Electrochemical characterization of manganese porphyrins fixed onto silica and layered dihydroxide matrices

Abstract

Immobilization of metalloporphyrin catalysts on polymer and inorganic supports has been researched intensively in recent years. Methods being actively pursued at present are the electrochemical polymerization of a suitably designed pyrrole-substituted porphyrin [l-7], the chemical polymerization of readily available halogenated metalloporphyrins [8,9], and the fixation of the complexes by adsorption on silica or alumina [lo-121 and by ion-exchange reaction on clay minerals (i.e. montmorillonite) [12-161, zeolites [171, layered dihydroxides [10,18,191 and ion-exchange resins [20-221. In the case of manganese porphyrins, these new supported catalysts have been used in oxidation catalysis and involved in efficient biomimetic systems. In fact, recent publications have shown that polypyrrole + manganese porphyrin films are good catalysts for electroassisted oxidation of hydrocarbons by molecular oxygen [23,241 and that multicharged porphyrins supported on silica and mineral clays are particularly efficient for alkene epoxidation and alkane hydroxydation by iodosylbenzene [lo-12,20-221 or molecular oxygen [El. A new easy access to polyhalogenated metalloporphyrins covalently bound to silica and polystyrene supports as efficient catalysts for hydrocarbon oxidation by iodosylbenzene has recently been reported by Battioni et al. [9].