Collaborative Research: CAS-SC: Development of Heavy Atom - Free Photocatalysts for Chemical Reactions

With the support of the Chemical Catalysis (CAT) and Chemical Synthesis (SYN) programs in the Division of Chemistry, the Critical Aspects of Sustainability metaprogram (CAS) and the Office of Multidisciplinary Activities (OMA), Tatiana Esipova of Loyola University-Chicago and Tomoyasu Mani of the University of Connecticut are developing a new family of metal- and halogen-free catalysts that are activated by visible light. Upon activation these catalysts are capable of promoting a number of chemical reactions. In contrast to this work, most visible light-activated reactions require catalysts that contain precious metals or halogen atoms and therefore are not considered to be environmentally sustainable. With a focus on overcoming this limitation, the collaborative Mani/Esipova team is employing computational modeling to design and optimize their catalysts and will subsequently test them in light-driven transformations. In addition to all of this, this research program is providing valuable opportunities for students. Undergraduate and graduate students that are involved in this work, including students who have been historically underrepresented in the sciences, are developing intellectually while building skill sets that lie at the intersection of synthetic organic chemistry and physical chemistry. Such training is valuable for their future careers, be it in academia or industry. This research aims to develop a new family of organic heavy atom–free photoredox catalysts that contain a general motif that consists of orthogonal electron donor-acceptor aromatic chromophores. Generally speaking, photocatalysts absorb light and create electronically excited states that facilitate electron transfer reactions in a mild and controlled manner; as a result, they can produce highly reactive intermediates that lead to value-added bond-forming events. Most currently utilized photoredox catalysts employ halogens or precious metals to enhance the production of these excited states. The photoredox catalysts that are developed in this study not only take advantage of an underexplored photophysical phenomenon to produce excited states in pi-conjugated organic molecules, but they avoid the use of heavy atoms including metals and halogens. The research is demonstrating the unique properties and versatility of this new class of organic photoredox catalysts. This research is expected to establish structure-function correlations of donor-acceptor molecules in terms of the efficiency of the generation of the excited state and the associated catalytic activity. This work and the continued development of sustainable catalysts is providing a firm foundation for the continued exploration and the development of organic photoredox catalysis. 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.