In this work, the effect of the electronically different ancillary ligands on the overall properties of the (RuL)-L-II moiety (L = 2,6-bis(phenylazo)pyridine) in heteroleptic complexes of general formula [RuLQCl](0/+) was investigated. Four different ancillary ligands (Q) with different electronic effects were used to prepare the heteroleptic compounds from the precursor complex, [RuL(CH3CN)Cl-2] (1); Q = pcp: 2(4-chloro-phenylazo)pyridine (strong pi-acceptor), [2](+); bpy: 2,2'-bipyridyl (moderate pi-acceptor), [3](+); acac(-): acetylacet-onate (strong sigma-donor), 4; and DTBCat(2-): 3,5-di-tert-butyl catecholate (strong pi-donor), 5. The complexes [2](+), [3](+), 4, and 5 were fully characterized and structurally identified. The electronic structures of these complexes along with their redox partners were elucidated by using a host of physical measurements: nuclear magnetic resonance, cyclic voltammetry, electronic paramagnetic resonance, UV-vis-NIR spectroscopy, and density functional theory. The studies revealed significant effects of the coligands on azo bond lengths of the RuL moiety and their redox behavior. Aerobic alcohol oxidation reactions using these Ru complexes as catalysts were scrutinized. It was found that the catalytic efficiency is primarily controlled by the electronic effect of the coligand. Accordingly, the complex [2](+) (containing a strong Tr-acceptor coligand, pcp) brings about oxidation efficiently, producing 86% of benzaldehyde. In comparison, however, the complexes 4 and 5 (containing electron donating coligand) furnished only 15-20% of benzaldehyde under identical reaction conditions. Investigations of the reaction mechanism suggest that an unstable Ru-H species is formed, which is transformed to a Ru-hydrazo intermediate by H-walking as reported by Hall et al. (J. Am. Chem. Soc., 2015, 137, 12330). Aerial O-2 regenerates the catalyst via oxidation of the hydrazo intermediate.