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Dieter Freude, Institut fr Experimentelle Physik I der Universitt Leipzig

Skiseminar in the Dortmunder Htte in Khtai, Sunday 30 March 2008, 7:308:30 p.m.

Principles of NMR spectroscopyPrinciples of NMR spectroscopy

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NMR is far from nuclear spectroscopyNMR is far from nuclear spectroscopy

HF VHF UHF SHF EHF far middle near u vacuum -rays

radio frequency spectroscopy X-ray spectr. nuclear sp.optical spectroscopy

visible

kT300MR PR

photoelectronspectroscopy

Mss-bauer

S X Q W

molec.rotation

latticevibr.

molec.vibration

over

-ton

-, n-electr.

outer -electrons

inner

electrons

nuclear

transitions

/m 10010

1 10

1 10

210

310

410

510

6 10

710

810

910

1010

11

107 108 109 1010

/Hz

102

103

104

105

E/eV10410

310

210

1

SW USW microwaves infrared UV X-rays

/cm

1

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NMR is near to Nobel PrizesNMR is near to Nobel Prizes

Physics 1952 Chemistry 1991 2002 Medicine 2003

Felix Bloch and Edward Purcell Richard R. Ernst Kurt Wthrich Paul Lauterbur and Peter Mansfield

Stanford Harvard University ETHZ ETHZ Urbana Nottingham

USA USA Switzerland Switzerland USA England

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Some of the 130 NMR isotopesSome of the 130 NMR isotopes

WEB of Science: 35% of NMR studies focus to the nuclei 1H, 25% to 13C, 8% to 31P, 8% to 15N,

4% to 29Si,and 2% to 19F. In these nuclei, we have a nuclear spin I= .

If we look at nuclei with a quadruple moment and half-integer spin I> , we find 27Al in 3% of

all the NMR papers and 1% for each of the nuclei 11B, 7Li, 23Na and 51V.For even numbered spin, only the I= 1-nuclei are frequently encountered: 2H in 4% and 14N

and 6Li in 0.5% of all NMR papers.

nucleus natural

abundance/%

spin quadrupole

momentQ/fm2

gyromagnetic

ratio /107Ts

-frequency

100 MHz(1H)

rel. sensitivity

at naturalabundance

1H 99.985 1/2 26.7522128 100.000000 1.000

2H 0.015 1 0.2860 4.10662791 15.350609 1.45 106

6Li 7.5 1 0.0808 3.9371709 14.716106 6.31 104

7Li 92.5 3/2 4.01 10.3977013 38.863790 0.27211

B 80.1 3/2 4.059 8.5847044 32.083974 0.13213

C 1.10 1/2 6.728284 25.145020 1.76 10414

N 99.634 1 2.044 1.9337792 7.226330 1.01 10315

N 0.366 1/2 2.71261804 10.136784 3.85 10617

O 0.038 5/2 2.558 3.62808 13.556430 1.08 05

19F 100 1/2 25.18148 94.094008 0.83423

Na 100 3/2 10.4 7.0808493 26.451921 9.25 10227AI 100 5/2 14.66 6.9762715 26.056890 0.21

29Si 4.67 1/2 5.3190 19.867187 3.69 104

31P 100 1/2 10.8394 40.480742 6.63 102

51V 99.750 7/2 5.2 7.0455117 26.302963 0.38

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Chemical shift of the NMRChemical shift of the NMR

H+

external magnetic field B0shielded

magnetic

field

B0(1)

OH

electron

shell

We fragment hypothetically a water molecule into hydrogen cation plus hydroxyl anion.

Now the 1H in the cation has no electron shell, but the 1H in the hydroxyl anion is

shielded (against the external magnetic field) by the electron shell. Two signals witha distance of about 35 ppm appear in the (hypothetical) 1H NMR spectrum.

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Chemical shift and J-couplingChemical shift and J-coupling

1 2 3 40

10 20 30 40 50 60 700

t/ms

t/s

012345

/ppm

The figure shows at left the free induction decay (FID) as a function of time and at right the

Fourier transformed 1H NMR spectrum of alcohol in fully deuterated water. The individual

spikes above are expanded by a factor of 10. The singlet comes from the OH groups, which

exchange with the hydrogen nuclei of the solvent and therefore show no splitting. The quartet

is caused by the CH2 groups, and the triplet corresponds to the CH3 group of the ethanol. The

splitting is caused by J-coupling between 1H nuclei of neighborhood groups via electrons.

An NMR spectrum is not shown as a function of the frequency = ( / 2) B0(1),but rather on a ppm-scale of the chemical shift = 106 (ref ) /L, where thereference sample is tetramethylsilane (TMS) for1H, 2H, 13C, and 29Si NMR.

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Chemical shift range

of some nuclei

Chemical shift range

of some nuclei

Ranges of the chemical shifts of a few

nuclei and the reference substances,

relative to which shifts are related.

1, 2H TMS

6, 7Li 1M LiCl

11B BF3O(C2H5)2

13C MS = (CH3)4Si

14, 15N NH4+

19F CFCl3

23Na 1M NaCl

27Al [Al(H2O)6]3+

29Si TMS = (CH3)4Si

31P 85% H3PO4

51V VOCl3

1000 100 10 0 10 100 1000

/ ppm

129, 131Xe XeOF4

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NMR spectrometerNMR spectrometer

H. Pfeifer:

Pendulum feedback

receiver

Diplomarbeit,

Universitt Leipzig,

1952

Bruker's

home

page

AVANCE 750

wide-bore in

Leipzig

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NMR spectrometer for liquidsNMR spectrometer for liquids

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Campher

H3C CH3

CH3

O

1.00

0.94

1.09

0.98

1.12

2.10

3.143.0

1

3.2

0

Integ

ral

2.5 2.0 1.5 1.0 ppm

H

45 40 35 30 25 20 15 10 5ppm

2.5 2.0 1.5 1.0ppm

2.5

2.0

1

.5

1.0

ppm

2

.5

2.0

1.5

1.0

ppm

45 40 35 30 25 20 15 10 5ppm

2.5 2.0 1.5 1.0pp m

0.8

0.9

1.0

ppm

Structure NMR-Spektrum

CHHH

1

H-NMR13

C-NMRHH-COSYHC-COSYHETCORNOESYR. Meusinger, A. M. Chippendale, S. A. Fairhurst,

in Ullmanns Encyclopedia of Industrial Chemistry, 6th ed., Wiley-VCH, 2001

Structure determination by NMRStructure determination by NMR

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How works NMR: a nuclear spin I = 1/2 in an magnetic field B0How works NMR: a nuclear spin I = 1/2 in an magnetic field B0

B0, z

y

x

LB0, z

y

x

L

Many atomic nuclei have a spin, characterized by the nuclear spinquantum numberI. The absolute value of the spin angular momentum is

The component in the direction of an applied field isLz = Iz m = for I= 1/2.

.)1( IIL

Atomic nuclei carry an electric charge. In nuclei with a spin, the rotation

creates a circular current which produces a magnetic moment.

An external homogenous magnetic field B results in

a torque T= B with a related energy of E=B.

The gyromagnetic (actually magnetogyric) ratio is defined by

=L.The zcomponent of the nuclear magnetic moment is

z= Lz = Iz m .

The energy for I = 1/2 is split into 2 Zeeman levels

Em = zB0 =mB0 = B0/2 = L /2.Pieter Zeeman observed in 1896 the splitting of optical spectral lines in the field of an electromagnet.

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Larmor frequencyLarmor frequency

Joseph Larmor described in 1897 the precession of electron orbital magnetization in an external magnetic field.

Classical model: the torque Tacting on a magnetic dipole is definedas the time derivative of the angular momentum L. We get

By setting this equal to T = B , we see that

The summation of all nuclear dipoles in the unit volume gives us the magnetization.

For a magnetization that has not aligned itself parallel to the external magnetic field,it is necessary to solve the following equation of motion:

.d

d1

d

d

tt

LT

.d

dB

t

.d

dBM

M

t

B0, z

M

y

xL

We define B (0, 0, B0) and choose M(t 0) |M| (sin, 0, cos). Then we obtainMx |M| sincosLt, My |M| sinsinLt, Mz |M| cos with L =B0.

The rotation vector is thus opposed to B0 for positive values of . The Larmor frequency

is most commonly given as an equation of magnitudes: L = B0 or .20L B

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Macroscopic magnetizationMacroscopic magnetization

energyEm =

E= hLE

m =

Nm =

Nm =

hL kTapplies at least for temperatures above 1 Kand Larmor frequencies below 1 GHz. Thus,

spontaneous transitions can be neglected, and the

probabilities Pfor absorption and induced emission

are equal. It follows P = B+, wL= B,+ wL, where Brefers to the Einstein coefficients for induced

transitions and wL is the spectral radiation density at the Larmor frequency.

A measurable absorption (or emission) only occurs if there is a difference in the two

occupation numbers N. In thermal equilibrium, the Boltzmann distribution applies to

Nand we have.expexp L0

2/1

2/1

kT

h

kT

B

N

N

If L 500 MHz and T300 K, hL/kT 8 10 is very small, and the exponentialfunction can be expanded to the linear term:

.108 5L

2/1

2/12/1

kT

h

N

NN

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Longitudinal relaxation time T1Longitudinal relaxation time T1

All degrees of freedom of the system except for the spin (e.g. nuclear oscillations,

rotations, translations, external fields) are called the lattice. Setting thermal

equilibrium with this lattice can be done only through induced emission. The

fluctuating fields in the material always have a finite frequency component at the

Larmor frequency (though possibly extremely small), so that energy from the spin

system can be passed to the lattice. The time development of the setting of

equilibrium can be described after either switching on the external field B0

at time

t0 (difficult to do in practice) with

,1 10

T

t

enn

T1 is the longitudinal or spin-lattice relaxation time an n0 denotes the difference inthe occupation numbers in the thermal equilibrium. Longitudinal relaxation time

because the magnetization orients itself parallel to the external magnetic field.

T1 depends upon the transition probability Pas

1/T1 = 2P2B,+ wL.

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T1 determination by IRT1 determination by IR

The inversion recovery (IR) by -/2

1

210T

enn

By setting the parentheses equal to zero, we get 0 T1 ln2 as the passage of zero.

0

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Line width and T2Line width and T2

A pure exponential decay of the free

induction (or of the envelope of the

echo, see next page) corresponds to

G(t) = exp(t/T2).

The Fourier-transform gives fLorentz = const. 1 / (1 +x2) with x= (0)T2,

see red line. The "full width at half maximum" (fwhm) in frequency units is

.1

2

2/1T

Note that no second moment exists for a Lorentian line shape. Thus,an exact Lorentian line shape should not be observed in physics.

Gaussian line shape has the relaxation function G(t) = exp(t2M2 / 2) and a line

form fGaussian = exp (2/2M2), blue dotted line above, where M2denotes thesecond moment. A relaxation time can be defined by T2

2 = 2 / M2. Then we get

21/2=2/T2=1/2

0

fLorentz

1

1/2

( ) ( ) ( ) .Hz/12.7

4lnHz/=

s/

2=s/

2

2/1

22

2/12

2

2-

2

T

M

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Correlation time c, relaxation times T1 and T2Correlation time c, relaxation times T1 and T2 tftfG

c

GG exp0

2L2

L06

24

1 21

8

1

2

4

1

5

11

c

c

c

cII

rT

2

L

2

L0

6

24

2 21

2

1

53

4

1

5

11

c

c

c

cc

II

rT

T1

T2

ln T1,2

1/T

T1 min

T2 rigid

The relaxation times T1 and T2 as a function of the reciprocal absolute temperature

1/T for a two spin system with one correlation time. Their temperature dependency

can be described by c0 exp(Ea/kT).

It thus holds that T1 T2 1/c when Lc 1 and T1L2 c when Lc 1.

T1 has a minimum of at Lc 0,612 or Lc 0,1.

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Rotating coordinate system and the offsetRotating coordinate system and the offset

For the case of a static external magnetic field B0 pointing in z-direction and the

application of a rf field Bx(t) = 2Brfcos(t) in x-direction we have for the

Hamilitonian operator of the external interactions in the laboratory sytem (LAB)

H0 + Hrf= LIz + 2rfcos(t)Ix,

where L

= 2L

= B0

denotes the Larmor frequency, and the nutation

frequency rf is defined as rf= Brf.

The transformation from the laboratory frame to the

frame rotating with gives, by neglecting the part that

oscillates with the twice radio frequency,

H0 i + Hrf i = Iz + rf Ix,

where = L denotes the resonance offset and

the subscript i stays for the interaction representation.

0

x

y

z

0

x

y

z

Magnetization phases develop in this interaction

representation in the rotating coordinate system like

= rf or = t.

Quadratur detection yields value and sign of .

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Bloch equation and stationary solutionsBloch equation and stationary solutions

We define Beff (Brf, 0, B0/) and introduce the Bloch equation:

1

0

2

effd

d

T

MM

T

MM

tzx zyyx eeeBM

M

Stationary solutions to the Bloch equations are attained for dM/dt 0:

.

1

1

,21

,21

0

21

2

rf

22

2

2

L

2

2

2

L

rf0rf

21

2

rf

22

2

2

L

2

rf0rf

21

2

rf

22

2

2

L

2

2L

M

TTBT

TM

HMBTTBT

TM

HMBTTBT

TM

z

y

x

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Hahn echoHahn echo

B z B

Mx

y

z B z

5 4

12

3

B z

1 2

54

3

B0

Mx

y

z

rfpulses

t

/2

tmag

netization

free inductionecho

/2 pulse FID, pulsearound the dephasing around the rephasing echo

y-axis x-magnetization x-axis x-magnetization

(r,t) =(r)t (r,t) = (r,) + (r)(t )

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T2 and T2*T2 and T2*

/2

2

t

t

( )2

2

e=T

G

( )2

e=T

t

tG

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EXSY, NOESY, stimulated spin echoEXSY, NOESY, stimulated spin echo

stimulatedecho

0

t1t2

tmixt1

time

FIDFID

after mixing

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Pulsed field gradient NMR diffusionmeasurements base on NMR pulse

sequences that generate a spin echo,

like the Hahn echo (two pulses) and the

stimulated spine echo (three pulses).

At right, the 13-intervall sequence foralternating gradients consisting of

7 rf pulses, 4 gradient pulses of duration

, intensity g, and diffusion time and2 eddy current quench pulses is described.

NMR diffusometry (PFG NMR)NMR diffusometry (PFG NMR)

free induction

decay

rf pulses

gradient pulses

g

ecd

pgDSS

2

4exp

2

0

The self-diffusion coefficient D of molecules in bulk phases, in confined geometries and in

biologic materials is obtained from the amplitude S of the free induction decay in dependence

on the field gradient intensity gby the equation

Application of MAS technique in addition to PFG (pulsed field gradient) improves drastically

the spectral resolution, allowing the study of multi-component diffusion in soft matter or

confined geometry.

ffff

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The difference between solid-state and liquid NMR,

the lineshape of water

The difference between solid-state and liquid NMR,

the lineshape of water

10 20 30 400

/ kHz-30 -20 -10-40

0.1 0.2 0.3 0.40

/ Hz

-0.3 -0.2 -0.1-0.4

solid water (ice)

liquid water

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Fast rotation (160 kHz) of the sample aboutan axis oriented at 54.7 (magic-angle) with

respect to the static magnetic field removes

all broadening effects with an angular

dependency of

o7.54

3

1cosarc

That means

chemical shift anisotropy,dipolar interactions,

first-order quadrupole interactions, and

inhomogeneities of the magnetic

susceptibility.

It results an enhancement in spectral

resolution by line narrowing also for soft

matter studies.

High-resolution solid-state MAS NMRHigh-resolution solid-state MAS NMR

2

1cos3 2

rotor with sample

in the rf coil zr

ro t

gradient coils for

MAS PFG NMR

B0

Laser supported high temperature MAS NMRLaser supported high temperature MAS NMR

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Laser supported high-temperature MAS NMR

for time-resolved in situ studies of reaction steps

in heterogeneous catalysis: the NMR batch reactor

Laser supported high-temperature MAS NMR

for time-resolved in situ studies of reaction steps

in heterogeneous catalysis: the NMR batch reactor

MAS Rotor

7 mm

CO2 Laser

Cryo Magnet

B0

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Dieter Freude, Institut fr Experimentelle Physik I der Universitt Leipzig

Skiseminar in the Dortmunder Htte in Khtai, 31 March 2008, 7:308:30 p.m.

Some applications of solid-state

NMR spectroscopy

Some applications of solid-state

NMR spectroscopy

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NMR on the topNMR on the top

WEB of Science refers for the year 2006 to about

16 000 NMR studies, mostly on liquids, but including

also 2500 references to solid-state NMR.

Near to 12 000 studies concern magnetic resonance

imaging (MRI).

The next frequently applied technique, infraredspectroscopy, comes with about 9 000 references in the

WEB of Science.

Solid state NMR on porous materialsSolid state NMR on porous materials

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Solid-state NMR on porous materialsSolid-state NMR on porous materials

1H MAS NMR spectra including TRAPDOR 29Si MAS NMR

27Al 3QMAS NMR

27

Al MAS NMR 1H MAS NMR in the range from 160 K to 790 K

1H MAS NMR on moleculesadsorbed in porous materials

1H MAS NMR on moleculesadsorbed in porous materials

Hydrogen exchange in bezene loaded H-zeolites

In situ monitoring of catalytic conversion of molecules

in zeolites by 1H, 2H and 13C MAS NMR

MAS PFG NMR studies of the self-diffusionof acetone-alkane mixtures in nanoporous silica gel

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1H MAS NMR spectra, TRAPDOR1H MAS NMR spectra, TRAPDOR

0

t2

time

FID echo

t1 t1

1H MAS NMR with 27Al dephasing

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1H MAS NMR spectra, TRAPDOR1H MAS NMR spectra, TRAPDOR

H-ZSM-5

activated

at 550 C

420246810/ ppm

2046810/ ppm

4

4.2 ppm 2.9 ppm2.9 ppm

2.2 ppm

1.7 ppm

2.2 ppm1.7 ppm2.9 ppm2.9 ppm

with dephasing

without dephasing

difference spectra

2

Without and with dipolar dephasing by27

Al high power irradiation and difference spectra areshown from the top to the bottom. The spectra show signals of SiOH groups at framework

defects, SiOHAl bridging hydroxyl groups,AlOH group.

H-ZSM-5

activated

at 900 C

4.2 ppm

4.2 ppm

4.2 ppm

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1H MAS NMR of porous materials1H MAS NMR of porous materials

4202467 5 ppm

3 1 1 2

Bridging OH groups in small channelsand cages of zeolitesSiOHAl

Disturbed bridging OH groups in zeoliteH-ZSM-5 and H-Beta

SiOH

Bridging OH groups in large channelsand cages of zeolitesSiOHAl

Cation OH groups located in sodalite cagesof zeolite Y and in channels of ZSM-5which are involved in hydrogen bonds

CaOH, AlOH,LaOH

OH groups bonded to extra-framework aluminium specieswhich are located in cavities or channels and which areinvolved in hydrogen bonds

AlOH

Silanol groups at the externalsurface or at framework defects

SiOH

Metal or cation OH groups in large cavitiesor at the outer surface of particles

MeOH

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29Si MAS NMR spectrum of sil icalite-129Si MAS NMR spectrum of sil icalite-1

SiO2 framework consisting of 24 crystallographic different silicon sites per unit cell (Fyfe 1987).

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29Si MAS NMR29Si MAS NMR

130110907060 80 ppm100 120

Si(1 Zn

Si(2 Zn zincosilicate-type zeolitesVP-7, VPI-9Q

4

alkali and

alkaline earth

Q

Q2Q

Q4

Si(1 Al)

Si(0 Al)

Si(2 Al)

Si(3 Al)Si(4 Al)

Si(3Si, 1OH)

aluminosilicate-

type zeol ites

Q

Q4

Q

3

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Determination of the Si/Al ratio by 29Si MAS NMRDetermination of the Si/Al ratio by 29Si MAS NMR

For Si/Al = 1 the Q4 coordination represents a SiO4 tetrahedron that is surrounded by four

AlO4-tetrahedra, whereas for a very high Si/Al ratio the SiO4 tetrahedron is surrounded

mainly by SiO4-tetrahedra. For zeolites of faujasite type the Si/Al-ratio goes from one

(low silica X type) to very high values for the siliceous faujasite. Referred to the siliceous

faujasite, the replacement of a silicon atom by an aluminum atom in the next coordinationsphere causes an additional chemical shift of about 5 ppm, compared with the change

from Si(0Al) with n = 0 to Si(4Al) with n = 4 in the previous figure. This gives the

opportunity to determine the Si/Al ratio of the framework of crystalline aluminosilicate

materials directly from the relative intensities In (in %) of the (up to five)29Si MAS NMR

signals by means of the equation

4

0

400Al

Si

n

nnITake-away message from this page:

Framework Si/Al ratio can be determined by 29SiMAS NMR. The problem is that the

signals for n = 04 are commonly not well-resolved and a signal of SiOH (Q3) atabout 103 ppm is often superimposed to the signal for n = 1.

2929

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29Si MAS NMR shift and Si-O-Si bond angle 29Si MAS NMR shift and Si-O-Si bond angle Considering the Q4 coordination alone, we find a spread of 37 ppm for zeolites in theprevious figure. The isotropic chemical shift of the 29Si NMR signal depends in addition on

the four Si-O bonding lengths and/or on the four Si-O-Si angles i, which occur between

neighboring tetrahedra. Correlations between the chemical shift and the arithmetical mean

of the four bonding angles iare best described in terms of

The parameterdescribes the s-character of the oxygen bond, which is considered to be

an s-p hybrid orbital. For sp3-, sp2- and sp-hybridization with their respective bondingangles = arccos(1/3) 109.47, = 120, = 180, the values= 1/4, 1/3 and 1/2 areobtained, respectively. The most exact NMR data were published by Fyfe et al. for an

aluminum-free zeolite ZSM-5. The spectrum of the low temperature phase consisting of

signals due to the 24 averaged Si-O-Si angles between 147.0 and 158.8 (29Si NMR

linewidths of 5 kHz) yielded the equation for the chemical shift

1coscos

44.216.287ppm Take away message from this page:

Si-O-Si bond angle variations by a distortion of the short-range-order in a crystallinematerial broaden the 29Si MAS NMR signal of the material.

2727

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27Al MAS NMR27Al MAS NMR

010203040060708090100 10110120 ppm

aluminates

aluminosilicates

aluminoborates

aluminophosphates

aluminates

aluminosilicates

aluminoborates

aluminophosphates

aluminates

aluminosilicates

aluminoborates

aluminophosphates

aluminosilicates3-fold

coord.

4-fold

coordinated

5-fold

c

oordinated

6-fold

coordinated

20

27Al MAS NMR shift and Al O T bond angle27Al MAS NMR shift and Al O T bond angle

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27Al MAS NMR shift and Al-O-T bond angle27Al MAS NMR shift and Al-O-T bond angle

Aluminum signals of porous inorganic materials were found in the range -20 ppm to 120 ppm

referring to Al(H2O)63+. The influence of the second coordination sphere can be demonstrated

for tetrahedrally coordinated aluminum atoms: In hydrated samples the isotropic chemical

shift of the 27Al resonance occurs at 7580 ppm for aluminum sodalite (four aluminum atomsin the second coordination sphere), at 60 ppm for faujasite (four silicon atoms in the second

coordination sphere) and at 40 ppm for AlPO4-5 (four phosphorous atoms in the secondcoordination sphere).

In addition, the isotropic chemical shift of the AlO4 tetrahedra is a function of the mean of the

four Al-O-T angles (T = Al, Si, P). Their correlation is usually given as

/ppm = -c1 + c2.c1 was found to be 0.61 for the Al-O-P angles in AlPO4 by Mller et al. and 0.50 for the Si-O-

Al angles in crystalline aluminosilicates by Lippmaa et al. Weller et al. determined c1-values

of 0.22 for Al-O-Al angles in pure aluminate-sodalites and of 0.72 for Si-O-Al angles in

sodalites with a Si/Al ratio of one.Aluminum has a nuclear spin I= 5/2, and the central transition is broadened by second-order

quadrupolar interaction. This broadening is (expressed in ppm) reciprocal to the square of the

external magnetic field. Line narrowing can in principle be achieved by double rotation or

multiple-quantum procedures.

/

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27Al 3QMAS NMR study of AlPO4-1427Al 3QMAS NMR study of AlPO4-14

40 30 20 10 0

40

30

20

10

0

1/ ppm

2/ ppm

position 1

position 2

position 3

position 5

AlPO4-14,27Al 3QMAS spectrum (split-t1-whole-echo, DFS pulse) measured at 17.6 T with a

rotation frequency of 30 kHz.

The parameters CS, iso = 1.3 ppm, Cqcc = 2.57 MHz, = 0.7 for aluminum nuclei at position 1, CS, iso = 42.9 ppm,Cqcc = 1.74 MHz, = 0.63, for aluminum nuclei at position 2, CS, iso = 43.5 ppm, Cqcc = 4.08 MHz, = 0.82,

for aluminum nuclei at position 3, CS, iso = 27.1 ppm, Cqcc = 5.58 MHz, = 0.97, for aluminum nuclei at position 5,

CS, iso = 1.3 ppm, Cqcc = 2.57 MHz, = 0.7 were taken from Fernandez et al.

27Al MAS NMR spectra27Al MAS NMR spectra

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S spect a

of a hydrothermally treated zeolite ZSM-5

S spect a

of a hydrothermally treated zeolite ZSM-5

L

= 195 MHz

Rot = 15 kHz

/ ppm 6040 20020406080100

L = 130 MHzRot = 10 kHz

four-fold

coordinated

five-fold

coordinatedsix-fold

coordinated

Take-away message:

A signal narrowing by MQMAS or DOR is not possible, if the line broadening is

dominated by distributions of the chemical shifts which are caused by short-range-order

distortions of the zeolite framework.

Mobility of the Brnsted sitesMobility of the Brnsted sites

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and hydrogen exchange in zeolitesand hydrogen exchange in zeolites

O O O OO

OOO OO OO

Al SiSi Al

H

O

NH4+

OO

OO

Al

H

OO

OO

Al

H

OO

OO

Al

H

OO

OO

Al

HO O O OO

OOO OO OO

Al SiSi Al

H

O

Proton mobility of bridging hydroxyl groups in zeolites H-Y and H-ZSM-5 can be monitored in

the temperature range from 160 to 790 K. The full width at half maximum of the 1H MAS NMR

spectrum narrows by a factor of 24 for zeolite H-ZSM-5 and a factor of 55 for zeolite 85 H-Y.

Activation energies in the range 20-80 kJ mol have been determined.

one-site jumps around

one aluminum atom

O O O OO

OOO OO OO

Al SiSi Al

H

O

multiple-site jumps

along several

aluminum atoms

Narrowing onset and correlation timeNarrowing onset and correlation time

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Narrowing onset and correlation timeNarrowing onset and correlation time

2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0

1

10

1000 T1/ K

1

20

1,5

0,1

1

10

2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5

1000 T / K

fwhm

ofthesidebandenvelope/kHz

40 C

120C

3,2 kHz

17 kHz

The correlation time corresponds to the mean residence time of an ammonium ion at an

oxygen ring of the framework.

2H NMR, H-Y: at50 Cc=5 s1

H NMR, H-Y: at 40 C c=20 s2H NMR, H-ZSM-5: at 120 C c=3,8 s

=rigid/2

rigid

c1

1

=rigid/2

2H MAS NMR, deuterated

zeolite H-ZSM-5, loaded with

0.33 NH3 per crossing

1H MAS NMR, zeolite H-Y, loaded

with mit 0.6 NH3 per cavity

The correlation time corresponds to the mean residence time of an ammonium ion at an

oxygen ring of the framework.

1D 1H EXSY (exchange spectroscopy)1D 1H EXSY (exchange spectroscopy)

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1D 1H EXSY (exchange spectroscopy)1D 1H EXSY (exchange spectroscopy)

Evolution time t1 = 1/4 .

denotes the frequency difference of the exchanging species.

MAS frequency should be a multiple of

Two series of measurements should be performed at each temperature:

Offset right of the right signal and offset left of the left signal.

0

tm

time

/2

FIDt1

/2 /2t2

EXSY pulse sequence

Result of the EXSY experimentResult of the EXSY experiment

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Result of the EXSY experimentResult of the EXSY experiment

Stack plot of the spectra of zeoliteH-Y loaded with 0.35 ammoniamolecules per cavity. Mixing timesare between tm = 3s and15 s.

0 2 4 6 8 10 12

ammonium ions

OH

Intensity

0 2 4 6 8 10 12

mixing time tm / s

/ ppm10 0

97 C

Intensities of the signals of ammonium

ions and OH groups for zeolite H-Y

loaded with 1.5 ammonia molecules per

cavity. Measured at 87 C in the field of9,4 T. The figure on the top and bottom

correspond to offset on the left hand side

and right hand side of the signals,

respectively.

Basis of the data processingBasis of the data processing

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0AmmmAA exp1exp12

1)( MD

DtD

DtI

t

0BmmmBB exp1-exp121)( MDDtDDtI

t

DMtDtD

D

MtDtDtItI

A

0Bmm

B

0AmmmBAmAB

1expexp

2

1

1expexp

2

1)()(

BBAA

2

1LL 2

1

ABAB2 LLD BBAA21 LL

diagonal peaks

cross peaks

BA

BA

B1

A1

BBBA

ABAA

11

11

10

01

KRL

T

T

LL

LL

dynamic matrix (without spin diffusion):

Laser supported 1H MAS NMR of H-zeolitesLaser supported 1H MAS NMR of H-zeolites

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Spectra (at left) and Arrhenius plot

(above) of the temperature dependent

1H MAS NMR measurements whichwere obtained by laser heating. The

zeolite sample H-Y was activated at

400 C.

2002040 40

/ ppm

297 K

723 K

773 K

673 K

423 K

573 K

623 K 1.0 1.5 2.0 2.5 3.0 3.5

0.1

1

10

1000 T / K

1/2

/kHz

Proton transfer between Brnsted sites and

b l l i l it H Y

Proton transfer between Brnsted sites and

b l l i l it H Y

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benzene molecules in zeolites H-Ybenzene molecules in zeolites H-Y

4810 0

/ppm

0 200 400 600 800t /min

intensity

t

85 H-Y with

fully deuteratedbenzene at

400 K

In situ 1H MAS NMR spectroscopyof the proton transfer betweenbridging hydroxyl groups and

benzene molecules yieldstemperature dependent exchangerates over more than five orders ofmagnitude.

8 6 4 2

8

6

4

2

/ppmF 2

F 192 H-Y withbenzene at520 K with amixing periodof 500 ms

H-D exchange andNOESY MAS NMRexperiments were

performed by bothconventional andlaser heating up to600 K.

Exchange rateExchange rate

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as a dynamic measure of Brnsted acidityas a dynamic measure of Brnsted acidity

Arrhenius plot of the H-Dand H-H exchange rates for

benzene molecules in thezeoli tes 85 H-Y and 92 H-Y.The values which aremarked by blue orred weremeasured by laser heatingor conventional heating,

respectively.

The variation of the Si/Al ratio in the zeolite H-Y causes a change of the

deprotonation energy and can explain the differences of the exchange rate of

one order of magnitude in the temperature region of 350600 K. However, ourexperimental results are not sufficient to exclude that a variation of the pre-

exponential factor caused by steric effects like the existence of non-framework

aluminum species is the origin of the different rates of the proton transfer.

10

10

10

10

1.5 2.71.9 2.3

92 H-Y

85 H-Y

1000

T/ K

k/min

In situ monitoring of catalytic conversion of

l l i li t b 1H 2H d 13C MAS NMR

In situ monitoring of catalytic conversion of

l l i li t b 1H 2H d 13C MAS NMR

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molecules in zeolites by 1H, 2H and 13C MAS NMRmolecules in zeolites by 1H, 2H and 13C MAS NMR

Kinetics of a double-bond-shift reaction, hydrogen exchange

and13

C-label scrambling of n-butene in H-ferrierite

6 4 2 0

/ ppm

CH=5.6

CH31.7

65 min

4 min

1H MAS NMR spectra of n-but-1-ene-d8

adsorbed on H-FER2 (T=360K).

Hydrogen transfer occurs from the acidic

hydroxyl groups of the zeolite to the

deuterated butene molecules. Both methyl

and methene groups of but-2-ene are

involved in the H/D exchange. The ratiobetween the intensities of the CH3 and

CH groups in the final spectrum is 3:1.

*

**

*

*

*

*

126

200 160 120 80 40 0

/ ppm

17

13

*

17 min

at 323 K

20 h

at 323 K

*

**

*

*

*

*

126

200 160 120 80 40 0

/ ppm

17

13

*

17 min

at 323 K

20 h

at 323 K

13C CP/MAS NMR spectra of

[2-13C]-n-but-1-ene adsorption on

H-FER in dependence on reaction

time. Asterisks denote spinning

side-bands. The appearance of the

signals at 13 and 17 ppm and

decreasing intensity of the signal at126 ppm show the label scrambling.

1.7

5.02.0

0246 / ppm

1.0

5.9

5 min

18.5 h

2H MAS NMR spectra of n-but-1-ene-d8

adsorbed on H-FER (T = 333K). n-But-

1-ene undergoes readily a double-bond-

shift reaction, when it is adsorbed on

ferrierite. The reaction becomes slow

enough to observe the kinetics , if the

catalyst contains only a very smallconcentration of Brnsted acid sites.

MAS PFG NMR for NMR diffusometryMAS PFG NMR for NMR diffusometry

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1.02.0 / ppm

CH3 (n-but)CH3 (iso)

CH2 (n-but)

CH (iso)

= 0.4 ppm

gradient

strength

MAS PFG NMR diffusion experiment

om 54.7

3

1cosarc

rotor with sample

in the rf coil zr

g gradient pulses

rotm

gradient

coil

B0

3

4exp/

2

0

gDSS

0.51.01.52.0

= 0.02 ppm

ppm

-2024 ppm

* * ****

r= 0 kHz

r= 1 kHz

r= 10 kHz

FAU Na-X , n-butane + isobutane

rfpulses

gpulses

FID

g

Gz

r. f.

T

ecd

MAS PFG NMR studies of the self-diffusionMAS PFG NMR studies of the self-diffusion

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of acetone-alkane mixtures in nanoporous silica gelof acetone-alkane mixtures in nanoporous silica gel

The self-diffusion coefficients of mixtures of acetone with several alkanes were studied bymeans of magic-angle spinning pulsed field gradient nuclear magnetic resonance (MAS

PFG NMR). Silica gels with different nanopore sizes at ca. 4 and 10 nm and a pore

surface modified with trimethylsilyl groups were provided by Takahashi et al. (1). The silica

gel was loaded with acetone alkane mixtures (1:10). The self-diffusion coefficients of

acetone in the small pores (4 nm) shows a zigzag effect depending on odd or evennumbers of carbon atoms of the alkane solvent as it was reported by Takahashi et al. (1)

for the transport diffusion coefficient.

(1) Ryoji Takahashi, Satoshi Sato, Toshiaki Sodesawa and Toshiyuki Ikeda: Diffusion coefficient of ketones in liquid media within

mesopores;Phys. Chem. Chem. Phys.5 (2003) 24762480

Semi-logarithmic plot of the decay of the CH3signal of ketone in binary mixture with acetone

at 298 K The diff sion time is 600 ms and

Stack plot of the 1H MAS PFG NMR spectra

at 10 kHz of the 1:10 acetone and octane

mixture absorbed in E material as function

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0,00 0,05 0,10 0,15 0,20 0,250,01

0,1

1 = 600 ms

= 2 ms

Em / acetone + alkane (C6,C7,C8,C9)

S/S

0

g2 / T

2m

-2

nonane C9

octane C8

heptane C7

hexane C6

at 298 K. The diffusion time is = 600 ms and

a gradient pulse length is = 2 ms:

/ppm0.40.81.21.62.02.42.8

CH3

CH3

CH2

acetone

octane

gradient

strength

mixture absorbed in Em material as function

of increasing pulsed gradient strength for a

diffusion time = 600 ms:

6 7 8 9 10

8,0x10-12

1,0x10-11

1,2x10-11

1,4x10-11

Acetone diffusivity in alkane mixture

D

/m

2s

-1

Carbon number of alkane solvent

% (= 600 ms)

% (= 800 ms)

% (= 1200 ms)

Diffusion coefficient of acetone in mixture within Emin dependence of the number of carbons in the

alkane solvent. The measurements were carried

out with diffusion time = 600 ms, = 800 ms and

= 1200 ms and the gradient pulse length = 2 ms.

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Horst Ernst

Moiss Fernndez

Clemens Gottert

Johanna KanellopoulosBernd Knorr

Thomas Loeser

Toralf Mildner

Lutz MoschkowitzDagmar Prager

Denis Schneider

Alexander Stepanov

Deutsche Forschungsgemeinschaft

Max-Buchner-Stiftung

I acknowledge

support from