Redox properties of bis(1,10-phenanthroline)-(pyridine)ruthenium(II) complexes

The redox properties of a series of [Ru(phen)₂(py)X]ⁿ⁺ cations (X = pyridine, NH₃, Cl, Br, I, CN, SCN, N₃ and NO₂) have been investigated in acctonitrile. Two reversible reduction steps are seen at ? 1.35 and ? 1.6 V vs Ag/AgCl; the invariance of these processes with X-group is indicative of electron addition to molecular orbitals mainly of phenanthroline ligand π^* origin. Irreversible multi-electron reductions follow below ? 2.20 V. The Ru(II)/Ru(III) couple is seen as a reversible wave near + 0.8 V vs the normal hydrogen electrode, from calibration with ferrocene, except in the cases of the NO₂ and SCN complexes, where rapid reactions involving these ligands occur.