Electrochemical properties of gold(III) complexes with 2,2′-bipyridine and oxygen ligands

The electrochemical behavior of a series of five cationic species containing the Au(bipy)3+ moiety and additional oxygen-donor ligands, and of the relevant common precursor, i.e. the dichloride [Au(bipy)Cl2][PF6] species, have been investigated using cyclic voltammetry and controlled-potential coulometry. All the compounds with oxygen-containing ligand(s) (2–6) undergo an easy, irreversible one-electron reduction process. The first reduction process of the dichloride consists of an equally easy but quasi-reversible charge transfer, as evidenced by voltammetric tests at a very high scan rate, followed by an irreversible second-order chemical reaction. Correlations between the relative values of the reduction potentials and the corresponding molecular structure are made and hypotheses on the nature of the reduction mechanisms are advanced.