Increasing transmission of electronic interaction in dinuclear unsymmetric mixed-valent ruthenium complexes

Abstract The preparation and characterization by spectroscopic and electrochemical techniques of new dinuclear complexes of the type [(tpm)(bpy)Ru II (L)Ru II/III (NH 3 ) 5 ] 4+/5+ (bpy = 2,2′-bipyridine), tpm = tris(1-pyrazolyl)methane, L = pz (pyrazine), 4,4′-bpy (4,4′-bipyridine), BPE ( trans -1,2-bis(4-pyridyl)ethylene) and PCA (= 4-pyridinecarboxaldehyde azine), are described in this work. The analysis of the visible spectral data for the metal-to-metal charge transfer (MMCT) bands in the corresponding mixed-valent species [ Ru b II , Ru a III ] (Ru b  = Ru bonded to bpy; Ru a  = Ru bonded to NH 3 ) allows the determination of the reorganization energies λ and electronic coupling elements H AB for the intramolecular electron transfers Ru b II → Ru a III mediated by L. An increased transmission of the metal-to-metal electronic interaction is disclosed for this series, when comparing the distance dependence of H AB to that of the analogous series with trpy (2,2′:6′,2″-terpyridine) acting as a spectator ligand instead of tpm.