ELECTROCHEMICAL, SPECTROSCOPIC, AND SPECTROELECTROCHEMICAL PROPERTIESOF SYNTHETICALLY USEFUL SUPRAMOLECULAR LIGHT ABSORBERS WITH MIXED POLYAZINE BRIDGING LIGANDS

The trimetallic complexes [{(bpy)(2)M(dpp)}(2)Ru(dpq)](6+) (M = Ru-II Or Os-II, bpy = 2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, and dpq = 2,3-bis(2-pyridyl)quinoxaline) have been prepared and the detai ls of their spectroscopic, electrochemical, and spectroelectrochemical properties investigated. These mixed bridging ligand complexes are a new group of synthons that can be useful for the construction of supra molecular devices for a wide variety of functions. It is the presence of the terminal dpq ligand that allows for their incorporation into la rger supramolecular systems. This dpq ligand serves as an acceptor lig and that will possess a lower lying pi orbital than the dpp ligands o nce these chromophores are incorporated into larger systems. The [{(bp y)(2)M-(dpp)}(2)Ru(dpq)](6+) systems display overlapping terminal meta l oxidations at 1.66 and 1.18 V vs Ag/AgCl for the Ru and Os systems, respectively. This indicates that within this framework, these termina l, M, metals are largely electronically uncoupled. No oxidative proces s for the central Ru metal center is observed within our solvent windo w. The [{(bpy)(2)M(dpp)}(2)Ru(dpq)](6+) systems have M --> dpp charge transfer (CT) lowest lying excited states. The [{(bpy)(2)Ru(dpp)}(2)Ru (dpq)](6+) Ru --> dpp CT state displays an emission centered at 775 nm with a lifetime of 65 us at room temperature in deoxygenated CH3CN so lution. The details of the electrochemical, spectroscopic, and spectro electrochemical studies of these supramolecular light absorbers and th e dichloro synthons, [{(bpy)(2)M(dpp)}(2)RuCl2](4+), are reported here in.