Interaction of Silver(II) and Gold(III) meso-Tetraphenylporphine Complexes with Concentrated Sulfuric Acid

Abstract

The reaction of meso-tetraphenylporphine (H2TPP) with Ag(OAc) or KAuCl4in boiling acetic acid affords AgIITPP and (Cl)AuIIITPP complexes. The complexes are purified by column chromatography and identified by thin layer chromatography and IR and electronic absorption spectroscopy. The transfer of a proton to the porphyrin macrocycle and dissociation of the complexes via the metal–nitrogen bonds in concentrated H2SO4at different temperatures and H2SO4concentrations are studied by spectrophotometric and kinetic methods. The formation of the stable ion-molecular H-associate of the metalloporphyrin with a doubly-charged metal cation is found for the first time for silver(II) tetraphenylporphine. Gold(III) tetraphenylporphine exists in a sulfuric acid solution in the monomolecular form. The numeric values of true rates and activation parameters of the complex dissociation are determined. The stability, state in solution, and mechanism of dissociation of the silver(II) and gold(III) tetraphenylporphine complexes are determined by the metal electronic configuration of the complex cation and, especially, by the contribution of the π component to the donor–acceptor M–N interaction.