Spectroelectrochemical studies of the intervalence charge transfer (IVCT) characteristics of both diastereoisomeric forms of the dinuclear complex [{Ru(bpy)(2)}(2)(mu-dpi(-))](n+) [bpy = 2,2'-bipyridine; dpi(-) = 4,5-di(2-pyridyl)imidazolate] showed that the degree of inter-metal electronic coupling (or valence delocalization) is dependent on stereochemical identity. Increasing the relative concentration of the strongly associating anion toluene-4-sulfonate in acetonitrile/[(n-C4H9)(4)N]{B(C6F5)(4)} solution differentially decreased the level of delocalization for the two diastereoisomers. In a comparative investigation of electrochemical and spectroelectrochemical techniques of the anion-induced electron localization in [{Ru(bpy)(2)}(2)(mu-dpo)](5+) [dpo = 3,4-di(2-pyridyl)-1,2,5-oxadiazole], differences were observed between the two methods in the order and extent of effects induced by a number of inorganic anions (PF6-, BF4-, ClO4-). It was determined that the measure of coupling derived from electrochemical methods was less reliable than that obtained from spectral methods. Comparative electrochemical studies were undertaken on [{M(bpy)(2)}(2)(mu-BL)](n+) {M = Ru, Os; BL = dpo, dpi(-)), which revealed substantial differences in Delta E-ox (the separation between the redox potentials for the M-II-M-II/M-III-M-II and M-II-M-III/M-III-M-III couples) for the two metal centers and therefore the comproportionation constant K-c, dependent on the neutral or anionic nature of the bridging ligand.