Ligand-Ligand Charge-Transfer Excited States of Os(II) Complexes

Article abstract of DOI:10.1021/j100348a025

This paper examines the photophysics of metal-to-ligand charge-transfer (MLCT) and ligand-to-ligand charge-transfer (LLCT) excited states in a series of <(bpy)2Os^II(CO)L>(2+)(Os-L) complexes.For each of the compounds studied, the d?(Os) --> ?^*(bpy) absorption band is the lowest energy transition that is apparent.For L = pyridine and benzonitrile, only long-lived, highly luminescent MLCT states are observed.However, when L = an electron-donor aminobenzonitrile (ABN) species (DMABN, TMABN, or CMI; see text), MLCT emission is quenched and in <30 psLLCT excited states are formed, ^*<(bpy^.-)-(bpy)Os^II(CO)ABN^.+>(2+).The observed, weighted-average radiationless decayz of the LLCT excited states in acetonitrile and dichloromethane follow the sequence Os-DMABN