Electrochemical Behavior of meso-Tetra (4-Sulfonatophenyl) Porphyrin and Its Copper Complex

Abstract

The complex of Cu-TPPS was formed directly by mixing equal-molar concentrations of Cu 2+ and meso-tetra(4-sulfonatophenyl) porphyrin(TPPS)in an acetate buffer solution at pH 4-6, and its electrochemical behavior was studied by the techniques of polarography, cyclic voltammetry and spectroelectrochemistry. Three different methods were applied to accelerating the formation of Cu-TPPS in aqueous solution, i.e. heating of solution,using vitamin C as a catalyst and preadsorbing TPPS on a hanging mercury electrode. The voltammetric reductions have shown 2e - for the first step of TPPS and 4 e - for Cu-TPPS with a peak potential at -1.04V. By applying the method of spectroelectrochemistry using a selfdesigned long-optical-path cell with Hg working electrode, the amount of saturated adsorption of TPPS and Cu-TPPS on mercury surface is found to be the same. Hence, the area of the adsorbed molecule calculated by measuring the area (i×t) under the voltammetric peak is also the same as 395 A 2 .