Electrochemistry of Ruthenium Bis(imino)pyridine Compounds: Evidence for an ECE Mechanism and Isolation of Mono and Dicationic Complexes.

The electrochemical properties of a series of ruthenium complexes bearing the redox noninnocent bis(imino)pyridine ligand were investigated with cyclic voltammetry. An unexpected electrochemical feature in one of the complexes indicated a possible electrochemical-chemical-electrochemical (ECE) process. Further investigation into the oxidation mechanism included the synthesis and isolation of cationic and dicationic analogues of the complex. Density functional theory calculations suggested that a solvent interaction facilitated the ECE mechanism, so a solvent adduct was also synthesized and isolated. Calculations of this series of compounds were used to investigate the stabilizing role of the ligands over various oxidation states. As the overall charge of the complex was varied from anion to dication, a relatively constant Ru metal center oxidation state was found over all four states probed. This result suggests the strong involvement of the coligands in the redox behavior of the complexes investigated.