Factors Influencing Coordinated Ni(II) Cysteinate Basicity and Redox Potentials

在这个由美国国家科学基金会化学部化学结构、动态和机制B项目资助的项目中，内华达大学化学系的Jason Shearer教授将致力于了解硫化物连接的过渡金属中心如何促进质子耦合电子转移（PCET）反应。PCET反应涉及氢原子的净转移，在化学和生物学中具有重要的基础意义。尽管它们很重要，但这些反应的细节仍然是激烈辩论和研究的主题。这个项目的重点是了解质子化硫酸盐配体在这种反应中的作用，这些配体与减少的第一排晚期过渡金属中心（R-S(H+)-M）协调。由R-S(H+)-M基团支持的反应在许多生物系统中具有潜在的重要性，从促进产氢到远程电子转移到底物还原。因此，PCET反应的这一部分在开发与氢经济和工业催化（底物氧化还原化学）相关的新生物启发技术方面具有潜在的应用前景。除了设计和生产能够促进R-S(H+)-M介导的PCET反应的小分子系统外，该项目还将研究这些系统的基本物理性质如何促进整个PCET反应。学生培训和新的科学技术的发展，将适用于超出具体的研究在这一倡议下进行是这个项目的基本方面。质子和电子几乎同时转移是一个基本重要的化学过程。有强有力的证据表明，质子化硫酸盐配体在低氧化态(R-S(H+)-M；M = Fe - Ni)可以通过PCET工艺还原衬底。该项目的总体目标是a)了解这些反应的普遍性，b)探索它们在重要的生物和化学过程中的适用性（即氢气生产，远程电子转移和底物还原）。具体来说，本研究旨在了解使用还原性硫酸盐连接的Ni（II）和Ni(I)复合物和金属肽的R-S(H+)-Ni介导的还原反应的基本方面。将特别强调金属酶镍超氧化物歧化酶，它可能利用Cys-S(H+)-Ni片段来促进氧阴离子还原。质子化镍-硫酸盐配合物的几何结构、物理性质（R-S(H+)-Ni酸度、氧化还原电位）和电子结构与其进行PCET反应的能力将相互关联。还将注意到整个PCET过程的基本细节（即区分协调、顺序PCET和氢原子转移反应）。

In this project funded by the Chemical Structure, Dynamic & Mechanism B Program of the NSF Division of Chemistry, Professor Jason Shearer of the Department of Chemistry at the University of Nevada, Reno will pursue research aimed at understanding how thiolate ligated transition metal centers facilitate proton coupled electron transfer (PCET) reactions. PCET reactions involve the net transfer of a hydrogen atom, and are of fundamental importance in chemistry and biology. Despite their importance, the details of such reactions are still a subject of intense debate and study. This project focuses on understanding the role of protonated thiolate ligands coordinated to reduced late first-row transition metal centers (R-S(H+)-M) in such reactions. Reactions supported by the R-S(H+)-M moiety have potential importance in many biological systems ranging from those that facilitate hydrogen production to long-range electron transfer to substrate reduction. As such, this subset of PCET reactions have potential applications in the development of new bioinspired technologies with relevance to the hydrogen economy and industrial catalysis (substrate redox chemistry). In addition to the design and production of small molecule systems that can facilitate R-S(H+)-M mediated PCET reactions, the project will also examine how the fundamental physical properties of these systems contribute to the overall PCET reaction. Student training and the development of new scientific techniques that will be applicable beyond the specific research pursued under this initiative are fundamental aspects of this project.The near simultaneous transfer of a proton and an electron is a fundamentally important chemical process. There is strong evidence that protonated thiolate ligands coordinated to late first-row transition metals in low oxidation states (R-S(H+)-M; M = Fe - Ni) can reduce substrates through PCET processes. The overall goals of this project are to a) understand how general such reactions are, and b) explore their applicability to important biological and chemical processes (i.e. hydrogen production, long range electron transfer, and substrate reduction). Specifically, this research seeks to understand the fundamental aspects of R-S(H+)-Ni mediated reduction reactions using reduced thiolate ligated Ni(II) and Ni(I) containing complexes and metallopeptides. Special emphasis will be given to understanding the metalloenzyme nickel superoxide dismutase, which likely utilizes a Cys-S(H+)-Ni moiety to facilitate oxygen anion reduction. The geometric structure, physical properties (R-S(H+)-Ni acidity, redox potentials), and electronic structure of protonated nickel-thiolate complexes with their ability to perform PCET reactions will be correlated. Attention will also be given to the fundamental details of the overall PCET process (i.e. distinguishing between concerted vs. sequential PCET vs. hydrogen atom transfer reactions).