Temperature-dependent hyperfine splitting constants in the electron spin resonance spectra of some heterocyclic ethanedione radical anions

Abstract

The radical anions of di-2-furanyl-, bis-2-(5-methylfuranyl)-, di-2-thienyl-, di-2-pyrrolyl-, and diphenyl-ethanediones have been prepared by electrochemical reduction in dimethylformamide, dimethyl sulphoxide, and acetonitrile. Their e.s.r. spectra have been recorded and interpreted over a wide temperature range and the temperature dependence of the various hyperfine splitting constants obtained. The spectra of the heterocyclic ethanedione radical anions are asymmetric at low temperature possibly as a result of equilibration between various conformers. The temperature dependence of the hyperfine splitting constants of these radical anions is linear, but is much greater for those of the heterocyclic ethanediones than for diphenylethanedione.