A trimetallic mixed Ru(II)/Fe(II) terpyridyl complex with a long-lived excited state in solution at room temperature

The photophysical behavior of a series of mono- and trimetallic Ru(II) and mixed Ru(II)/Fe(II) bis-terpyridyl complexes was examined. The complexes have bridging terpyridyl ligands linked by phenylene-vinylene substituents on the terpyridyl. For the complexes bridged by a single phenylene-vinylene, the lowest-energy excited state is metal-to-ligand charge transfer (MLCT), and excited-state decay is on the 1-10 ns time scale. The complexes with two phenylene-vinylene groups have thermally equilibrated excited states that are localized on the phenylene-vinylene bridge and have much longer lifetimes (>200 ns). Remarkably, the trimetallic complex having an Fe(II) terpyridyl center also has a long-lived excited state, despite the fact that low-energy iron-localized excited states exist on the complex.