Visible Light and Divalent Lanthanides in Photoredox Catalysis

在这项由化学系化学催化计划资助的项目中，韦恩州立大学化学系马修·J·艾伦教授正在研究新的稀土体系，这些体系在可见光下可以催化进行还原和成键反应。催化剂是允许化学反应以最小的能源消耗快速进行的物质。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来开启和关闭的催化剂。此外，它们在与现有催化剂不兼容的条件下运行。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培养成有技能、有道德的科学家。高中生来自科学界代表性较低的群体，他们有机会参与研究，从而产生一支受过更多教育和更多样化的科学工作队伍。该项目专注于新的含稀土络合物，可以驱动可见光促进的光氧化还原催化作用。具体地说，该项目测试了一种假设，即如果含有三价稀土的氮杂环己酸酯暴露在牺牲性还原剂和可见光下，它们在氧化还原电位比单独的二价稀土盐更负的情况下执行催化作用。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)需要可在多种电位和波长范围内调节的光氧化还原催化剂，以提高化学选择性；(2)需要空气稳定、无毒的六甲基磷酰胺替代品。研究内容包括合成了一系列二价和三价铕、镱的配合物。通过紫外可见光谱和荧光光谱、电化学势、热力学和动力学稳定性、晶体结构、溶解度和金属间相互作用的倾向性对这些配合物进行了表征。此外，还研究了这些配合物催化重要类别的光氧化还原反应的能力，包括还原、碳-碳键的形成和环的关闭。最后，对学生进行科学方法和负责任的研究行为的培训。

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.