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

In this work the oxidation and reduction reactions of MnIII–Coproporphyrin-I (MnIII-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 [MnIV(O)CPI(OH)]− that was unstable and, after a short time, formed again [MnIIICPI(OH)2]−. With an excess of NaClO, a further oxidation of the complex [MnIV(O)CPI(OH)]−, provoked a significant spectral change for the [MnV(O)CPI(OH)] formation that showed, in the time, a partial polymerization. [MnIIICPI(OH)2]− was reduced by sodium dithionite to form the very unstable complex of [MnIICPI(OH)]− that successively degraded with Mn(II) release.