Electron Transfer Photooxygenations With New and Improved Electron Transfer Sensitizers in Homogeneous and Heterogeneous Media

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With this award, the Organic and Macromolecular Chemistry Program supports the work of Professor Edward L. Clennan of the University of Wyoming. This research will investigate the synthesis and characterization of a series of new light harvesting molecules that carry two positive charges for which the word pyrylogens has been suggested. The two positive charges have been incorporated in these new materials as a unique and key structural feature designed to provide superior performance as efficient photochemically initiated electron transfer (PET) catalysts. In contrast to other PET catalysts, electron transfer from a substrate to these pyrylogens will generate two repulsive positively charged species that will rapidly separate thereby preventing energy wasting back electron transfer. Preliminary studies have demonstrated that these molecules absorb light that closely mimics the solar spectrum and have superior optical properties that will allow excitation without competitive absorption by the substrates. Both their photochemical and electrochemical properties will be investigated. Further, the effectiveness of these new materials as electron transfer catalysts to introduce oxygen into organic molecules will be demonstrated. These new materials will also be imbedded in an inert matrix to generate stabilized heterogeneous catalysts that can be used in otherwise incompatible environments. Broader Impacts. Photochemically initiated electron transfer (PET) reactions are a broad fundamental class of transformations and as a consequence, the development of these new materials has far reaching impact well beyond the uses described in this proposal. Their use will represent a positive step toward the design of "greener" environmentally friendly processes that will allow access to new, otherwise inaccessible products. The heterogeneous catalysts derived from these materials have potential use as photocatalysts for the remediation of polluted wastewater since it is anticipated that they will function to degrade and mineralize organic pollutants. Finally, this project will provide an outstanding vehicle for the training of students who will enhance the scientific workforce.