Theoretical Studies of Proton-Coupled Electron Transfer Reactions

宾夕法尼亚州立大学的Sharon Hammes-Schiffer获得了理论与计算化学项目的一项研究奖项，该奖项旨在继续她对质子耦合电子转移反应（PCET）的理论和计算研究。这项工作采取了三管齐下的方法：i)正在阐明决定温度依赖性和动力学同位素效应的物理原理；ii)正在修改核电子（NEO）轨道方法，以便计算振动耦合；电化学中研究PCET反应的理论方法正在发展。PCET反应对多种化学和生物过程至关重要，包括电化学、光合作用、呼吸作用和酶反应。第一个项目的目标是确定温度如何影响溶液中PCET反应的速率和动力学同位素效应。速率表达式已经推导出来，并将应用于两种经实验证明具有不同温度依赖性的喹啉氧化反应。该应用程序将提供对PCET反应基本方面的见解，并将促进其他化学和生物学重要应用的分析和解释。第二个项目将着眼于电子转移过程的具体量子力学方面，并将为理论提供更大的预测能力。第三个项目旨在发展电化学的理论方法。由此产生的理论将应用于实验研究的由锇络合物连接到金电极的PCET反应。这些计算将有助于电化学PCET数据的解释，并将产生实验可测试的预测。电化学PCET的一般理论公式将为包括太阳能转换系统在内的广泛的技术重要应用提供框架。因此，这项工作对可持续能源技术的发展产生了更广泛的影响，同时也通过哈默斯-希弗的指导活动和对当地学校的推广工作产生了更广泛的影响。

Sharon Hammes-Schiffer of Pennsylvania State University is supported by an award from the Theoretical and Computational Chemistry Program for research which seeks to continue her theoretical and computational investigations of proton-coupled electron transfer reactions (PCET). The work takes a three-pronged approach: i) the physical principles dictating temperature dependence and kinetic isotope effects are being elucidated; ii) nuclear-electronic (NEO) orbital methods are being modifed in order to allow for the calculation of vibronic couplings; and iii) theoretical methods for studying PCET reactions in electrochemistry are being developed.PCET reactions are essential for a variety of chemical and biological processes, including electrochemistry, photosynthesis, respiration, and enzyme reactions. The objective of the first project is to determine how temperature affects rates and kinetic isotope effects for PCET reactions in solution. Rate expressions have been derived and will be applied to two quinol oxidation reactions that have been shown experimentally to exhibit qualitatively different temperature dependences. This application will provide insight into fundamental aspects of PCET reactions and will facilitate the analysis and interpretation of other chemically and biologically significant applications. The second project will look at specific quantum mechanical aspects of the electron transfer process and will provide greater predictive power for the theory. The third project is aimed at developing theoretical methods for electrochemistry. The resulting theory will be applied to an experimentally studied PCET reaction consisting of an osmium complex attached to a gold electrode. These calculations will assist in the interpretation of electrochemical PCET data and will generate experimentally testable predictions. The general theoretical formulation for electrochemical PCET will provide the framework for a wide range of technologically important applications including solar energy conversion systems. The work is, thus, having a broader impact on developing technology for sustainable energy as well as through Hammes-Schiifer's mentoring activities and outreach efforts to local schools.