Testing the Limits of Proton Coupled Electron Transfer (PCET) from Samarium(II)-Proton Donor Complexes

美国国家科学基金会化学部化学结构、动力学和机理b项目支持里海大学化学系Robert Flowers教授的研究。在这项研究中，弗劳尔斯教授和他的学生正在研究碘化钐（SmI2）的反应机制，这是一种广泛用于有机合成的试剂。该项目旨在扩展试剂的反应性并开发新的反应。该研究结果可能导致新的有机反应的发展，对合成生物学和药学上相关的化合物很重要。在这个项目中，学生接触到当代化学的重要领域。教育体验围绕着在机械化学的背景下进行研究。对高中生的指导为那些对科学事业感兴趣的人提供了有意义的研究经验。在这个项目中，机制研究旨在测试质子耦合电子转移（PCET）在含有配位和螯合质子供体的Sm（II）试剂还原中的作用、优势和应用。这些研究用于研究和开发新的和合成相关的反应，这些反应通过PCET从Sm(II)-质子供体配合物到通常难以单独进行电子转移的底物。这些研究包括以下具体目的：1)检验质子供体与Sm（II）试剂之间配位强度的关系及其对O-H、N-H和C-H键弱化程度的影响；2)利用Sm(II)-质子供体配合物，扩大了可通过PCET还原的底物范围，以改进和开发新的反应；3) Sm(II)-质子供体配合物异常稳定性的基础研究。所提出的工作的机理结果导致Sm(II)-质子供体配合物引发的新的和有用的反应的发展，并为试剂体系的独特反应性提供了基本原理。为有机底物的还原制定的协议被用作在室温下开发直接还原分子氮的替代方法的基础。整合了一系列实验技术以及质子耦合、电子转移在合成中的应用，为包括高中生在内的各级学生提供了一个动态的智力环境。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Chemical Structure, Dynamics, and Mechanisms-B Program of the NSF Chemistry Division supports the research of Professor Robert Flowers in the Department of Chemistry at Lehigh University. In this research, Professor Flowers and his students are examining the mechanism of reactions of samarium (II) iodide (SmI2), a widely used reagent in organic synthesis. This project is designed to extend the reactivity of the reagent and to develop new reactions. The research outcome could lead to the development of new organic reactions important for the synthesis of biologically and pharmaceutically relevant compounds. In this project, students are exposed to important areas of contemporary chemistry. The educational experience centers around carrying out research in the context of mechanistic chemistry. Mentoring of high school students provides meaningful research experiences for those interested in scientific careers. In this project, mechanistic studies designed to test the role, advantages, and applications of proton-coupled electron transfer (PCET) in reductions by Sm(II) reagents containing coordinating and chelating proton donors are examined. These investigations are used to study and develop new and synthetically relevant reactions that proceed through PCET from Sm(II)-proton donor complexes to substrates which are typically recalcitrant to electron transfer alone. These studies include the following specific aims: 1) Examination of the relationship between the strength of coordination between proton donors and Sm(II) reagents and its implication on the degree of O-H, N-H, and C-H bond weakening; 2) The use of Sm(II)-proton donor complexes to expand the range of substrates that can be reduced through PCET to refine and develop new reactions; and 3) Examination of the basis of the unusual stability of Sm(II)-proton donor complexes. The mechanistic results of the proposed work lead to the development of new and useful reactions initiated by Sm(II)-proton donor complexes and provide a rationale for the unique reactivity of the reagent system. The protocols developed for the reduction of organic substrates are used as the basis to develop alternative approaches for the direct reduction of molecular nitrogen at room temperature. Integration of a range of experimental techniques along with synthetic applications of proton-coupled, electron-transfer in synthesis provides a dynamic intellectual environment for students at all levels of study, including high school students.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.