The Impact of Huge Structural Changes on Electron Transfer and Measurement of Redox Potentials: Reduction of ortho -12-Carborane
The Impact of Huge Structural Changes on Electron Transfer and Measurement of Redox Potentials: Reduction of ortho -12-Carborane
复制标题
巨大结构变化对电子转移和氧化还原电位测量的影响：邻-12-碳硼烷的还原
DOI：
10.1021/acs.jpcb.9b08151
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Michl, Josef
中科院分区：
文献类型：
--
作者：
Miller, John R.;Cook, Andrew R.;Šimková, Ludmila;Pospíšil, Lubomír;Ludvík, Jiří;Michl, Josef
大量的结构变化伴随着1，2-二碳-闭合-十二硼烷笼状分子的电子捕获（1）。通过脉冲辐解进行的双分子电子转移（ET）发现，1的还原电位E0 = −1.92 V（相对于Fc+/0），当氧化还原伙伴的电位接近E0时，ET的速率常数大大降低。类似地，两种电化学技术在E0附近没有检测到电流，而是在-3.1 V附近发现峰或极谱波，这比E0负1.2 V。DigiSim模拟可以描述不可逆伏安图，但要求在E0时的电化学速率常数接近1 × 10- 10 cm/s，这是相对于容易进行ET的分子的10- 10倍。与双分子ET的10- 5相比，10- 10的这个因子提出了一个难题。这个难题可以被理解为“弗鲁姆金效应”之一的表现，其中只有部分施加的电压可用于驱动电极处的ET。
A massive structural change accompanies electron capture by the 1,2-dicarba-closo-dodecaborane cage molecule (1). Bimolecular electron transfer (ET) by pulse radiolysis found a reduction potential ofE0= −1.92 V vs Fc+/0for1and rate constants that slowed greatly for ET to or from1when the redox partner had a potential near thisE0. Similarly, two electrochemical techniques could detect no current at potentials nearE0, finding instead peaks or polarographic waves near −3.1 V, which is 1.2 V more negative thanE0. Voltammetry could determine rate constants, but only near −3.1 V. DigiSim simulations can describe the irreversible voltammograms but require electrochemical rate constants near 1 × 10–10cm/s atE0, a factor of 10–10relative to molecules undergoing facile ET. This factor of 10–10compared to ∼10–5for bimolecular ET presents a puzzle. This puzzle can be understood as a manifestation of one of the “Frumkin Effects” in which only part of the applied voltage is available to drive ET at the electrode.