Electropolymerisable bipyridine ruthenium(II) complexes: synthesis, spectroscopic and electrochemical characterisation of 4-((2-thienyl)ethenyl)- and 4,4'-di((2-thienyl)ethenyl)-2,2'-bipyridine ruthenium complexes

Four new Ru polypyridyl complexes with mono- or di((2-thienyl)ethenyl) substituted bipyridines were synthesized. The complexes were characterized by NMR, elemental anal., UV-visible absorption and electrochem. (differential pulse and cyclic voltammetry). Electroactive polymer films of these complexes were prepd. by oxidative electropolymn. and characterized by UV-visible absorption spectroscopy and electrochem. The electrochem. induced polymn. of the complexes resulted in a significant shift of the oxidn. potential of the Ru(II)-Ru(III) process towards more pos. potentials. Also, MLCT absorption band of the polymeric complexes is shifted towards shorter wavelengths. These results are interpreted in terms of an interruption of the conjugated system of the (2-thienyl)ethenyl-substituted bipyridine ligands due to a radical polymn. mechanism affecting rather the ethenyl part of the ligand than the thienyl.