Mechanistic Investigation into the Cleavage of a Phosphomonoester Mediated by a Symmetrical Oxyimine-Based Macrocyclic Zinc(II) Complex
Mechanistic Investigation into the Cleavage of a Phosphomonoester Mediated by a Symmetrical Oxyimine-Based Macrocyclic Zinc(II) Complex
复制标题
对称氧亚胺基大环锌 (II) 配合物介导的磷酸单酯裂解的机理研究
DOI：
10.1002/cphc.201301216
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发表时间：
2014
期刊：
影响因子：
2.9
通讯作者：
Zhao Cunyuan
中科院分区：
文献类型：
--
作者：
Zhang Xuepeng;Xu Xianyan;Xu Huiying;Zhang Xiting;Phillips David Lee;Zhao Cunyuan
利用密度泛函计算探讨了对称锌（II）配合物催化4 -硝基苯基磷酸磷同构酯的水解机理。验证了活性催化剂的形成过程和性能。提出了八种合理的机制，并将其分为三类。除机制7外，所有被提出的机制都是SN2型加成-取代反应途径。理论位亲核攻击发生在机制7中，反应势垒相对较高。单催化剂模型中的机制1和机制2，夹层-双催化剂模型中的机制5至机制7，以及机制8中的亲核加成-取代步骤是一致的反应途径，而其余的似乎是逐步发生的。同时，利用显式溶剂模型考虑了直接氢键和溶剂化相互作用，结果表明，加入的水分子参与了水解过程，但没有显著改变水解机理。机制8反应势垒最低，是八种被提出的机制中最受青睐的反应途径，尽管机制1、4和6与机制8存在竞争。考虑到锌（II）配合物浓度，机制1仅是低锌（II）配合物浓度下的主要反应途径；机制4和机制6随着锌（II）配合物浓度的增加而更具竞争性，机制8在高锌（II）配合物浓度下更有利。我们的计算结果与实验结果一致，并可用于系统地解释实验结果。更重要的是，对催化剂的设计和反应环境的选择提出了有见地的建议。
Density functional calculations are utilized to explore the hydrolysis mechanisms of the phosphomonoester 4‐nitrophenyl phosphate catalyzed by a symmetrical zinc(II) complex. The formation process and properties of the active catalyst are verified. Eight plausible mechanisms are proposed and categorized into three groups. All of the proposed mechanisms, except for Mechanism 7 (see text), are SN2‐type addition–substitution reaction pathways. Nucleophilic attack at theorthoposition occurs in Mechanism 7 with a relatively high reaction barrier. Mechanisms 1 and 2 in the monocatalyst model, Mechanisms 5 to 7 in the sandwich‐dual‐catalyst model, as well as the nucleophilic addition–substitution step in Mechanism 8 are concerted reaction pathways, whereas the rest appear to occur in a stepwise manner. Meanwhile, the explicit solvent model is utilized to consider direct hydrogen bonds and solvation interactions and these results indicate that the added water molecule is involved in the hydrolysis process, but does not change the mechanisms significantly. Mechanism 8, with the lowest reaction barrier, is the most favored reaction pathway of the eight proposed mechanisms, although Mechanisms 1, 4, and 6 are in competition with Mechanism 8. In consideration of the zinc(II) complex concentration, Mechanism 1 is only the predominant reaction pathway at a low zinc(II) complex concentration; Mechanisms 4 and 6 tend to be more competitive with increasing concentration of the zinc(II) complexes, and Mechanism 8 is favored at high zinc(II) complex concentrations. Our calculated results are consistent with, and can be used to systematically interpret, experimental observations. More importantly, insightful suggestions are made regarding the catalyst design and selection of the reaction environment.