Mechanisms of Proton Coupled Electron Transfer

Thomas J. Meyer博士，北卡罗来纳大学教堂山分校化学系，由化学系无机、生物无机和有机金属化学项目资助，研究质子耦合电子转移（PCET）反应的机理。具体来说，本研究将针对一种特殊类型的PCET反应，电子质子转移（EPT），其中电子-质子从供体上的轨道分离位点转移到受体或受体上的轨道分离位点。虽然比电子转移和质子转移更复杂，但EPT可以通过避免高能中间体来控制PCET的反应性。光驱动或光学EPT将研究分子内、氢键结合配合物内和配体桥接混合价配合物中的电荷转移。这项工作将利用光谱和动态测量的结合来表征光学EPT，包括超快测量。目标是展示光学EPT现象的广度，并使用光谱和动态信息与理论相结合，在与我们目前对电子转移的理解相当的水平上获得关于EPT的见解。此外，我们还将探索一种基于质子耦合转移的EPT猝灭的新型金属配合物激发态反应。将利用瞬态吸收、发射和红外技术来研究EPT猝灭和反反应，以跟踪交换质子，并建立正常和倒置区域的kH/kD动力学同位素效应和自由能依赖关系。最重要的能量相关和/或生物相关的能量转换反应涉及催化的多电子，多质子变化。例如，在生物反应中，催化剂的活化通常发生在空间分离的位置上，每次只发生一个电子。该项目将研究电子和质子在这些过程中如何转移的详细机制，从而揭示电子转移反应实际发生的重要性。除了科学贡献外，该项目还将提供综合和测量与理论应用之间的交叉，为本科生、研究生和博士后研究人员的参与和培训创造一个良好的环境。

Dr. Thomas J. Meyer, Chemistry Department, University of North Carolina - Chapel Hill, is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division for studies of the mechanism of proton coupled electron transfer (PCET) reactions. Specifically, this study will target a particular type of PCET reactions, Electron Proton Transfer (EPT) in which concerted electron-proton transfer occurs from orbitally separated sites on the donor to orbitally separated sites on an acceptor or acceptors. Although more complex than electron transfer followed by proton transfer or vice versa, EPT can dominate PCET reactivity by avoiding high energy intermediates. Light-driven or optical EPT will be investigated for charge transfer within molecules, within H-bonded association complexes, and in ligand-bridged mixed valence complexes. This work will utilize a combination of spectroscopic and dynamic measurements to characterize optical EPT, including ultrafast measurements. The goal is to demonstrate the breadth of optical EPT phenomena and to use spectroscopic and dynamic information combined with theory to gain insight about EPT at a level comparable to our current understanding of electron transfer. Additionally, a new type of metal complex excited state reactivity based on EPT quenching with coupled proton transfer will be explored. EPT quenching and back reactions will be investigated using transient absorption, emission, and infrared techniques to follow the exchanging proton and to establish kH/kD kinetic isotope effects and free energy dependences in the normal and inverted regions.Most important energy related and/or biologically relevant reactions for energy conversion involve catalyzed multi electron, multi proton changes. For example, in biological reactions, catalyst activation typically occurs one electron at a time at spatially separated sites. This project will examine the detailed mechanism of how electrons and protons are transferred in such processes and, thus, will shed light on how important electron transfer reactions actually occur. In addition to the scientific contributions, this project will provide a cross over between synthesis and measurements with application of theory creating an excellent environment for engaging and training undergraduates and graduate students, and postdoctoral research fellows.