Synthesis of rodlike ruthenium(II) coordination polymers having metal-nitrogen and metal-carbon bonds in their main chains

Abstract

Well-defined coordination polymers are described whose main chains are held together by pseudo-octahedral ruthenium(II) complexes in which five ligands are nitrogen and one ligand is carbon. In the first step of polymer synthesis, the bis-tridentate ligand 4,4″-bis[4′-(2,2′:6′,2″-terpyridine)]-2′,5′-dihexyl-p-terphenyl is treated with two equivalents of ruthenium(III) chloride. The resulting dinuclear metal-monomer is subsequently activated by exchanging the remaining three chloro ligands at each ruthenium center by acetone as a more easily substitutable ligand. The activated metal monomer is treated with equimolar amounts of 4,4″-bis[4′-(6′-phenyl-2,2′-bipyridine)]-2′,5′-dihexyl-p-terphenyl as a bis-tridentate ligand monomer. During this conversion, rodlike chains grow through the formation of two further metal-nitrogen bonds and one carbon-nitrogen bond at every ruthenium center. The homogeneous constitution of the readily soluble polymers is proven, and their degrees of polycondensation are roughly estimated to be Pn • • 20, using 1H and 13C NMR spectroscopy. UV-vis absorption spectra show the polymers to behave like chains of electronically independent metal complexes. Due to the carbon-ruthenium bond, however, • •max appears at a longer wavelength (approx. 530 nm) than in the related coordination compounds with only nitrogen-ruthenium bonds. There, • •max is around 500 nm.