Organic and biological spectrochemical studies. XXV. Properties of the p-bis(methylthio)benzene and p-bis(ethylthio)benzene cation radicals

The electron spin resonance spectra of the sulfur analogs of the p-dimethoxy and p-diethoxy benzene cation radicals, i.e. the cation radicals of p-bis(methylthio)benzene (1) and p-bis(ethylthio)benzene (2), were investigated in aluminium chloride – nitromethane. The spectra are interpreted in terms of cis–trans isomerism. Empirical molecular orbital calculations support this assignment and yield qualitatively correct spin densities at the ring positions. Comparison of the spectral properties of these species with corresponding compounds containing oxygen atoms indicates changes which can be associated with the greater tendency of the sulfur atom to attract spin density. There is also evidence from the β-alkyl proton splitting constants that the conformation of the radical of 2 differs from that of its oxygen analog. Slightly different g values are again observed for the cis and trans isomers, as previously noted for related compounds.