CAS: Toward Molecular Control of Cage Escape Yields in Bimolecular Photochemistry

CAS：双分子光化学中笼逃逸率的分子控制

• 批准号: 2247589
• 负责人: Gerald Meyer
• 金额: $ 57.5万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247589&HistoricalAwards=false
• 关键词: CAS; Toward; Molecular; Control; Cage

With support from the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Gerald Meyer of the Department of Chemistry at the University of North Carolina at Chapel Hill and his team are studying chemical reactions that are initiated with visible light with the aim of improving the efficiency of such transformations. The goal in most cases is to optimize the reactivity such that each absorbed photon produces one desired product. Downstream applications of the findings from this research may include solar energy conversion, as well as the photosynthesis of high-value organic compounds. The project lies at the interface of photochemistry and inorganic chemistry, with a focus on electron transfer reactivity that is well suited to the education of scientists at all levels. The Meyer research team endeavors to support the training of students underrepresented in science. Outreach activities involving K-12 students in the Research Triangle and rural North Carolina are being planned as part of the project. This project seeks to obtain mechanistic insight into photo-initiated electron transfer between a photosensitizer and a quencher that will allow optimization and a means to predict quantum yield. Focus will be placed on excited state electron transfer and charge recombination within the ‘encounter complex’ inherent to bimolecular redox reactions. Charge recombination within the encounter complex is known to significantly lower the yield of most photochemical reactions to values far below one, yet the origin(s) of such behavior remain largely unknown. Professor Gerald Meyer and his team propose systematic electron transfer studies that will exploit the charge-transfer excited states of vintage second- and third-row transition metal photosensitizers, as well as emerging earth abundant photosensitizers-based on cobalt, iron, zirconium, and copper. Electron donor and acceptor quenchers with tailored charge, size, and reduction potentials are expected to provide the insight into encounter complex structure that is necessary to understand the factors that control escape of desired products, i.e., the cage escape yield. A fundamental question to be addressed is whether the photosensitizer and/or the quencher structure can be tuned at the molecular level to impact the encounter complex and thereby the cage escape yield. Supramolecular assembly will be used to quantify the impact of non-covalent interactions within the encounter complex on electron transfer and cage escape. Variable temperature kinetic measurements are proposed to quantify the electronic coupling within the encounter complex and to determine the adiabaticity of the excited state electron transfer reaction. The proposed research is fundamental in nature yet are expected to impact approaches used in solar energy conversion and organic photoredox catalysis. In the long term, insights gained from these studies have the potential to provide a rational means for the molecular-level design of photosensitizer encounter complexes capable of efficiently harvesting solar photons, driving electron transfer reactions, and releasing the sought-after products.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.

北卡罗来纳大学教堂山分校化学系的杰拉尔德·迈耶教授和他的团队在化学系化学结构、动力学和机理B项目的支持下，正在研究由可见光引发的化学反应，目的是提高这种转化的效率。在大多数情况下，目标是优化反应性，使每个吸收的光子产生一个期望的产物。这项研究成果的下游应用可能包括太阳能转换，以及高价值有机化合物的光合作用。该项目位于光化学和无机化学的界面，重点研究电子转移反应性，非常适合各级科学家的教育。迈耶的研究团队努力支持培训在科学领域代表性不足的学生。研究三角地区和北卡罗莱纳州农村地区的K-12学生参与的外展活动正在计划中，作为该项目的一部分。该项目旨在获得光敏剂和猝灭剂之间光引发电子转移的机理，这将允许优化和预测量子产率的手段。重点将放在激发态电子转移和电荷重组内的“遇到复合物”固有的双分子氧化还原反应。已知偶遇复合物中的电荷重组会显著降低大多数光化学反应的产率，其值远低于1，但这种行为的起源在很大程度上仍然未知。杰拉尔德·迈耶教授和他的团队提出了系统的电子转移研究，将利用老式的第二和第三行过渡金属光敏剂的电荷转移激发态，以及基于钴、铁、锆和铜的新兴地球丰富的光敏剂。电子供体和受体猝灭剂具有定制的电荷、尺寸和还原电位，有望提供对相遇复杂结构的洞察，这对于理解控制所需产物逃逸的因素是必要的，即笼型逃逸率。要解决的一个基本问题是，光敏剂和/或猝灭剂结构是否可以在分子水平上进行调整，以影响遇到络合物，从而影响笼型逃逸率。超分子组装将用于量化偶遇复合物内非共价相互作用对电子转移和笼状逃逸的影响。提出了变温动力学测量方法来量化偶遇络合物内的电子耦合和确定激发态电子转移反应的绝热性。这项研究在本质上是基础性的，但预计将影响太阳能转换和有机光氧化还原催化中使用的方法。从长远来看，从这些研究中获得的见解有可能为光敏剂偶遇复合物的分子水平设计提供合理的方法，这些复合物能够有效地收集太阳光子，驱动电子转移反应，并释放受欢迎的产品。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。