RUI: Production of Highly Reactive Metal-Oxo Species with Molecular Oxygen and Visible Light for the Selective Oxidative Catalysis

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With this award from the Chemical Catalysis Program in the Division of Chemistry, Prof. Rui Zhang and his students at the Western Kentucky University (WKU) will develop sustainable, "green" and selective oxidation catalysis via high-valent transition metal-oxo species using molecular oxygen and visible light (sunlight). The proposed photocatalytic cycle involves the following: 1) visible light-induced disproportionation of the mu-oxo metal(IV) macrocycle dimeric complex to form metal(III) and metal(V)-oxo oxidizing species; 2) substrate oxidation by the resulting reactive metal(V)-oxo species to give oxidized products and a second metal(III) species; concluding with 3) aerobic oxidation of the metal(III) complex to regenerate the mu-oxo dinuclear metal(IV) complex. The approach will include synthesis and identification of ligand and metal(IV) dimer types for efficient photo-disproportionation reactions and optimization of the catalytic conditions by elucidating key factors. An important goal will be to reveal the reaction scope of the developed photocatalytic methods. This work will address globally important energy and environmental issues. The use of molecular oxygen and sunlight without the need for an external co-reductant in oxidative catalysis is particularly relevant to realizing innovative and economically advantageous processes for conversion of hydrocarbons into oxygenates and, at the same time, to move toward a "sustainable chemistry" that has a minimal environmental impact. This work will also generate insight into important chemical and structural factors that govern photocatalytic properties and processes. Furthermore, it will integrate research and education through training and educating students at WKU, a primarily undergraduate institution. This interdisciplinary research is of significant interest to students and offers them a broad view of chemical research that will enhance student learning and success as emerging professionals. Many of these students will pursue doctorate degrees upon graduating. The PI and the research team have a strong record of actively involving and training undergraduate researchers. This project will also reach out to the exceptional science students attending the newly formed Commonwealth of Kentucky residential Math and Science Gatton Academy located on the campus of WKU as well as the recently established 5-year B.S./M.S. program in the Department of Chemistry.