Synthesis and Solution Characterization of [Ru(bpy)2]^2+ Modified Polyazines

A series of [Ru(bpy)2]^2+ complexes linked by a controlled number of azine units (one to seven) were synthesized and studied in the solution phase. Polymers and dimer model compounds were examined by cyclic voltammetry and IR, NMR, and visible-NIR spectroscopies. The NMR spectra and the cyclic voltammograms indicated that the Ru^2+ sites influenced the main chain properties at least 15 (ANGSTROM) from the metal site. The first oxidation in each material was assigned to a ligand-centered process, but DFT calculations suggested that the Ru^2+ has an important influence. The first oxidized state of the polymers has a spectroscopic band that is consistent with an intervalence transfer (IT) transition, but this absorption is not seen in the dimer model compounds. Thus, the IT feature is assigned to a ligand-ligand transition that spans several repeat units in the polymer.