Krishna, Bal

Sharma, Suresh C.

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INDIAN J. CHEM., VOL. 14A, JUNE 1976methods=P, given in Table 1, shows that the valuesobtained by us are very close to those obtained byDewar et al.1I and using IOC-w techique-t, butgenel1i.llylower than those obtained using semi-empiricalSCF-MO method-" and simplified version of IOC-wtechnique-s. For molecules for which experimentalvalues 'of vertical ionization potentials are available th efirst two methods give very encouraging results, whilethe latter two generally give high values. Since, in thecalculations molecular geometry has been assumedto remain unchanged, these values are the so calledvertical ionization potentials and therefore, should beessentially higher than the spectroscopic values1S-15•Table 2 reports the heats of formation of somenitrogen containing heterocyclic molecules. Ourresults are in fair agreement with the experimentalvalues1' although these are not as good as thoseobtained by Dewar and Harget-t,References1. (a) SHARMA, S. C., SRIVASTAVA, A. K. & KRISHNA, B.,]. chem. Soc. Faraday Trans. II, 71 (1975), 168; 172.2. KRISHNA, B. & GUPTA, S. P.,]. Am. cbem. Soc., 92 (1970),7247.3. BOYD, G. V. & SINGER, N., Tetrahedron, 22 (1966), 3383.4. WHELAND, G. W. & PAULING, L., ]. Am. chem, Soc., 57(1935), 2086.5. MURRELL, J. N., Malec. Phys., 1 (1958), 384.6. BROWN, R. D., ]. chem, s«; (1956), 272.7. SRIVASTAVA, A. K. & KRISHNA, B., Indian]. pure appl.Phys., 11 (1973), 246.8. DEWAR, M. J. S. & GLEICHER, G. J.,]. chem, Phys., 44(1966), 759.9. DEWAR, M. J. S., HASHMALL, J. A. & VERNIER, C. G.,]. Am. chem, s«., 90 (1968), 1953.10. DEWAR, M. J. S., HASHMALLL, J. A. & TRINA]STIC, N.,]. Am. chem, Soc., 92 (1970), 5555.11. GUPTA, S. P., Quantum mechanical evaluation of bondparameters in some molecules, D. Phil, thesis, Universityof Allahabad, Allahabad, 1970, 34.12. SRIVASTAVA, A. K., Studies in theoretical evaluation ofsome bond parameters of some molecules, D. Phil. thesis,University of Allahabad, Allahabad, 1973, 50, 52.13. MASTEN, F. A., ]. chem. Phys., 24 (1956), 602.14. BRIEGLEB, G. & CZEKELLA, Z., Z. Elecktrochem.,63 (1959), 6.15. PRICE, 'V. C. & WALSH, A. D., Proc. R. s«.. London A,185 (1945), 182.16. DEWAR. M. J. S., Molecular orbital theory of organicchemistry (McGraw-Hill, New York), 1969, 382.17. DEWAR, M. J. S. & HARGET, A. J., Proc. R. Soc., LondonA, 315 (1970), 457.An Improved IOC-m Technique: Oxidation &Reduction Potentials & Charge TransferEnergies of Some Conjugated HydrocarbonsSURESH C. SHARMA* & BAL KRISHNADepartment of Chemistry, University of AllahabadAllahabad 211002Received 24 February 1975; accepted 25 August 1975The polarographic half-wave oxidation and reductionpotentials of conjugated hydrocarbons and chargetrans~energies of their complexes with iodine have been calcu-latedfrom the values of ionization potentials and electronafllnities calculated using a recently described improved10e-co technique. The results are compared and foundto be in good agreement with the experimental values.*Present address: Naval Chemical & MetallurgicalLaboratory, Bombay 400023.436COR&ELA TIONS between the polarographic half-. wtllre reduction potentials (-El/2 red.) ofconjugated hydrocarbons and the lowest unoccupiedHMO energies have been described by variousworkers='. Similar correlations have also beenobserved+s between polarographic half-wave oxida-tion potentials (El/2 ox.) and energies of highestoccupied HMOs. Dewar et al.7,8 have obtainedexcellent correlations between reduction potentialsand electron affinities and oxidation potentials andionization potentials using a variable ~-semi-empiricalSCFMO method for hydrocarbons as well as hetero-molecules. Pysh and Yang' have calculated ion-ization potentials of some aromatic hydrocarbonsfrom these correlations and measured values ofoxidation potentials. The following relations canbe derived theoretically between oxidation andreduction potentials and ionization potentials (1) andelectron affnities (A )6,7:E1/2(OX.) =ml +e ...(1)and-El/2(red.) =m'A -l-C" ... (2)In a series of charge transfer complexes betweena single acceptor and a series of polynuclear hydro-carbons if the interactions between the donor andacceptor are small, the transition energy, AECT forthe first charge transfer (CT) band should be givenbye,AEcT = 1-A -l-const. . .. (3)1is the ionization potential of hydrocarbon and A,the electron affinity of acceptor molecule. For agiven acceptor molecule Eq. (3) becomes:AETc = 1 -l-const,and a linear plotand 1:MCT =m"l +e" ... (5)On the basis of above correlations, we have cal-culated, in the present paper polarographic half-wave oxidation and reduction potentials of someconjugated molecules and charge transfer transitionenergies of some iodine-hydrocarbon complexesfrom the values of ionization potentials and electronaffinities, obtained using an improved IOC-w tech-nique". Method of calculation and some of theresults have already been reported9,lo. The para-meters m and e have been obtained by theoreticallycalculating the slope and intercept respectively ofa plot betweenE1/2(oX.) (on Y-axis) and 1(on X-axis).Similarly parameters m', C', mil and C" can alsobe obtained. Here, we have obtained, m = 0·90,e = -5·88, m' = -0·86, C' = 2·07,m" = 1·032andC" = -5·098.Polarographic half-wave oxidation and reductionpotentials of some conjugated hydrocarbons andcharge transfer transition energies of some iodine-hydrocarbon complexes have been compared withrespective experimental values6,ll,12 in Table 1. Forcomparison we have used the values which refer tomeasurements done under identical experimentalc?nditions for a large number of hydrocarbons,SInce, although the relative values of oxidation and. .. (4)can be obtained between AECTNOTESTABLE 1 - POLAROGRAPHICHALF-WAVEOXIDATIONAND REDUCTION POTENTIALSOF SOME HYDROCARBONSANDTRANSITIONENERGIES OF THEIR COMPLEXESWITH IODINEMolecule I (eV) A (eV) Et (ox) (V) -E, (red) (V) !:lEer (eV)Calc. Exp. Calc. Exp. Calc. Exp,Benzene 9·03 2·25 2·30 4·221 4'184Naphthalene 8·26 0·27 1·55 1'54 1-84 1·98 3·426 3·452Anthracene 7-81 0'78 1-15 1·09 HO H6 2'962 2·890Phenanthrene 8·19 0·28 1·49 1'50 1-83 1·94 3'354 3'288Chrysene 7'96 0'45 1·28 1'35 1·68 1·81 3-117 30154Triphenylene 8'18 0·05 1·48 1·55 2·03 1·97 3'344 30154Pyrene 7·86 0·63 1'19 1-16 1-53 1'61 3·014 2·959Biphenyl 8·29 0·01 2·06 2·08 30457 3-654-Stilbene 8·01 30168 3'331Naphthacerie 7'52 HO 0·89 0·77 1-12 1'143,4-Benzphenanthrene 0·34 1'78 1·751;2-Benzanthracene 7·79 0·56 1-13 1·18 1'59 1'53Pentacene 1'32 0'93 0·86Dibenz-(1,2: 5,6)-anthracene 7-87 0'57 1·20 1-19 1'S8 1'55Dibenz(L2: 7,8)a.nthracene 7·93 0'61 1·26 1·26 1'55 1·57Dibenz(1,2: 3,4)2.nthracene 7'94 0·48 1·27 1·33 1·66 1·54Pentaphene 0·69 1'48 1·53Perylene 7·55 0·89 0·92 0'85 1·31 1·25Benz(4,5)pyrene 7·87 0'51 1·20 1·27 1-63 1·67Benz(1,2)pyrene 7-64 0·84 1'00 0·94 1'35 1·36Benz(1,12)pyrelene 7·71 1·06 1·01Coronene 7·88 0·40 1·21 1·23 1'73 l'MAnthanthrene 1·08 1·14 1·19Benz(1,2: 4,5)pyrene 7·69 0·69 1·04 1-01 1-58 1·45Dibenz(1,2: 6,7)pyrene 1·01 1·20 1·16Dibenz(1,2: 7.8)pyrene 0·90 1'30 1·32Dibenz(4,5: 9,10)pyrene 0·34 1·78 1·69p-Terphenyl 0·23 1·87 1·91p,p-Diphenyl-biphenyl 0·35 1·77 1'77Azulene 7·31 0·70 0·71Fluoranthene 8'15 0·87 1·46 1·45 1·32 1·35Benz(8,9)fiuoranthene 0·73 1·44 1'39reduction potentials, etc. seem to be same indifferent solvents, their absolute values vary13.From the table it is clear that our calculatedvalues are in excellent agreement with experimentalvalues.References1. MACCOLL,A., Nature, 163 (1948), 178.2. HOIJTINK, G. J. & VANSCHOOTEN,J" Reel. Trav. chim,Pays-Bas. Belg., 71 (1952), 1089.3. KOUTECKY, J., Z. Phys. Chem., 52 (1967), 8.4. HOIJTINK, G. J., Reel. Trau, chim. Pays-Bas. Belg., 77(1955), 555.5. GLEICHER, G. J. & GUICHER, M. K., J. phys. Chem., 71(1967), 3693.6. PvSH, E. S. & YANG, N. C., J. Am. chem. Soc., 85 (1963),2124.7. DEWAR, M. J. S., HASHMALL, J. A. & TRINAJSTIC, N.,J. Am. chem, Soc., 92 (1970), 5555.8. DEWAR,M. J. S. & TRINAJSTIC,N., Tetrahedron, 25 (1969),4529.9. SHARMA,S. C., SRIVASTAVA,A. K. & KRISHNA, B., J.chem, Soc., Faraday Trans. II, 71 (1975), 168;172.10. SHARMA, S. C. & KRISHNA, B., Indian J. chem., 14A(1976), 43 S.11. BERGMAN, I., TranS. Faraday Soc., 50 (1954),829.12. BHATTACHARYA,R. & BASU, S., Trans. Faraday Soc., 54(1958), 1286.13. GIVEN, P. A., J. chem. Soc., (1958), 2684.Exchange of Metal Ions on Dowex A-l(H+)S. GANAPATHYIYER & CH. VENKATESWARLUAnalytical Chemistry Division, Bhabha Atomic ResearchCentre, Modular Laboratory, Trombay, Bombay 400085Received 2 May 1975; accepted 1 September 1975Distribution of about forty metal ions between DowexA-l(H+) and aqueous solutions (pH 1·0 to 6·0) in thepresence and absence of 1,10-phenanthroline is report-ed. The data are compared with the results of similarexperiments with a carboxylic acid exchanger (Z£o-Karb- 226, H+).SORPTION characteristics of metal ions on DowexA-I as a function of PH have been reportedr+,employing the exchanger in acid or salt form andadjusting the P!:f with or without buffers. The PHof decomplexation of some metal ions from the ex-changer is also available+",Recently, sorption characteristics of about fortycations on a carboxylic acid exchanger (ZeoKarb-226, H+) as a function of PH (1·0 to 6·0 withoutbuffers) have been studied in our laboratorys, Forcomparison, the study of sorption of metal ions onDowex A-I as a function of PH (ref. 4) has beenextended to other cations and the results are reported437

An Improved IOC-ω Technique: Oxidation & Reduction Potentials & Charge Transfer Energies of Some Conjugated Hydrocarbons

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An Improved IOC-ω Technique: Oxidation & Reduction Potentials & Charge Transfer Energies of Some Conjugated Hydrocarbons

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