RUI: Molecular Alkali Metal Catalysts for Selective Reduction of Oxygen-Containing Functionalities

在化学系化学催化项目的支持下，纽约市立大学约翰·杰伊刑事司法学院的张国琦正在研究碱金属(锂、钠和钾)与特殊设计的配体相结合，以促进潜在的有用过程，以从可再生生物质衍生原料中制造燃料和其他有益于社会的商品化学品。碱金属是地壳中最丰富的金属元素之一，但与现代化学工业中常用的稀有和昂贵的贵金属催化剂相比，它们催化化学反应的能力尚未得到充分开发。得到支持的研究侧重于开发简单的方法，从现成的起始材料中创建定义明确的碱金属-配体络合物，并调查其作为催化剂对一系列相关化学过程的有效性。实现该项目目标所需的实验是严格的，但设计得足够简单，可以由初级本科生甚至高中生进行，这项研究将为不同的年轻科学家群体提供获得动手实验室经验的机会。约翰·杰伊学院被归类为主要的拉美裔服务机构，其科学系为大量学生提供服务，这些学生属于传统上在STEM(科学、技术、工程和数学)领域代表性较低的群体。因此，预计资助的活动不仅将提供化学催化、有机化学和无机化学方面的教育和培训，而且还将作为一种工具，帮助多样化未来的科学专业人员。张博士参与了国家认可的指导计划，如理科专业研究计划(PRISM)，这进一步扩大了该奖项的广泛影响。目前，人们对探索用来自地球上丰富的金属的催化剂取代当今许多重要化学过程中使用的贵金属催化剂产生了极大的兴趣。这样的改变可能会降低化学制造的成本，同时也会改善其环境可持续性。碱金属络合物是近年来出现的催化平台，其在还原化学中的成功应用可以提高生物质加工的可持续性。因此，该资助项目的重点是研究和开发与2，2‘：6’，2‘-三联吡啶(或冠醚)连接的定义明确的Li、Na和K阳离子络合物，用于还原一系列含氧官能团，包括羧基衍生物(例如，羧酸、酯、酰胺)和醚，使用硅烷或分子氢作为化学计量比的还原剂。更复杂的底物中的官能团兼容性将与其他重要参数一起探索，例如各种催化还原转化的区域、立体和化学选择性。这些研究将集中在寻找最具活性和选择性的催化剂候选者，以及考察基于受挫的Lewis对的假定的双活化反应模式，通过该模式，提出了配合物发挥其催化作用。机理研究将通过基于密度泛函理论(DFT)的实验和理论相结合的方法进行，以了解观察到的结构-活性关系和金属-配体合作的重要性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Catalysis Program in the Division of Chemistry, Guoqi Zhang of the John Jay College of Criminal Justice at the City University of New York is studying alkali metals (lithium, sodium, and potassium) in combination with specially designed ligands to promote processes of potential utility for the manufacture of fuels and other commodity chemicals of benefit to society from renewable biomass-derived feedstocks. Alkali metals are among the most abundant metallic elements in the Earth’s crust but their ability to catalyze chemical reactions is underexplored as compared to rare and expensive precious metal-based catalysts, which are commonly used in the contemporary chemical industry. The supported research focuses on the development of simple methods to create well defined alkali metal-ligand complexes from readily available starting materials and investigation of their effectiveness as catalysts for a range of relevant chemical processes. The experiments necessary to pursue the aims of the project are rigorous but designed to be straightforward enough to be conducted by entry-level undergraduate students, or even high school students, and the research will provide a diverse group of young scientists with the opportunity to gain hands-on laboratory experience. John Jay College is classified as a major Hispanic-Serving Institution and its Science Department serves a large number of students belonging to groups traditionally underrepresented in STEM (science, technology, engineering and mathematics) fields. As such, it is anticipated that the funded activities will not only provide education and training at the interface of chemical catalysis, organic chemistry, and inorganic chemistry, but also serve as a vehicle to help diversify the pool of future science professionals. The broader impacts of the award are further extended by the participation of Dr. Zhang in nationally recognized mentoring programs such as the Program for Research Initiatives for Science Majors (PRISM).There is currently great interest in exploring the replacement of precious metal-based catalysts used in many of today's important chemical processes with catalysts instead derived from earth abundant metals. Such a change would likely reduce the costs of chemical manufacturing while also improving its environmental sustainability. Alkali metal complexes have emerged in recent years as platforms for catalysis and their successful application in reduction chemistry could improve the sustainability of biomass processing. Accordingly, the funded project is focused on the study and development of well defined complexes of Li, Na, and K cations ligated with 2,2':6',2''-terpyridines (or crown ethers) for the reduction of a wide range of oxygen-containing functionalities, including carboxyl derivatives (e.g., carboxylic acids, esters, amides) and ethers, using silanes or molecular hydrogen as stoichiometric reductants. Functional group compatibility within more complex substrates will be explored alongside other important parameters such as the regio-, stereo-, and chemo-selectivity of the various catalytic reductive transformations. These investigations will be concentrated on discovery of the most active and selective catalyst candidates and on scrutiny of a putative dual-activation reactivity mode based on a frustrated Lewis pair, through which the complexes are proposed to exert their catalytic effects. Mechanistic studies will be conducted via a combination of experimental and theoretical, density functional theory (DFT)-based methods in order to understand both the observed structure-activity relationships and the importance of metal-ligand cooperativity.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.