Electrochemical approach to proton-coupled electron transfers: recent advances
Electrochemical approach to proton-coupled electron transfers: recent advances
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DOI：
10.1039/c2ee03241d
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发表时间：
2012-06
影响因子：
32.5
通讯作者：
J. Savéant
中科院分区：
文献类型：
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作者：
J. Savéant
质子和电子转移之间的关联在生物反应（光系统II和无数其他系统）和合成反应（想想大量可用的Pourbaix图）中无处不在。对这些质子耦合电子转移（PCET）的重新关注是由于质子（P）和电子（E）转移是协同的（“CPET”）而不是逐步的“EPT”或“PET”的可能性。CPET途径的优点是它们跳过了分步途径中涉及的高能中间体。因此，CPET途径的表征对于理解许多自然反应至关重要。它们还可能在设计旨在应对当代能源挑战的催化工艺方面发挥相当大的作用。电化学，特别是通过非破坏性技术，如循环伏安法，是解决这些问题的有效手段。CPET动力学的建模是基于重原子（包括溶剂）的半经典处理和质子和电子的量子处理。驱动力、溶剂重组和质子隧穿是反应动力学的主要组成部分。该模型的应用说明与氧化的氨基苯酚，模仿酪氨酸-组氨酸对光系统II，以及与无机的例子涉及的水-羟基-氧代序列，MIIOH 2，MIIIOH，MIVO，在过渡金属络合物。速率定律和速率控制因素是相同的电化学和均相版本的模型。简单苯酚的氧化提供了一个例子，说明了相同反应的电化学和光化学方法相结合的兴趣。这也是一个潜水到水（在水中）作为质子载体的显着性能的大距离感谢氢键网络与电子转移的场合。将该Grotthuss型CPET与在质子供给和质子接受基团之间含有H-键中继的合成模型分子的行为进行比较，其中质子通过与电子转移一致的该H-键链进行运输。最后，它表明，它是可能的，以打破重原子之间的键通过质子和电子转移，这三个事件是协调一致的，因此，以获得大量的动力学效益。本文介绍了该理论并将其应用于O-O键的断裂。
Association between proton and electron transfer is omnipresent in biological reactions (Photosystem II and a myriad of other systems) and in synthetic reactions (think of the huge number of available Pourbaix diagrams). The renewed interest for these proton-coupled electron transfers (PCET) is due to the possibility that proton (P) and electron (E) transfers be concerted (“CPET”), rather than stepwise, “EPT” or “PET”. The advantage of CPET pathways is that they skip the high energy intermediates involved in the stepwise pathways. Characterization of CPET pathways is therefore essential to the comprehension of a number of natural reactions. They are also likely to play a considerable role in the design of catalytic processes with the aim of tackling contemporary energy challenges. Electrochemistry, especially by means of non-destructive techniques like cyclic voltammetry, is an efficient means to address these problems. Modelisation of the CPET kinetics is based on a semi-classical treatment of heavy atoms (including the solvent) and a quantic treatment of protons and electrons. Driving force, solvent reorganization and proton tunneling are the main ingredients of the reaction kinetics. Application of the model is illustrated with the oxidation of an amino-phenol, mimicking the tyrosine–histidine couple in Photosystem II, as well as with an inorganic example involving the aquo–hydroxo–oxo sequence, MIIOH2, MIIIOH, MIVO, in transition metal complexes. The rate law and rate controlling factors are the same in the electrochemical and homogeneous versions of the model. Oxidation of simple phenol provides an illustration of the interest of combining electrochemical and photochemical approaches of the same reaction. It was also the occasion of a dive into the remarkable properties of water (in water) as proton carrier over large distances thanks to H-bond networks in concert with electron transfer. This Grotthuss-type CPET is compared to the behavior of a synthetic model molecule containing an H-bond relay between the proton donating and proton accepting groups, where the proton is transported by means of this H-bond train in concert with electron transfer. Finally it is shown that it is possible to break a bond between heavy atoms by means of proton and electron transfer, the three events being concerted, and consequently to obtain a substantial kinetic benefit. The attending theory is described and applied to the cleavage of an O–O bond.