Generic series of complexes [Ru(bpy) 3 - n (LL) n ] 2 + (bpy=2,2'-bipyridine), where LL is a diimine ligand including specifically 2,2'-bipyrazine (bpz), 2,2'-azobipyridine (abpy), and o-benzoquinonediimine (bqdi), are studied with respect to their electrochemistry, optical spectroscopy and electronic structure as elucidated using Zerner's INDO/S method. Characteristics of their electrochemistry and optical spectroscopy are explained in terms of mixing between ruthenium d orbitals and diimine ligand π and π* orbitals, increasing in importance from bpy to bpz to abpy to bqdi. In this last case, these species have characteristics not unlike fully delocalized organic molecules.