = 0UTPUT)C PROGRAM TO CALCULATE SUSEPTABILITIES OF IRON PORFYRIN GIVEN PK.KD C AND THE PH AND TOTAL IRON CONCENTRATIONS C

DIMENSION PROTON(30),SUSEPTC(3Q),RMONTOT(30),CONST 1(30)DIMENSION RMUC(30),PEHACH(30).CONCN(30)READ(5,*)I POINTS.PEEKAY.DIMER.SUSEPTM.SUSEPTD READ(5,*)(PEHACH(J),J=1,IPOINTS)READ(5,*)(CONCN(J),3=1,IPOINTS)DISOCN=10.0**(-PEEKAY)

CDO 100 J=1,IPOINTS PROTON(J)=10.0**(-PEHACH(J))CONST 1(J) = (DISOCN + PROTONt J))**2

100 CONTINUE C

CONST2=A.0*DIMER*DISOCN**2 SUSEPT1=SUSEPTD/2.0 SUSEPT2=SUSEPTM-SUSEPT1

CDO 200 J=1.IPOINTSRMONTOT(J)=(SQRT(CONST1(J)**2+2.0*CONST2*CONST1(J)*CONCN(J)) C-CONST1(J))/CONST2SUSEPTC(J)=(RMONTOT(J)/CONCN(J)) *SUSEPT2 + SUSEPT1 RMUC(J)=797.66*SQRT(SUSEPTC(J)*308.2)

200 CONTINUE C

RMUM=797.66*SQRT(SUSEPTM*308.2)RMUD=797.66*SQRT(SUSEPT1*308.2)RQD=CONST2/4.0 WRITE( 6,3 00 )

300 FORMAT(1H1)WR I TE(6.310)

310 FORMAT(/17H SUSEPTABILITIS )WR ITE( 6,320 )

320 FORMAT(21H MONOMER DIMER)WRITE(6,*)SUSEPTM,SUSEPTD WRITE(6.330)

330 FORMAT(/19H MAGNETIC MOMENTS)WRITE(6,340)

340 FORMAT(21H MONOMER DIMER)WRITE(6,*)RMUM,RMUD WR I TE( 6,350 )

350 FORMAT(/12H CONSTANTS)WR ITE( 6,360 )

360 FORMAT(31H PK K QD)WR I TE(6,*)PEEKAY.DIMER.RQD WRITE(6,370)

370 FORMAT(//57H TOT FE CONC TOT MON CONC SUSEPT MAG MOMENTC PH)DO 400 3=1,IPOINTSWRITEt 6,*)CONCN(3),RMONTOT(3).SUSEPTC(3),RMUC(3),PEHACH(3)

400 CONTINUE STOP END

249

1 . 6 E f f e c t o f b u f f e r c o o r d i n a t i o n

1 . G. 1 I n t r o d u c t i o n

Th i s s e c t i o n d e a l s w i t h t h e a l g e b r a f o r t i t r a t i o n s i n

g e n e r a l . Subsequent s e c t i o n s d e a l w i t h t h e s i m p l i f i c a t i o n s

t h a t occur f o r s p e c i f i c t i t r a t i o n s .

1 . 6 . 2 No t i t r a n t l i g a n d bu t b u f f e r p r e s e n t

The f o l l o w i n g e q u i l i b r i a a r e o f i n t e r e s t

KB1P F e ( OH _) _ + B * ° - P F e ( OH, ) ( B) + H_02 2 ----------------5^ 2 2

[ P F e ( OH ) ( B ) ]K = --------------------------------

C P F e ( O H ) 3 . [B]{1 }

PFe ( OH ) ( B ) + B ^ B--— ■ P F e ( B ) 2 + H2 0

C P F e ( B ) 3K = ---------------------------------

B 2 C P F e ( 0H2 ) ( B ) ] . CB3

where B i s a b u f f e r m o l e c u l e

From { 1 } C P F e ( OH 2 ) (B) 3 ii

CD C B 3 . [ P F e ( 0 H 2 ) 2 ]

From { 2 } CPFe(B) 3 CM03

II [ B 3 . CPFe( 0H2 ) ( B)3

= , .B 1 KB2 . [ B ] 2 . t P F e ( 0 H2 ) 2 ]

From t he d e f i n i t i o n o f K . „A 1

[ P F e ( 0 H 2 ) ( O H ) ] = KA 1 . [ P F e ( OH

1—1+Xi_ii—iCMCM


C P F e ( X ) { Y )3 =

[ PFe ( OH2 ) 2 3 + CPFe( OH2 ) (OH) 3 + C P F e ( 0 H2 ) ( B ) 3 + CPFe ( B) 2 3

Where X = 0H2 , B

and Y = X , 0H~

2 5 0

S u b s t i t u t i n g f o r [ P F e ( 0 H2 ) ( OH ) ] , [ P F e ( O H M B ) ] a n d

CPFe( B) ] u s i n g t h e e x p r e s s i o n s above and

g i v e s :

[ P F e ( OH^ ) 2 ] =

CPFe( X) ( Y ) ] / ( 1 + {K / C H * ] } * K . C B ] + K .K

1 . 6 . 3 T i t r a n t l i g a n d and b u f f e r p r e s e n t

The f o l l o w i n g e q u i l i b r i a a r e o f i n t e r e s t

P F e ( 0 H 2 ) 2 + L S P F e ( O H 2 ) ( L ) + H2 0

CPFetOH ) ( L ) ]K = ---------------------------------

CPFe(OH ) ] . CL]

K2P F e ( OH 2 ) ( L ) + L ^ P F e ( L ) 2 + H2 0

CPFe( L) ]

K2 = ---------------------------------------------------------[ P F e ( OH 2 ) ( L ) ] . CL]

The r a t i o and t h e p r o d u c t o f K1 and K

i n t e r e s t .

K1 CPFe( OH2 ) ( L ) ] 2

K2 [ PFe ( OH 2 ) 2 ] [ P F e ( L ) 2 ]

CPFe( L) ]P = K . K = ------------------ --------2 1 2 2 C PFe ( 0H2 ) 2 3 Cl_ 3 ^

r e a r r a n g i n g

CB] 2 ) {3 }

a r e a l s o o f

{ 4 }

{5}

25 1

At t h i s p o i n t t he f o l l o w i n g e q u i l i b r i u m must a l s o be

c o n s i d e r e d .

P Fe ( OH ) ( L ) + b * B- — P F e ( B ) ( L ) + H2 0

CPFe(B) ( L) ]K = --------------------------------- { 6 }

[ PF e ( OH ^ ) (L) ] . C B 3

From e q u a t i o n { 6 }

[ P F e ( B) ( L ) ] = K . C P F e ( O H ) ( L ) ] . C B ]□ L c.So C P F e ( X ) ( L ) ] = CPFe(OH ) ( L ) ] (1 + K . C B ] ) { 7}

C P L

Using e q u a t i o n s { 3 } and { 7 } t o s u b s t i t u t e f o r CPFelOH^)^]

and [ P F e ( OH ) ( L ) ] i n t h e d e f i n i t i o n s o f and g i v e s :

C P F e ( X M L ) ] (1 + C K / C H + ] } + K C B ] + K K C B ] 2 )^ __ ____________________ __________ A 1_____________________ p 1 ______________p i B Z ________K -

CPFe(X) ( Y ) ] CL] ( 1 + KBLCB] }

K2

CPFe( L) ]---------- --------- ---------- . ( 1 + K CB])C P F e ( X ) ( L ) ] CL]

CPFe( X) ( L) ]Le t ------------------------------ = K ‘

C P F e ( X ) ( Y ) ] CL] 1

CPFe( L) ]And --------------------— ------ = K ’

C P F e ( X ) ( L ) ] CL] 2

Let k ; .

- CM CQ.II- CM

C P F e ( L ) ]So p :

2c C P F e ( X ) ( Y ) ] . C L ] *

Where X = 0 H2 , B

Y =

iXoX

2 5 2

I f CB] >> [ F e ] ^ t h en CB] i s p r a c t i c a l l y u n a f f e c t e d by

c o o r d i n a t i o n . The [H ] i s h e l d c o n s t a n t by t he b u f f e r . So

under t he se c o n d i t i o n s and |3 a r e c o n s t a n t s .

1 . 6 . 4 No b u f f e r c o o r d i n a t i o n

In t h e absence o f any b u f f e r c o o r d i n a t i o n , t h a t i s when

CB] << K , u s i n g t h e e q u a t i o n s f o r K' , K' and K. / K_0 1 1 2 1 2

K

So

/ K 2 = K ’ / K ' z ( 1 + K

k ;r—l

+Xl—l

1 ______

k 2 K 2 '+r—i

+X 1_1

______1K^/ K^ i s pH i n d e p e n d e n t , so as CHf ] d e c r e a s e s be low ,

then K ’ / K^ w i l l d e c r e a s e .

1 . 6 . 5 P r o t o n a t i o n o f l i g a n d

The p r o t o n a t i o n o f t h e t i t r a n t l i g a n d must be t aken

i n t o account

Ka+ ^ A +L-H ^ L + H

C L ] . CH+ ]Ka = -----------------

A C L - H + ]

where L i s t h e u n c o o r d i n a t e d l i g a n d and L - H + i s - t he

p r o t o n a t e d l i g a n d

l e t C L ] p = C L - H + ] + CL]

2 5 3

S u b s t i t u t i n g f o r [ L ~ H + ] g i v e s

II<

CL] . CH + ]

( CL]_ - C L ] ) F

R e a r r a n g i n g g i v e s

CL] =k r u

------ £---------L----- { 8 }( K a + CH+ ] )A

2 5 4

1 . 7 M a g n e t i c t i t r a t i o n s

T h i s s e c t i o n d e a l s w i t h t he s i m p l i f i c a t i o n s t h a t

occur under the c o n d i t i o n s o f the m a g n e t i c t i t r a t i o n s .

[ P F e - O - F e P ] . [ H * ] 2By d e f i n i t i o n Q = -------------------------------------

[ P F e ( O H 2 ) 2 ] 2

S u b s t i t u t i n g f o r [ PF e ( OH2 ) 2 ] us i ng e q u a t i o n { 3 } s e c t i o n 1 . 6

g i v e s t he f o l l o w i n g f o r

[ P F e - O - F e P ] . [H + ] 2

CPFe( X) (Y) ] 2 1 + 7 ^ 7 - + K8 1 ' CB1 * KB 1 - KB2 - CB] 2L H J

l e tCPFe-O-FeP] . CH+ ] 2

C P F e ( X ) ( Y ) ] e f f

S i nce [B] >> [ F e ] ^ t h en CB] i s e s s e n t i a l l y unchanged by

c o o r d i n a t i o n . The l a t t e r t e r m i s a c o n s t a n t a t c o n s t a n t

[B] and CH ] . S i nce Q_ i s a c o n s t a n t t he n K „ „ must a l s oD e f f

be a c o n s t a n t a t a g i v e n v a l u e o f [B] and [ H + ] .

C P F e ( X ) ( Y ) ]

“e f f [ PFe ( OH2 ) 2 ]

So CPFe(OH ) ] = [ P F e ( X ) ( Y ) ] . / K r x / Qn2 2 V e f f D { 1 }

I n i t i a l p o i n t i n t i t r a t i o n j_ j t o t i t r a n t

S i nce t h e pH i s h e l d c o n s t a n t i t i s c o n v e n i e n t t o d e f i n e

a n o t h e r c o n s t a n t :

En = [H + ] 2 / K _ = [ PF e ( X ) ( Y )3 2 / [ D] { 2}D eff

2 5 5

Under t h e s e c o n d i t i o n s

C Fe]T = [P Fe(X ) (Y )] + 2. CD] {3}

Using e q u a t i o n {3 } to s u b s t i t u t e f o r CD] i n e q u a t i o n { 2 }

and ex p an d i n g g i v e s

2CPFe( X) ( Y) ] 2 ♦ E^CPFe( X) ( Y) 3 - EQ C Fe ] y = 0

Th i s i s a q u a d r a t i c i n C P F e ( X M Y ) ] w i t h a p o s i t i v e r o o t :

E0 ( - 1 * y i - 8 f F^ T / E D ) A { 4}

The i n i t i a l s u s c e p t i b i l i t y i s g i v e n by

C P F e ( X M Y ) ] CD]x t = XM. + x n •

T M C Fe ] T ° C Fe] T{ 5}

S u b s t i t u t i n g f o r CD] us i ng e q u a t i o n { 3 } and r e a r r a n g i n g

g i v e s

( 2 Xy " Xq )C P F e ( X M Y ) ] = -------!----------— . C Fe ]

( 2x - X ) T *M a D

{ 6 }

S u b s t i t u t i n g f o r C P F e ( X ) ( Y ) ] us i ng

r e a r r a n g i n g g i v e s

e q u a t i o n { 3 } and

(XM - xT >CD] = ---- 111--------- — . CFe]

( 2 Y “ X )* D

( 7 }

Using e q u a t i o n s { 6 } and { 7 } t o s u b s t i t u t e

g i v e s

( 2 x t - XD ) 2 • i Fe]E = --------- !--------------------------- !-----

( 2 x - x ) • ( X - Y ) a m * d * m

i n e q u a t i o n { 2 }

2 5 6

T i t r a n t l i g a n d p r e s e n t

L e t [ C ] T = CPFe( OH2 ) ( L) ] + [ P F e ( B ) ( L ) 3 + CP F e ( L ) 2 ]

= [ P F e ( X ) ( L ) ] + [ P F e ( L ) ] { 8 >

Where X = 0H2 , B

So [ F e ] T = [ P F e ( X ) ( V )3 + 2 . CD] + [ C ] T { 9}

S u b s t i t u t i n g f o r [ P F e ( X ) ( Y ) 3 i n e q u a t i o n { 2 } us i ng e q u a t i o n

{ 9 } and c o l l e c t i n g t er ms i n [D] g i v e s

4 C D] 2 - { E d + 4 ( C F e ] T - CC] ) } [ D ] + ( C F e ] y - C C 3 y ) 2 = 0

The r o o t s o f t h i s q u a d r a t i c a r e g i v e n by

Eq + CONST 1 Eq + CONST 1 ) 2 -C0NST1 2

Where CONST 1 = 4 ( [ F e 3 T - C C] T )

S u b s t i t u t i n g f o r [ P F e ( OH ) ( L ) 3 and CPFe(OH2 ) 2 3 i n

e q u a t i o n { 4 } s e c t i o n 1 . 6 u s i n g e q u a t i o n { 7 } s e c t i o n 1 . 6 and

e q u a t i o n { 1 } s e c t i o n 1 . 7 , g i v e s

K 1 [ P F e ( X M L ) ] 2 / “o^ 1— - — ■ ■ ■ ■ —— ^ / - ^ ' i

K2 CPFe( X) ( Y) 3 [ P F e ( L ) 2 3 J Kg f f (1 + K ^ . C B ] ) 2

C P F e ( X ) ( L ) ] 2 K ‘NB: -------------------------------------------- = — { 11}

C P F e ( X ) ( Y ) 3 C P F e ( L ) 2 3 K2

I t i s seen t h a t f o r a p a r t i c u l a r b u f f e r a t a p a r t i c u l a r

c o n c e n t r a t i o n , ( K.j / K2 ) i s a c o n s t a n t .

S u b s t i t u t i n g f o r [ P F e ( X ) ( L ) 3 i n e q u a t i o n { 1 1 } , us ing

e q u a t i o n { 8 } and e x p a n d i n g g i v e s

2 5 7

[ P F e ( L ) 2 ] 2 - ( 2 [ C] T + C0NST2 ) . CP F e ( L ) 2 ] + CC] 2 = 0

Where CONST2 = ( K* / K ' ) [ P F e ( X ) ( Y ) ]

The r o o t s o f t h i s q u a d r a t i c a r e

2 [ C] + C0NST2 ± / U . C0NST2. CC] + C0NST22--------1-------------------------------------------------- !-------------------- { 1 2 >

2

For l i g a n d s such as i m i d a z o l e K >> , hence ( l ^ / K g ) = 0

and C K ^/ K ^ ) = 0 . The above r o o t s t hen r e d uc e to

[ P F e ( L ) 2 ] = C C 3 , i e t h e r e i s no mono i m i d a z o l e complex .

S u b s t i t u t i n g f o r CPFe( OH2 ) 2 ] i n e q u a t i o n { 5 } s e c t i o n 1 .6

u s i n g e q u a t i o n { 1 } s e c t i o n 1 . 7 g i v e s :

P2

CPFe( L) ]

CP F e ( X MY ) ] . CL] 2

D

e f f

Hence P 2

S u b s t i t u t i n g f o r CL] u s i n g e q u a t i o n { 8 } s e c t i o n 1 . 6 g i v e s

rC P F e ( L ) 2 ]

f % ~

1-----r—i

+X

1_1+<1___

C P F e ( X ) ( Y ) ] . CL] 2X / X

/ Ke f f . ka .

CPFe( L) ]

C P F e ( X ) ( Y ) ] . CL] 2F

*P2

2

{ 13}

*The e v a l u a t i o n o f p 2 i s more c o n v e n i e n t s i n c e i t i n v o l v e s

t h e measurement o f t o t a l c o n c e n t r a t i o n s .

SoK + CH ] A

2 5 8

The v a l u e o f (3 and t h e s u s c e p t i b i l i t y a r e g i v e n by

. [ P F e ( L ) 1p = ------------------------------------ ------------------------------------- - n u

CPFe( X) ( Y ) ] . ( [ L] - C C ] T - CPFe( L) ] ) ‘

XT = ( XM. CPFe( X) ( Y ) ] + Xn -CD] + x r . CC] T ) / CFe] { 1 5 }T M D C T T

Where [L]^. i s t h e t o t a l c o n c e n t r a t i o n o f l i g a n d

c o o r d i n a t e d , u n c o o r d i n a t e d , p r o t o n a t e d or u n p r o t o n a t e d .

Computer program

The main program uses e q u a t i o n s { 4 } and { 5 } t o

c a l c u l a t e t h e i n i t i a l s u s c e p t i b i l i t y . T h i s v a l u e i s no t a *

f u n c t i o n o f P2 . A s u b r o u t i n e was w r i t t e n t o c a l c u l a t e the

s u s c e p t i b i l i t y f o r p o i n t s o t h e r t han t h e f i r s t p o i n t . For*

a r e q u i r e d v a l u e o f p^ , t h e f o l l o w i n g sequence was

a p p l i e d

1. Take a s e n s i b l e v a l u e f o r [ C] ^

2. C a l c u l a t e CD] u s i n g e q u a t i o n { 10}

3. C a l c u l a t e CPFe( L) ] u s i n g e q u a t i o n { 1 2 }*

4. C a l c u l a t e t h e v a l u e o f P^ u s i ng e q u a t i o n { 1 4 }

6I f ( K j / K 2 ) > 10 t h e n s t e p 3 was o m i t t e d and

*[ P F e t L ) ^ ] = 0 . I f t h e v a l u e o f d i d not match t he

r e q u i r e d v a l u e t h e w h o l e p r o c e s s was r e p e a t e d u n t i l a match

was o b t a i n e d .

The v a l u e s o f CC] , CD] and [ P F e ( L ) 2 ] were o b t a i n e d

i n t h i s way f o r a l l e x c e p t t h e i n i t i a l p o i n t i n t he

t i t r a t i o n . The s u s c e p t i b i l i t y c o r r e s p o n d i n g t o each p o i n t

was t hen c a l c u l a t e d , u s i n g e q u a t i o n { 1 5 } .

The main pr ogr am c a l c u l a t e s t h e d e v i a t i o n o f t he

c a l c u l a t e d f rom t h e e x p e r i m e n t a l s u s c e p t i b i l i t i e s by

259

- yc a l exp . The b e s t f i t t e d *

e v a l u a t i n g t h e f u n c t i o n , ^7x*

v a l u e o f P2 i s found by c ho o s i n g r e q u i r e d v a l u e s o f P2

u n t i l t h i s f u n c t i o n i s m i n i m i s e d .

The main program can a l s o o p t i m i s e t he v a l u e s o f

( K ; / K - ) or X c • T h i s i s done i n t h e f o l l o w i n g sequence .

1. Choose a v a l u e o f x

2. F i nd t h e opt imum v a l u e o f (3 2

3. S t o r e t h e d e v i a t i o n

Th i s p r oc e ss i s r e p e a t e d u n t i l t h e d e v i a t i o n i s

m i n i m i s e d . ( K ' / K ' ) can be v a r i e d i n p l a c e o f xr .1 u v*

however v a r y i n g both (and P2 ) uses up much computer t i m e

and l e a d s t o u n r e a l i s t i c v a l u e s .*

E q u a t i o n { 1 3 } i s used t o c o r r e c t P2 f o r b u f f e r

c o o r d i n a t i o n and l i g a n d p r o t o n a t i o n t o g i v e a v a l u e f o r

P2 . The v a l u e o f ( K^/ K ^ ) can not be c o r r e c t e d f o r b u f f e r

c o o r d i n a t i o n , s i n c e K i s unknown ( see e q u a t i o n 11) . Nop L

c o n s i s t e n c y i s t h e r e f o r e e x p e c t e d between ( K^ /K ^) v a l u e s

f rom d i f f e r e n t c o n d i t i o n s .

Program v a r i a b l e | E x p l a n a t i o n

B ( J ) = B 2 ( J , K )

BASE( J )

BETA = BETAR( J)

BETAH( J )

BTA

BTAR( J) = BTAPRM( J. K)

CDIM

C H I ( J ) = C H I T ( J )= C H I T ( J , K)

[ L ] T - C C 3 T - CPFe( L) ]

c l1t

P 2 o r i f ( K * / ) > 106 t hen K.j

c u r r e n t v a l u e o f P 2 or Kj*

f i n a l , matched , v a l u e o f P 2 or Kj

mole f r a c t i o n o f d i m e r

c a l

2 6 0

CHICCHIC Xc

CHID XD

CH IM XM

CHITEXt 3 ) Xexp

CHI 1 S T ( J ) = CHI ( 1 ) i n i t i a l s u s c e p t i b i l i t y

CMON mole f r a c t i o n o f P F e ( X M Y )

CONST QD

COORD C C 3 T

CORR IC 4 ( CF e ] T - CC] )

DEL TAP( J ) Af

DEV2

DIFF

Six - x ) 2£ / e x p A c a 1 1*

a b s o l u t e d i f f e r e n c e o f p ( o r K .j ) f rom i t s r e q u i r e d v a l u e

DIMER CD]

DISOCT

EQU IL

ka

e d ( = CH + ^ Ke f f>

FERRI C( J ) C Fe ] T

FSTDEV ( CHI T EX( 1 ) - C H I ( 1 ) ) * * 2

IPOINT = POINT number o f p o i n t s i n t i t r a t i o n

LIGAND c o n c e n t r a t i o n o f t i t r a n t s o l u t i o n

NBASE I POINT - NLAST

NB ETA number o f v a l u e s o f t o be r e a d i n

NLAST number o f i n d i v i d u a l l y d e t e r m i n e d s u s c e p t i b i l i t e s

NUM o r d e r o f r e a c t i o n w . r . t . l i g a n d

OLDEV2*

v a l u e o f DEV2 f o r p r e v i o u s P^

OLDIFF p r e v i o u s v a l u e o f DIFF

PEEKAY p«A o f l i g a n d

PEHACH pH

PER S T E P * 100.

26 1

PERC STEPC* 100.

PREVS v a l u e o f 0EV2 f o r p r e v i o u s x c p r e v i o u s K j / 2 )

or

PROTON CH + ]

RATIO ( K j / K j )

RATIOL CL ] T / C F e ] T

RLIG2 CPFe( L) ]

RMON C P F e ( X ) ( Y)J

RMUC cRMU 0

m d

RMUM |j m

RMU T ( J , K) Mc a l

RMUTEX( J ) “ exp

ROOT r o o t o f a q u a d r a t i c i n CD]

ROOTL r o o t o f a q u a d r a t i c i n [ PF e ( L )

RTM ( K ’ / K ' 2 ) . CPFe (X) C Y ) ]

SUM - u j 2£ exp c a l

STDEVN ysU M / ( n- 1 )

STEP p r o p o r t i o n a l i n c r e m e n t i n [ Fe ] T

STEPC p r o p o r t i o n a l i n c r e m e n t i n p or ( K ’ / K' 2 )

T I TRNT( J ) t i t r e / p i

TOLNCE*

maximum i n c r e m e n t i n a match

TOLNCE1 maximum i n c r e m e n t i n DEV2 f o r*

P 2 tobe o p t i m i s e d C.

TOLNCE2 maximum i n c r e m e n t i n DEV2 f o r xc ort o be o p t i m i s e d

W( J ) =W2 ( J , K ) C P F e ( X ) ( Y ) 3

X1 ST( J ) = X1 ST 2 ( J , K ) CPFe( X ) ( L ) ]

X 2 N D ( J ) =X2ND2( J , K) C P F e ( L ) 2 3

Y ( J ) = Y 2 ( J , K ) CD]

26 2

F o r t r a n p r o g r a m

PROGRAM FEP4 (INPUT,OUTPUT,TAPE5=INPUT,TAPE6=OUTPUT)CCC PROGRAM TO CONTROL TWO SUBROUTINES IN FITTING OR GENERATING MAGNETIC C MOMENT CURVES.ASSUMES T=308K, INITIAL VOL=400UL OELTAF CORRECTED FOR C DIAMAGNETIC BUT NOT DILUTION MAX POINTS=20 MAX BETA=30 C C

DIMENSION BASE(40),BETAH{30).FERRIC(40),TITRNT(40)DIMENSION CHIT(40.30),CHITEX(40),DELTAF(40)DIMENSION BETAR(4 0),BTAPRM(4 0,3 0 ) .B2(40,30),W2(40.30)DIMENSION X1ST2(40.30),X2ND2(40,3Q),Y2 ( 4 0,3 0 )REAL LIGAND

C READ IN DATAREAD(5,*)FERRIC(1),LIGAND.PEHACH.PEEKAY,CHIM.CHID,CHIC,EQUIL PR0T0N=10.**(-PEHACH)DIS0CT=10.**(-PEEKAY)CONST=PROTON**2/EQUIL READ(5,*)IPOINT.NLAST NBASE=IPOINT-NLAST TITRNT(1)=0.READ(5,*)(TITRNT(J),J=2,NBASE)

C WORK OUT IRON AND LIGAND CONCENTRATIONS BASE(1)=0 .IF(TITRNT(2).GE.1.0)G0 TO 60 DO 55 J = 2,N8ASE FERRIC(J ) =FERRIC(1)BASE(J)=TITRNT(J)TITRNT(J)= 0 .

55 CONTINUE GO TO 66

60 DO 65 J = 2,NBASEFERRIC ( J)= FERRIC ( 1 )*( 400./(400.+TITRNT(J)))BASE(J)=LIGAND*(TITRNT(J)/(400.+TITRNT(J)))

65 CONTINUE66 IF (IPOINT.EQ.NBASEJGO TO 70

C READ IN INDIVIDUALLY DETERMINED LIGAND AND IRON CONCENTRATIONS READ(5.*)(FERRIC!J).J = NBASEM.I POINT)READ(5,*)(BASE!J).J = NBASE+1,I POINT)

7 0 CALL CURVElBASE,CHIC.CHID.CHIM.CONST.DISOCT.EQUIL,FERRIC,I POINT.CPROTON,BETAH,BETAR.BTAPRM,B2,CHIT,CHI TEX,DELTAF,NBETA,RATIO.W2. CX1ST2,X2ND2,Y2)IF(NBETA.LT.1)GO TO 00CALL PRINT2!BETAR,BTAPRM,B2,CHIT,CONST,I POINT,NBETA.PEEKAY, CPEHACH,RATIO,W2,X1ST2,X2ND2,Y2)

8 0 CALL RESULT(BASE, BETAH.CHIC.CHID,CHIM,CHIT,CHITEX,CONST,DELTAF,CFERRIC,I POINT.LIGAND,NBETA,N8ASE,PEHACH,PEEKAY,RAT 10,TITRNT)STOPEND

263

SUBROUTINE CURVE(BASE,CHIC.CHID,CHIM.CONST,DISOCT,EQUIL.FERRIC, Cl POINT,PROTON,BETAH,BETAR,BTAPRM,82,CHIT,CHI TEX,OELTAF,NBETA, CRATIO,W2.X1ST2.X2ND2,Y2 )0IMENSION 8ASE(40).FERRIC(40).BETAH(30)

CHIT(40,30),CHI(40),CHITEX(40),DELTAF(40)BETAR(40).BTAPRM(40,30),82(40,30),W2(40,30)X1ST2(40,30),X2ND2(40,30),Y2(40,30)0(40),BTAR(40),W(40 ) .X1 ST(40),X2NO(40),Y(40) SUSCEPTABILITY

DIMENSION DIMENSION DIMENSION DIMENSION

C WORK OUT FIRSTCMON=EQUIL*(-1 . > SORT ( 1 . + 8 . *FERR IC ( 1 ) / EQUIL ) ) / 4 . / FERRIC ( 1 )CDIM=0.5-0.5*CMON CHI 1ST = CMON*CHIM»-CDIM*CHID READ(5,*)NBETA

C ARE THERE ANY BETA VALUESIF(NBETA.LT.1)GO TO 200 DO 120 K=1,NBETA CHIT(1,K)= CH11 ST 82(1,K) =0.0W2(1,K)=CMON*FERRIC(1)Y2(1,K)=CDIM*FERRIC(1)X1ST2(1,K)= 0.0 X2ND2(1,K)=0.0

120 CONTINUEC SET SUEDO DATA TO ZERO

CHITEX(1)=0.DELTAF(1)=0 .READ(5,*)(BETAH(K),K=1.NBETA) READ(5,*)RATIONUM = 2I F ( RATIO. GE. 1 . 0E6) NUM=1 DO 170 K=1.NBETA

C WORK OUT EFFECTIVE BETA AND CALL MAGNETBETA=BETAH(K)*(DISOCT/(DISOCT+PROTON)) **NUM*SQRT(CONST/3. 562E-8) BETAR( K) =BETACALL MAGNET3(BASE,BETA,CHIC,CHID,CHIM,EQUIL.FERRIC,IPOINT,NBETA,

CB,BTAR,CHIl RATIO,W,X1ST,X2ND,Y)DO 165 J=2,IPOINT CHIT(J, K)=CHI( J )B2(J,K)=B(J)W2(J,K)=W(J)Y2(J,K)=Y(J)X1ST2(J,K)=X1ST(J)X2ND2( J , K) =X2ND( J )BTAPRM(J,K)=BTAR(J)

165 CONTINUE 170 CONTINUE

GO TO 285 200 TOLNC1=0.0003

TOLNC2=0.0009REAO(5,*)(DELTAF(J),J=1.IPOINT)

C CALCULATE EXPERIMENTAL SUSEPTABILITIES DO 210 J - 1 , IPOINTCHI TEX( J)=6 . 6 6 67E-11*DELTAF( J)/FERRIC( J)

210 CONTINUECHI(1)= CH11 ST

C INITIALISE DEVIATIONFSTDEV=(CHITEX(1) -CHI (1 ) ) * * 2 DEV2=FSTDEV

264

C INITIALISE BETAREAD(5,*)8ETAH(1).RATIO NUM= 2IF(RATIO.GE.1.0E6)NUM= 1BETA = BETAH(1)*(DISOCT/(DISOCT + PROTON))**NUM*SQRT(CONST/3.56 2E-8) IF(NBETA.NE.0)GO TO 240

C BEST FITTED BUT CHIC NOR RATIO ALTERED C INITIALISE STEPS

STEPC=-0.4 STEP=-0.5

C BETA GENERATOR220 BETA = BETA«-STEP*BETA

CALL MAGNET3(BASE,BETA.CHIC.CHID,CHIM,EQUIL,FERRIC.I POINT.NBETA, CB.BTAR,CHI,RATIO,W.X1ST.X2NO,Y)

C STORE OLD DEVIATION AND RESET OLDEV2 = DEV2 DEV2=FSTDEV

C CALCULATE NEW DEVIATION DO 230 J = 2,I POINT DEV2 = DEV2MCHITEX( JJ-CHK J) )**2

230 CONTINUEC IS RATE OF CHANGE IN DEVIATION SMALL ENOUGH

IF(A8S(DEV2-OLDEV2).LE.DEV2*T0LNC1.AND.ABS(STEP).LE.0.001)GOTO 275 C IS THE DEVIATION GETTING WORSE OR NO BETTER

IF((DEV2-OLDEV2).GE.0.)STEP = -STEP/2.1 GO TO 220

C BEST FITTED AND CHIC OR RATIO ALTERED240 STEPC=-0.4

GO TO 255245 IF(RATIO.NE.Q.O)GO TO 250

CHIC=CHIC+STEPC*CHICIF(CHIC.GT.1.0E-8.AND.CHIC.LT.3.5E-8)GO TO 255 WRITE(6,246)

246 FORMAT(/20H CHIC OUTSIDE LIMITS)GO TO 275

250 RATIO=RATIO+STEPC*RATIO 255 PREVS=DEV2

STEP=-0 5260 BETA=BETA+STEP*BETA

CALL MAGNET3(BASE.BETA,CHIC,CHID.CHIM.EQUIL.FERRIC,IPOINT.NBETA, CB,BTAR,CHI,RAT 10,W.X1 ST,X2ND,Y)OLDEV2=OEV2 DEV2 = FSTDEV DO 265 J = 2,I POINT DEV2=DEV2+(CHITEX(J)-CHI(J))**2

265 CONTINUEIF(ABS(DEV2-OLDEV2).LE.DEV2*T0LNC1.AND.ABS(STEP).LE.0.001 )GOTO 270 IF((DEV2-OLDEV2).GE.O.) STEP=- STEP/2.1 GO TO 260

270 IF(ABS(DEV2-PREVS).LE.DEV2*TOLNC2.AND.ABS(STEPC).LE.0.001)GOTO 275 WRITE(6,241)DEV2,PREVS.STEP.STEPC,BETA.RATIO IF((DEV2-PREVS).GE.O.)STEPC=-STEPC/3.1

241 FORMAT(/6(IX,1PE12.4))GO TO 245

265

C CHECK FOR FLUKY RESULTS275 PERC=STEPC*100.

WRITE(6,276)PERC276 FORMAT(/19H LAST STEP IN CHIC=,F7.3,0HPER CENT)

PER=STEP*100.WR ITE( 6,278)PER

278 FORMAT(/19H LAST STEP IN BETA=,F7.3,0HPER CENT)8ETAH(1)=BETAM(DIS0CT+PR0T0N)/DIS0CT)**NUM*SQRT(3.562E-8/C0NST) WRITE(6,241)DEV2.PREVS,STEP,STEPC,BETA,RATIO 00 280 J=1,IPOINT CHIT(J,1)= CHI(J)


RETURN END

SUBROUTINE MAGNET3{BASE,BETA,CHIC,CHID,CHIM,EQUIL,FERRIC,I POINT, CNBETA,B,BTAR,CHIT,RAT 10,W,X1 ST,X2ND,Y)

C A SUBROUTINE TO FIND SELF CONSISTANT VALUES OF DIMERIC AND C COORDINATED PORPHYRIN CONCENTRATIONS,GIVEN A VALUE OF BETA AND THE C BASE CONCENTRATION AND HENCE TO CALCULATE MAGNETIC SUSCEPTABILITY

DIMENSION BASE(40).FERRIC(40),CHIT(40)DIMENSION B(40),BTAR(40),W(40),X1ST(40),X2ND(40),Y(40) TOLNCE=BETA*0.0001

C CHOOSE A VALUE OF BASE CONCENTRATION DO 165 J = 2,IPOINT

C SET A VALUE FOR COORDINATED PORFN COCN COORD=0.001

10 IF(COORD.LT.BASE(J))GO TO 20 COORD=COORD/10.0 GO TO 10

20 CORRIC=4.*(FERRIC(J)-COORO)C WORK OUT VALUE OF DIMER CONCENTRATION

ROOT=((EQUIL+CORRIC)-SQRT((EQU IL + CORRIC)**2-CORRIC**2)}/8.IFtROOT.GT.O.AND.ROOT.LT.CORRIC/8.)GO TO 50ROOT =((EQUIL + CORRIC)+SQRT((EQUIL + CORRIC)* *2-CORRIC**2))/8.

50 DIMER=ROOTRMON=FERRIC(J)-2.*DIMER-COORD BTA=COORD/{RMON*(BASE(J)-COORD))RLIG2 = 0.0IF(RATIO.GE.1.0E6)GO TO 71 RTM=RATIO*RMONROOTL=(2.*COORD+RTM-SQRT(4.*COORD*RTM+RTM**2))/2. IF(ROOTL.GE.O.AND.ROOTL.LT.COORD)GO TO 60 ROOTL=(2.*COORD+RTM+SQRT(4.*COORD*RTM+RTM**2))/2.

60 RLIG2 = ROOTLIF(RLIG2+COORD.LT.BASE(J))GO TO 70COORD=COORD/10.0GO TO 20

C WORK OUT THE FIRST VALUE OF BETA70 BTA=RLIG2/(RMON*(BASE(J)-COORD-RLIG2)**2)71 DIFF=A8S(8TA-BETA)

C SET INITIAL VALUE FOR INCRIMENTS IN COORD STEP =.1

C THE COORD GENERATOR75 COORD=COORD+STEP*FERRIC(J)

C IS COORD SENSIBLEIF(COORD.GT.0.0.AND.COORD.LT.FERRIC(3).AND.COORD.LT.BASE(3 ))GO

266

CTO 100C REGENERATE PREVIOUS COORO

00 COORD=COORD-STEP*FERRIC(J)C LOWER INCRIMENT

STEP = STEP/3.5 GO TO 75

C WORK OUT DIMER AS BEFORE100 CORRIC=4.*(FERRIC(J)-COORD)

ROOT =((EQUIL + CORRIO-SQRT!(EQUIL+CORRIC)**2-CORRIC**2))/8 IF(ROOT.GT.O.AND.ROOT.LT.CORRIC/8.)GO TO 120 ROOT =((EQUIL+CORRIC)+SQRT((EQUIL+CORRIC)**2-CORRIC**2))/8

120 DIMER = ROOTRMON=FERRIC!J)-2.*DIMER-COORD BTA=COORD/(RMONMBASE!J)-COORD))RLIG2=0.0IF(RATIO.GE.1.0E6)GO TO 126 RTM=RATIO*RMONROOTL=(2.*COORD+RTM-SQRT(4.*COORD*RTM+RTM**2))11. IF(ROOTL.GE.O.AND.ROOTL.LT.COORD)GO TO 125 ROOTL=(2.*COORD+RTM+SQRT(4.*COORD*RTM+RTM**2))11.

125 RLIG2=ROOTLIF(RLIG2+COORD.GE.BASE(3))G0 TO 80 BTA=RLIG2/(RMON*(BASE!J)-COORD-RLIG2)**2)

C STORE OLD DIFF AND CALCULATE NEW VALUE126 OLDIFF=DIFF

DIFF=ABS(BTA-BETA)C IS 8TA GOOD ENOUGH

IF(DIFF.LE.TOLNCE)GO TO 140 C HAS DIFFERENCE GOT BETTER

IF(DIFF.LT.OLDIFF)GO TO 130 C LOWER INCREMENT AND CHANGE DIRECTION

STEP = -STEP/3.5 130 GO TO 75

C INDEX CHI TO ITS DATA POINT140 CHIT(J)=(CHIM*RMON+CHID*DIMER+CHIC*COORD)/

CFERRIC(J)IFtNBETA.LT.1)GO TO 160B(J)=BASE(J)-COORD-RLIG2BTAR!J)=BTAW(J)= FERRIC(J)-2*DIMER-COORD Y(J)= DIMER X1ST!J)=COORD-RLIG2 X2ND(J)=RLIG2


RETURN END

267

SUBROUTINE PRINT2(BETAR,BTAPRM,B2,CHIT,CONST,I POINT,NBETA.PEEKAY, CPEHACH,RATIO,W2,X1ST2,X2ND2,Y2)DIMENSION BETAR(30),BTAPRM(A0,30),B2(40.30)(CHIT(40,30)DIMENSION W2 ( 40,30),X1ST2(40,30),X2ND2(4 0,3 0).Y2 ( 40.30 )WRITE(6,5)

5 FORMAT(1H1)DO GO K=1,NBETA WR I TE(6,10)

10 FORMAT(///55H BETA PRIME K1:K2 DIMER CONST PKCPH)WRITE(6,20)BETARt K),RAT 10,CONST,PEEKAY,PEHACH

20 FORMAT(1X,3(1PE11.4,2X),3X,2(G9.3))WRITE(6,30)

30 FORMAT(//111H POINT BETA MATCH SUSCEPTABILITY MONOMER CONCN C DIMER CONCN 1ST COMX CONCN 2ND COMX CONCN LIGAND CONCN)

DO 50 J=1 , IPOINTWRITE(6,40)J,BTAPRM(J,K).CHITtJ.K),W2(J.K),Y2(J,K),X1ST2(J,K) .

CX2ND2(J,K),B2(J,K)40 FORMAT(/1X,I2,4X,7(1PE12.4,3 X))50 CONTINUE60 CONTINUE

RETURN END

SUBROUTINE RESULT(BASE,BETAH,CHIC,CHID,CHIM,CHIT.CHITEX,CONST, CDELTAF,FERRIC,I POINT,LIGAND,NBETA,NBASE,PEHACH,PEEKAY,RAT 10, CTITRNT)

C A PROGRAM TO PRINT OUT RESULTS OF THE DATA USED,THE BEST CURVE(S) AND C THE VALUE(S) OF BETA.20 DATA POINTS ONLY MAY BE USED.

DIMENSION BASE(40),BETAH(30) .FERRIC(40),TITRNT(40)DIMENSION CHIT(40,30).CHITEX(40),DELTAF(40).RMUT(40,30)DIMENSION RMUTEX(40),RATIOL(40)REAL LIGAND

C DATA USED IN ARRIVING AT RESULTS DO 5 J=2,IPOINT RATIOL(J)=BASE(J)/FERRIC(J)

5 CONTINUERMUM=797.66*SQRT(CHIM*308. )RMUD=797.66*SQRT(CHID/2.0*308. )RMUC = 797.66*SQRT(CHIC*308. )NUM = 2IF(RATIO.GE.1.0E6)NUM=1 WRITE(6,10)

10 FORMAT(1H1)WR ITE(6,15)

15 FORMAT(/02H PH PK DIMER CONST K1:K2 CHI MONOMERC CHI DIMER CHI COMPLEX)WRITE(6,25)PEHACH,PEEKAY,CONST,RAT 10,CHIM,CHID,CHIC

25 FORMAT( 1X,F5.2,2X,F5.2,5(1PE12.4,2X))WRITE(6,26)

26 FORMAT(//25H MAGNETIC MOMENTS AT 308K)WRITE(6,27)

27 FORMAT(/24H MONOMER DIMER COMPLEX)WRITE(6,28)RMUM,RMUD,RMUC

28 FORMAT(1X,3(F4.2,4X))WRITE(6,35)LIGAND

35 FORMAT(//26H THE TITRNT CONCENTRATION=,F7.3,1HM)WRITE(6,45)(J,J=1.IPOINT)

268

45 FORMAT(//9H POINT ,20(4X,I?);WRITE(6,55)(TITRNT!J), J=1,NBASE)

55 FORMAT!IX,9HALIQ0UT ,20(1X.F5.0))WRITE(6,75)(FERRIC!J).J =1,I POINT)

75 FORMAT(1X,9HI RON C0CN.20F6.4)IF(CHITEX(1).EQ.0.AND.DELTAF(1).EQ.0.)GO TO 160

C POGRAM CARRIES ON IF CURVE IS BEST FITTED C VALUES OF MU AND STANDARD DEVIATION CALCULATED

POINT=FLOAT(IPOINT)SUM= 0.0DO 80 J=1,IPOINTRMUT(J,1 )=797.66*SQRT(CHIT(J , 1 )*3 08. ) RMUTEX(J)=797.66*SQRT(CHITEX(J)*308. )SUM= SUM+(RMUTEX(J)-RMUT(J,1) )**2

80 CONTINUESTDEVN=SQRT(SUM/(P0INT-1.0) )

C GRAPH DATA WRITTEN OUTWRITE(6,90)BETAH(1),NUM

90 FORMAT(///36H BEST VALUE OF EQUILIBRIUM CONSTANT=,1PE12.4 ,2HM-,11) WRITE(6,100)(J,J =1,IPOINT)

100 FORMAT(/11H DATA POINT,20(14,2X))WRITE!6,110)(DELTAF(J),J=1,IPOINT)

110 FORMAT(8H DELTA F,2X,20F6.2)WR I TE(6,120)

120 FORMAT(/11H MAG MOMENT)WRITE(6,130)(RMUTEX!J),J=1,IPOINT)

130 FORMAT(1 OH EMPIRICAL.20(1X,F5.2))WRITE(6,140)(RMUT!J,1),J=1,IPOINT)

140 FORMAT(11H CALCULATED,20(F5.2,1X))WRITE(6,150)(BASE!J),J = 1.IPOINT)

150 FORMAT(1 OH BASE C0CN.20F6.4)WRITE!6,151)(RATIOL!J),J = 2,IPOINT)

151 FORMAT(12H EQUIVALENTS,5X.19F6.2)WRIT E(6,155)STDEVN

155 FORMAT(//24H ONE STANDARD DEVIATION=,F6.4)GO TO 240

C PROGRAM CARRIES ON HERE IF CURVES GENERATED ON REQUEST 160 DO 180 K =1,NBETA

DO 175 J=1.IPOINTRMUT!J,K)=797.66*SQRT(CHIT!J,K) *308. )


C GRAPH DATA WRITTEN OUT DO 230 K=1,NBETA WRITE(6,195)BETAH(K),NUM

195 FORMAT(///22H EQUILIBRIUM CONSTANT =,1PE12.4,2HM-,I1)WRITE(6,205)(J,J=1,IPOINT)

205 FORMAT(/11H DATA POINT,20(14,2X))WRITE!6,215)(RMUT(J,K),J=1.IPOINT)

215 FORMAT!1X,10HMAG MOMENT,20(F5.2,1X))WRITE(6,225)(BASE!J),J=1.IPOINT)

225 FORMAT!1X.9HBASE COCN.1X,20F6.4)WRITE(6,151)(RATIOL!J),J=2,IPOINT)


RETURN END

269

1 . a S p e c t r o p h o t o m e t r i e t i t r a t i o n

This s e c t i o n d e a l s w i t h t he s i m p l i f i c a t i o n s and

e x t e n s i o n s t o s e c t i o n s 1.1 and 1 . 6 t h a t occur f o r

s p e c t r o p h o t o m e t r i e t i t r a t i o n s .

V a r i o u s f o r m a t i o n c o n s t a n t s can be d e f i n e d . As l o n g

as t h e e q u i l i b r i u m e q u a t i o n s a r e mass b a l a n c e d t h e s e

e q u i l i b r i u m c o n s t a n t s a r e r e l a t e d t o each o t h e r i n a s i m p l e

manner . C o n s i d e r i n g t h e s i t u a t i o n s where e i t h e r

K1 >> ^ 2 = ° r K2 >> = ^K?

P Fe ( OH ^ ^ + n L ^ ^ PF .e (L)n + n H2 0

CPFe(L) ]K? = -------------------------------

CPFetOH ) ] . C L ] n

I f n = 1 ■ K? = K i

I f n = 2 ’ K? = P 2

I n s p e c t i o n o f t h e e q u a t i o n s f o r K . and 0„ 1 2 i n s e c t i o n 1 . 6

shows t h a t s i n c e t h e v a l u e s o f KB1 . KB2 andk bl

a r e

unknown . i t i s not p o s s i b l e t o c o r r e c t K, f o r b u f f e r

c o o r d i n a t i o n . I f b u f f e r c o o r d i n a t i o n i s i n s i g n i f i c a n t ,

t h a t i s [B] << K81 and [ B] < < K_. t he n □ L

+r-1+X

1_11 ______ K A „

K , = K'. A 1 { 1 }+CH ]

CPFe(L) ]Where K ’ = ---------------------- ------------

CPFe(X) ( Y ) ] . C L ] n

So i f n = 1 ,, K' = K i

And i f n = 2 ,, K'

2 7 0

No d i mer p r e s e n t

For t hose t i t r a t i o n s c a r r i e d ou t where t h e r e i s no

s i g n i f i c a n t c o n c e n t r a t i o n o f d i m e r and f o r t he two l i m i t i n g

cases r e p r e s e n t e d by n = 1 , 2 , t h e r e w i l l be two a b s o r b i n g

s p e c i e s P F e ( X ) ( Y ) and P F e ( L ) . Under t h e s e c o n d i t i o n s t h en

t h e o r y i n s e c t i o n 1.1 a p p l i e s .

CPFe(L) ] (A - An )__________ n _ _________ 0

C P F e ( X ) ( Y ) ] ( A ioo " A)

AndCPFe(L) ] _________n

[ F e ] T

(A V(A100 - V

From the d e f i n i t i o n o f

{2 }

{ 3 }

CPFe(L) ]----------------- - ----- = K ^ . [ L ] n[PFe(X )(Y ) ]

Using e q u a t i o n { 2 } t o s u b s t i t u t e f o r t h e LHS and t a k i n g

l ogs

l o g(A - A )

<A_„„ - A ) 100l o g

So a p l o t o f l o g { ( A - AQ) / ( A

have a s l o p e o f n and a

- l o g { K ^ } / n .

P r o t o n a t i o n o f l i g a n d

From e q u a t i o n { 8 } s e c t i o n 1 . 6

CL] = (CL]_ - n .[PFe(L ) ] ) / ( 1T n

+ n . l o g [ L ]

Q0 - A ) } v e r s u s l o g CL ] w i l l

h o r i z o n t a l i n t e r c e p t o f

+ CH+ ] / K . )A {4}

Using a P*<A1 o f 9 . 3 1 f o r hyd ro gen c y a n i d e and s u b s t i t u t i n g

f o r [ P F e ( L ) ] g i v e sn

27 1

CCN

i

c<1<<__

"

CKCN]t - n. U . C F e ] TA - A

. L 1 00 0J

1 0 3 1 - p H j

Dimer p r e s e n t

I n t h e pH r a n ge 8 . 0 t o 1 0 . 0 , i f t h e r e i s a s i g n i f i c a n t

c o n c e n t r a t i o n o f d i m e r bu t i n s i g n i f i c a n t c o o r d i n a t i o n o f

b u f f e r , t he n t h e f o l l o w i n g e q u a t i o n s a r e t r u e

CFel = 2 . CD] + CPFe(0Ho ) ( O H ) ] + CPFe(L) ] T 2 n { 5 }

A = ( 2 . C D ] . e + CPFe(OH ) (OH) ] . e + CPFe(L) ] . e ) . l { 6 }D 2 M n C

We need e q u a t i o n s { 5 } and { 6 } i n te rms o f j u s t one

c o n c e n t r a t i o n , say [ P F e ( L ) ] . From t h e d e f i n i t i o n s o f Kn

and K „

A 1

[ P F e ( OH ^ ) (OH) ]KA i . CPFe(L) ] A 1___________n

K? .CH+ ] . C L ] n

Using e q u a t i o n { ^ } t o s u b s t i t u t e f o r CL]

[ P F e ( OH^ ) (OH) ]KA 1 . [ P F e ( L ) ] ( 1 + 10PKA~p H ) n A1__________n____________________K . CH + ] . ( CLl - n. CPFe(L) ] ) n ? T n

{ 7 }

From t h e d e f i n i t i o n s o f and K „D A 1

CD]Qq .CPFe ( 0 H 2 ) ( O H ) ]

A1

Using e q u a t i o n {7} t o s u b s t i t u t e f o r CPFe( OH^ ) ( OH) ]

CD]Q . C P F e ( L ) ] 2 . ( 1 + 1 0 pKA " pH) 2nD_________ n_________________________

K0 2 . C H + ] 2 . (CLT - n . C P F e ( L ) ] ) 2n ? T n

{ 8 >

2 7 2

Let F a c t o r 1Z . 0 D .(1 ♦ i o p K A ~ p H ) 2n

K? 2 . C H + ] 2

Le tK . ( 1 * 1 0 pKA ' p H) n

A 1_______________________ _

K? . [ H + ]F a c t o r 2

Using t h e s e s i m p l i f i c a t i o n s and e q u a t i o n s { 7 } and { 8 } t o

s u b s t i t u t e f o r CD] and [ P F e ( OH ) ( OH) ] i n e q u a t i o n s { 5 } and

{6 > g i v e s

CFe]CPFe(L) ] . F a c t o r l n

( C L ] - n . CPFe(L) ] )T n2n

CPFe(L) 3 . F a c t o r 2 _________ n____________

( CL] - n . C P F e ( L ) ] ) T n

- + CPFe(L) 3n n { 9 }

A CPFe(L) ] 2 . F a c t o r 1 . e__ _ _________ n________________D

1 ( C L ] T - n . [ P F e ( L ) ] ) 2n

CPFe(L) ] . F a c t o r 2 . e+ ------- ------------- — + CPFe(L) ].e {10}

( CL 3 _ - n.C P F e ( L ) ] ) n "T n

E x t i n c t i o n c o e f f i c i e n t s

S i n ce t h e computer p r ogr am t a k e s i n t o ac c ou nt CD] ,

[ PF e ( OH^) ( OH) ] and [ P F e t L ) ^ ] , t h e e x t i n c t i o n c o e f f i c i e n t s

f o r each must be s p e c i f i e d a t t h e w a v e l e n g t h used . I n t he

absence o f any l i g a n d L

A = e . C P F e ( O H ) ( O H ) ] . 1 + 2 . e n . [ D ] . l0 M 2 u

S u b s t i t u t i n g (CFe] - CPFe( 0H2 ) ( OH) ] ) / 2 f o r CD] and


2 7 3

I A Q / 1 ) e . [ P F e ( O H , ) ( O H ) ]M Z

{ 1 1 }C F e ] T - [ P F e ( OH ^ ) ( OH ) ]

When t h e complex has f u l l y formed

A100 EC - t F e ] T ' 1

So CO n

n A / ( [ F e ] T • 1) { 1 2 }

The v a l u e s o f eM a t t h e v a r i o u s w a v e l e n g t h s used wer e

c a l c u l a t e d f rom t he s p e c t r a r e c o r d e d i n a p r e v i o u s

s p e c t r o p h o t o m e t r i c pH t i t r a t i o n , and a r e t a b u l a t e d be l ow .

G iven v a l u e s f o r p K A „ , Q , pH and [ F e ] _ t h e v a l u e s o f CD]A I D Tand [ P F e ( OH ) ( OH) ] can be c a l c u l a t e d . E q u a t i o n { 1 1 } can be

used t o c a l c u l a t e and e q u a t i o n { 1 2 } was used t o

c a l c u l a t e t h e v a l u e s o f .

Wavelength/nm 533 534 537 540

e../ 1 0 3 mol 1cm M 8.32 8.21 8 . 02 7.71CD]/10~4moll"1 2.26 3.42 3 . 23 2.91CPFe(0H2)(OH)]/10“4moll~1 2.05 2.52 3.00 2.32

M n 3 - 1 . - 1 e^/10 mol 1cm 1 . 79 1 . 80 1 .93 2.17e^/103 mol 11cm 1 7.54 7.43 7.68 7.55

Computer program

Given v a l u e s f o r a l l o f t h e o t h e r p a r a m e t e r s i n

e q u a t i o n { 9 } , t h e e q u a t i o n can be s o l v ed f o r CPFe(L) ] by

i t e r a t i v e methods . T h i s v a l u e i s used t o e v a l u a t e

e q u a t i o n { 1 0 } t o g i v e t h e a b s o r ba nc e .

An i n i t i a l check showed t h a t s m a l l v a r i a t i o n s i n

[ P F e ( L ) ] cause l a r g e v a r i a t i o n s i n t h e v a l u e o f [ F e ] ^

274

c a l c u l a t e d f rom e q u a t i o n { 9 } . So t h e program matches t h e

l ogs o f t he a c t u a l and c a l c u l a t e d CFe]^ , u n t i l t h e match

i s w i t h i n 0 .1 I. . LogCFe]^ i s a c o n t i n u o u s f u n c t i o n .

[C] i s an a b b r e v i a t i o n f o r CPFe(L) ] and f [ C ] A i sn A

e q u a t i o n { 9 } e v a l u a t e d f o r [ C ] ^ . S u b s c r i p t A and B r e f e r

to i n i t i a l guesses a t [C] and s u b s c r i p t C r e f e r s to a t h i r d

b e t t e r guess by a p p r o x i m a t i n g l i n e a r

b e h a v i o u r ( F i g u r e A 1 . 1 ) .

(EC] - [C] )CC] = CC] + ( logC Fe ] _ - l o g f C C ] ) x ----------------------------------------------

( l o g f C C ] . - l o g f C C ] A) B A

The n e x t guess a t CC] can be made by r e p e a t i n g t he p r oc e ss

w i t h C C 3 B and C C] c i n p l a c e o f C C 3 A and CC]0 r e s p e c t i v e l y .

27 5

FIGURE A1.1 To SOLVE EQUATION (9) f or (PFe(CN)J

ICJ

[Clc = 1C 1. +• Hog IFe 1T - log flC ).)» [og $ } . V 1 f (c l t |

Prog v a r i a b l e Explana t i on

ABSORB c a l c u l a t e d a bs or bance

AQKCN [CN ] - u n c o o r d i n a t e d and u n p r o t o n a t e d

BASE( J ) t o t a l c o n c e n t r a t i o n o f c y a n i d e

CONST QD

DIMER CD]

EXPABS e x p e r i m e n t a l abs or bance

EXTC e cEXTD e DEXTM

FACTOR 1

FACTOR 2

GM

2 . Q 0 (l + 10 9 ' 3 , ' pH) 2n/ ( k , . CH+ ] ) 2

KA 1 . ( 1 ♦ 1 0 9 ' 3 1 - pH) n/ ( K , . C H + ] )

FERRIC( J ) C Fe ] T

FERRLG( J ) i ° g 1 0CFe ] T

FTNCNST( J ) K?

FUNCTA , FUNCTB e q u a t i o n 9 e v a l u a t e d f o r CPFe(CN) n A

FUNCTC CPFe(CN) ]_ or CPFe(CN) ],, r e s p e c t i v e l y n B n C y

HYDROL

HYDROL2

PKA1

KA1IPOINT number o f d a t a p o i n t s

LIGAND c o n c e n t r a t i o n o f t i t r a n t s o l u t i o n

PEHACH pH

PROTON CH + ]

ORDER n

RLIGA , RLIGB f i r s t second and t h i r d guess

RLIGC a t [ P F e ( C N ) n ] r e s p e c t i v e l y

RMON [ P F e ( OH ^ ) (OH ) ]

T I T RN T (J ) t i t r e

2 7 7

F o r t r a n progr am

PROGRAM CUB I CO( INPUT,OUTPUT,TAPE5=INPUT,TAPEG=OUTPUT)0IMENSION FERRIC( 2 0 ) , FERRLG( 2 0 ) , TITRNT( 2 0 ) .BASE(20) DIMENSION FUNTION( 2 0 ) .ABSORB( 2 0 ) ,EXPABS(20)DIMENSION RUG (20) .DIMER (20) .RMON(20)REAL LIGAND

C READ IN DATAREAD( 5 , * ) FERRIC( 1 ) . LIGAND. PEHACH. HYDROL READ( 5 . * ) ORDER.FTNCNST.CONST READ(5,*)EXTM,EXTD,EXTC READ( 5 , * ) IPOINTREAD( 5 , * ) (EXPABS(J). J = 1 .IPOINT)REAO( 5 , * ) (TITRNT(J) . J=2. IPOINT)

C INITIALISE VARIABLES BASE( 1 )=0.TITRNT(1)= 0 .RLIG(1)= 0 .HYDROL2=10**(-2.*HYDROL)PROTON=10**(-PEHACH)RMON( 1 ) = (SORT(HYDROL2**2+8. *HYDR0L2*C0NST*FERRIC(1))

C-HYDROL2)/ ( 4 . *CONST)DIMER( 1 )=(FERRIC(1)-RMON( 1 ) ) / 2 .ABSORB( 1 ) = (EXTD*(2.*DIMER(1 ) ) +EXTM*RMON( 1 ) ) / 1 0 .

C WORK OUT TOTAL LIGAND AND TOTAL IRON CONCNS.DO 10 J=1.IPOINTFERRIC( J ) =FERRIC( 1 ) * ( 3 0 0 . / ( 3 0 0 . +TITRNT(J) ) ) FERRLG(J)=ALOG10(FERRIC(J)) BASE(J)=LIGAND*(TITRNT(J)/ (300.+TITRNT(J)))

10 CONTINUE

C WRITE OUT DATA WRITE(6.20 )

20 FORMAT(1H1)WRITE(6,30 )

30 FORMAT( 48H PH PK PORF DIMER CONST TITRNT CONCN)WRITE(6.40) PEHACH,HYDROL.CONST.LIGAND

4 0 FORMAT(1X,2(F5.2.4X).1 PE 1 2 . 4 , 4X. F7.4)WR ITE(6,4 5 )

45 FORMAT( /25H EXTINTION COEFFICIENTS)WRITE(6,50)

50 FORMAT(4OH MONOMER DIMER COMPLEX)WRITE( 6 . 5 5 ) (EXTM.EXTD.EXTC)

55 FORMAT( 1X,3(1PE12.4.3X))IF(ORDER.EQ.2.0)GO TO 65 WRITE(6,60 )

60 FORMAT( / / 1 8H K2: K1= 0 )GO TO 72

65 WRITE(6,70 )70 FORMAT( / / 1 8H K1:K2=0)72 IPOWER=IFIX(ORDER)

WRITE( 6 , 7 5 ) FTNCNST. I POWER 75 FORMAT(17H FORMATION CONST=,1PE12.4.2HM-.I1)

278

C WORK OUT FACTORS IN FUNCTIONFACTOR 1=2.*CONST*(1 . H 0 . * * ( 9 . 3 1-PEHACH) ) * * ( 2 . *OROER)/

C(FTNCNST*PROTON)**2FACTOR2=10.**(-HYDROL)*( 1 . + 1 0 . * * ( 9 . 3 1 -PEHACH) )**ORDER/

C(FTNCNST*PROTON)

C OPTOMISE A VALUE OF CYANIDE COMPLEX CONCN DO 130 J = 2 , IPOINT

C SET INITIAL COMPLEX CONCNS AND FUNCTION VALUES T IMESA = 0.1 TIMESB=0.9

80 RLIGA=TIMESA*8ASE(J)/ORDERAQKCN = BASE( J) -ORDER * RLIGAFUNCTA=ALOG10(RLIGA**2*FACTOR1/(AQKCN)**(2*ORDER)

C +RLIGA*FACTOR2/{AQKCN)**ORDER+RLIGA)RLIG8=TIMESB*BASE(J)/ORDER AQKCN = BASE( J ) - ORDER * RLIGBFUNCTB=ALOG10(RLIG8**2*FACTOR1/(AQKCN)**(2*ORDER)

C ♦RLIGB*FACTOR2/(AQKCN)**ORDER+RLIGB)C CHECK VALIDITY OF CONCNS

IF (RLIGB .LT. FERRIC(J)) GO TO 90 C RECALCULATE INITIAL VALUES

TIMESA=TIMESA/10.TIMESB=TIMESB/10.GO TO 80

C ESTIMATE VALUE OF CYANIDE COMPLEX CONCN9 0 RLIGC = RLIGB+(FERRLG(J) - FUNCTB ) * ( RLIGB-RLIGA) / ( FUNCTB-FUNCTA)

IF(RLIGC.LT.O.O)RLIGC=-RLIGC95 AQKCN = BASE( J ) - ORDER*RLIGC

C MAKE SURE AQKCN NOT -VEI F {AQKCN .GT. 0.0)GO TO 96RLIGC = RLIGC*1 0 . 0 * * ( - 0 .95*ABS(AL0G10(RLIGA/RLIGB)))GO TO 95

96 FUNCTC=ALOG10(RLIGC**2*FACTOR1/(AQKCN)**(2*ORDER)C +RLIGC*FACTOR2/(AQKCN)**ORDER+RLIGC)

C MAYBE CHECK HERE : ( RLIGC-RLIGB) < ( RLIGC/10000) ?C IS THE FUNCTION VALUE A GOOD MATCH TO TOTAL IRON CONCN ?

DIFF=FUNCTC-FERRLG(J)I F ( DIFF .GT.-4.34E-4 .AND. DIFF .LT. 4.34E-4)GO TO 100

C RESET CONCNS TO INITIAL CONCNS RL IGA = RLIGB RLIGB=RLIGC FUNCTA=FUNCTB FUNCTB = FUNCT C GO TO 90

100 CONTINUE

C CHECK VALUE OF CYANIDE COMPLEX +VE < BASE( J ) /ORDER < FERRIC(J)VAL = RLIGCIF(VAL.GT.0 . AND.VAL.LT.FERRIC( J ) . AND. VAL. LT. BASE( J ) /ORDER) GOTO 120 WRITE(6,110)

110 FORMATt 29H CYANIDE COMPLEX OUT OF RANGE)

279

C STORE CONCENTRATIONS OF EACH SPECIES 120 RLIG(J)=RLIGC

DIMER(3)=FACTOR1*RLIG(3)**2/(2*AQKCN**(2*ORDER)) RMON(3)=FACTOR2*RLIG(3)/(AQKCN**ORDER)FUNTIONCJ) = FUNCTC

C WORK OUT ABSORBANCE - DIVIDE BY 10 SINCE PATH LENGTH 1 MMABSORB ( J ) = (EXTDM2.*DIMER(J) ) +EXTM*RMON ( 3 ) +EXTC*RLIG ( 3 ) ) / 1 0 .

130 CONTINUE

C WRITE OUT RESULTS C BLOCK ONE

WRITE(6,135)135 FORMATt/ / / 5 6H

C*** )WRITE(6,K0)

HO FORMAT(61H NO. TITRE CYANIDE CONCN C NO. )

DO 160 3=1, IPOINTWRITE( 6 . 1 5 0 ) ( J , TITRNT( J ) . BASE( J ) , ABSORB(J

150 FORMAT( / 1 X, 12 , 3X, F6. 2 , 3X,1 PE 1 2 . 4 , 3X, 2 ( OPE 160 CONTINUE

C BLOCK TWOWRITE(6.165)

165 FORMAT(1H1 )WRITE(6,170)

170 FORMAT( / / / 9 2 H NO. MON DIMER COMPLEX TOTCIRON LOG TOT IRON FUNCTION NO.)

DO 190 J= 1 , IPOINTWRITE( 6 , 1 8 0 ) ( J , RMON( 3 ) .DIMER(3) ,RLIG(3) ,FERRIC(3) , FERRLG(3) .

CFUNT ION( 3 ) . 3 )180 FORMAT(/1X, I2,6(2X,1 PE 1 2 . 4 ) . 2X. 12)190 CONTINUE

STOPEND

* * * * * * * ABSORBANCE****

CALCULATED EMPIRICAL

) , EXPABS(3) , 3 )11. 3 . 3 X ) .12)

28 0

1 .9 Theor y and computer program f o r t he e v a l u a t i o n o f

NMR i n t e g r a l d a t a

I t i s a p p a r e n t f rom t h e v a l u e o f d e t r m i n e d here t h a t t h e

c o n c e n t r a t i o n o f d i m e r i s a t a l l t im es c o m p a r a t i v e l y

s m a l l , under t h e c o n d i t i o n s (pH 3 . 7 5 , 0 . 2 5 M sodium

f o r m a t e ) o f t he e x p e r i m e n t . I t i s assumed t h a t t h e FeTMPyP

i s c o o r d i n a t e d by b u f f e r or c y a n i d e . The f o l l o w i n g

e q u i l i b r i a o n l y need be c o n s i d e r e d .

KiPFe ( 8 ) + CN ^ — P F e ( B M C N ) + B

C P F e ( B ) ( C N ) ]K’ = ----------------------------

CPFe(B) ] . [CN]

K2P F e ( B ) ( CN) + CN ^ - P F e ( C N ) 2 + B

CPFe(CN) ]k2 = ----------------------------------

CPFe( CN) ( B) ] . CCN]

Thr ee mole f r a c t i o n s a r e d e f i n e d :

XM = [ P F e ( B ) ] / [ F e ]

X 1 = [ P F e ( B) ( CN) ] / [ F e ] T

X2 = [ P F e ( CN) 2 ] / [ F e ] T

By i n s p e c t i o n

X1k ; = ------ !------ n >

XM. [C N ]M

X2And K* = --------------- { 2 }X . C CN]

From { 1 } X, = K * . X m . [ C N ] { 3 }1 1 M

20 1


01 Kr K2 X^.CCN]M

So X f32 . XM. Cc NJ { 4 }

CFe] [ P F e ( B ) ] + [ P F e ( B ) ( CN) ] + [ P F e ( C N ) 2 ]

So f rom t he d e f i n i t i o n s f o r K' and

CFe] CPFe(B) 3 . ( 1 + K ‘ C CN ] + (3 C CN 3 )

Us ing t h i s to s u b s t i t u t e f o r [ F e ] _ i n t h e d e f i n i t i o n f o r X.,T M

and d i v i d i n g t h r o u g h o u t by [ P F e ( B ) 2 ] , g i v e s :

1

M 1 + K* [CN] + p^CCN] 2{5}

Us ing t h i s i n e q u a t i o n s { 3 } and { 4 }

K ’ [CN]

1 + K ’ CCN] + |3 2 C CN ]

P2 CCN]

1 + K'CCN] + |3 2 C CN ]

{ 6 }

{ 7 }

From e q u a t i o n { 8 } s e c t i o n 1 . 6 i t i s a p p a r e n t t h a t [CN] i s

a l s o a f u n c t i o n o f X^ , X 1 and X2 .

[CN]CKCN]T - X [ F e ] T - 2X2 [ Fe] T

7 \ .. _9 . 3 1 -pH .( 1 + 1 0 )

Where 9 . 3 1 i s t h e p « A f o r HCN .

We r e q u i r e an e q u a t i o n i n t e r ms o f [CN] wh ich i s

i n d e p e n d e n t o f X^ , X and X 2 .

2 8 2

L e t F 1 1 + 10 9 . 3 1 -pH

So by r e a r r a n g e m e n t

[ KCN] T - F1.CCN] = X1 . C F e ] T + 2 . X 2 . [ F e ] T

Using e q u a t i o n { 2 } to s u b s t i t u t e f o r X^ and r e a r r a n g i n g

[KCN] - F 1 . [CN]X = --------------------------------------

[ F e ] (1 t 2K ^ • C CN] )

E q u a t i n g t h i s t o e q u a t i o n { 6 } r e r r a n g i n g and c o l l e c t i n g

te rms i n [CN] g i v e s

F 1 . P2 [ CN ] 3 + ( { 2 [ Fe ] T - [KCN3T }|3^ + F 1 . K ’ ) [ C N ] 2

+ ( F 1 + K * { [ F e ] y - [ K C N ] T > ) [ C N ] - [ KCN] T = 0

L e t F 2 = [ F e ] T - [ k c n ] t

And F3 = 2 [ Fe ] T - [KCN]

So F 1 .3 2 [ CN] 3 + ( F 1 •K’ + F 3 . 3 2 ) [ C N ] 2

+ ( F 1 + F 2 . K ’ ) [ CN] - [ KCN ] t = 0 { 8 }

T hi s i s a c u b i c i n [CN] and may be s o l v e d by s u c c e s s i v e

a p p r o x i m a t i o n s us i ng N e w t o n ’ s method :

f [ CN ][CN1 = [ CN ] - -----------—

B A f ‘ [ CN] A

Where s u b s c r i p t B r e f e r s t o a c u r r e n t a p p r o x i m a t i o n o f t he

r o o t and s u b s c r i p t A r e f e r s t o t h e p r e v i o u s a p p r o x i m a t i o n .

f i s e q u a t i o n { 8 } and f ’ i s t he f i r s t d e r i v a t i v e o f

e q u a t i o n { 8 } .

D i f f e r e n t i a t i n g e q u a t i o n { 8 } g i v e s

3 . F1 . P2 . [ C N ] 2 + 2 ( F 1 . K ’ + F 3 . P 2 ) [CN] + F1 + F 2 . K ' = 0

2 8 3

The v a l u e s o f C Fe ] and CKCN]T a r e known f o r each p o i n t i n

t he t i t r a t i o n and the v a l u e s o f and (3 a r e chosen . So

CCN] may be found f o r each p o i n t i n t h e t i t r a t i o n by

s u c c e s s i v e a p p r o x i m a t i o n .

Computer program

A computer p r ogram was w r i t t e n wh i ch uses t h e

f o l l o w i n g e x p r e s s i o n t o mea sur e t h e match between t h e

c a l c u l a t e d and e x p e r i m e n t a l mol e f r a c t i o n s .

D e v i a t i o n

S u b s c r i p t

c a l c u l a t e d

n

1

E i s f o r e x p e r i m e n t a l , s u b s c r i p t C i s f o r

and n i s t h e number o f d a t a p o i n t s .

S t a n d a r d d e v i a t i o n / D e v i a t i o n / ( n- 1 )

A b e s t f i t was a c h i e v e d by v a r y i n g t h e v a l u e s o f and

K ‘ / K ! t o m i n i m i s e t h e s t a n d a r d d e v i a t i o n .1 2In o r d e r t o a v o i d r e p e a t c a l c u l a t i o n s , t h r e e f u n c t i o n s

were d e f i n e d

F 1 M = K ’ CCN]

F2M = (3* CCN]2

FTM = 1 + F 1M + F2M

So deviat ion1 2 F1M 2 F2M

XEM ' FTM+ +

- L

284

Program v a r i a b l e E x p l a n a t i o n

BASE( J ) C KCN ]

8 ETA

DEVN

FACT 1

( X E, - X C , ’ 2 * ' X E2 - XC 2 1 * ( X EH ‘ X CM)2, * 1 0 9 - 3 1 - P H

FACT2( J ) C F e ] T - CKCN]t

FACT3( J ) 2. C F e ] T - CKCN]t

FERR I C( J ) [ F e ]

FTM 1 + F 1M + F2M

FUNCO f [ C N ] . A

FUNC1 f ’ [ C N ] A A

F 1 M

F2M

K * . [CN]

P j . C C N ] 2

IB 1 i f |3 v a r i e d or e l s e 0

IPOINT number o f d a t a p o i n t s

IR 1 i f K ‘ / K ‘ v a r i e d or e l s e 0 1 2

KAY 1 k ;PEEKAY pK1 o f l i g a n d

PEHACH pH

PREVB v a l u e o f DEVN f o r p r e v i o u s (3 v a l u e

PREVC v a l u e o f DEVN f o r p r e v i o u s K ‘ /K1 v a l u e1 2

RATIO k ; / k 2

R L I G ( J )

i—i

izol—l

ROOTA [ C M ' ] A AROOT B i—

i o z1

l—l CD

STEPB f a c t o r by w h i ch {3 i n c r e m e n t e d

STEPR f a c t o r by wh i ch K* /K1 i s i n c r e m e n t e d1 2

STDEVN s t a n d a r d d e v i a t i o n

2 8 5

XMEMP( 3 ) XEM

XMCAL( J ) X CM

X 1 EMP( 3 ) x e i

X1CAL ( 3 ) x c ,

X2EMP( J ) X E 2

X2CAL( J ) X C 2


PROGRAM 0RUKER( INPUT,OUTPUT,TAPE5=INPUT,TAPE6=OUTPUT)

PROGRAM TO BEST FIT CURVES THROUGH MOLE FRACTION DATA DERIVED DIRECTLY OBSERVED PROTON NMR ON BRUKER .

DIMENSION DIMENSION DIMENSION DIMENSION REAL KAY 1

FERRIC( 2 0 ) .BASE( 2 0 ) . RLIG(20 ) XMEMP( 2 0 ) ,X1EMP( 2 0 ) ,X2EMP(20) XMCAL( 2 0 ) , X1 CAL( 2 0 ) ,X2CAL(20) FACT2( 2 0 ) , FACT3(20)

FROM

C READ IN INITIAL PARAMETEERSREAD( 5 , * ) I POINT, PEHACH, PEEKAY. BETA,IB.RATIO, IR READ( 5 . * ) (FERRIC(J). J=1. I POINT)READ( 5 , * ) ( BASE( J) ,J=2, IPOINT)READ( 5 , * ) ( XMEMP( J ) . J = 2 , I POINT)READ(5,*) (XIEMP(J) . J = 2, IPOINT)READ( 5 . * ) ( X2EMP( J ) . J = 2 , IPOINT)

C INITIALISE PARAMETERS FOR FIRST POINT BASE(1) = 0.0RLI6(1) = 0 . 0XMEMP(1) = 1.0 X1EMP(1) = 0.0 X2EMP(1) = 0 . 0

C WORK OUT FUNTIONS 1,2,3 AND INITILISE DEVN FACT 1 = 1.0 * 10**(PEEKAY-PEHACH)DO 20 J=1, IPOINTFACT2( J ) = FERRIC(J) - BASE(J)FACT3( J ) = 2 . 0*FERRIC( J ) - BASE(J)

20 CONTINUE DEVN = 0 . 1

286

C INCREMENT BETA* , STORE OLD DEVN AND INITIALISE STEPR STEPB=FLOAT(I 8 ) /10 .0

50 BETA=BETA+STEPB*BETA PREV8 = DEVN

C INCREMENT K1*/K2* , STORE OLD DEVN AND INITIALISE STEPR STEPR=FLOAT( IR) /10 .0

70 RATIO=RATIO+STEPR*RATIO PREVR=DEVNKAY1=SQRT(BETA*RATIO)

C TO COLVE A CUBIC IN FREE BASE CONCN USING NEWTONS METHOD C ZERO DEVN

DEVN=0.0DO 100 J = 2 , IPOINT

C SET AN INITIAL GUESS AT ROOT ROOTB=BASE(JJ/FACT1

90 R00TA=R00T8FUNCO=BETA*FACT1*ROOTA**3+(KAY1*FACT1+BETA*FACT3(J))*R00TA**2

CMFACT1*KAY1*FACT2( J) ) *ROOTA-8ASE{ J ) FUNC1=3.0*BETA*FACT1*ROOTA**2+2.0*(KAY1*FACT1+BETA*FACT3(J))

C*ROOTA+FACT1+KAY1*FACT2(J)ROOTB=ROOTA-FUNCO/FUNC1

C TEST TO SEE IF CHANGES IN ROOT LESS THAN 0.01 PER CENT IF(ABS(ROOTB-ROOTA)/ROOTB .GT. O.OOODGOTO 90

C WORK OUT DEVNS AT THIS DATA POINT F1M=KAY1*ROOTB F2M=BETA*ROOTB**2 FTM=1 . 0+F1M+F2MDEVN = DEVN+(XMEMPtJ ) - 1 / FTM) ** 2+(X1 EMP ( J ) -F1M/FTM)**2 +

C(X2EMP(J)-F2M/FTM)**2 C STORE RESULT

RL IG( J J =ROOTB 100 CONTINUE

C ARE CHANGES IN DEVN AND STEPR SMALL ENOUGH ?IF(ABS(DEVN-PREVR)/DEVN .LE. 0.0003

C .AND. ABS( STEPR) .LE. 0.0003)GOTO 110 C IF DEVN INCREASING , DECREASE AND CHANGE SIGN OF STEPR

I F ( DEVN .GE. PREVR) STEPR= -STEPR/8.9 GOTO 70

C ARE CHANGES IN DEVN AND STEPB SMALL ENOUGH ?110 IF(ABS(0EVN-PREV8)/0EVN .LE. 0.0009

C .AND. ABS( STEPB) .LE. 0.0009)GOTO 150 C IF DEVN INCREASING . DECREASE AND CHANGE SIGN OF STEPB

I F ( DEVN .GE. PREVB) STEPB= -STEPB/8.3 GOTO 50

150 CONTINUE

287

C WRITE OUT INITIAL AND BEST FITTED PARAMETERS WRITE(6,310)

310 FORMAT( / 1 H1 )WRITE( 6 ,320 J

320 FORMAT(51H PH PK BETA* K1*/K2*)WRITE(6,330) PEHACH, PEEKAY, BETA, RATIO

33 0 FORMAT( 2 ( F5. 2 , 9X) ,2(1 PE 1 2 . 4 , 2X))

WR ITE( 6,3 4 0 )340 FORMAT( / / 39H ********C0NCENTRATI0NS*******)

WR ITE( 6.3 50 )350 FORMAT(61H NO TOTAL LIGAND TOTAL IRON EQUIVALENTS

C NO/)DO 370 J=1, IPOINTWRITE(6,360)J,BASE!J), FERRIC{J ) , BASE(J ) /FERRIC( J) , J

360 FORMAT(IX, I2.5X,3(1PE12.4.5X) 12)370 CONTINUE

C WRITE OUT CALCULATED AND EMPIRICAL RESULTS

WRITEI6,400)400 FORMAT( / / / / 8 9 H * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * moLE FRA

CCTIONS******** * * * * * * * * * * * * * * * * * * * * * * * )WRITE(6,410)

410 FORMAT!102H MONOMER FIRST COMPLECX SECOND COMPLEX FREE LIGAND)

WRITE(6,420)420 FORMAT(106H NO EMPIRICAL CALCULATED EMPIRICAL CALC

CULATED EMPIRICAL CALCULATED CONCN NO/)

DO 500 J=1, IPOINT F1M = KAY1 * RLIG( J )F2M=BETA*RLIG(J)**2 FTM=1 . 0+F1M+F2M XMCAL( J ) =1 . 0/FTM X1 CAL( J)=F1M/FTM X2CAL(J)=F2M/FTMWRITE( 6 ,510 ) J.XMEMP!J).XMCAL(J),X1EMP( J ) , X1CAL( J ) ,X2EMP(J),

CX2CAL(J), RLIG( J ) , J 500 CONTINUE510 FORMAT!1X,12 , 6 ( 9 X , F 5 . 3 ) , 2 X , 1PE12.4,3X,12)

POINT=FLOAT(IPOINT)STDEVN=SQRT!DEVN/( (POINT-1 . 0 ) * 3 . 0 ) ) WRITE(6,520)STDEVN

520 FORMAT!/ / / / 25H ONE STANDARD DEVIATION = , F 6 . 4 / / / / )

STOPEND

2 8 8

A P P E N D I X 2

NiTMPyP

289

A p p e n d i x 2.

Th i s a p p e n d i x cov er s t h e a l g e b r a and computer programs f o r

t h e e v a l u a t i o n o f d a t a f rom e x p e r i m e n t s u s i ng NiTMPyP . I t

i s d i v i d e d i n t o t h r e e s e c t i o n s c o r r e s p o n d i n g to

measurements o f m a g n e t i c moment ; NMR c h e m i c a l s h i f t s

and ^H NMR l i n e w i d t h s .

The f o l l o w i n g e q u i l i b r i u m i s o f i n t e r e s t

PNi + 2 H O ^ - - ---- PNi ( OH )2 k1 ^

D i a m a g n e t i c P a r a m a g n e t i c

[ P a r a m a g n e t i c ]

C D i a m a g n e t i c ]

XAl so K = ------------

1 - X

1So X = -------------r

1 ♦ k " 1

Where X i s t h e mole f r a c t i o n o f t h e p a r a m a g n e t i c form

Assuming a s i m p l e Bo l t zmann d i s t r i b u t i o n between t h e two

forms

K = E x p ( AS/ R - AH/RT) {1}

1So X -----------------------------------------------------{ 2 }

1 + E x p ( AH/ RT - AS/R)

2 . 1 M a g n e t i c momentsV

D i s r e g a r d i n g t h e s m a l l c o n t r i b u t i o n t o t h e s u s c e p t i b i l i t y

f rom t h e d i a m a g n e t i c NiTMPyP

[ p a r a m a g n e t i c ]

ENi]

c a l2

MH

2 9 0

Where p i s t h e m a g n e t i c moment , s u b s c r i p t s a r e H f o r h i g h

s p i n and c a l f o r t h e c a l c u l a t e d a p p a r e n t m a g n e t i c moment

f o r t h e m i x t u r e .

A l so C N i ] T = [ p a r a m a g n e t i c ] + [ d i a m a g n e t i c ]

R e a r r a n g i n g and s u b s t i t u t i n g f o r [ p a r a m a g n e t i c ] g i v e s

2 2[ d i a m a g n e t i c ] = [ N i ] ^ - [ N i ] T ( pH )

= C N i ] T (

Us ing t h e s e e x p r e s s i o n s t o s u b s t i t u t e i r r to

o f K and s i m p l i f y i n g g i v e s

- 2 , , 2 2 , K = * ' c a l / “ , H ' Mc a l >

t h e d e f i n i t i o n

E q u a t i n g t h i s t o e q u a t i o n { 1 } , t a k i n g r e c i p r o c a l s and


M2H/Mc a l

So c a l

1 + E x p ( AH/ RT - AS/R)

p h / / l + E x p ( A H / R T - AS/R)

A computer program was w r i t t e n t o v a r y AH and AS so as t o

m i n i m i s e t h e e x p r e s s i o n

2c a l

2 . 2 M )exp

Where s u b s c r i p t exp i s f o r e x p e r i m e n t a l .

The v a l u e o f mu can be s i m u l t a n e o u s l y v a r i e d , but

t ook up much computer t i m e and gave u n r e a l i s t i c a l l y

v a l u e s f o r pu •H

t h i s

h igh

29 1

Proram v a r i a b l e A l g e b r a i c e x p r e s s i o n

CO CN C N i ] T

DELTAF Af

DELTAH(M) AH

DELTAS( N ) AS

r r 2 2 . 2DEVN / c a l exp

FREQ e f f e c t i v e o p e r a t i n g f r e q u e n c y

KMAX number o f i t e m s o f d a t a

LAST 10 i f p i s t o be v a r i e dn

o t h e r w i s e 1 . 0

L S , MS, NS c o o r d i n a t e s o f L , M, N f o r

v a l u e o f DEVN

t he l e a s t

MUCALC c a l

MU EXP exp

MUHIGH( L )m h

STDEVN y S U M / ( KMAX - 1)

STEPL p r o p o r t i o n a l i n c r e m e n t i n

STEPM p r o p o r t i o n a l i n c r e m e n t i n AH

STEPN p r o p o r t i o n a l i n c r e m e n t i n

. 2 2 , 2AS

SUM ( p i “ M )c a l exp

TEMP t e m p e r a t u r e

2 9 2


PROGRAM NIC ( INPUT, OUTPUT, TAPE5=INPUT, TAPE6=0UTPUT)CC PROGRAM TO FIND BEST VALUES OF HIGH SPIN MU, DELTA H AND DELTA S FOR A C SPIN EQUILIBRIUM.MAXIMUM P0INTS=30. READ TEMPERATURE IN AS CELCIUS,C DELTA H AS KJMOL-1 , DELTA S AS JK-1MOL-1, DELTAF IN HERTZ CORRECTED FOR C DIAMAGNETIC CONTRIBUTION . CONCN AS MOL L-1 CORRECTED C FOR TEMPERATURE CHANGE. OSCILLATOR FREQUENCY IN MHZ.C IF MU IS VARIED LAST=10.OTHERWISE=t .C

DIMENSION DELTAH( 1 0 ) , DELTAS( 1 0 ) .TEMP( 3 0 ) .DELTAF( 3 0 ) . COCN(30)REAL MUHIGH(10) ,MUCALC(30),MUEXP(00)

C READ IN DATAREAD(5,*)KMAX,LAST,MUHIGH(1 ) , DELTAH( 1 ) . DELTAS( 1 ) .FREQ READ( 5 . * ) (COCN(K),K=1, KMAX)READ( 5 , * ) ( DELTAF(K). K=1 , KMAX)READ( 5 . * ) ( TEMP( K) ,K=1 . KMAX)

C CHECK ON VALIDITY OF DATAIF(0ELTAH(1 ) * DELTAS( 1 ) . GT. 0 . 0 ) GO TO 40 WRITE(6,30 )

30 FORMAT( 70H1 THE SIGNS OF DELTA H AND DELTA S ARE OPPOSITE NO EQUILI CBRIUM POSSIBLE)

GO TO 180040 DELTAH(1)= DELTAH( 1 ) * 1 000.0

C CELCIUS TO KELVINDO 100 K =1.KMAX TEMP(K)=TEMP(K)+273.2

100 CONTINUEC WORK OUT MAGNETIC MOMENTS( EXPERIMENTAL)

00 150 K= 1 .KMAXMUEXP(K)=0.061786*SQRT(TEMP(K)*DELTAF(K)/(FREQ*COCN(K)))

150 CONTINUE C INITILISE DATA

1 = 1 LS= 1 MS= 1 NS= 1STEPL=1.0IF(LAST.EQ.10)STEPL=1.015 STEPM=1.5 STEPN=1.3

C RESET DATA160 MUHIGH( 1 )=MUHIGH(LS)/STEPL**4.5

DELTAH( 1 ) =DELTAH(MS)/STEPM**4.5 DELTAS( 1 )=DELTAS(NS)/STEPN**4.5 DO 200 J=2 . 10MUHIGH(J)=STEPL*MUHIGH(J-1)DELTAH( J ) =STEPM*DELTAH( J - 1 )DELTAS(J)=STEPN*DELTAS(J-1)

200 CONTINUE

293

C CALCULATE DEVNS, FIND LEAST DEVN AND STORE COORDINATES PREVS =1.0E6 DO 600 L=1 .LAST

DO 500 M=1.10 DO 400 N= 1 , 1 0

DEVN = 0.0 DO 300 K=1 . KMAXDEVN=DEVN+(MUHIGH(L)**2/(1. 0+EXP( DELTAH(M)/ ( 8 . 3 H3*TEMP( K))

C -DELTAS(N)/8.3143))-MUEXP(K)**2)**2 300 CONTINUE

I F ( DEVN.GT.PREVSJGO TO 350PREVS=DEVNLS = LMS = MNS =N

350 CONTINUE 400 CONTINUE 500 CONTINUE 600 CONTINUE

C IS MINIMUM ON EDGE OF GRID?IFUS.EQ. 1 .AND. LAST. NE. 1 )GO TO 800 IF(MS.EQ.1.OR.NS.EQ.1)GO TO 800 IFUS.EQ. 10.OR.MS.EQ. 10.OR.NS.EQ. 1 0 ) GO TO 800

C RESET STEP SIZE 1 = 1+1STEPL=STEPL**0.75 STEPM=STEPM**0.25 STEPN=STEPN**0.25

800 I F ( I . LE. 5 ) GO TO 160 C WORK OUT MAGNETIC MOMENTS AND STND DEVN

SUM=0.0DO 900 K=1.KMAXMUCALC(K)=MUHIGH(LS)/SQRT(1 . O+EXP( DELTAH(MS) / ( 8 . 3 H3*TEMP( K))

C-DELTAS(NS)/8.3143) )SUM=SUM+(MUCALC(K)-MUEXP(K)) **2

900 CONTINUESTDEVN=SQRT(SUM/FLOAT{KMAX-1))

C WRITE OUT RESULTS WRITE(6.1000)FORMAT(1H1)DELTAH(MS)=DELTAH(MS)/1000.0 WRITE( 6 . 1 100)DELTAH(MS)FORMAT( / 9 H DELTA H=,1 PE 1 2 . 4 , 7HKJMOL-1)WRITE(6 ,1200)OELTAS( NS)FORMAT( 9H DELTA S=. 1PE12.4.9HJK-1MOL-1)WRITE(6,1300 )MUHIGH( LS )FORMAT( / / 2 8 H BEST VALUE OF HIGH SPIN MU=,F6.3)WRITE(6,1400)FORMAT( / / 5 3 H POINT CONCN SEPN/HZ MU EMP MU CALC TEMP/K POINT) DO 1500 K=1 . KMAXWRITE(6 .1600)K. COCN(K), DELTAF( K) , MUEXP( K) , MUCALC( K) . TEMP( K) , K CONTINUEFORMAT!1X.12 . 4X. F7. 5 . 3X. F5. 2 . 2X. 2 ( F5. 3 . 3X) , F 5 . 1, 3 X . 12)WRITE( 6 . 1700)STDEVNFORMAT( / / 2 4 H ONE STANDARD DEVIATION=. F6.4)CONTINUE STOP END

1000

1100

1200

1300

1400

15001600

17001800

294

2 . 2 H NMR c h e m i c a l s h i f t s

The e x p e r i m e n t a l p a r a m a g n e t i c s h i f t s o f NiTMPyP a r e g i v e n by

5 = c h e m i c a l s h i f t - 8 . 9 7 4 9exp

8 . 9 7 4 9 ppm 5 i s t h e c h e m i c a l s h i f t o f t he p y r r o l e p r o t o n s

i n ZnTMPyP as found h e r e .

Assuming C u r i e Law b e h a v i o u r f o r t h e h i gh s p i n form .

5 = C/Too

Where C i s t h e C u r i e C o n s t a n t and 5 i s t h e p a r a m a g n e t i cOO

s h i f t o f t h e h i g h s p i n f or m .

So i n f a s t exchange c o n d i t i o n s a s i n g l e r e s o n a n c e i s seen ,

w i t h a p a r a m a g n e t i c s h i f t 5 g i v e n by .

5 , = X . C / T { 3 }c a lWhere X i s t h e mole f r a c t i o n o f t h e h i g h s p i n form .

We need t o know t h e v a l u e o f t h e C u r i e C o n s t a n t . We know

X c a l /M2H

So r e a r r a n g i n g e q u a t i o n { 3 } and s u b s t i t u t i n g f o r X g i v e s

C T . 5 c a l2 H/ M

2c a l

Using d a t a f rom t h e s u s c e p t i b i l i t y and c h e m i c a l s h i f t

measurements , t h e f o l l o w i n g v a l u e s o f t h e C u r i e C o n s t a n t

were c a l c u l a t e d .

T/K T . 5 / ppm K exp Mexp C / 1 0 3 ppm K

283 6076 1 . 6 9 5 2 1 . 7293 475 1 1 . 506 2 1 .4303 3758 1 . 3 0 9 2 2 . 53 1 3 3090 1 . 1 0 8 2 5 . 8

T h i s g i v e s an a v e r a g e o f C 22 . 8 ± 1 . 7 x 10 3 ppm K

29 5

From e q u a t i o n s { 2 } and { 3 }

^ c a l

C

T (1 + E x p ( AH/RT - A S / R ))

A computer p rogram was w r i t t e n t o v a r y t h e v a l u e s o f AH and

AS so as to m i n i m i s e t h e e x p r e s s i o n

yia - 5 )2c a l exp

Proram v a r i a b l e A l g e b r a i c e x p r e s s i o n

C C

CTEMPoT e m p e r a t u r e / C

DELTAH AH

DELTAS AS

DEVN V ( 5 - 5 ) 2 Z_ c a l exp

IPOINT Number o f i t e ms o f d a t a

PREVH P r e v i o u s DEVN f o r AH

PREVS P r e v i o u s DEVN f o r AS

PSHIFTC(K) ^ c a l

SHIFTC(K) C a l c u l a t e d c h e m i c a l s h i f t

SHIFTD D i a m a g n e t i c c h e m i c a l s h i f t

S H I F T E ( K) E x p e r i m e n t a l c h e m i c a l s h i f t

STDEVN ./JCC5 - 5 ) 2 / ( n - 1 ) > V L. c a l exp

STEPH P r o p o r t i o n a l i n c r e m e n t i n AH

STEPS P r o p o r t i o n a l i n c r e m e n t i n AS

TEMP( K ) A b o s o l u t e t e m p e r a t u r e

2 9 6


PROGRAM SHIFTS!INPUT,OUTPUT,TAPE5=INPUT,TAPE6=0UTPUT)CCC PROGRAM TO BEST VALUES OF DELTAS AND DELTAH TO PARAMAGNETIC SHIFT C DATA , FROM VARIABLE TEMPERATURE NMR FOR NICKEL PORPHRIN SYSTEM .C READ IN DELTA H IN KJM-1 , DELTA S IN JK-1M-1 , THE CHEMICAL SHIFTS C IN PPM DELTA , AND TEMPERATURE IN CELCIUS .CC

DIMENSION SHI FTC( 3 0 ) . SHIFTE( 3 0 ) . PSHFTE(3 0 ) .TEMP( 3 0 ) . CTEMP(30)

C READ IN DATA AND INITIAL PARAMETERS READ( 5 . * ) IPOINT,C,DELTAH.DELTAS READ( 5 . * ) (SHIFTE(J) . J=1. I POINT)READ( 5 , * ) ( CTEMP( J ) . J=1. I POINT)

C CHECK TO SEE THAT DELTA S AND DELTA H ARE OF THE SAME SIGN IF(DELTAS*DELTAH .GE. O.OJGOTO 7 WRITE(6,5)

5 FORMAT( 43H DELTA H AND DELTA S ARE OF OPPOSITE SIGN)GOTO 190

C CONVERT TO JM-17 DELTAH=DELTAH*1000.0

C WORK OUT EMPIRICAL PARAMAGNETIC SHIFTS AND ABSOLUTE TEMP SHIFTD=8.9749 DO 10 J=1. IPOINT PSHFTE(J)=SHIFTE(J)-SHIFTD TEMP(J)=CTEMP(J)+273.2

10 CONTINUE

C INITIALISE DEVIATION DEVN=Q.0DO 20 J=1 , IPOINT DEVN=DEVN+( PSHFTE( J )

C-C/(TEMP( J ) * ( 1 . 0+EXP(DELTAH/(8.3143*TEMP(J)) -DELTAS/8. 3 1 4 3 ) ) ) ) **2 20 CONTINUE

STEPH=0.1C INREMENT VALUE OF DELTA H

30 DELTAH = DELTAH+STEPH*DELTAH PREVH=DEVN

STEPS=0.1C INREMENT VALUE OF DELTAS

40 DELTAS=DELTAS+STEPS*DELTAS PREVS = DEVN

C CALCULATE DEVIATION DEVN=0.0DO 50 J=1, IPOINT DEVN=DEVN+( PSHFTE( J )

C-C/ ( TEMP( J ) * ( 1 . 0+EXP(DELTAH/(8.3143*TEMP(3 ) ) -DELTAS/8.3143 ) ) ) ) **2 50 CONTINUE

297

C ARE CHANGES IN DEVN AND STEPS SMALL ENOUGH ? IF(ABS(DEVN-PREVS)/DEVN .LE. 0.0001

C .AND. ABS ( STEPS) .LE. O.OOODGOTO 60 C IF DEVN INCREASING , DECREASE ANO CHANGE SIGN OF STEPS

I F (DEVN .GE. PREVS)STEPS= -STEPS/3.1 GOTO 40

C ARE CHANGES IN DEVN AND STEPH SMALL ENOUGH ?60 I F (ABS( DEVN-PREVH) / DEVN .LE. 0.0005

C .AND. ABS( STEPH) .LE. O.OOQ5)GOTO 70 C IF DEVN INCREASING . DECREASE AND CHANGE SIGN OF STEPH

I F (DEVN .GE. PREVH) STEPH= -STEPH/3.1 GOTO 30

70 CONTINUE

C WORK OUT CALCULATED CHEMICAL SHIFTS DO 80 J=1 , I POINT SHIFTC!J)=SHIFTD+

C C/(TEMPI J )* ( 1 . O + EXPIDELTAH/(8 .3143*TEMP( J} ) -DELTAS/8. 80 CONTINUE

C WORK OUT STANDARD DEVIATION AND CONVERT TO KJM-1 POINT = FLOAT(I POINT)STDEVN=SQRT(DEVN/( POINT-1 .0) )DELTAH=DELTAH/1000.0

C WRITE OUT THE RESULTS WRITEI6,100)

100 FORMAT!1H1)WRITE(6 ,110)C

110 FORMAT(13H VALUE OF C = .1PE12 . 4 , 8H PPM K-1 / / / )

WRITEI6,120)120 FORMAT I67H POINT

C POINT)WRITE(6,130)

130 FORMAT( 57H CE/)

DO HO J=1 . IPOINT WRITEI6,150) J.SHIFTE!J)

HO CONTINUE150 FORMAT!1X, 1 2 . 10X.2IF7.3

WRITE( 6 ,160)DELTAH 160 FORMAT( / / / 1 OH DELTA H =,1PE12.4.6H KJM-1)

WR ITE( 6 . 170)DELTAS170 FORMAT( / / 1 OH DELTA S =,1PE12.4,8H JK-1M-1)

WRITE(6,180)STDEVN180 FORMAT!// 25H ONE STANDARD DEVIATION =,F5.3,4H PPM//) 190 CONTINUE

STOPEND

CHEMICAL SHIFTS

EMPIRICAL CALCULATED

.SHIFTC!J).CTEMP!J), J

, 10X) , F5.0,1 OX , 12)

143) ) )

CELCIUS

TEMPERATUR

29 8

2 . 3 1H NMR l i n e h a l f w i d t h s

The e x p r e s s i o n f o r t h e r e l a x a t i o n t i m e g i v e n by

S w i f t ( 1 3 7 ) t a k e s i n t o a c c o u n t t he p a r a m a g n e t i c b r o a d e n i n g

and t h e exchange b r o a d e n i n g o f reson ances between t h e f a s t

exchange l i m i t and t he c o a l e s c e n c e s i t u a t i o n .

1 / T, PA / T 2A e B/ T 2B2 2o . Q ( w ( A ) y A y b 0 ujq ( B ) ) (T V

Where T r e f e r s to r e l a x a t i o n t i m e , g to mole f r a c t i o n , ui

to t h e c h e m i c a l s h i f t e x p r e s s e d as an a n g u l a r f r e q u e n c y and

t t o l i f e t i m e . The s u b s c r i p t s A and B r e f e r t o two

d i f f e r e n t s p i n s t a t e s .

S u b s t i t u t i n g W/ir f o r 1 /T^ * where W i s t h e w i d t h i n Hz a t

h a l f h e i g h t , g i v e s t h e f o l l o w i n g f o r Wc a l ^ n

( 1 -X ) W / IT + X. Wp/Tr + ( 1- X ) 2 . X 2 (250 . 5 xoo 2 n ) 2 . ( T D * V

Where

Wc a l = c a l c u l a t e d w i d t h

WD ’ w i d t h f o r d i a m a g n e t i c f o r m i n f a s t exchange l i m i t

WP = w i d t h f o r p a r a m a g n e t i c f o r m i n f a s t exchange l i m i t

1 ppm = 250 Hz

1 Hz = 2tr r a d s ^

H O

II

1 / k i

t p “ 1 / k - i

So K = V t d = X/ ( 1 - X)

From t h i s T 0 * T P = T Q/ ( 1 - X)

= 1 / { k1 (1 - X ) }

2 9 9

Using t he A r r h e n i u s E q u a t i o n t o s u b s t i t u t e f o r g i v e s

E x p ( E A/ RT)* T = ----------* --------

° P A ( 1 - X )

Where A i s t h e p r e e x p o n e n t i a l f a c t o r and E^ i s t h e

a c t i v a t i o n ene r gy . Both r e f e r t o t he f o r w a r d r e a c t i o n .

S u b s t i t u t i n g f o r x + x and us i ng t h e a p p r o x i m a t i o nU P

(W - W ) . X + W ** W .X i n e q u a t i o n { 4 } g i v e s P U D P

4 rr 3 ( 2 5 0 C ) 2 x 2 ( 1 - X )

c a l Wp.X + - -------. Ex p( EA/RT)

The l a t t e r t e r m r e f e r s t o exchange b r o a d e n i n g . so i f a t

t h e h i g h e s t t e m p e r a t u r e i t i s assumed t h a t t h e r e i s no

exchange b r o a d e n i n g , a v a l u e o f Wp may be c a l c u l a t e d :

Ww = — x-£ = w . { 1 + Exp ( AH / RT - A S / R ) }P exp

Where W i s t h e e x p e r i m e n t a l h a l f w i d t h . exp

Given t h e f o l l o w i n g d a t a a t 363 K

AH = -21 .38 KJmol „ - 1

JK“ 1molAS = - 83 . 84

W = 1 2 . 32 Hzexp

A v a l u e o f 261 Hz was c a l c u l a t e d f o r Wp

Computer program

A computer program was w r i t t e n t o v a r y A and E^ so as t o

m i n i m i s e t h e e x p r e s s i o n

SI - W /W _ ) 2 exp c a l /

3 0 0

Th i s c o r r e s p o n d s to m i n i m i s i n g t he d e v i a t i o n s o f t h e

n o r m a l i s e d w i d t h (W /W „ ) f rom t h e i d e a l v a l u e o f' exp c a l /

u n i t y .

Program v a r i a b l e A l g e b r a i c e x p r e s s i o n

ACTENGe a

C C

CTEMP ( J ) T e m p e r a t u r e / ° C

CONST 1 ( J )

C0NST2( J )

Wp.X

x 2 (1 - X)

C0NST3 4 it3 ( 250 . C ) 2

DELTAH AH

DELTAS AS

DEVND 1 ' We * p /Wc a l ) 2

HSMF(J) X

IPOINT number o f i t e ms o f d a t a

PREVA l e a s t DEVN f o r p r e v i o u s E*A

PREVP l e a s t DEVN f o r p r e v i u o s A

PREXP A

STDEVN / [ ( 1 - We x p /Wc a l ) 2/ , n - 1 >

STEPA p r o p o r t i o n a l i n c r e m e n t i n E,A

STEPP p r o p o r t i o n a l i n c r e m e n t i n A

WCAL( J ) Wc a l

WEMP( J ) wexp

WPARAwp

TEMP( J ) T e m p e r a t u r e / K

301


PROGRAM WIDTHS{ INPUT,OUTPUT,TAPE5=INPUT,TAPE6=0UTPUT)C PROGRAM TO BEST FIT WIDTH DATA FROM VARIA8LE TEMPERATURE PROTON C NMR OF NICKEL PORPHRIN . ENTHALPY IN KJ MOL-1, ENTROPY IN J K-1 MOL-1 C WIDTHS IN S-1 , TEMPERATURE IN CELCIUS .

DIMENSION WEMPI30). WCAL( 3 0 ) ,CTEMP(30), TEMP(30)DIMENSION CONST 1 ( 30 ) ,C0NST2(30),HSMF(30)

C READ IN DATA AND INITIAL PARAMETERS READ( 5 , * ) IPOINT,C,DELTAH,DELTAS READ(5,*)WPARA,PREXP,ACTENG READ( 5 , * ) (WEMP(J),3 = 1 , I POINT)READ( 5 , * ) ( CTEMP( J ) , J=1, I POINT)

C CHECK TO SEE THAT DELTA S AND DELTA H ARE OF THE SAME SIGN IF(DELTAS*DELTAH .GE. 0.0)GOTO 7 WRITE(6,5)

5 FORMAT(43H DELTA H AND DELTA S ARE OF OPPOSITE SIGN)GOTO 220

C CONVERT TO JM-1 , MAKE SURE PREXP AND ACTENG BOTH +VE 7 DELTAH=DELTAH*1000.0

PREXP=ABS(PREXP)ACTENG=ABS(ACTENG*1000.0)

C WORK ABSOLUTE TEMPERATURES . CONSTANTS AND MOLE FRACTIONS DO 10 J =1 , IPOINT TEMP(J)=CTEMP(J)+ 27 3.2HSMF( J) = 1 . 0 / ( 1 . 0+EXP( DELTAH/(8 .3143*TEMP( 3 ) ) -DELTAS/8.3143)) CONST1(J)=WPARA*HSMF(J)CONST2( J ) = ( 1 . 0-HSMF( J ) )*HSMF(J)**2

10 CONTINUECONST3 = 7.751GEG * C**2

C INITIALISE DEVIATION DEVN=0.0DO 20 J = 1 , IPOINTDEVN = DEVN+( 1 . 0-WEMP( J ) / ( CONST 1(J ) +CONST3*CONST2( 3 )

C*EXP(ACTENG/(8.3143*TEMP(J)) ) / { PREXP*TEMP( J ) * * 2 ) ) ) * * 2

20 CONTINUE

STEPP=0.1C INREMENT VALUE OF PRE EXPONENTIAL FACTOR

30 PREXP = PREXP+STEPP*PREXP PREVP=DEVN

STEPA=0.1C INREMENT VALUE OF ACTENG

40 ACTENG=ACTENG+STEPA*ACTENG PREVA=DEVN

C CALCULATE DEVIATION DEVN=0.0DO 50 J=1 , IPOINTDEVN=DEVN+( 1 .0-WEMP(J)/(CONST1( J )+CONST3*CONST2 ( J )

C*EXP(ACTENG/(8.3143 * TEMP( J ) ) ) / ( PREXP*TEMP( J ) * * 2 ) ) ) **2 50 CONTINUE

302

C ARE CHANGES IN DEVN AND STEPA SMALL ENOUGH ? IF(ABS(DEVN-PREVA)/ DEVN .LE. 0.0001

C .AND. ABS ( STEPA) .LE. O.QOOUGOTO 60 C IF DEVN INCREASING . DECREASE AND CHANGE SIGN OF STEPA

I F ( DEVN .GE. PREVA) STEPA= -STEPA/3.1goto 40

C ARE CHANGES IN DEVN AND STEPP SMALL ENOUGH ?60 IF(ABS(DEVN-PREVP)/DEVN .LE. 0.0005

C .AND. ABS( STEPP) .LE. 0.0005)GOTO 70 C IF DEVN INCREASING , DECREASE AND CHANGE SIGN OF STEPP

I F ( DEVN .GE. PREVP)STEPP= -STEPP/3.1 GOTO 30

70 CONTINUE

C WORK OUT CALCULATED WIDTHS DO 00 J=1, IPOINTWCAL(J ) =CONST1(J)+CONST3*CONST2(J)

C*EXP(ACTENG/ (8.3H3*TEMP( J) ) ) / ( PREXP*TEMP ( J ) * * 2 )80 CONTINUE

C WORK OUT STANDARD DEVIATION AND CONVERT TO K JM-1 POINT=FLOAT(IPOINT)STDEVN=SQRT(DEVN/( POINT-1.0) )DELTAH=DELTAH/1000.0 ACTENG=ACTENG/1000.0

C WRITE OUT THE RESULTS WRITE(6,100)

100 FORMAT(1 H1 )WRITE(6.110 ) C

110 FORMAT(13H VALUE OF C =,1PE12.4,8H PPM K-1)WRITE( 6 ,120)WPARA

120 FORMAT( / / 27H LIMITING HIGH SPIN WIDTH = . 1PE12.4.3H HZ)WRITE( 6 . 130)DELTAH

130 FORMAT{ / / 1 OH DELTA H =,1PE12.4,6H KJM-1)WRITEI6,140JDELTAS

HO FORMAT( / / 1 OH DELTA S =,1PE12.4,8H JK-1M-1/ / / )

WRITE(6,150)150 FORMAT( 67H POINT WIDTHS

C POINT)WRITE(6 ,160)

160 FORMAT( 57H EMPIRICAL CALCULATEDCE/ )

DO 170 3=1, IPOINTWR I TE(6 ,180 ) J,WEMP(J),WCAL(J),CTEMP(J), J

170 CONTINUE180 FORMAT( 1X,12,1 OX, 2 ( F8. 2 . 9X) , F5.0,1 OX, 12)

WR I TE(6 ,190 ) PREXP190 FORMAT( / / / 25H PRE EXPONENTIAL FACTOR =,1PE12.4,4H S-1)

WRITE(6,200)ACTENG200 FORMAT( / / 2 OH ACTIVATION ENERGY =,1PE12.4.6H KJM-1)

WRITE(6,210)STDEVN210 FORMAT( / / 45H ONE STANDARD DEVIATION IN NORMALISED WIDTH 220 CONTINUE

STOP END

CELCIUS

TEMPERATUR

= , F5.3/ / )

303

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magnetic and spectroscopic studies of … · relative basicity of the tmpyp isomers 35 ......

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