Ångström Laboratory, Department of Chemistry, Uppsala University, Box 523, SE75120 Uppsala, Sweden.
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.
J Am Chem Soc. 2021 Jan 20;143(2):560-576. doi: 10.1021/jacs.0c09106. Epub 2021 Jan 6.
Proton-coupled electron transfer (PCET) reactions are fundamental to energy transformation reactions in natural and artificial systems and are increasingly recognized in areas such as catalysis and synthetic chemistry. The interdependence of proton and electron transfer brings a mechanistic richness of reactivity, including various sequential and concerted mechanisms. Delineating between different PCET mechanisms and understanding why a particular mechanism dominates are crucial for the design and optimization of reactions that use PCET. This Perspective provides practical guidelines for how to discern between sequential and concerted mechanisms based on interpretations of thermodynamic data with temperature-, pressure-, and isotope-dependent kinetics. We present new PCET-zone diagrams that show how a mechanism can switch or even be eliminated by varying the thermodynamic (Δ and Δ) and coupling strengths for a PCET system. We discuss the appropriateness of asynchronous concerted PCET to rationalize observations in organic reactions, and the distinction between hydrogen atom transfer and other concerted PCET reactions. Contemporary issues and future prospects in PCET research are discussed.
质子耦合电子转移 (PCET) 反应是自然和人工系统中能量转换反应的基础，并且在催化和合成化学等领域越来越受到重视。质子和电子转移的相互依存关系带来了丰富的反应机制，包括各种顺序和协同机制。区分不同的 PCET 机制并理解为什么特定机制占主导地位对于设计和优化使用 PCET 的反应至关重要。本观点提供了基于对热力学数据的解释，如何根据温度、压力和同位素依赖的动力学来辨别顺序和协同机制的实用指南。我们提出了新的 PCET 区域图，展示了通过改变 PCET 系统的热力学（Δ 和 Δ）和耦合强度，一种机制如何切换甚至消除。我们讨论了异步协同 PCET 用于合理化有机反应中观察结果的适当性，以及氢原子转移和其他协同 PCET 反应之间的区别。讨论了 PCET 研究中的当代问题和未来展望。
