Unstable intermediates. Part XXXVII. The electron spin resonance spectra of nitro-radical anions in fluid and rigid media

Abstract

The anions of various mono- and di-nitro aromatic compounds and their conjugate acids have been studied by electron spin resonance at room temperature and 77°K. The anisotropic hyperfine coupling constants to 14N deduced from the solid-state spectra have been used to estimate the spin-density on nitrogen. A marked decrease in the ratio of the anisotropic to the isotropic coupling as the spin-density increases has been interpreted in terms of a slight tendency for the nitro-group to become pyramidal.