Costentin Cyrille, Evans Dennis H, Robert Marc, Savéant Jean-Michel, Singh Pradyumna S
Laboratoire d'Electrochimie Moléculaire, Université de Paris 7--Denis Diderot, Case Courrier 7107, 2 place Jussieu, 75251 Paris Cedex 05, France.
J Am Chem Soc. 2005 Sep 14;127(36):12490-1. doi: 10.1021/ja053911n.
Concerted proton and electron transfers (CPET) currently attract considerable theoretical and experimental attention, notably in view of their likely involvement in many enzymatic reactions. Electrochemistry, through techniques such as cyclic voltammetry, can provide a quite effective access to CPET in terms of diagnosis and quantitative kinetic characterization. The relationships expressing the rate constant of an electrochemical CPET are given. Besides the CPET standard potential, it depends on two main factors. One is the reorganization energy, which appears as the sum of an intramolecular contribution and two solvent reorganization energies corresponding to proton and electron transfers, respectively. The other is the pre-exponential factor that mainly depends on proton tunneling through the activation barrier. Procedures for estimating these various factors as well as the H/D kinetic isotope effect are described. Application of the theory is illustrated by the experimental results obtained for the cyclic voltammetric reduction of the water-superoxide ion complex in dimethylformamide and acetonitrile.
协同质子和电子转移（CPET）目前吸引了大量的理论和实验关注，特别是考虑到它们可能参与许多酶促反应。电化学通过循环伏安法等技术，在诊断和定量动力学表征方面能够为CPET提供相当有效的研究途径。给出了表示电化学CPET速率常数的关系式。除了CPET标准电位外，它还取决于两个主要因素。一个是重组能，它表现为分子内贡献以及分别对应于质子和电子转移的两个溶剂重组能之和。另一个是指前因子，它主要取决于质子隧穿活化能垒。描述了估算这些各种因素以及H/D动力学同位素效应的方法。通过在二甲基甲酰胺和乙腈中对水 - 超氧离子络合物进行循环伏安还原所获得的实验结果说明了该理论的应用。
