Free radical production by hydroxy-salen manganese complexes studied by ESR and XANES.

Three salen-Mn(II) complexes bearing hydroxyl groups in either the ortho, para or meta positions have been synthesized and the structures of the metal complexes and their potential to produce free radicals investigated by electron spin resonance (ESR) and X-ray absorption near edge structures (XANES) spectroscopy. All three compounds were shown to generate a high level of superoxide anions in dimethyl sulfoxide (DMSO) solution. The production of oxygen radicals results from a one electron process oxidation of Mn(II) species leading to the formation Mn(III) redox state species, as revealed by a higher XANES edge energy of 2.