Understanding Electronic Ligand Perturbation over Successive Metal-Based Redox Potentials in Mononuclear Ruthenium–Aqua Complexes

A family of new ruthenium complexes containing a combination of polypyridyl and carbene ligands has been prepared and characterized from structural, spectroscopic, and redox viewpoints both experimentally and computationally. Interestingly, a correlation between ΔE_1/2, defined as the difference between E_1/2(Ru^IV/III) and E_1/2(Ru^III/II), and the activity and selectivity of some catalytic oxidation processes has been clearly established. A density functional theory study on the synthesized species has been carried out revealing a correlation between the number of carbene ligands and ΔE_1/2, and consequently with the Ru^III disproportionation. The reactivity of these complexes has been tested with regard to the electrocatalytic oxidation of benzyl alcohol.