SusChEM: Applying Redox Noninnocence: Tetrazine-Assisted Reduction of N2

该项目由美国国家科学基金会化学合成计划资助，支持印第安纳大学的Kenneth Caulton教授设计和制备新的配体结构，这些配体结构将围绕低成本和可持续的金属中心进行研究。所得到的配合物用于将反应性差、热力学稳定的分子氮转化为增值产品的不寻常的催化转化。新的配体含有亚胺功能，这使得它们很容易被还原，因此它们可以暂时储存电子，有利于氮的捕获和还原。理想的含氮产物是使用有机捕获试剂或质子形成的。考尔顿集团在催化剂中使用低成本元素，如铁和钒，使材料比使用贵金属催化剂的材料更具可持续性。该项目还系统化并利用了新的配体连通性和电子结构。博士后、研究生和本科生研究人员积极参与该项目的实验和理论方面。学生接受多种表征技术的优秀培训，包括电子顺磁共振和x射线光电子能谱。考尔顿教授活跃于当地的化学社区，经常为不同的听众讲授诺贝尔奖获奖研究。本研究项目的重点是设计和实验研究一种新的三齿，氧化还原活性配体，双（四氮基）吡啶（btzp），它支持金属中心，多电子还原过程，如用第一排过渡金属铁和钒还原分子氮。富亚胺的btzp配体作为电子储层，在很窄的电位范围内促进氧化还原反应。钳形配体上许多氮位点的可用性导致新的反应性，包括质子耦合电子转移或氢原子转移过程。钳形氮指向外，并具有已证明的穿梭氢的能力，其将结合的氮转化为氨和胺；这些产品是商业上重要的化学品。将分子氮转化为增值产品是特别有趣的，因为它在活性催化剂中使用环保和低成本的金属。

This project, funded by the NSF Chemical Synthesis Program, supports the research of Professor Kenneth Caulton of Indiana University to design and prepare new ligand structures that will wrap around low cost and sustainbable metal centers. The resultant complexes are used in the unusual catalytic conversion of poorly-reactive, thermodynamically-stable molecular nitrogen into value-added products. The new ligands contains imine functionalities, which makes them readily reducible so that they can temporarily store electrons to favor both the capture and reduction of nitrogen. Desirable nitrogen-containing products are formed using either organic trapping reagents or protons. The Caulton group employs low cost elements such as iron and vanadium in their catalysts making the materials more sustainable that those using precious metal catalysts. This project also systematizes and utilizes new ligand connectivities and electronic structures. Postdoctoral, graduate, and undergraduate researchers are actively involved in both the experimental and theoretical aspects of the project. The students receive excellent training in multiple characterizational techniques including electron paramagnetic resonance and x-ray photoelectron spectroscopies. Professor Caulton is active in the local chemistry community often lecturing on Nobel Prize-winning research to diverse audiences.This research project focuses on the design and experimental investigation of a new tridentate, redox-active ligand, bis(tetrazinyl) pyridine (btzp), which acts in supporting metal-centered, multi-electron reduction processes such as the reduction of molecular nitrogen using the first row transition metals iron and vanadium. The imine-rich btzp ligand serves as electron reservoir, promoting redox reactions within a very narrow potential range. The availability of a number of nitrogen sites on the pincer ligand leads to novel reactivity including proton-coupled electron transfer or hydrogen atom transfer processes. The pincer nitrogens are directed outward and have a demonstrated ability to shuttle hydrogens, which converts the bound nitrogen to ammonia and amines; these products are commercially important chemicals. The conversion of molecular nitrogen into value-added products is of particular interest as it uses environmentally-friendly and low cost metals in the active catalyst.