为什么乙E2H2 (E=Si-Pb) 的重原子类型表现出不寻常的结构?
Matthias Lein1, Andreas Krapp, Gernot Frenking
1Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany.
Journal of the American Chemical Society
|April 28, 2005
概括
更重的14组化物E(2) H(2) (E = Si-Pb) 由于与碳相比,电子相互作用的差异,采用了不寻常的非平面几何形状. 这些结构通过特定的轨道贡献和静电相互作用来稳定.
科学领域:
- 计算化学计算化学
- 量子化学 是一个量子化学.
- 无机化学 无机化学
背景情况:
- 14组化物E(2) H(2) 的电子结构和结合对于理解它们的化学性质至关重要.
- 碳 (C) 基C(2) H(2) 与其更重的同类 (Si,Ge,Sn,Pb) 相比,具有不同的结合特性.
研究的目的:
- 用理论计算阐明在较重的14组化物 (E = Si-Pb) 中观察到的不寻常的平衡几何形状.
- 解释控制不同异构体E(2) H(2) 的稳定性的电子因子.
主要方法:
- 密度函数理论 (DFT) 的计算使用BP86/QZ4P理论水平进行.
- 对潜在能量表面 (PES) 的分析,以确定稳定和不稳定的异构体.
- 使用能量分解分析 (EDA) 来量化债券贡献.
主要成果:
- 发现更重的E(2) H(2) (E = Si-Pb) 的全球能量最小值是非平面的双桥结构 (A).
- 其他研究的异构体包括单桥平面 (B),维尼利丁类型 (C) 和跨曲 (D1) 结构.
- 不寻常的几何形状来自于EH部分在 (X(2) Pi) 基态中的有利相互作用,与C(2) H(2) 相反,它涉及a(4) 符号(-) 兴奋状态.
结论:
- 较重的EH碎片的较高激发能 (X(2) Pi --> a(4) Sigma(-)) 在基本状态下有利于结合,从而导致非平面结构.
- 稳定轨道贡献,包括西格玛键,E-H供体-接受体键和单对供体-接受体键,决定了异构体的相对稳定性.
- 准经典的静电相互作用也在整体结合中发挥着重要作用.
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