Polarographic Studies of Some Porphyrins and Metalloporphyrins in N,N-Dimethylformamide

Abstract

Abstract Electrochemical behavior of protoporphyrin IX dimethylester (PPDM), mesoporphyrin IX dimethylester(MPDM), Fe(III)Cl-protoporphyrin, Ni(II)-, Cu(II)-, Co(II)-, Zn(II)- and Mn(III)Cl·H2O–PPDM was investigated in dimethylformamide by use of AC polarography, cyclic voltammetry and DC polarography. These porphyrins and divalent metal complexes of PPDM gave, for the most part, three reduction waves. The first and second waves were reversible one-electron steps in each case, but the third step was an irreversible one. Mn(III)-complex gave four reduction waves and one oxidation wave. The first three reduction waves were one-electron steps and the oxidation wave was identified as that due to chloride anion. Fe(III)-complex gave five reduction waves and one oxidation wave. The first two reduction waves were one-electron steps. All these compounds showed specific adsorption at the potential more positive than −1.1 V vs. SCE. Assignment of the reduction steps of the metalloporphyrins is described. The observed order of increasing negative half-wave potentials is discussed in terms of Zerner and Gouterman’s molecular orbital calculation.