Long-Lived Near-Infrared MLCT Emitters

Abstract

A series of near-infrared emitters based on metal-to-ligand charge transfer (MLCT) excited states has been prepared. In the series, systematic variation of the coordinated ligands in polypyridyl complexes of RuII and OsII are used to vary the excited-to-ground-state energy gap. Emission energies are shifted by a combination of electron donor ligands and ligands with low-energy π* acceptor orbitals. Excited-state lifetimes are enhanced by use of acceptor ligands which are rigid and extensively delocalized. Emission from [(Ru(bpy)2)2(dpop)]4+ in acetonitrile is illustrated, along with a spectrum calculated by using a standard Franck−Condon analysis of the spectral profile.