Electron and ligand transfer reactions between cyclometallated platinum(II) compounds and thallium(III) carboxylates

Article abstract of DOI:10.1016/S0020-1693(00)90234-2

The relative redox potentials of amine adducts of tetra(p-isopropylphenyl)porphinatocarbonyl-ruthenium(II) have been measured in order to study the dependence of porphyrin ring oxidation on axial base. The potentials observed for aromatic heterocyclic amines vary over a range of 0.09 volts; are dependent on the π-base and hydrogen bond donor strength of the amine; and are independent of base strength and steric bulk of the ligand. These results indicate that tension in the imidazole linkage is not a mechanism for protein control on porphyrin ring oxidations and that changes in the hydrogen bonding of the bound imidazole may be a mechanism for controlling porphyrin ring redox potential. The potentials to within experimental uncertainty and independent of the hydrogen bond donor strength of the axial ligand. The latter result indicates that hydrogen bonding effects are transmitted via the π-bonds of the metal porphyrin complex. A direct correlation between the axial ligand dependence of porphyrin ring and metal center oxidation has been found and this implies that the same mechanisms may be operative in either porphyrin ring or metal center oxidation.