Linewidth variations in the electron resonance spectrum of the trinitromethyl radical dianion

Abstract

An alternating linewidth effect observed in the electron resonance spectrum of the trinitromethyl radical dianion in aqueous solution is analysed in terms of a modulation of the 14N isotropic hyperfine coupling constants. A model invoking a rapid interchange between three equivalent conformations is in good agreement with the observed spectra and, from the temperature dependence of the linewidths, the activation energy of the dynamical process is estimated to be -6·55 kcal mole-1. From a consideration of various mechanisms it is concluded that the observed effects are probably caused by steric hindrance and a consequent non-coplanarity of the nitro groups.