Solvent Effects on the Oxidative Electrochemical Behavior of cis-Bis(isothiocyanato)ruthenium(II)-bis-2,2‘-bipyridine-4,4‘-dicarboxylic Acid

The redox properties of cis-[Ru(dcbpyH<INF>2</INF>)<INF>2</INF>(NCS)<INF>2</INF>] ([Ru(dcbpyH<INF>2</INF>)<INF>2</INF>(NCS)<INF>2</INF>]; dcbpyH<INF>2</INF> = 2,2‘-bipyridine- 4,4‘-dicarboxylic acid) have been investigated in various solvents by combining electrochemical techniques (cyclic voltammetry (CV) and spectroelectrochemistry), mass spectrometry, digital simulation techniques, and semiempirical quantum chemical calculations. The electrochemical study has shown that while in polar solvents such as acetonitrile and ethanol the complex undergoes, following oxidation, the rapid loss of SCN ligands, forming the corresponding solvato complexes. In the less polar solvent tetrahydrofuran, a reversible oxidative CV behavior is observed at relatively low scan rates. On the basis of the CV and spectroelectrochemical studies and supported by quantum chemical calculations, a complex parallel ECE mechanism is proposed, comprising the loss of the SCN ligands in their pristine (anionic) form, which is initiated by the metal-centered oxidation process.