Novel titanium dioxide binding motifs for solar energy applications.

摘要

One of the great challenges facing modern scientists involves ensuring that future generations will be able to experience the same quality of life as the present generation. Currently, research into improving sustainability focuses on addressing this concern. For synthetic chemists, improving sustainability can involve increasing the efficiency of industrial processes and developing ways to harness renewable sources of energy. In practice, this can involve designing catalysts that make certain chemical transformations more efficient and finding ways to increase the efficiency of utilizing solar energy. The work described in this thesis presents the development of a low-donor, chelating N-heterocyclic carbene (NHC) ligand and its coordination to different metal centers for catalytic applications. The development of novel binding motifs to sensitize TiO2 surfaces for solar energy applications is also described.;A new chelating NHC ligand, bitriazole-2-ylidene (bitz) has been developed that exhibits uniquely low donor power when compared to other chelating NHCs. The absence of CH2 groups connecting the NHCs makes this ligand less likely to undergo Hoffman elimination in the presence of strong base. Metal complexes of bitz containing Rh, Ru, and Pd have been synthesized and tested for catalytic activity. The Rh(III) complexes containing bitz were found to be active for transfer hydrogenation catalysis.;Solar energy is an abundant source of renewable energy. Many current devices that convert solar energy to electricity utilize TiO2 photoanodes that participate in oxidation chemistry. Attachment of catalysts to the surfaces of these TiO2 anodes can increase the efficiency of the device. Unfortunately, detachment of these catalysts from the surface can limit the effectiveness of current systems. Acetylacetone (acac) groups have been found to bind to TiO2 in a robust fashion and are resistant to detachment under oxidative conditions. This attachment has also been found to resist detachment during the assembly of a desired biomimetic MnIII/IV dimer in the presence of KMnO4. Hydroxamic acid groups have also been found to bind to TiO2 more tightly than conventional carboxylic acid groups. Dyes containing hydroxamic acid binding groups were found to resist detachment under acidic, basic, and near-neutral conditions when compared to carboxylic acids. These novel TiO2 binding groups could prove useful in developing future devices for solar energy conversion.