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

将二氧化碳转化为一氧化碳和将一氧化碳逆转化为二氧化碳是极其重要的工业过程，其需要相当大的能量。此外，一氧化二氮是造成空气污染和烟雾的氮氧化物之一。其转化为无害的氮气具有环境重要性。有天然存在的物质，一氧化碳还原酶（CODH）和一氧化二氮还原酶（N2 O还原酶），可以快速和节能的方式进行这两种转化。在这两种情况下，化学转化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有效，杜兰大学化学系的James P. Donahue博士在化学部化学合成计划的支持下，正在制备模拟CODH和N2 O还原酶中铜位点的小铜/硫化合物。这些化合物被设计为像CODH和N2 O还原酶一样起作用，并提供新的更经济的方法来进行上述反应。作为该项目的一部分，对本科生和研究生进行培训，使其成为科学和技术工作者。此外，还与附近通常为少数民族服务的机构建立了合作关系，以提供使用仪器设备的机会，并为研究机会很少或根本没有机会的大学本科生提供暑期研究机会，该项目的目标是合成两种含铜酶（CODH和N2 O还原酶）活性部位的小分子类似物。这些金属酶分别介导一氧化碳的两电子氧化为二氧化碳和一氧化二氮的两电子还原为二氮。制备了具有桥连羰基和硫基配体的钼铜异双金属化合物，作为CODH催化循环中的中间体类似物。这部分的研究首先涉及CO结合到两个协调的铜（I）双（硫醇盐）配合物的调查。这类似于CODH中CO氧化途径的第一步。所得的三个配位加合物被转化成类似于CODH中的活性位点的Mo-Cu化合物。在连接与N2 O还原酶，各种双（氨基）双（硫醇盐）配体的制备和检查其支持的能力，形成多铜复合物的组成相关的N2 O还原酶的催化位点。的配体的空间体积的变化和给体原子集的硬度的变化，探讨其对多铜团簇的聚集的影响。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，包括晶体学光谱学，电化学和计算。来自新奥尔良地区提供很少本科生研究机会的机构的暑期学生参与其中，这些机构通常是少数民族服务，可以使用PI的晶体设施。该奖项反映了NSF的法定使命，并被认为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来支持。

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.