Ionic interactions. Part 2.—Structure of the monoprotonated pyrazine radical and the origin of linewidth alternation

Abstract

Extended Hückel calculations have been carried out on the monoprotonated pyrazine radical. The sites for ion-pairing are unequivocally located in the molecular plane on a twofold symmetry axis in the region of the nitrogen lone-pair electrons. The most probable path of migration is above the molecular plane but does not lie in a pyrazine symmetry plane. The molecular processes involved in the phenomenon of linewidth variation in electron spin resonance spectra are discussed in the light of these results.