CAREER: Earth-Abundant Transition Metal Photosensitizers Using Ligand-to-Metal Charge Transfer

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In this CAREER project, funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Carsten Milsmann of the Department of Chemistry at West Virginia University is investigating a new class of early transition metal complexes that are promising candidates for the development of molecular photosensitizers due to their interesting optical and electrochemical characteristics. Molecular photosensitizers find application in a wide variety of solar energy applications including photovoltaics, solar fuel production, and photocatalysis. The goal of these research efforts is to provide access to photoactive compounds based on readily-available, earth-abundant metals that can improve upon and/or replace currently available technology based on precious metals. This will further the development of more cost-efficient solar energy applications for which scalability is not hindered by the limited availability of the metal component. The project requires expertise in the fields of inorganic, physical, and organic chemistry and is ideally suited for the training and education of highly qualified scientists at all levels. Outreach activities aimed at middle school students in rural areas of West Virginia will be conducted in collaboration with the West Virginia University Center for Excellence in Science Education and support efforts to train the next generation of science teachers in the state.The electron-deficient nature of early transition metals requires new approaches to initial charge separation via absorption of a photon compared to the well-established functional principles of electron-rich precious metal photosensitizers. This project investigates ligand-to-metal charge transfer processes to convert light energy into chemical potentials. Through a combination of synthetic chemistry, spectroscopic studies, and quantum-chemical calculations this project are answering the following questions: 1)What are the fundamental design principles to generate long-lived excited states in early transition metal complexes? 2)How can systematic modifications of the supporting ligand framework be used to fine-tune the optical and electron transfer properties of the complexes? 3)Can the photo-induced electron transfer properties of early transition metal complexes be utilized to enable transformations requiring highly reducing conditions (e.g. dinitrogen reduction)?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.