80..J IIHLI I)?<l

600c'":z:I GO<l

'0 /1III.. 201/1:J

'">...:::

°'" d5d

fi d7 d8 d9 d 100;a: 25 26 27 28 29 30 31

Atomic No.

Fig. 1- Values of AHH (curve A) and !:>.HL (curve B) forcomplexes of Mn(II). Fe (II). Co(II), Ni(II) and Zn(II)

relative to correspondence values for Mn(II)

From the log K 1 values of the complexes formedby metals having 3d5 and 3d10 configurations, thevalues of thermodynamic stabilization energy ('SH)were calculated according to the method describedby George and McClure13. The values have beenfound to be 19, 25 and 35 for the Fe(II), Co(II)and Ni(II) complexes respectively.

The Er (Mn-Zn) value found to be 49, is of thesame order as observed for many other ligandswhich coordinate to the metal ion through onenitrogen atom. The values of 'SH observed for theCo(II) and Ni(II) are also of the same order.This indicates that the metal ions are bondedthrough one nitrogen and one oxygen to the ligandmolecule. Shift of vN= N to lower values in theIR spectra of some complexes, which were isolatedin solid state, confirms this mode of coordination.

The fact is further supported by a slight shift tohigher atomic numbers in the curve of ~HL (heatof complexation) against atomic number (Fig. 1,curve B) as compared to the curve of 6HH (heatof hydration of metal ion) against atomic number(Fig. 1, curve A). The straight lines joining Mnand Zn represent the situation in the absence ofcrystal field stabilization.

One of the authors (JP.G.) is thankful to theUGC, New Delhi, for providing financial assistance.

References

1. GaEL, D. P., Stability constants and analytical applica-tions of metal chelates with pyridine and salicylaldehydederivatives, Ph.D. thesis, University of Delhi, Delhi,1969, 78.

2. MEHTA, Y. L., GARG, B. S. & KATYAL MOHAN, Analyt.chim. Acta, 86 (1976), 323.

3. GUPTA, J. P., MEHTA, Y. L., GARG, B. S. & SINGH, R. P.,Indian 1- Chem., 15A (1977), 256.

4. GARG, B. S., MEHTA, Y. L. & KATYAL MOHAN, Tulanta,23 (1976), 71.

5. IRVING, H. M. & ROSSOTTI, H. S., 1- chem. Soc., (1954),2904.

6. IRVING, H. M. & ROSSOTTI, H. S., J. chem. Soc., (1953),3397.

7. BJERRUM, J., Metal ammine formation in aqueoussolution (P. Haase, Copenhagen), 1941.

8. IRVING, H. & WILLIAMS, R. J. P., J. chem. Soc., (1953),3192.

9. ALBERT, A., Biochem. j., 54 (1953), 646.

NOTES10. IRVING, H. & WILLIAMS, R. J. P., J. chem. Soc., (1953),

3206.11. GEARY, W. J., NICKLESS, G. & POLLARD, F. H., Analyt .

cbim. Acta, 27 (1962), 71.12. RISHI, A. K., Metal chelates of 1-(2-pyridylazo)-2-phenan-

throl, Ph.D. thesis, University of Delhi, Delhi, 1972, 46.13. GEORGE, P. & MCCLURE, D. S., Progress in inorganic

chemistry, Vol. I (Interscience, New York), 1959, 428.

Stability Constants of Mg(II), Ca(II), Mn(II),Al(III), V(IV) & Th(IV) Chelates of

nr-c-Aminobutyrtc Acid

J. P. N. SRIVASTAVA, (Miss) R. JOHRI & M. N. SRIVASTAVA

Department of Chemistry, University of AllahabadAllahabad 211002

Received 26 February 1977; accepted 9 June 1977

Stability constants of Mg(II), Ca(II), Mn(II), AI(III),V[IV] and Th[IV] chelates with DL-a-aminobutyrlcacid have been determined potentiometrically at 20°and 0·1,\1'ionic strength (NaClO.) by the method ofIrving and Rossotti.

THE stability constants of some amino acid metalchelates including those of nt-e-aminobutyric acid

have been reported by Srivastava and coworkers>",The stability constants of some more chelates formedwith nt-e-aminobutyric acid at 20° and O·IM ionicstrength have been evaluated potentiometrically bythe method of Irving and Rossotti+,

The protonation constants K~ and K~ werecalculated as log K~ = 9·62 and log K~ = 2·35at 20° and 0-lM ionic strength (NaCI04).

The pH titrations reveal that in Mg(II) , Ca(II)and V(IV) systems the solutions remain clearthroughout the titrations but in the case of Mn(II),AI(III) and Th(IV) systems precipitation occurs atpH ,,-,9·00, 5·5 and 5-0 respectively. ii calculationshave been made only up to those points beforewhich precipitation occurs.

The formation curves (ii vs PL) of the metalchelates (Fig. 1) show that ii attains a maximumvalue of :::::1 for Mn(II), :::::2 for Mg(II) , Ca(II) andAl(III) and :::::3 for V(IV) and Th(IV).

In Mn(II) chelate since ii attains a value of :::::1(before precipitation occurs) the stability constanthas been computed by average value method.

In the case of Mg(II) and Ca(II) chelates sincethe two stability constants K; and J{2 are veryclose (log K, -log K2 = <0·5), Kl and K2 cannotbe computed separatelys. An attempt to compute K,and K2 separately by the least square method provedfutile. The overall stability constant ~2 (K1.K2) hasbeen satisfactorily determined by employing Albert'sequation:

log ~2 = log ii-log (2-ii) -2 log [LJIn the case of AI(III) chelate PL;.=1/2 = 8-0 and

PL,,=3/2 = 7-43 and the stability constants have beencomputed by the least squares method.

For V(IV) chelate K; and K2 values are rathervery close (PL~=1/2 = 8-08 and PL;'=S/2 = 7-69)

1109

INDIAN J. CHEM., VOL. lSA, DECEMBER 1977

TABLE 1 - STABILITYCONSTANTSOF CHELATESOF DL-Gt-AMINOBUTYRICACID WITHMg(II), Ca(II), Mn(II), Al(lII) AND V(IV)

Metal ion Computational method log tc,Mg(II) Albert's equation for K1.K2Ca(II) doMn(II) Average value method 3·23+0·02Al (III) Least squares method 6'91::[;0'02V(IV) Albert's equation (0< ii < 2)

Least squares method 6·9S±0·02(0<n<2)Half n value for u,

Th(IV) Half 12 values 8·55±0·02

log K2 log Ka log ~n St dev* (cr)

S·20±0·035'58±0'033·23±0·02 0·0074

0·0092lS·80±0·03

20'7S±0'05 0·0107

8'S4± 0·02

8'83±0'02

*cr= [~(6n)/number of observationsjt/a, where 6ii = nexp - neale.

8·45±0·024'97±O'018·39±0·01

veTID

2.0

1. 5 -I~ Cu (ill

~:\\\M9t~~~ Mnm)

o L...,,_--=,-::-'l._ll.._-f'-::---,-l-I ---::-,-' ---="C---;::'::--;;:-;2.0 3.0 4.0 5.0 6.0 7.0

pLFig. 1 - Formation curves of DL-Gt-aminobutyric acid chelates

of some metal ions at 20° and fL = 0·1111 (NaClO.)

whereas K3 is quite apart (PL"=1/2 = 4·97) and thusmay be taken to be almost independent of KI andK2• Hence the whole formation curve can be resolvedinto two regions: (i) (0<ii<2) and (ii) (2<ii<3) andeach region treated separately. The value of K3could be directly read from the curve where thefirst region was taken as a system for which N = 2.The values of K; and K2 were computed by leastsquares method, and overall K1.J{2 value usingAlbert's equation.

For the Th(IV) system, Kl' K2 and K3 are veryclose (difference being <0·1 log unit) and hence thesecould not be computed. Therefore for Th(IV) system,half ii values representing the temporary stabilityconstants are reported.

The stability constants data are given in Table 1.

References1. SINGH. 1\1.K. & SRIVASTAVA.M. N .. j. inorg. nucl. Chern ..

34 (1972), 567. 2067. 2081; Talanta, 19 (1972), 699.2. TEWARI. R. C. & SRIVASTAVA,M. N., j. inorg, nucl.

Chern .. 35 (1973), 2441, 3044; T'alanta, 20 (1973). 133,360; Indian j. Chem .. 11 (1973), 700, 1196; ActaChem. (Hungary), 83 (1974), 259.

1110

3. SRIVASTAVA.J. P. N. & SRIVASTAVA.M. N., Indian j.Chem., 14A (1976), 818; T'alanta, 23 (1976) (in press);Vijnan Parishad Anusandhan Patrika (Allahabad),19 (1976), 117; Rev. Chim. Minerale, 14 (1977), 263;Curr. Sci., 46 (1977), 443.

4. IRVING, H. & ROSSOTTI,H. S., j. chem, Soc., (1953), 3397,1954, 2904.

5. ALBERT, A., Biochem. j., 54 (1953), 646.

Composition & Stability Constants of DiphenicAcid Complexes of Th(IV), Ce(IV), U(VI) &of Th(IV)-EDT A-Diphenic Acid Mixed Ligand

Complex

C. L. SHARMA& P. K. JAINChemistry Department, University of Roorkee

Roorkee 247667

Received 27 January 1977; accepted 25 June 1977

Amperometric, conductometric and potentiometricstudies of Th(IV), Ce(IV) and U(VI)-diphenic acidsystems indicate the formation of 1: 2 (M :L) complexin 40% (v/v) dioxane medium. The values of stabilityconstants of these three metal complexes are 13'90,6·40 and 5·50 respectively. The only thorium andcerium diphenic acid complexes could be isolated inthe solid form and characterized. Mixed ligand com-plex formation in Th(IV)-EDTA-diphenic acid (R)system has also been investigated using the pH-titra-tion technique. The stability constant (log KMAR) ofthe mixed complex came out to be 6·78.

DIPHENIC aC.idhas b~en used in the precip!tationand separation studies of some common bivalent

transition metal ions1,2. However data on its metalcomplexes are not available. It was, therefore,planned to carry out systematic studies on thenature, composition and stability of the productsformed by the reaction of diphenic acid with someless familiar metal ions, Th(IV), Ce(IV) and U(VI)in 40% (v/v) aq. dioxane medium. Th(IV) is capableof forming a 1:2 complex with EDTA3,4 showingthat the 1:1 cornnlex (metal-Efr'I'A) can furtherreact with other donor groups. Formation of suchmixel complexes with catechol, salicylic acid deri-vatives and r,allic acid have been investigated+".No mixed cornnlex with diphenic acid is known.This paper also describes the determination ofstability constant of the mixed ligand complex in