Functional Interfaces

Dinuclear ruthenium-terpyridine complexes, bearing highly conjugated bridging ligands, have been investigated by time and temperature dependent emission spectroscopy, time-dependent density functional theory calculations and femtosecond time-resolved transient-absorption spectroscopy. These terpyridine compounds show room temperature emission around 640 nm and lifetimes between 140 and 230 ns. Reduction of the temperature results in an overall increase of emission lifetime. However, the specific temperature dependence of the luminescence lifetime depends on the particular bridging ligand. This ligand-specific behavior is found to correlate with the electronic structure of the ligand, which allows for an excited-state equilibrium between a highly-delocalized 3MLCT and a ligand-centered 3ππ* excited state. Caused by this equilibrium a prolonged room-temperature lifetime is observed.