Electron spin resonance study of some polycyclic nitrogen heterocyclic radical anions

In dimethylformamide the ESR spectra of the radical anions of dibenzo[f,h]quinoxaline and dibenzo[a,c]phenazine both exhibit line broadening due to slow molecular tumbling over a wide temperature range. Similar effects are also observed in the spectra of the radical anions of quinoxaline and phenazine. The ESR spectra of the radical anions of dibenzo[f,h]quinoxaline and dibenzo[a,c]phenazine have been interpreted by computer reconstruction and the hyperfine splitting constants assigned with the aid of Hückel unpaired electron density calculations.