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

Abstract

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 III 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 V (O)(porphyrin)(H 2 O) 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.

Surface Modification Using Phosphonic Acids and Esters

“…Similarly, manganese porphyrins functionalized with phosphonic acid functions were assembled as zirconium phosphonate multilayer films on ITO electrodes to obtain supported oxidation catalysts. 340 On the other hand, Fu and co-workers have reported a series of polystyrene-based scaffolds used for the design of supported catalysts. Condensation of polystyrene oligomers having phosphonic acid end-groups with zirconium oxychloride and sodium dihydrogen phosphate result in the self-assembly of a zirconium phosphate/phosphonate hybrid containing polystyryl units in which the aromatic moieties can be then functionalized to anchor chiral salen catalysts.…”

Self-Organized Porphyrinic Materials

“…Mn(III) porphyrins are known catalysts for olefin epoxidation. Incorporation of Mn(III)bis-arylphosphonate porphyrin derivatives into multilayer films on ITO using the aforementioned zirconium-phosphonate chemistry, results in a catalytic system with longer lifetimes and higher turnover numbers for the epoxidation of styrene compared to the metalloporphyrins in solution 170. In terms of electroactive materials, the film’s pores can be electrochemically filled with a conductive polymer such as polyaniline 140.…”

Catalytic bleach: Most valuable applications for smart oxidation chemistry

“…On the other hand, an adverse effect is often the start of a superior alternative technology. More lately, a variety of tools has become available to build and to analyze novel solid state materials with most interesting physical and chemical properties [55]. Various heterogeneous catalysts to disproportionate excess H 2 O 2 as well as organic peroxides are known (cf.…”