Electrochemical and spectroscopic investigations of oxime complexes of bis(bipyridyl)ruthenium(II)

A series of cis-[Ru(bpy)2(oxime)]2+ complexes (where bpy=2,2′-bipyridine and oxime=cyclohexanedione dioxime (cyclodioxH2), diphenylglyoxime (dpgH2), difurilglyoxime (dfgH2), and 2-acetylpyridine oxime (acetoxH)) have been synthesized and characterized. 1H and 13C NMR spectra indicate that the complexes are cis-configured. The vicinal dioxime complexes display solvent and pH-dependent electronic spectra as well as proton-coupled electron transfer, as determined by cyclic and differential pulse voltammetries. pKa determinations on the ruthenium complexes were conducted and correlated with electronic and NMR spectroscopic and electrochemical data. The energy of the visible region MLCT band correlates with the redox potential of the Ru(III/II) center.