Crystalline heterocyclic radical cation salts as stable intermediates of new redox-mediating systems

Abstract

N,N′-Dialkyl-pyrazinium and -quinoxalinium radical cations have been isolated as stable iodide or tetraphenylborate salts. E.s.r. spectroscopy of these materials reveals delocalization of seven π electrons in the 1,4-diazine ring, but no intermolecular spin-pairing in the solid state, results which are supported by structural data for the pyrazinium radical cation salt. The thermodynamic stability and chemical persistence of these intermediates suggest their use as electron-transfer mediators by analogy with the methyl viologen system.