Electron paramagnetic resonance and cyclic voltammetry studies of the cations and anions of α-aminoanthraquinones obtained by electrochemical oxidation/reduction

Abstract

The 1,4-diaminoanthraquinone dyes Disperse Violet 1 and Disperse Blue 14 have been studied by cyclic voltammetry and EPR spectroscopy. The cation radicals, obtained by in situ electrochemical one-electron oxidation, can be characterised as aromatic diamino radicals (semiquinonediimines), with a spectroscopic pattern similar to those of Wurster's Blue-type radicals. The anion radicals, obtained by one-electron reduction, are of the semiquinone type. For the cation radicals all amino protons are unequivocally identified by deuterium exchange.

The new data show that single-line spectra observed from the antitumour antibiotics mitoxantrone and ametantrone must have arisen by a process more complex than simple one-electron oxidation of the parent compounds.