Synthesis, characterization and cyclic voltammetric studies of ruthenium oximates

Using 1,2-naphthoquinone-1-oxime (HL) as the principal ligand, four mixed-ligand ruthenium oximate complexes - namely [Ru(bipy)(2)(L)]ClO4, [Ru(pap)(2)(L)]-ClO4, [Ru(bipy)(L)(2)] and [Ru(PPh(3))(2)(L)(2)], where bipy = 2,2'-bipyridine and pap = 2-(phenylazo)pyridine - have been synthesized and characterized. In all these complexes, Ru exists in the +2 state. They are diamagnetic and, in solution, show several intense metal-to-ligand charge transfer (MLCT) transitions in the vis. region. In MeCN solution, all four complexes show a reversible Ru-II-Ru-III oxidation on the positive side of a standard calomel electrode (s.c.e.), the potential of which varies with the compositions of the complexes. Reductions of the coordinated co-ligands (bipy or pap) are also observed.