A series of species [Ru^III(NH3)4(Cat-R)]ⁿ⁺ have been synthesized where Cat-R is a catecholate dianion having the substituent Râ =â CO2^â, CO2H, OMe or H. These so-called parent species were characterized by their electronic spectra, FTIR, mass spectrum, cyclic voltammetry and EPR. Controlled potential reduction yields [Ru^II(NH3)4(Cat-R)]^{(nâ â â 1)+} while controlled potential oxidation yields [Ru^II(NH3)4(Q-R)]^{(nâ +â 1)+} (Q-Râ =â substituted quinone). Density Functional Theory (DFT) was primarily used to explore the electronic structures of these complexes. Application of the INDO semi-empirical model proved less useful. Time dependent density functional response theory was used to calculate the electronic spectra of the species with Râ =â H. The electronic spectra of the closed shell species are well reproduced by the calculations. The physical properties of these complexes indicate a charge delocalized system reminiscent of a delocalized organic molecule. The simple valence descriptions noted above are convenient to use but do not reflect the actual electronic structure. The electronic spectra of the parent species are temperature dependent. The visible region charge transfer band shifts by about 1500 cm^{â 1} to higher energy in acidic media at liquid nitrogen temperature. This is interpreted in terms of solvent effects rather than valence tautomerism. The electrochemical properties of [Ru^III(NH3)4(Cat-R)], in aqueous solution, reveal the first example of a reversible and stable Ruâ quinone species in that medium. The pKa values for several dioxolene species, with Râ =â CO2^â, are derived from a Pourbaix diagram.