Mimicking the function of amine oxidases and phenoxazinone synthase by a manganese(IV)-monoradical complex

A tridentate redox-active ligand, based on 2-aminophenol, yields a manganese(IV) complex with an iminobenzosemiquinone radical, 1. The crystal structure of 1 was determined by X-ray diffraction and the electronic structure was established by various physical methods, including EPR and variable-temperature (2–290 K) susceptibility measurements. The Mn(IV)-radical complex 1 catalyses the oxidation of primary amines with aerial oxygen as the sole oxidant to afford aldehydes under mild conditions to mimic the function of the copper-containing enzyme amine oxidases (CAO). Moreover, 1 is an efficient catalyst for the generation of phenoxazinone chromophore, thus models the catalytic function of the copper-containing enzyme phenoxazinone synthase (PHS). An ‘on–off’ mechanism of the radicals together with redox participation of the metal center is proposed for the catalytic oxidation processes.