Interaction of silver(II) and gold(III) meso-tetraphenylporphine complexeswith concentrated sulfuric acid

The reaction of meso-tetraphenylporphine (H2TPP) with Ag(OAc) or KAuCl4 in boiling acetic acid affords (AgTPP)-T-II and (Cl)(AuTPP)-T-III complexes. T he complexes are purified by column chromatography and identified by thin l ayer chromatography and IR acid electronic absorption spectroscopy. The tra nsfer of a proton to tile porphyrin macrocycle and dissociation of the comp lexes via the metal-nitrogen bonds in concentrated H2SO4 at different tempe ratures and H2SO4 concentrations are studied by spectrophotometric and kine tic methods. The formation of the stable ion-molecular H-associate of the m etalloporphyrin with a doubly-charged metal cation is found for the first t ime for silver(II) tetraphenylporphine. Gold(III) tetraphenylporphine exist s in a sulfuric acid solution in the monomolecular form. The numeric values of true rates and activation parameters of the complex dissociation are de termined. The stability, state in solution, and mechanism of dissociation o f the silver(II) and gold(III) tetraphenylporphine complexes are determined by the metal electronic configuration of the complex cation and, especiall y, by the contribution of the pi component to the donor-acceptor M-N intera ction.