An electron spin resonance and polarographic study of the sulphone group

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Abstract
The electron spin resonance spectra of the radical anions of diphenyl sulphone, dibenzothiophene S, S-dioxide and thianthrene S, S, S′, S′-tetroxide have been measured and the proton hyperfine splitting constants assigned to the various protons by measurement of the spectra of deuterio and methyl derivatives. The experimentally determined spin populations were correlated by molecular orbital calculations, using the formalism of Koch and Moffit to describe the sulphone group, and it is shown that irrespective of the mutual orientation of this group and the conjugated system it may be described as far as the electron spin resonance spectra are concerned as contributing a vacant symmetric orbital to the conjugated system whose coulomb integral (αSO2 ) and sulphur carbon resonance integral (βC-SO2 ) are given by αSO2 =αC – 2·0β, βC-SO2 =0·8β where α and β are the carbon coulomb integral and carbon-carbon resonance integrals respectively. The polarographic half wave reduction potentials of these compounds and some of their methyl derivatives dissolved in anhydrous dimethylformamide were also determined and the effect of methyl substitution on this quanttiy is also well described by the above parameters for the sulphone group. Finally a difference between the results obtained here and those previously obtained by Vincow from the electron spin resonance spectrum of thioxanthone S, S-dioxide radical anion is noted and discussed.