The temperature dependence of the ECL emission yield, φECL, of Ru(bpy)32+ in acetonitrile has been determined and was found to correlate closely with the luminescence quantum yield, φe, of the lowest Ru(bpy)32+ dπ* metal-to-ligand charge transfer (MLCT) excited state. Evidence is presented that at low temperatures (< 30 °C) the ECL emission yield becomes equal to the luminescence quantum yield implying an efficiency for excited state formation in the electron transfer reaction of Ru(bpy)33+ with Ru(bpy)3+ of near 100%. High efficiencies for excited state formation are rationalized on the basis of the excited state spectroscopic properties of Ru(bpy)32+ and the resulting implications to electron transfer theory and the ECL mechanism are discussed. © 1979 American Chemical Society.
