Solvent effects on the electrochemical properties of IrCl 2(bpy) 2+

Abstract

To investigate the solvent dependence of the d-d contribution to the redox orbital of the cis-dichloro- bis-(s,2′-bipyridine) iridium(III) ion, the first reduction electron transfer has been studied in various non-aqueous and aqueous solvents by cyclic voltammetry and spectroelectrochemistry. Totally irreversible electrochemical processes and chloride release have been observed in water, methanol and formamide, which are consistent with the proposed pre-dominantly metallic nature of the redox orbital in these solvents. In other solvents the electron reduction sequence and the low chemical reaction rate of chloride release suggest a strong interaction between the ligand and metal-centered redox orbitals. Correlation of the reduction potential with the Gutmann's acceptor number and dielectric constant of the solvents indicates that chloride release depends strongly upon the dissociative properties of the solvent. The electrochemical behaviour and photochemical observations are compared.