Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris Diderot, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France.
J Am Chem Soc. 2011 May 4;133(17):6668-74. doi: 10.1021/ja110935c. Epub 2011 Apr 8.
The oxidation of PhOH in water by photochemically generated Ru(III)(bpy)(3) is taken as prototypal example disclosing the special character of water, in the solvent water, as proton acceptor in concerted proton-electron transfer reactions. The variation of the rate constant with temperature and driving force, as well as the variation of the H/D kinetic isotope effect with temperature, allowed the determination of the reaction mechanism characterized by three intrinsic parameters, the reorganization energy, a pre-exponential factor measuring the vibronic coupling of electronic states at equilibrium distance, and a distance-sensitivity parameter. Analysis of these characteristics and comparison with a standard base, hydrogen phosphate, revealed that electron transfer is concerted with a Grotthus-type proton translocation, leading to a charge delocalized over a cluster involving several water molecules. A mechanism is thus uncovered that may help in understanding how protons could be transported along water chains over large distances in concert with electron transfer in biological systems.
以 PhOH 在水中被光化学生成的 Ru(III)(bpy)(3)氧化为例，揭示了溶剂水作为协同质子-电子转移反应中的质子接受体的特殊性质。速率常数随温度和驱动力的变化，以及 H/D 动力学同位素效应随温度的变化，允许确定反应机制，该机制的特点是三个固有参数：重组能、前指数因子，用于测量电子态在平衡距离处的振子耦合，以及距离敏感性参数。对这些特性的分析以及与标准碱基磷酸氢盐的比较表明，电子转移与 Grotthus 型质子迁移协同进行，导致电荷在涉及多个水分子的簇上离域。因此，揭示了一种可能有助于理解在生物体系中电子转移时质子如何沿着水分子链长距离协同传输的机制。
