Spectroelectrochemical investigations of pyrimidine-2-thionato-bridged binuclear platinum(III) complexes

Abstract

The electrochemical behavior of the binuclear platinum(III–III) complexes [Pt2(C4H3N2S)4X2] (C4H3N2S−=pyrimidine-2-thionate; X−=Cl−, Br−, I−) have been studied by cyclic voltammetry and in-situ spectroelectrochemistry in an acetonitrile–tetrabutylammonium tetrafluoroborate solvent-electrolyte couple. An irreversible metal based reduction appears during the cathodic scan for each of the three complexes. The changes in UV–Vis spectra observed in-situ during the reductive electrolysis indicate that all three complexes give the same product, [Pt2(C4H3N2S)4], with a Pt(II)–Pt(II) system. The changes in the reduction potentials of the complexes on changing the axial ligands are interpreted by the changes in the energy of the LUMO level, which is determined by the degree of σ- and π-interactions of the axial halide ligands with the metal atoms. DFT (B3LYP/LanL2DZ) calculations support our experimental data.