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

总结 该项目的长期目标是开发下一代交叉偶联反应。我们 目的在于消除偶联配偶体之间的区分需要，同时保持高反应性， 通过利用极化自由基物种的选择性。我们将利用这样一个事实， 这些自由基物质将仅与具有相反极化的另一自由基物质反应。核心假设是， 发射强圆偏振发光（CPL）的配合物具有高能量的高布居数， 极化激子，可以收集用于反应性。CPL是具有优先圆形的光的发射， 偏振，并已成为下一代光源。镧系配合物是最好的CPL 发射体和铈络合物已知是能够产生自由基物质的光敏剂。我们将 合成显示CPL的发光对映体纯手性配合物，并将检查它们转移的能力 极化电子为了获得更强的CPL和光敏化能力，我们将手性刚性胍作为目标 配体。我们还将研究这些复合物转移极化电子并产生 极化自由基与猝灭研究的配合物在其光激发态。我们还将评估 极化自由基对Csp 3-Csp 3交叉偶联反应的反应性， 荧光研究和流动化学。在建议的拨款期内，我们预计会提供首个 CPL活性铈络合物的实例，以及极化电子转移的原理证明。我们还将 开发基于极化自由基的交叉偶联反应的早期概念验证。

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.