Role of solvent in the phosphatase activity of a dinuclear nickel(II) complex of a Schiff base ligand: mechanistic interpretation by DFT studies
Role of solvent in the phosphatase activity of a dinuclear nickel(II) complex of a Schiff base ligand: mechanistic interpretation by DFT studies
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溶剂在希夫碱配体双核镍 (II) 配合物磷酸酶活性中的作用：DFT 研究的机理解释
DOI：
10.1039/c6nj01043a
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发表时间：
2016
影响因子：
3.3
通讯作者：
Das Debasis
中科院分区：
文献类型：
--
作者：
Sanyal Ria;Zhang Xuepeng;Chakraborty Prateeti;Giri Sanjib;Chattopadhyay Shyamal Kumar;Zhao Cunyuan;Das Debasis
合成了一种新的双核μ-二苯氧-μ-乙酰基金属水解酶[Ni 2L 2（NCS）（Ac）（H2O）0.5（MeOH）0.5]·1.25H2O（HL = 2-（（E）-（2-（吡啶-2-基）乙基亚氨基）甲基）-4-氯苯酚），其金属间化合物分离度为3.099 μ mol/L，并对其进行了结构和光谱表征.温度依赖（2-300 K）的磁化率测量表明，该化合物通过diphenoxido和syn-syn acetate桥（J = 7.21 cm−1）表现出整体的分子内铁磁相互作用。研究还发现，在极低温度下，Ni（II）离子的弱反铁磁分子间相互作用或反铁磁效应对χMT的降低起作用。该化合物的磷酸酶活性，对4-硝基苯磷酸盐（4-NPP）的催化活性研究，证明了优异的催化效率。此外，使用DMF介质比使用乙腈（MeCN）时促进了更好的催化途径（8.18 s-1）。利用密度泛函理论（DFT）对4-NPP水解反应机理进行了研究，结果表明4-NPP水解反应是一个类似于SN 2的加成-取代反应，具有两种可能的催化剂-底物结合模式（RC 1 -1和RC 1 -2）. RC 1 -2被认为是直接反应物，因为水分子邻近衬底的缺电子磷中心。更重要的是，在MeCN介质中的不良催化行为可以归因于MeCN分子具有比DMF分子更好的配位性质，因为根据PCM计算，[Ni-MeCN]和[Ni-DMF]的形成能分别为-2.5和-1.2 kcal mol-1。
A novel dinuclear μ-diphenoxo-μ-acetato metallohydrolase [Ni2L2(NCS)(Ac)(H2O)0.5(MeOH)0.5]·1.25H2O (HL = 2-((E)-(2-(pyridin-2-yl)ethylimino)methyl)-4-chlorophenol) with an intermetallic separation of 3.099 Å has been synthesized and characterized both structurally and spectroscopically. Temperature dependent (2–300 K) magnetic susceptibility measurements show that the compound exhibits a global intramolecular ferromagnetic interaction through the diphenoxido and syn–syn acetate bridges (J = 7.21 cm−1). It is also noticed that a weak antiferromagnetic intermolecular interaction or ZFS effect of the Ni(II) ions is working for lowering of χMT at extreme low temperature. The compound’s phosphatase activity, investigated spectrophotometrically on 4-nitrophenylphosphate (4-NPP), demonstrates excellent catalytic efficiency. Additionally, using a DMF medium facilitated a better catalytic pathway (8.18 s−1) than when acetonitrile (MeCN) was used. A plausible 4-NPP hydrolytic reaction mechanism was proposed by utilizing DFT calculations and the results suggest a SN2-like addition–substitution pathway with two possible catalyst–substrate binding modes (RC1-1 and RC1-2). RC1-2 is regarded as the direct reactant since the water molecule is adjacent to the electron-deficient phosphorus center of the substrate. More importantly, the poor catalytic behavior in the MeCN medium could be ascribed to MeCN molecules having better coordination properties than DMF molecules, since the formation energies of [Ni–MeCN] and [Ni–DMF] are −2.5 and −1.2 kcal mol−1, respectively, according to PCM calculations.