Electrochemiluminescence studies of phosphine chelated osmium(II) complexes

The electrochemiluminescence (ECL) properties of five different yellow/orange emissive osmium(II) complexes of general formula Os(L2L’) with three different kinds of bidentate phosphine ligands L’ have been studied in acetonitrile/dioxane 1:1 solution by means of the triple-potential-step technique. The investigated complexes contain either two substituted pyrazolate or triazolate ligands L. The obtained ECL results have been interpreted in terms of the ligands nature, showing that the efficiency of ECL seems to be sensitive to the π-acidity of the phosphine ligand. To the authors’ best knowledge, the reported ECL efficiencies are the highest found for Os(II) complexes under similar conditions to date, that are at maximum five times higher than that of the famous image based ECL systems.