Developing electron transfer from chiral circularly polarized luminescence-based photocatalysts towards selective radical cross-coupling reactions

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Summary The long-term goal of the proposed project is to develop the next generation of cross-coupling reactions. We aim at eliminating the need of differentiation between coupling partners, while retaining high reactivity and selectivity by utilizing polarized radical species. We will take advantage from the fact that a polarized radical species will only react with another radical species with the opposite polarization. The central hypothesis is that complexes emitting strong circularly polarized luminescence (CPL) possess a high population of high energy polarized excitons that can be harvested for reactivity. CPL is the emission of light with preferential circular polarization and has emerged as the next generation light source. Lanthanide complexes are the best CPL emitters, and cerium complexes are known to be photosensitizers capable of generating radical species. We will synthesize luminescent enantiopure chiral complexes exhibiting CPL, and will examine their ability to transfer polarized electrons. To attain strong CPL and photosensitizing ability, we will target chiral rigid guanidinate ligands. We will also examine the ability of these complexes to transfer polarized electrons and generate polarized radicals with quenching studies of the complexes in their photoexcited states. We will also evaluate the reactivity of polarized radicals toward Csp3-Csp3 cross-coupling reactions using a combination of fluorescence studies and flow chemistry. During the proposed funding period, we expect the delivery of the first examples of CPL-active cerium complex, as well as proof-of-principle for polarized electron transfer. We will also develop early stage proof-of-concept for the polarized radical-based cross-coupling reactions.