Homogeneous and Heterogeneous Ligand Centered Catalysts for Reversible Proton Reduction

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With this award, the Chemical Catalysis Program in the Chemistry Division is funding Professor Craig Grapperhaus of the University of Louisville to develop catalysts for the production of hydrogen as a renewable fuel source. Finding practical renewable energy sources is a great challenge we currently face, and the transformation and storage of solar energy as chemical energy is one of the solutions that is actively pursued because plants have achieved this feat through photosynthesis. The research focuses on catalysts in which a metal coordinates ligands that can accept or donate electrons; consequently, the ligands rather than the metal would be directly involved in the chemical interaction with the protons and the molecular hydrogen production. This research creates educational opportunities for undergraduate and graduate students from the University of Louisville and the Campbellsville University, a neighboring undergraduate institution. These students will gain expertise and experience in synthesis, electrochemistry, computational chemistry, and catalysis. The project will also create opportunities for interactions with engineers in the Conn Center for Renewable Energy Research at the University of Louisville, which focuses on research on renewable energy and sustainability issues.The focus of the research is to develop ligand-centered catalysts for the reversible reduction of protons to hydrogen. The catalysts will be designed to promote a ligand-centered mechanism facilitated by the incorporation of non-innocent, redox-active thiolate donors. The function of the catalyst depends on the interaction between the metal center and the ligand. The catalysts under development employ strong metal-ligand interactions that favor electron delocalization, thus supporting new mechanistic pathways for catalytic proton reduction/hydrogen evolution. Catalysts will be prepared and characterized in solution. Electrochemical investigations will probe the reaction mechanism. Ligand modification coupled with computational studies will be used to address the electronic effects on overpotential and ligand basicity. Additionally, the isolation and characterization of reaction intermediates will be pursued to validate the proposed mechanism. Successful candidates will then be immobilized on a solid support for the development of heterogeneous derivatives that could have greater practical utility.