Visible Light and Divalent Lanthanides in Photoredox Catalysis

Wayne州立大学化学系的Matthew J. Allen教授在化学系化学催化项目资助的这个项目中，正在研究新的镧系系统，当暴露在可见光下时，它可以催化还原和成键反应。催化剂是一种能使化学反应以最小的能量消耗迅速进行的物质。它们被用于各种工业过程中。在这个项目中，正在开发利用可见光并可以通过可见光开关的催化剂。此外，它们在与现有催化剂不相容的条件下工作。研究了几个重要的过程，包括形成碳-碳键的反应。研究生、本科生和高中生都被训练成有技能、有道德的科学家。来自科学领域代表性不足群体的高中生有机会参与研究，从而形成一支受过更好教育、更多样化的科学队伍。这个项目的重点是新的含镧配合物，可以驱动可见光促进光氧化还原催化。具体来说，该项目测试了一个假设，即如果三价含镧系盐的氮杂化盐暴露于牺牲还原剂和可见光下，它们的氧化还原电位比单独的二价镧系盐更负。验证这一假设同时解决了氧化还原化学中两个长期存在的挑战：(1)需要光氧化还原催化剂在一系列电位和波长范围内可调，以提高化学选择性；(2)需要空气稳定、无毒的钐（II）六甲基磷酰胺替代品。本研究包括一系列二价和三价铕、镱配合物的合成。这些配合物通过紫外/可见光谱和荧光光谱、电化学电位、热力学和动力学稳定性、晶体结构、溶解度和变形倾向进行了表征。此外，还研究了这些配合物催化重要类型的光氧化还原反应的能力，包括还原、碳-碳键形成和环闭合。最后，培养学生的科学方法和负责任的研究行为。

In this project funded by the Chemical Catalysis program of the Chemistry Division, Professor Matthew J. Allen, Chemistry Department, Wayne State University, is studying new lanthanide systems that catalytically perform reductions and bond-forming reactions when exposed to visible light. Catalysts are substances that permit chemical reactions to be run rapidly with minimum energy consumption. They are used in a variety of industrial processes. In this project, catalysts are being developed that utilize and can be switched on and off by visible light. In addition, they operate under conditions that are not compatible with current catalysts. Several important processes including reactions that form carbon-carbon bonds are studied. Graduate, undergraduate, and high school students are trained to become skilled and ethical scientists. High school students, who are from groups underrepresented in science, have an opportunity to participate in research, leading to a more educated and diverse scientific workforce.This project focuses on new lanthanide-containing complexes that can drive visible-light-promoted photoredox catalysis. Specifically, the project tests the hypothesis that if trivalent lanthanide-containing azacryptates are exposed to a sacrificial reductant and visible light, they perform catalysis at redox potentials more negative than divalent lanthanide salts alone. Testing this hypothesis simultaneously addresses two long-standing challenges in redox chemistry: (1) the need for photoredox catalyts tunable across a range of potentials and wavelengths for improved chemoselectivity and (2) the need for air-stable, non-toxic alternatives to samarium(II) hexamethyl phosphoramide. The research includes the synthesis of a series of complexes of divalent and trivalent europium and ytterbium. These complexes are characterized by UV/visible and fluorescence spectra, electrochemical potentials, thermodynamic and kinetic stabilities, crystal structures, solubilities, and propensities for transmetallation. Additionally, the complexes are studied with respect to their ability to catalyze important classes of photoredox reactions including reductions, carbon-carbon bond formations, and ring closures. Finally, students are trained in the scientific method and the responsible conduct of research.