BIS(DIOXOLENE)BIS(PYRIDINE)RUTHENIUM REDOX SERIES

A series of ruthenium complexes containing noninnocent 1,2-dioxolene ligands (dioxolene refers to any of the series catechol-semiquinone-quinone) have been prepared. These have the formula t-[Ru(RPy)2(dioxolene)2]n, where the RPy ligands are a series of substituted pyridines and n = -1, 0, +1. Their electrochemical and spectroscopic (NMR, ESR, IR, PES, electronic) properties are reported and discussed in terms of their electronic structures, described by using simple qualitative molecular orbital models. Their electronic structures are subtly different from those of the related c-[Ru(bpy)(dioxolene)2]n species reported previously (bpy = 2,2'-bipyridine). The neutral (n = 0) complexes have a fully delocalized, mixed-valence Ru(III)(RPy)2(catechol)(semiquinone) electronic structure. The oxidized (n = +1) and reduced (n = -1) species are also Ru(III) species. The electronic absorption data show a variety of different charge-transfer bands whose assignments are based upon energy variations with change of pyridine and/or dioxolene substituent and upon the net oxidation state.