Photophysical behavior of Ru(II) and Os(II) terpyridyl phenylene vinylene complexes: perturbation of MLCT state by intra-ligand charge-transfer state

摘要

The photophysical behavior of novel bimetallic Ru(II) and Os(II) complexes having a bridging ligand consisting of two terpyridyl moieties covalently linked in the 4′ position through a distyrylbenzene bridge (tp vp vpt) is reported. The Ru(II) complex has a unique red emission with an excited state lifetime nearly 2000-times longer than the parent complex, [Ru(mpt)2](PF6)2 (mpt=4′-(methylphenyl)-2,2′,6′,2″-terpyridine). Combined spectral data suggest the presence of an emissive intra-ligand charge-transfer (ILCT) state lower in energy than the metal-to-ligand charge transfer (MLCT) state. The Os(II) complex exhibits red emission that is similar to that of the parent complex [Os(mpt)2](PF6)2. However, the excited state absorption spectrum reveals a unique transient absorption in the far red that suggests perturbation of the MLCT state by the ILCT state.