New one-dimensional Ru polymers
Abstract
Polynuclear Ru complexes are well-known for their Intervalence Transfer (IT) transitions in the mixed-valence states and this property induces their application in photochemical molecular device design. Until now, most research in this area is concentrated on polypyridine as the bridging ligand. In our research we designed a strategy to synthesize polynuclear ruthenium bipyridyl complexes with one-dimensional oligoazines as bridging ligands. In this dissertation, we synthesized and studied a series of relevant compounds from oligoazines (as ligands), [Ru(bpy)2L]2+ where L is a linear oligoazine (as monomers), and Ru polymers. Oligoazines with two different types of end groups, ketone and hydrazone, were studied by 1H NMR, 13C NMR and UV-vis spectroscopies. The large changes found in the UV-vis spectra show that the electronic properties of the oligoazine are strongly affected by the nature of the end groups. NMR evidence shows that, in solution, multiple conformations exist in the oligoazines with hydrazone end groups. All the results gave a consistent estimate of the band gap in a poly(methylazine) of 3.31 eV. [Ru(bpy)2L] 2+ were studied by cyclic voltammetry, 1H NMR, emission, and UV-vis spectroscopies. The electronic structure of these complexes, as calculated by Density Functional Theory, was able to account for the changes in the methyl group chemical shifts and the different features in the UV-vis spectra as a function of the L ligand. Ru polymers and dimer model compounds with [Ru(bpy)2]2+ complexes linked by a controlled number of azine units (one to seven) were examined by cyclic voltammetry and IR, NMR, and visible-NIR spectroscopies. The NMR spectra and the cyclic voltammograms indicated that the Ru2+ sites influenced the main chain properties at least 15 Å from the metal site. The first oxidation in each material was assigned to a ligand-centered process. A simple model based on overlap between adjacent Ru2+ sites can account for the first oxidation potential in both the dimers and the polymers. The first oxidized state of the polymers has a spectroscopic band that is consistent with an IT transition. The IT feature is assigned to a ligand-ligand transition that spans several repeat units in the polymer. ^
Subject Area
Chemistry, Inorganic|Chemistry, Organic|Chemistry, Polymer
Recommended Citation
Meng Cheng,
"New one-dimensional Ru polymers"
(2002).
Dissertations and Master's Theses (Campus Access).
Paper AAI3077995.
http://digitalcommons.uri.edu/dissertations/AAI3077995