Intramolecular charge effects in the electrochemical oxidation of aminoxyl radicals

Abstract

The redox potentials of a series of aromatic nitroxides derived from tert-butyl phenyl nitroxide are determined by cyclic voltammetry in non-aqueous solution. It is shown that the first oxidation potential as well as the reduction potential strongly depend on the electron donating and withdrawing substituents of the compounds. The first results on the influence of a negative charge in proximity to the aminoxyl group on the redox properties of aromatic nitroxides, are reported. A remarkably strong intramolecular “charge effect” is probably responsible for the observed high potential shift of 560 mV in the case of the carboxylate 4b.