Long-range electron spin resonance coupling constants in radical adducts of maleic acid

Abstract

The e.s.r. spectra of a number of radical adducts of maleic acid have been observed and hyperfine structure arising from γ-, from δ- and from ε-coupling has been revealed. This provides a positive identification of the radicals involved. The origin of the long-range coupling constants is discussed in terms of simple molecular orbital theory and direct magnetic interaction. The difference between spectra observed in acidic and in alkaline conditions, is interpreted in terms of structural changes.