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.

在化学系化学结构、动力学与机理B项目的支持下，北卡罗来纳大学教堂山分校化学系的Gerald Meyer教授和他的团队正在研究可见光引发的化学反应，旨在提高此类转化的效率。大多数情况下的目标是优化反应性，以便每个吸收的光子产生一种所需的产物。这项研究结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交叉领域，重点关注电子转移反应性，非常适合各级科学家的教育。迈耶研究团队致力于支持科学领域代表性不足的学生的培训。作为该项目的一部分，正在计划开展涉及研究三角和北卡罗来纳州农村地区 K-12 学生的外展活动。该项目旨在深入了解光敏剂和猝灭剂之间的光引发电子转移，从而实现优化和预测量子产率的方法。重点将放在双分子氧化还原反应固有的“相遇复合物”内的激发态电子转移和电荷重组。已知相遇复合物内的电荷重组会显着降低大多数光化学反应的产率，使其值远低于 1，但这种行为的起源仍然很大程度上未知。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，将利用老式第二行和第三行过渡金属光敏剂的电荷转移激发态，以及新兴的地球丰富的基于钴、铁、锆和铜的光敏剂。具有定制电荷、尺寸和还原电位的电子供体和受体猝灭剂有望提供对遭遇复杂结构的深入了解，这对于了解控制所需产物逃逸的因素（即笼逃逸产率）是必要的。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遭遇复合物，从而影响笼逃逸率。 超分子组装将用于量化遭遇复合物内非共价相互作用对电子转移和笼逃逸的影响。提出了变温动力学测量来量化遭遇复合物内的电子耦合并确定激发态电子转移反应的绝热性。拟议的研究本质上是基础性的，但预计会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遇到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 NSF 的法定使命，并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，被认为值得支持。