Manganese porphyrin multilayer films assembled on ITO electrodes via zirconium phosphonate chemistry: chemical and electrochemical catalytic oxidation activity

A supported manganese porphyrin-based oxidation catalyst was prepared by zirconium-phosphonate multilayer assembly with [5,15-bis(4-phenylphosphonic acid)porphyrinato] manganese(III) chloride (2) and zirconium(IV) ions on indium–tin oxide electrodes. This assembly technique provided good control over the catalyst loading, which was confirmed by UV–Vis spectroscopy and cyclic voltammetry. Relative to its homogeneous counterpart, [5,15-bis(diethyl-4-phenylphosphonate)porphyrinato]manganese chloride (1), the film-based catalyst 2 showed moderately enhanced catalytic activity (up to 550 turnovers) for the oxidation of styrene by a soluble derivative of iodosylbenzene. Electrochemical oxidation of the film-based catalyst at pH 11 generated Mn(O)(porphyrin)(H2O) intermediate at a potential of 1.20 V. The electrochemically generated active intermediate exhibited oxidative catalytic activity toward both the solvent (water) and an olefin substrate (CBZ) affording both hydrogen peroxide and epoxide products.