Spectral and kinetic investigation on oxidation and reduction of water soluble porphyrin-manganese(III) complex

In this work the oxidation and reduction reactions of Mn(III)-Coproporphyrin-I (Mn(III)-CPI) have been studied and four forms of manganese-CPI complexes have been characterized. This complex was observed to be highly reactive (at basic pH) towards Mn(II), hypochlorite, hydrogen peroxide and oxone, forming [Mn(IV)(O)CPI(OH)] that was unstable and, after a short time, formed again [Mn(III)CPI(OH)(2)]. With an excess of NaClO, a further oxidation of the complex [Mn(IV)(O)CPI(OH)], provoked a significant spectral change for the [Mn(V)(O)CPI(OH)] formation that showed, in the time, a partial polymerization. [Mn(III)CPI(OH)(2)] was reduced by sodium dithionite to form the very unstable complex of [Mn(II)CPI(OH)] that successively degraded with Mn(II) release. Published by Elsevier B.V.