A study by electron spin resonance of some heterocyclic radicals containing elements of group VI

Abstract

The e.s.r. spectra of the series of cation radicals and nitroxide radicals derived from phenoselenazine, phenothiazine, and phenoxazine have been measured, together with the e.s.r. spectra of the neutral radicals from phenothiazine and phenoxazine. The proton and nitrogen hyperfine splittings in these radicals are compared with those calculated by a variety of molecular orbital methods. In some cases hyperfine splittings from ³³S and ⁷⁷Se have been observed and these are employed in the evaluation of the unpaired electron density distributions. From a study of the phenoselenazine cation radical, we conclude that spin–rotation relaxation causes an appreciable contribution to the line-width of the e.s.r. spectrum of this species in solution at room temperature.