DINUCLEAR RUTHENIUM AND OSMIUM COMPLEXES CONTAINING THE BIS(PYRIDIN-2-YL)-1,2,4-TRIAZOLATE BRIDGE

The electrochemical and photophysical properties of mononuclear and dinuclear ruthenium and osmium complexes involving the ligand 3,5-bis(pyridin-2-yl)-1,2,4-triazolate (bpt-) have been studied. The electrochemical data show that the lowest unoccupied molecular orbital (LUMO) is bpy based for all complexes. The asymmetric coordination environment (N1 and N4 of the triazole ring) causes a large splitting of the oxidation potentials for the dinuclear ruthenium complex. The presence of the different coordination sites is also reflected in the different electrochemical behaviour of the isomeric ruthenium-osmium (N1-N4 and N4-N1) complexes. The intense intervalence transition bands observed in the mixed-valence species indicate a strong interaction between the metal ions. The mixed-metal complexes exhibit efficient energy-transfer processes from the ruthenium-based 3MLCT to the osmium-based 3MLCT states.