Conducting redox polymers: investigations of polythiophene-Ru(bpy)(3)(n+) hybrid materials

A series of thiophene-appended Ru-II(bpy)(3) derivatives, Ru(1)(3), Ru(2)(3 ), Ru(3)(3), Ru(bpy)(2)(1), and Ru(bpy)(2)(2), and their resulting polymers have been synthesized and characterized. The bpy ligands 5,5'-bis(5-(2,2'- bithienyl))-2,2'-bipyridine, 1, 4,4'-bis(5-(2,2'-bithienyl))-2,2'-bipyridin e, 2, and 4-(5-(2,2'-bithienyl))-2,2'-bipyridine, 3, all contain electroche mically polymerizable bithienyl moieties. The monomers Ru(2)(3), Ru(3)(3), Ru(bpy)(2)(1) and Ru(bpy)(2)(2) display spectroscopic features that are sim ilar to the ligand-based and MLCT bands found for Ru(bpy)(3). The cyclic vo ltammograms of all of these polymers display both metal-centered and thioph ene-based electroactivity. High redox conductivity was found in poly(Ru(2)( 3)) and poly(Ru(3)(3)) for both the thiophene-based oxidation and metal-bas ed reduction processes. These results indicate that the polymers display ch arge localization for both the metal complexes as well as the tetrathienyl connecting units. The degree of interconnection (number of linkages) as wel l as the substitution pattern were found to control the conductivity of the se polymers. The highest conductivity (3.3x10(-3) S cm(-1)) was found for p oly(Ru(2)(3)), which is able to have up to 6 linkages with other ruthenium complexes as well as possessing a 4,4'-substitution pattern that allows eff ective orbital overlap of the conjugated polymer backbone with the rutheniu m centers.