Electrochemistry and electrogenerated chemiluminescence of a thin solid film of a hydrophobic tris(bipyridine) Ru(II) derivative in contact with an aqueous solution

The present study shows the electrochemistry, electrogenerated chemiluminescence and solid-state electroluminescence of [Ru(bpy)2(4,4¢-(CH3(CH2)12COO)bpy)](ClO4)2 as thin film deposited onto ITO. Cyclic voltammetry in aqueous solution of the Ru-LC film shows two reversible waves with peak potentials at about 1.27 V and )0.97 V. The apparent diffusion coefficient of the slowest species was found to be 4– 6·10 cm/s, with a concentration of active sites of about 0.4–0.5 M. Relatively strong ECL was observed during both oxidation and reduction, in both potential scans and potential step experiments. The reduced species appears to be much less stable than the oxidized one, as already known for other tris(bipyridine) Ru(II) derivatives in aqueous media. Two-electrode solid-state devices prepared by Ga-In printing on the tops of Ru-LC films are similar to the Ru(bpy)3 ones. The currents that flow through these devices are however about three orders of magnitude smaller than those for Ru(bpy)3 devices as a result of their low electron and hole mobilities.