INDIAN J. CHEM., VOL. 21A, MAY 1982

100 T6!-! 80 0w '"::J W0 ,;n 60ILl ra:..

40J: 0<!) 0i;j z~ 20 ILl

0100 200

Fig. 1 - TG and DTA of polymer 3 in air; heatingrate 5°C/min

skeleton of the polymer backbone and the conduc-tivity value are under investigation.

References1. EDGAR, O. B. & HILL, R., J. polym. Sci .• 8 (1952), 1.2. LENZ, R. W. & CARRINGTON, W. K., J. polym. Sci., 41

(1959),333.3. BUNNY, C. W., J. polym, Sci., 16 (19:55), 323.4. MACALLUM, A. D., J. org. Chem., 13 (1948),154.5. MAcALLUM, A. D., Chem. Abstr., 44 (1950), 8165.6. MACALLUM, A. D., Chem. Abstr., 45 (1951), 5193.7 BROPHY, J. J. & BUTTREY, J. W., Organic semiconductors,

. (Macmillan, New York), 1962, 155.8. VOGEL, A. I., A text book 0/ practical organic chemistry

(Longman, London), 1918, 175.9.BIELSTEINS HANDBUCH, Der organis chen chemie, B••nd VII

228, 420.10. PARTINGToN, J. R., A text book of inorganic chemistry (Mac-

millan, London), 1950,705.

ESR Studies on Oxovanadiom(lV) Complexes ofSalicylaldoxime & 0-Vanillin oxime

INDRA RANI, K. B. PANOEYA* & R. P. SINGHDepartment of Chemistry; University of Delhi, Delhi 110007

Received 26 June 1981; revised and accepted 4 December 1981

Electron spin resonance spectra of oxovanadium(lV) comp-lexes of .~icybildoxime and Q-vanillin oxime of compositiODV.OOigand-H). have been studied. ESR parameters. isotropiccontact term and bonding coefficients have been evaluated anddiscussed.

THE present note describes the .synthesis andcharacterization of oxovanadiumtIv) com-

plexes of salicylaldoxime (sal) and o-vanillin oxime(van). Electron spin resonance spectra of the com-plexes have been studied in detail and th.e bondingcoefficients have been evaluated and discussed.

Preparation of the complexes -Ethanolic s~lutionof the respective ligand and aqueous solution ofvanadyl sulphate were mixed together keeping themetal-ligand ratio as 1:2. The complexes separatedout instantaneously, which were filtered, washed

502

successively with water and 50% ethanol and driedin an electric oven at •......60"C.

VO(sal-H)2 : Found V, 13.2; C,44.0; H, 3.16; N,7.19 Calc. V, 15.2; C, 49.55; H,3.53; N, 8.26%.

VO(van-H)2 : Found V, 12.6; C,48.0; H,4.0; N,7.02 Calc. V, 12,8; C, 48.1; H, 4.01;N, 7.01%.

Both the complexes are insoluble in water slightlysoluble in ethanol and highly soluble in chloroform,acetone and other common organic solvents. Mag-netic susceptibility measurements on the solid com-plexes were made at room temperature by the Gouymethod, using Hg[Co(NCS)4l as the calibrant(lg = 16.44 X 1()-6c.g.s. units). The visible ab-sorption spectra (400-750nm) of the complexes wererecorded in chloroform medium on a Russian Cc,6-10automatic recording spectrophotometer. Infraredspectra of the complexes were recorded in KBr ona Perkin Elmer (model-137) infrared spectrophoto-.meter. Electron spin resonance spectra were recordedon a Varian E-4 EPR spectrometer operating at•......9.4GHz and 100 KHz field modulation.

The analytical data reveal that the complexes havegeneral formula VO(ligand-H)2' With two bidentateligands around a vanadyl ion, a square-pyramidalstructure may readily be considered.

Such bis-chelates formed with o-hydroxy oximesare known>+ to attain extra stability from the addi-tional rings formed through hydrogen bonding (I).In the square-pyramidal vanadyl complexes, theaxial oxygen is significantly closer to the vanadiumion than are the in-plane donor atoms. Also, vana-dium atom isconsiderably above this plane. Magneticmoments VO(sal-H)2' 1.63 B. M.; VO(van-H)2,1.64 B.M., infrared spectra (vV=0.990 cnr-') andelectronic spectra (Table 1) are consistent with sucha structure.

H O-H\ / '.C=N 0 \

(XI ~/o~

" ~/ \=c~I I IH-O !of

(I)

TABLE 1- VISIBLE ABSORPTION MAXIMA, IsoTROPIC CoNTACfTERMS AND BoNDING CoEFFICIENT FOR OxOVANADIUM(IV)

CoMPLEXES

Parameter VO(SaI-H)2 VO(van-H). VO(acac).t

17350 1520019200 168000.769 0.7500.&96 0.9700.614 0.730

0.512 0.820

194000.7590.8760.675

•(en)·

tRef. 7

ESR spectra of these complexes have been recor-ded for polycrystalline samples and for chloroformsolutions at room temperature and at liquid nitrogentemperature. Spectra of polycrystalline samplesgive one signal in each case. The g values are1.997 and 2.001 for VO(sal-H)2 and VO(van-H)2respectively. In chloroform solutions eight-line iso-tropic spectrum results at room temperature (Fig. 1)because of the free rotation of the vanadyl group."IV is in 99.8% natural abundance and has nuclearspin of 7/2. The eight lines are thus due to isotropicintramolecular dipolar interaction between the freeelectron and the vanadium nucleus. No superhyperfine sp1ittings are observed. This indicatesthat the unpaired electron is in b211 (d~v) orbital loca-Iised on the metal, thus excluding any possibilityof its direct interaction with the incoming Iigands''.In the frozen solution the spectra are anisotropicand two sets of resonance components, one eachdue to the parallel and the perpendicular features,are observed (Fig. 2). The ESR parameters obtainedfrom the spectra are given in Table 2. From thevalues of the ESR parameters and the visible absorp-

II)••••••

•• \OlUTJOM

ESR SPECTRUM OFVOCs.I-H). (IN CHCI3.JtlO·K)

Fig, l-ESR spectrum of VO (Sal-Hh (in CHCJ., 3000K)

ESR SPECTRUM OFvOCsal-H)z (IN CHCI,• nOK).

Fig .. 2-ESR spectrum of VO (Sal-H), (in CHCI.. 77°K)

NOTES

tion band energies, the isotropic contact term, K,and the various bonding coefficients have beenevaluated (Table 1), where (~~ )2, (~!)2 and (e; )2are the bonding coefficients for d~lI' dll' orbitals,respectively. Data? for VO(acac)2 are included forthe sake of comparison.

Boucher et 0/.8 in a survey of ESR and spectralproperties of oxovanadium complexes of a vareityof ligands have shown an empirical linear relation-ship between Ao and (ge-go) and Ao and (ge-gn).It has been demonstrated that 0 Ao increases as both(ge-go) and (ge-g!l) increase. The plots are shownin Fig. 3. The data points for the complexes under

eo~ 60x0; 40I~20

O\.--l--'--L.~.I.-..oL-&--'--L.-'-...L...~o 20 40 60 80 100 120

Ao(GAUSS)(a)

PRESENTDATA~ ...•..-ge-91l

ge-90

0·2 0·4 0·6 o-e 1·0K

( bJ

1·0 r-----------.0·8

0·6IVox 0·4

-I~0·2

0·2 0·4 0·6 0·8 1.0K

(e)

Fig. 3-Plots of ESR parameters of oxovanadium (IV)complexes

503

INDIAN J. CHEM., VOL. 21A. MAY 1982

TABLE 2 - ESR PARAMETERS FOR CHel3 SoLUTIONS OF THECoMPLEXES

Parameter VO(SaI-H)2

1.9611.994l.98017l.465.3

100.5

VO(van-H).

l.9631.993l.983173.564.7

10l.0

gngJ.goAll (G)Ai (G)Ao (G)

~tudy l~e quite close to these straight lines. TheIsotropIc contact. term, K, is dependent upon thed-orbltal population for the unpaired electron andis given by K::::: (~~)2 Ko. Boucher et af.8 havedisc.ussedthe variation of K with (~; )2 for a varietyof Iigands, Lowenng of the (~t )2 value indicatesincreasing covalent bonding which arises from the~elocalisation of. the electron onto the ligand viain-plane rr-bonding of the d"l1 orbital with theIt-orbitals of the basal ligands.

The value of the in-plane a-bonding coefficient(~!)2 generally follows the a-donor strength ofthe ligands, i.e., (M)2 decreases as the covalentbonding increases.. From this criterion, van appearsto be a stronger ligand as compared to sal, Un )2valu~s art: 0.614 and 0.675 respectively. A linearrelationship between K and (~!)2 has earlier beendemonstrated by Boucher et al», Data on thepresent co~plexes too obey this linearity (Fig. 3b).

Also, K IS dependent on the a-bonding effect of4s.. The. energ~ separation of the bonding andantibonding orbitals for the 4s-ligand interaction isinversely proportional'' to the indirect 4s. contri-bution to K. This energy separation should be afunction of the in-plane ligand, reflected in/:::,El (2B2 ~ 2B1) in the electronic absorption

spectra. A plot of /:::,IEl vs K for a variety of

l~gands i~ linear. The data points for the presentligands he quite close to .this line (Fig. 3).

(e~ )2, the bonding coefficient for the d.,z anddl/z orbitals, measures the covalency of the V=Obond. It also indirectly shows the strength of thein-plane ligands, since, stronger the in-plane donoratom, less covalent is the v=o bond. The value ofthis parameter for VO(van-H)2 is much smaller thanthat for VO(acac), suggesting stronger covalentcharacter ofV=O and weaker in-plane ligand fieldin the former.

References1. JARSKI, M. A. & LINGAFELTER, E. C., Acta Crystallogr., 17

(1964),1109.2. SRIVASTAVA, R. C., LINGAFELTER, E. C. & JAIN, P. C.,

Acta Crystallog; 22 (1967),922.3. BURGER, K: & EGYED, I., J inorg : nucl.Chem., 27 (1965),

2361.4. MERRITT, L. L., GAURE, C. & LESSOR, A. E., Acta Crystal-

logr.,9 (1956), 253.5. PFLUGER, C. E., HARLOW, R. L. & SIMONSEN, S. M.,

Acta Crystallogr-, B26 (1970), 163l.6. CONE. H. & SHARPLESS, N. E., J. chem. Phys" 42 (1965),

906 ; 70 (1966), 105.

504

7. ~~~5~ER, L. i.,& Fu. YEN, TBH., 1.00"8. Chemi, 7 (1968),

8. BoU.CHER, L. J., Tynan, E. C. & Fu. Y~N,Teh., Electronspin resonance 0/ metal complexes, edited by Teh, Fu.Yen, (Plenum Press, New York), (1969),111.

9. MCGARVEY,B. R., J. chem. Phys., 41 (1964), 3743:

Effect of Hydration on Annealing of ChemicalRadiation Damage in Cadmium Nitrate

S. M. K. NAIR* & C. JAMESDepartment of Chemistry, University of Calicut,

Kerala 673 635

Received 21 September 1981; accepted 16 November 1981

The effect of hydration on the annealing of chemical radiationdamage in anhydrous cadmium nitrate has been investigated.Rehydration induces direct recovery of damage and the rehydratedsalt is susceptible to thermal annealing but the extent of annealingis small compared to the anhydrous salt. The direct recoveryis due to enhanced lattice mobility on rehydration.

p~ASE trans~ormations, in irradiated crystalsInduce rapid rec?mb.inati?l'l of damage frag-

ments and the recombination virtually ceases oncethe phase t~ans~ormation has taken place>". Theeffect of lattice re~rr~ngement accompanying loss ofwat~r .of crystalhsa~lOn on annealing of chemicalradiation damage In calcium bromate monohy-drate-anh~drous systems"has also been investigated.It was ?f interest therefore, to investigate the effectof lattice rearr~ng~ment. accompanying regain ofwat~r .ofcrystalhs~tlOnon the annealing of chemicalradiation damage in solid substances. The cadmiumnitrate anhydrous-tetrahydrate system has beenchosen for this investigation because the regain ofwater by the anhydrous nitrate takes place at roomtemperature and more over the kinetics of thermalannealing of chemical radiation damage in thissystem ~as bet:n investigated in detail recently",

Cadmium nitrate (AR) was dried to a constant,,:eight at 250aC and stored over phosphorus pento-xide. The loss of weight on heating agreed with theloss of four molecules of water of crystallisation.Samples of anhrdro~s salt sealed in Vacuo in glassampoules were irradiated at room temperature with52Mrad lOCO y-rays at a dose rate of 0.2 Mrad hr-1

The irradiated samples were also preserved ove~phosphorus pentoxide. Due to highly hygroscopicnature of anhydrous cadmium nitrate it was always "handled in a dry box.

T~e .e!fect.of.regain of water of crystallisation onthe 1~ltIal ~Itflte content in y-irradiated anhydrousca~mlUm mtrate. wa~ studied by keeping knownweights of the irradiated material in a constanthumidity-controlled atmosphere? of relative humidity93.9% for various time intervals from 0-240 hr atroom temperature and determining the NO; presentat the end of each time interval spectrophotometri-cally=". The weight of the irradiated salt after ex-posure to moisture for 240hr agreed with the uptake