Concerted two-proton-coupled electron transfer from catechols to superoxide via hydrogen bonds
Concerted two-proton-coupled electron transfer from catechols to superoxide via hydrogen bonds
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DOI：
10.1016/j.electacta.2016.05.034
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发表时间：
2016-08-01
影响因子：
6.6
通讯作者：
Uno, Bunji
中科院分区：
文献类型：
--
作者：
Nakayama, Tatsushi;Uno, Bunji
基于电化学和电子自旋共振（ESR）光谱测量，并结合密度泛函理论（DFT）计算，研究了多酚类抗氧化剂中重要官能团邻苯二酚与电生成超氧阴离子（O-2（中心点-））的反应机理.邻苯二酚（CatH（2））的存在显著影响准可逆O-2/O-2（中心点-）氧化还原，显示相关反应，O-2（中心点-）+ CatH（2）-> H2 O2 + Cat（中心点-）。我们认为，该反应是在O-2之间形成氢键复合物后，通过一步单电子转移和两个酚质子的运动控制的（中心点-）和CatH（2），我们称之为协同的双质子耦合电子转移（2 PCET）反应，基于由B3 P86/6-31 + G（d，p）和B3 LYP/6-31 + G（d，p）计算。O-2（中心点-）与CatH（2）反应的协同2 PCET机理通过发现O-2（中心点-）和5，5-二甲基-1-吡咯啉-N-氧化物的HO 2中心点加合物作为自旋陷阱的信号在含CatH（2）的电生成O-2（中心点-）溶液的ESR谱中完全消失而得到证实。这表明，协同2 PCET反应是重要的分析含有邻苯二酚环的多酚类抗氧化剂。(C)2016爱思唯尔有限公司版权所有
The reaction mechanism between electrogenerated superoxide (O-2(center dot-)) and catechols as an important functional group of polyphenolic antioxidants was investigated based on electrochemical and electron spin resonance (ESR) spectral measurements and supported by density functional theory (DFT) calculations. The quasi-reversible O-2/O-2(center dot-) redox is significantly affected by the presence of a catechol (CatH(2)), showing the associated reaction, O-2(center dot-) + CatH(2) -> H2O2 + Cat(center dot-). We proposed that this reaction is governed by one-step one-electron transfer concerted with two phenolic proton movement after initial formation of the hydrogen-bonded complexes between O-2(center dot-) and CatH(2), which we refer to as concerted two-proton-coupled electron transfer (2PCET) reactions, based on the energetics and kinetics of the reaction obtained by B3P86/6-31 + G(d,p) and B3LYP/6-31 + G(d,p) calculations, respectively. The concerted 2PCET mechanism for the reaction between O-2(center dot-) and CatH(2) is demonstrated by the finding that a signal of the O-2(center dot-) and HO2 center dot adducts of 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap completely disappears in the ESR spectra of the electrogenerated O-2(center dot-) solution containing CatH(2). This indicates that the concerted 2PCET reaction is important for the analysis of polyphenolic antioxidants containing an o-diphenol ring. (C) 2016 Elsevier Ltd. All rights reserved.