Fundamentals of Chemistry that Guide Formation of Sulfur-bridged Bi- and Multi-metallic Molecular Units

指导硫桥双金属和多金属分子单元形成的化学基础

• 批准号: 2102159
• 负责人: Marcetta Darensbourg
• 金额: $ 50万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2102159&HistoricalAwards=false
• 关键词: Fundamentals; Chemistry; Guide; Formation; Sulfur

With the support of the Chemical Synthesis program in the Division of Chemistry, Professor Marcetta Y. Darensbourg and coworkers of Texas A&M University will study molecules that inform chemists about Nature’s choice of sulfur to connect metals in structures that perform as catalysts in biology. In contrast to the heavy, precious/expensive metals such as platinum and rhodium that one might find in the catalytic converter of an automobile, Nature must rely on the natural abundance distribution of metals on earth. Consequently, earth-abundant metals such as iron, nickel, and manganese are taken up in molecular motifs that utilize cooperativity between metals. In addition, their strategic positioning within a molecular environment, and timing of delivery of reactants and release of products, renders incredible reactions that are facile at ordinary temperatures and pressures. The importance of connections is vital to these molecular-binding motifs. Sulfur is a key ingredient in metalloenzymes that perform some of the most fundamental reactions of life. Examples include catalysts that facilitate hydrogen production, carbon dioxide reduction, and nitrogen conversion. How these molecular catalysts, imbedded in protein folds, work remains largely a mystery that inspires chemists to search for clues in small, well characterized molecules. This work will target connections between nickel and iron in new synthetic molecules outfitted with “reporter” molecules that indicate reactive centers. The Darensbourg team will analyze their structures and properties, monitoring changes as electrons are added or removed one by one. They will search for and characterize products of catalysis of proton reduction or synthesis. These fundamental studies are ideal for training graduate and undergraduate students and coworkers to recognize and appreciate sciences that connect biology and chemistry. With the support of the Chemical Synthesis program in the Division of Chemistry, Professor Marcetta Y. Darensbourg of Texas A&M University will establish a synthetic chemistry plan that targets an improved understanding of bimetallic constructs prevalent in redox-processing enzymes including diiron and nickel-iron hydrogenases. The overall goal is to understand how two (or multiple) abundant first-row metals share the burden of 2-electron transformations, whereby obviating the need for noble metals in natural catalysis and organic synthesis. Questions arise from the ubiquitous mediation by sulfur as a bridge between metal complexes that have redox activity either at the metal or the ligands, and how substrates are positioned on the reactive centers. Two principal classic “non-innocent” redox-active ligands will be engaged for this work, namely nitric oxide (NO) and dithiolenes. The Darensbourg group is developing NO-containing metallodithiolate ligands as bidentate S-donors to a transition metal Lewis acid receiver for examination of properties of the redox levels in a diiron trinitrosyl. The team proposes to monitor the electronic and vibrational coupling between two S-bridged iron as affected by redox level of the diiron complex using N-15 isotopic labelling and two-dimensional infrared spectroscopy. In addition, the effect of redox level on the observed scrambling of the NO ligand between the two irons is expected to inform our understanding of communications between metals in the sulfur-bridged bimetallics. The concerted effect of two different types of delocalization ligands with a nickel-dithiolene as receiver to the metallodithiolates will offer an opportunity to explore inter- and/or intramolecular magnetic quenching and electronic coupling. Studies of the properties of the new bimetallics will improve our understanding of multimetallic bioinorganic enzyme active sites.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.

在化学系化学合成项目的支持下，Marcetta Y.德克萨斯A M大学的Darensbourg和同事将研究分子，这些分子告诉化学家大自然选择硫来连接生物学中作为催化剂的结构中的金属。 与汽车催化转化器中可能发现的铂和铑等重金属相比，自然界必须依赖于地球上金属的自然丰度分布。 因此，地球上丰富的金属（例如铁、镍和锰）被吸收到利用金属之间协同作用的分子基序中。此外，它们在分子环境中的战略定位，以及反应物的递送和产物的释放的时机，使得在常温和常压下容易进行令人难以置信的反应。连接的重要性对这些分子结合基序至关重要。硫是金属酶的关键成分，金属酶执行生命中一些最基本的反应。 实例包括促进氢产生、二氧化碳还原和氮转化的催化剂。 这些嵌入蛋白质折叠中的分子催化剂是如何工作的，在很大程度上仍然是一个谜，激发了化学家在小的、特征明确的分子中寻找线索。这项工作将针对新合成分子中镍和铁之间的连接，这些分子配备了指示反应中心的“报告”分子。 Darensbourg团队将分析它们的结构和性质，监测电子逐一添加或移除时的变化。 他们将寻找和表征质子还原或合成的催化产物。 这些基础研究非常适合培养研究生和本科生以及同事认识和欣赏连接生物学和化学的科学。 在化学系化学合成项目的支持下，Marcetta Y.德克萨斯A M大学的Darensbourg将建立一个合成化学计划，目标是更好地理解氧化还原加工酶（包括二铁和镍铁氢化酶）中普遍存在的结构。 总体目标是了解两种（或多种）丰富的第一行金属如何分担2电子转换的负担，从而避免在天然催化和有机合成中对贵金属的需求。问题产生于无处不在的调解硫作为桥梁之间的金属络合物，具有氧化还原活性的金属或配体，以及如何基板上的反应中心定位。 两个主要的经典的“非无辜的”氧化还原活性配体将从事这项工作，即一氧化氮（NO）和二硫杂环戊烯。Darensbourg小组正在开发含NO的金属二硫代配体作为过渡金属刘易斯酸受体的双齿S-供体，用于检查二铁三亚硝酰基中氧化还原水平的性质。该团队建议使用N-15同位素标记和二维红外光谱法监测两个S-桥连铁之间的电子和振动耦合，这受到二铁络合物氧化还原水平的影响。 此外，氧化还原水平对观察到的两种铁之间NO配体的混乱的影响预计将为我们了解硫桥连双金属化合物中金属之间的通讯提供信息。两种不同类型的离域配体与镍-二硫纶作为接收器的金属二硫纶的协同效应将提供一个机会，探索分子间和/或分子内的磁淬灭和电子耦合。 新的双金属的性质的研究将提高我们的多金属生物无机酶活性sites的理解。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。