PHOTOCHEMICAL PROPERTIES OF MIXED-METAL SUPRAMOLECULAR COMPLEXES

We have prepared a series of mixed-metal trimetallic complexes of the form {[(bpy)2Ru(BL)]2MCl2}n+ (bpy = 2,2'-bipyridine; BL = 2,3-bis(2-py ridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq) or 2,3-bis(2 -pyridyl)-benzoquinoxaline (dpb); M = Ir(III), Rh(III) or Os(II). This new class of trimetallic complexes can be prepared with a good yield, often as high as 95%, using our building block strategy. The central rhodium and iridium fragments of these trimetallics, namely [M(BL)2Cl2 ]+, have been shown in our laboratory to be capable of delivering mult iple electrons, ''stored'' on the bridging ligand pi orbitals, to a s ubstrate as they functioned as electrocatalysts for the reduction of c arbon dioxide to formate. The two terminal ruthenium metals are good l ight absorbers designed to give rise to photochemical activity. These bichromophoric systems should be capable of absorbing two photons of l ight, each giving rise to a desired photochemical reaction, namely exc ited-state electron transfer. Thus these systems form the basis of a m olecular device for photoinitiated electron collection. The properties of these supramolecular complexes have been tuned by variation in the central metal and bridging ligand. Comparison of this array of nine c omplexes is described herein.