Electrochemical, Spectroscopic, and Spectroelectrochemical Properties of Synthetically Useful Supramolecular Light...

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 details 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 supramolecular devices for a wide variety of functions. It is the presence of the terminal dpq ligand that allows for their incorporation into larger supramolecular systems. This dpq ligand serves as an acceptor ligand that will possess a lower lying pi orbital than the dpp ligands once these chromophores are incorporated into larger systems. The [{(bpy)(2)M(dpp)}(2)Ru(dpq)](6+) systems display overlapping terminal metal 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 terminal, M, metals are largely electronically uncoupled. No oxidative process for the central Ru metal center is observed within our solvent window. 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 ns at room temperature in deoxygenated CH(3)CN solution. The details of the electrochemical, spectroscopic, and spectroelectrochemical studies of these supramolecular light absorbers and the dichloro synthons, [{(bpy)(2)M(dpp)}(2)RuCl(2)](4+), are reported herein.