Chemistry of some ruthenium phenolates. Synthesis, characterization and redox properties

Reaction of phenols containing a second donor site linked to the or^o-position [viz. 2,4,6-tribromophenol (HL^1), 2-nitrophcnol (HL^2) and 2,4,6-trinitrophcnol (HL^3)] with [Ru(bpy)2Cl2] in the presence of a base has afforded complexes of the type [Ru(hpy)2(L)]^+ (where L stands for the deprotonated ligands), which have been isolated as perchlorate salts in the solid state. The complexes are diamagnetic (low-spin d^6 S = 0) and in solution show several MLCT transitions in the visible region. Cyclic voltamnictry of the [Ru(bpy)2(L)]^+ complexes in acetonitrile solution (O.I M TEAP) shows a Ru"-Ru"* oxidation within 0.63 to 0.93 V vs SCE and one reduction of the coordinated bpy within -1.42 to -1.68 V vs SCE.