Effects of the Metal Ion on the Mechanism of Phosphodiester Hydrolysis Catalyzed by Metal-Cyclen Complexes
Effects of the Metal Ion on the Mechanism of Phosphodiester Hydrolysis Catalyzed by Metal-Cyclen Complexes
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DOI：
10.3389/fchem.2019.00195
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发表时间：
2019-04-05
影响因子：
5.5
通讯作者：
Prabhakar, Rajeev
中科院分区：
文献类型：
--
作者：
Hu, Qiaoyu;Jayasinghe-Arachchige, Vindi M.;Prabhakar, Rajeev
本文采用密度泛函理论（DFT）研究了六种二价和四价金属大环戊二烯（M-C）配合物（Zn-C，Cu-C，Co-C，Ce-C，Zr-C和Ti-C）催化磷酸二酯水解的机理。这些配合物的活性使用三种不同的机制进行了研究：（1）直接攻击（DA），（2）催化剂辅助（CA），和（3）水辅助（WA）。所有二价金属配合物（Zn-C、Cu-C和Co-C）以单齿方式配位到BNPP底物并活化其易断裂的磷酸酯键。然而，所有四价金属配合物（Ce-C，Zr-C，和Ti-C）与BNPP以双齿的方式相互作用，并加强这种键。DA机制对所有二价M-C配合物都是最可行的，而WA机制对四价配合物（Ce-C除外）都是有利的。研究发现二价配合物比四价配合物更具反应性。Zn-C配合物催化水解的势垒最低，Ti-C配合物催化水解的势垒最高。除Ti-C外，Ce-C和Zr-C的活性随金属离子配位数的增加而提高。在这项研究中提供的结构和机制的信息将是非常有帮助的发展更有效的金属配合物的这一关键反应。
In this study, mechanisms of phosphodiester hydrolysis catalyzed by six di- and tetravalent metal-cyclen (M-C) complexes (Zn-C, Cu-C, Co-C, Ce-C, Zr-C and Ti-C) have been investigated using DFT calculations. The activities of these complexes were studied using three distinct mechanisms: (1) direct attack (DA), (2) catalyst-assisted (CA), and (3) water-assisted (WA). All divalent metal complexes (Zn-C, Cu-C and Co-C) coordinated to the BNPP substrate in a monodentate fashion and activated its scissile phosphoester bond. However, all tetravalent metal complexes (Ce-C, Zr-C, and Ti-C) interacted with BNPP in a bidentate manner and strengthened this bond. The DA mechanism was energetically the most feasible for all divalent M-C complexes, while the WA mechanism was favored by the tetravalent complexes, except Ce-C. The divalent complexes were found to be more reactive than their tetravalent counterparts. Zn-C catalyzed the hydrolysis with the lowest barrier among all M-C complexes, while Ti-C was the most reactive tetravalent complex. The activities of Ce-C and Zr-C, except Ti-C, were improved with an increase in the coordination number of the metal ion. The structural and mechanistic information provided in this study will be very helpful in the development of more efficient metal complexes for this critical reaction.