ABSTRACT

This study describes some spectroscopic and electrochemical properties of iron tetrakis(N-methyl-4-pyridyl) porphyrin (FeTMPyP) and nickel tetrasulfonated phthalocyanine (NiTSPc) dissolved in aqueous solutions, adsorbed on carbon electrodes or attached to Nafion films and membranes.  It also presents results concerning mediation of NO electro-oxidation or reduction by the macrocyclic compounds.  The Fe(III)TMPyP complex ligates NO and mediates its electroreduction at low pH through the formation of a nitrosyl complex: Fe(II)TMPyP(NO⁺).  The formation of this complex is supported by the appearance of bands at 439 and 547 nm in the UV-Vis. Spectrum and by the disappearance of the Fe(III) reduction wave (-0.2 V at pH 2.5) in the differential pulse voltammogram.  Ligation of NO by Ni(II)TSPc is suggested to form a Ni(III)TSPc(NO^-) adduct as evidenced by FTIR (bands at 1640 and 1660 cm^-1), ESR (g_av =2.236) and cyclic voltammetry (mediation of NO oxidation at E< +1.2V).