Proton coupled electron transfer reaction of phenols with excited state ruthenium(II) - polypyridyl complexes

Abstract

The reaction of phenols with the excited state, *[Ru(bpy)₃]²⁺ (E₀ = 0.76V) and *[Ru(H₂dcbpy)₃]²⁺, (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) (E₀ = 1.55 V vs. SCE) complexes in CH₃CN has been studied by luminescence quenching technique and the quenching is dynamic. The formation of phenoxyl radical as a transient is confirmed by its characteristic absorption at 400 nm. The k_q value is highly sensitive to the change of pH of the medium and ΔG⁰ of the reaction. Based on the treatment of k_q data in terms of energetics of the reaction and pH of the medium, proton coupled electron transfer (PCET) mechanism has been proposed for the reaction.