An electron spin resonance and voltammetric investigation of some 2-mono- and 2,4-di-substituted pyridinyl radicals

The chemical reduction of some 2-monosubstituted and 2,4-disubstituted pyridinium ions has been investigated by means of e.s.r. spectroscopy and the results compared with those of an electrochemical study on the same species. By combining the electrochemical and e.s.r. data, a scale of stability has been determined for the investigated pyridinyl radicals. N-Methyl-2-cyanopyridinyl, which was found to be too unstable to be observed, eventually evolved to the 2,4-dicyano-substituted radical. E.s.r. studies have also been carried out on the structurally similar, although more persistent, N-germylpyridinyls.