Synthesis of CO Dehydrogenase Model Complexes for Catalytic Reductions of CO2

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DESCRIPTION (provided by applicant): The nickel enzyme CODH (carbon monoxide dehydrogenase) plays a critical role in carbon cycling via microbial metabolism that converts CO2 to cellular carbon and, as such, is essential to life on this planet. Functional model complexes are lacking and thus this proposal aims to prepare heterobimetallic complexes with Ni/Fe centers resembling CODH with the goal to answer questions regarding the enzyme function and ultimately design systems for selective and efficient CO2 reduction. Purely functional models, those that are electrocatalysts for CO2 reduction, contain only one type of metal ion and operate at large overpotentials. New synthetic CODH model complexes are needed to illuminate the details necessary for producing a structurally faithful functional model. Our strategy involves the synthesis of heterobimetallic Ni/Fe complexes for CO2 reduction, a first in synthetic chemistry. We will utilize functionalized diimineo-dioxime ligands that allow sie-selective incorporation of two distinct metal ions. Questions to be addressed with these model complexes include: how does CO2 bind to heterobimetallic Ni/Fe centers? How does the Lewis acidic metal ion affect CO2 binding? What is the binding equilibria and extent of activation at reduced Ni/Fe centers? What conditions favor electrocatalytic reduction of CO2? Can the presence of a Lewis acidic metal improve Faradaic efficiencies and/or lower the overpotential necessary for catalysis? The Peters lab is suited to conduct these studies. Prof. Jonas Peters is an expert in synthetic organometallic and inorganic chemistry. Additionally, he is knowledgeable in the field of electrochemistry and electrocatalytic methods. Finally, the academic environment and facilities available at Caltech encourages rich collaborative discussions that will ensure the success of the proposed studies.