Synthesis and Mechanistic Studies of Active Site Analogues of Carbon Monoxide Dehydrogenase and Nitrous Oxide Reductase

二氧化碳到一氧化碳的转化和一氧化碳到二氧化碳的反转化是极其重要的工业过程，需要相当大的能量。此外，一氧化二氮是造成空气污染和烟雾的氮氧化物之一。将其转化为无害的氮气具有重要的环境意义。有一些天然存在的物质，一氧化碳还原酶（CODH）和一氧化二氮还原酶（N2O还原酶），可以快速高效地完成这两种转化。在这两种方法中，化学转变都发生在被几个含硫基团包围的铜原子上。由于这些生物系统非常高效，杜兰大学化学系的James P. Donahue博士在化学系化学合成项目的支持下，正在制备小型铜/硫化合物，模拟CODH和N2O还原酶中的铜位点。这些化合物的功能类似于CODH和N2O还原酶，并为上述反应提供了新的更经济的方法。作为该项目的一部分，本科生和研究生将接受进入科技工作队伍的培训。此外，与附近的，通常是少数民族服务机构建立合作，提供仪器设备，并为来自研究机会很少或根本没有的大学的本科生提供暑期研究机会。本项目旨在合成CODH和N2O还原酶两种含铜酶活性位点的小分子类似物。这些金属酶分别介导一氧化碳的两电子氧化生成二氧化碳和氧化亚氮的两电子还原生成二氮。在CODH的催化循环中，制备了具有桥接羰基和硫基配体的钼铜杂二金属化合物作为中间体的类似物。本研究的这一部分首先涉及CO与双配位铜(I)双（硫酸盐）配合物结合的研究。这类似于CODH中CO氧化途径的第一步。得到的三个配位加合物转化为类似于CODH活性位点的Mo-Cu化合物。在N2O还原酶中，制备了各种双（氨基）双（硫酸酯）配体，并检测了它们支持形成与N2O还原酶催化位点组成相关的多铜配合物的能力。探讨了配体空间体积的变化和给体原子集硬度的变化对多铜簇聚集的影响。这项工作为本科生和研究生提供了广泛的经验，他们将接受合成和表征方法的培训，包括晶体学光谱，电化学和计算。来自新奥尔良地区机构的暑期学生很少提供本科研究机会，这些机构通常是少数民族服务，他们可以使用PI的晶体学设施。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 conversion of carbon dioxide to carbon monoxide and the reverse conversion of carbon monoxide to carbon dioxide are extremely important industrial processes that require considerable energy. Additionally, nitrous oxide is one of the oxides of nitrogen that contribute to air pollution and smog. Its conversion to innocuous nitrogen gas has environmental importance. There are naturally occurring substances, carbon monoxide reductase (CODH) and nitrous oxide reductase (N2O reductase), that can perform both of these transformations quickly and in an energy efficient manner. In both of these the chemical transformations occur at a copper atom that is surrounded by several sulfur containing groups. Since these biological systems are very efficient, Dr. James P. Donahue, Chemistry Department of Tulane University, with the support of the Chemical Synthesis Program of the Chemistry Division, is preparing small copper/sulfur compounds that mimic the copper sites in CODH and N2O reductase. These compounds are designed to function like CODH and N2O reductase and provide new more economical ways to perform the reactions mentioned above. As a part of the project undergraduate and graduate students are trained to enter the science and technology workforce. In addition, collaborations are established with nearby, often minority serving institutions, to provide access to instrumental facilities and to provide summer research opportunities for undergraduate students from colleges where research opportunities are minimal or nonexistent.This project targets the synthesis of small molecule analogues of the active sites of two copper-containing enzymes: CODH and N2O reductase. These metalloenzymes mediate the two electron oxidation of carbon monoxide to carbon dioxide and the two electron reduction of nitrous oxide to dinitrogen, respectively. Heterodimetallic Mo-Cu compounds with bridging carbonyl and sulfido ligands are prepared as analogues of intermediates in the catalytic cycle of CODH. This portion of the study first involves an investigation of the of CO binding to two-coordinate Cu(I) bis(thiolate) complexes. This resembles the first step of the CO oxidation pathway in CODH. The resulting three coordinate adducts are converted into the Mo-Cu compounds that resemble the active site in CODH. In connection with N2O reductase, various bis(amino) bis(thiolate) ligands are prepared and examined for their ability to support the formation of multi-copper complexes of compositional relevance to the catalytic site of N2O reductase. Variation in the steric bulkiness of the ligands and variation in the hardness of the donor atom set are probed for their effect upon the aggregation of the multicopper clusters. This work provides a breadth of experience to undergraduate and graduate students, who will be trained in synthesis and characterization methods including crystallography spectroscopy, electrochemistry, and computations. Summer students from New Orleans area institution that offer few undergraduate research opportunities are involved and these institutions, which are often minority serving, are provided access to the PI's crystallographic facility.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.