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

NSF化学部的化学结构，动力学和机制-B计划支持利哈伊大学化学系的罗伯特·弗劳尔斯教授的研究。 在这项研究中，弗劳尔斯教授和他的学生们正在研究碘化钐（II）（SmI 2）的反应机理，这是一种在有机合成中广泛使用的试剂。 该项目旨在扩展试剂的反应性并开发新的反应。 该研究成果可能会导致新的有机反应的发展，重要的生物学和药学相关化合物的合成。在这个项目中，学生接触到当代化学的重要领域。 教育经验围绕在机械化学的背景下进行研究。 高中生的指导提供了有意义的研究经验，为那些有兴趣在科学事业。 在这个项目中，旨在测试质子耦合电子转移（PCET）的作用，优点和应用的机制研究减少Sm（II）试剂含有协调和螯合质子供体进行检查。这些调查是用来研究和开发新的和合成相关的反应，通过PCET从Sm（II）-质子供体配合物的基板，这是典型的brachecitrant单独的电子转移进行。 这些研究包括以下几个方面：1）研究Sm（Ⅱ）与质子供体的配位强度与O-H、N-H和C-H键弱化程度的关系，2）利用Sm（Ⅱ）-质子供体配合物扩大PCET还原底物的范围，改进和发展新的反应;（3）Sm（II）-质子给体配合物异常稳定性的基础研究。所提出的工作的机制的结果导致开发新的和有用的反应发起的Sm（II）-质子供体配合物，并提供了一个理由的试剂系统的独特的反应性。 为减少有机底物开发的协议被用作开发替代方法的基础，用于在室温下直接还原分子氮。一系列的实验技术的集成沿着与质子耦合，电子转移在合成中的综合应用提供了一个动态的智力环境，为学生在各级学习，包括高中生。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.