SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF NEW 2,2'-BIPYRIDINE-BRIDGEDBIS[RUTHENIUM(II)TRIS-2,2'-BIPYRIDINE] COMPLEXES

We have synthesized a new type of tris-2,2'-bipyridine ligand with 4,4 '- and 6,6'-disubstituted 2,2'-bipyridine (bpy) units. The terminal 4, 4'-disubstituted 2,2'-bipyridine moieties are selectively coordinated by Ru(bpy), (bpy = 2,2'-bipyridine), whereas the central 2,2'-bipyridi ne ligand does not participate in any metal ion coordination. The two Ru(bpy), units of 7 and 8 do not interact appreciably, as is evident f rom their electrochemical and photophysical data. The lifetime of the excited state of compound 7 at 77 K is similar to that of Ru(bpy),(4,4 '-dimethyl-2,2'-bipyridine), whereas that of compound 8 under the same conditions is comparatively long.