Concerted proton-coupled electron transfers in aquo/hydroxo/oxo metal complexes: Electrochemistry of [OsII(bpy)2py(OH2)]2+ in water
Concerted proton-coupled electron transfers in aquo/hydroxo/oxo metal complexes: Electrochemistry of [OsII(bpy)2py(OH2)]2+ in water
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DOI：
10.1073/pnas.0905020106
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发表时间：
2009-07-21
影响因子：
11.1
通讯作者：
Teillout, Anne-Lucie
中科院分区：
文献类型：
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作者：
Costentin, Cyrille;Robert, Marc;Teillout, Anne-Lucie
通过对缓冲水中[Os-II(bpy)(2)py(OH2)]（2+）连续氧化循环伏安反应的动力学分析，以及H/D同位素效应的测定，可以确定将Os-II-水合物转化为os - iii -羟基配合物，再转化为os - iv -氧配合物的连续质子耦合电子转移机制。在第一种情况下，逐步途径优于协调途径。然而，很大浓度的碱，如醋酸盐，会引发协同反应的开始。当高局部浓度的羧酸盐附着在o络合物附近时，也出现同样的趋势，但程度要大得多。os - iii -羟基/ os - iv -氧偶对整体上要慢得多，协调途径比逐步途径占主导地位。然而，在这方面，水不是一个合适的质子受体。其他碱基，如柠檬酸盐或磷酸盐，在触发协同通路方面相当有效。在这里，我们提出了导致这些对比行为的因素，为协同过程是避免高能中间体的有效方法的预测提供了一个实际的例证。观察到非活性离子的强烈减速效应以及高浓度的局部羧酸盐对启动协同路径的积极作用，强调了多种结构和介质因素可能调节和控制协同路径的发生。这些对水-羟基-氧-氧系列中协同通路发生的论证和分析有望作为方法学和因子分析方面研究的指导方针。
Kinetic analysis of the successive oxidative cyclic voltammetric responses of [Os-II(bpy)(2)py(OH2)](2+) in buffered water, together with determination of H/D isotope effects, has allowed the determination of the mechanisms of the successive proton-coupled electron transfers that convert the Os-II-aquo complex into the Os-III-hydroxo complex and the later into the Os-IV-oxo complex. The stepwise pathways prevail over the concerted pathway in the first case. However, very large concentrations of a base, such as acetate, trigger the beginning of a concerted reaction. The same trend appears, but to a much larger extent, when high local concentration of carboxylates are attached close to the Os complex. The Os-III-hydroxo/Os-IV-oxo couple is globally much slower and concerted pathways predominate over the stepwise pathways. Water is, however, not an appropriate proton acceptor in this respect. Other bases, such as citrate or phosphate, are instead quite effective for triggering concerted pathways. Here, we suggest factors causing these contrasting behaviors, providing a practical illustration of the prediction that concerted processes are an efficient way of avoiding high-energy intermediates. Observation of a strong decelerating effect of inactive ions together with the positive role of high local concentrations of carboxylates to initiate a concerted route underscores the variety of structural and medium factors that may operate to modulate and control the occurrence of concerted pathways. These demonstrations and analyses of the occurrence of concerted pathways in an aquo-hydroxo-oxo series are expected to serve as guidelines for studies in term of methodology and factor analysis.