Mechanisms of Proton Coupled Electron Transfer

查佩尔山北卡罗来纳州大学化学系的托马斯·J·迈耶博士得到化学系无机、生物无机和有机化学项目的支持，研究质子耦合电子转移（PCET）反应的机制。具体而言，本研究将针对一种特定类型的PCET反应，电子质子转移（EPT），其中协同电子-质子转移发生从供体上的轨道分离位点到受体上的轨道分离位点。虽然更复杂的电子转移后，质子转移或反之亦然，EPT可以主导PCET反应，避免高能量的中间体。光驱动或光学EPT将研究分子内的电荷转移，氢键缔合复合物内，以及配体桥接的混合价态复合物。这项工作将利用光谱和动态测量的组合来表征光学EPT，包括超快测量。我们的目标是展示光学EPT现象的广度，并使用光谱和动态信息结合理论，以获得与我们目前对电子转移的理解相当的水平上的EPT的见解。此外，一种新型的金属络合物激发态反应的基础上EPT淬火耦合质子转移将被探索。EPT猝灭和逆反应将使用瞬态吸收，发射和红外技术来研究，以跟踪交换质子，并建立正常和反转区域中的kH/kD动力学同位素效应和自由能依赖性。例如，在生物反应中，催化剂活化通常在空间上分离的位点处一次一个电子地发生。本项目将研究电子和质子在这种过程中如何转移的详细机制，从而揭示电子转移反应实际上是如何发生的。除了科学贡献外，该项目还将提供合成和测量之间的交叉，并应用理论，为吸引和培训本科生和研究生以及博士后研究员创造良好的环境。

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.