三聚氰胺金属(II)配合物的结构、紫外-可见光谱和反应活性

三聚氰胺是婴幼儿“肾结石事件”的重要前体. 本文选取几个典型的二价金属离子与三聚氰胺(L)形成的三聚氰胺金属配合物ML2(OH)2(M=Ca, Mg, Zn, Cu, Ni, Fe), 使用密度泛函理论(DFT)、含时DFT和概念DFT等工具, 系统地计算和比较了ML2(OH)2的结构、紫外-可见光谱和反应性质的异同. 模拟结果揭示了ML2(OH)2的结构、光谱及其反应性质是一类不同于其前体L, 形成ML2(OH)2配合物后, 将有较高的亲电指数和较低的化学硬度以及呈现红外吸收峰红移; 在这些典型的二价金属配合物中, 金属M离子电荷与配体O和N原子之间的电荷、以及与金属M离子和配体原子之间的二级微扰相互作用能, 配合物最低空轨道能级与其亲电反应指数、最低空轨道能级与化学硬度指数等方面, 存在着一系列定量的相关关系, 相关系数(R2)达0.889-0.997; 前线分子轨道模拟结果表明, ML2(OH)2体系反应活性的差异源于金属离子对前线轨道贡献有所不同, FeL2(OH)2、CuL2(OH)2、NiL2(OH)2等过渡金属离子的配合物中, 金属离子贡献较多, 共价性成分较多. 这些结果将为进一步理解人体内三聚氰胺致结石的成因提供有益的启示.

Structure,UV-Vis Spectroscopy and Reactivity Properties of MelamineMetal(II) Complexes

Melamine is an important precursor of induced stones in the human kidney. Using density functional theory (DFT), conceptual DFT and time-dependent (TD) DFT, the structure, spectroscopy and reactivity properties of melamine (L) and its metal complexes ML2(OH)2 (M=Ca, Mg, Fe, Cu, Zn, Ni) were systematically investigated in this work.We found that ML2(OH)2 complexes were structurally and spectroscopically different fromtheir precursors (L) and more reactive in electrophilic and nucleophilic reactions. A few quantitative linear relationships were discovered between bonding interactions, charge distributions, and DFT chemical reactivity indices with R2=0.889-0.997, respectively. Results from frontier molecular orbital and electrostatic potential analyses show that ML2(OH)2 systems fromtransition metal cations such as FeL2(OH)2, CuL2(OH)2 and NiL2(OH)2 tend to be more covalently bound and they possess larger molecular twists and more electrophilic regions on the molecular contour surface. These results are believed to be implicative in our better understanding of the melamine stone production mechanism in the human body.