Variation in both metal and ligand frontier orbital levels in series of [RuCl6 − n(PrCN)n]z (n = 0–6) complexes

An extensive series of butyronitrile-substituted ruthenium chloride complexes [RuCl6 − nLn]z (n = 0–6; L═CH3(CH2)2CN or PrCN) has been prepared and characterized spectro-electrochemically. The complete series allowed the examination of the variation in electrode potential of RuIII/II couple and the accompanying trends in both Cl → Ru(III) and Ru(II) → PrCN charge-transfer spectra. Systematic analysis of electrochemical and spectroscopic data led to a conceptual representation of the relative frontier-orbital energies of ruthenium, chloride, and nitrile as a function of stoichiometry.