Kinetic studies on metalloporphyrin formation in aqueous solutions of meso-tetra(p-sulphonatophenyl)porphyrin and some metal(II) ions

Studies on kinetics of metalloporphyrin formation in weakly acidic aqueous solution (pH 3.8-4.7) in perchlorate medium have been carried out spectrophotometrically at 435 nm for the reactions of M(H2O)(2)(6+) (M = Mn, Fe, Co, Ni, Cu) with meso-tetra(p-sulphonatophenyl)prophyrin TPPS4-. The results have been compared with the corresponding reactions of meso-tetra(4-N-methylpyridyl)porphyrin and the water exchange rates of the aqua-metal(II) ions. Compared to water exchange rates, reduction in the rate of formation of metalloporphyrin with TPPS4- is by a factor of 10(7) to 10(10), the minimum and maximum values being observed with Ni-II and Mn-II respectively. The results have been interpreted on the basis of the general mechanism for metalloporphyrin formation.