甲基和相关组之间的吸引与排斥: (CH3NHCH3) 2和 (CH3SeBr2CH3) 2
Mariusz Michalczyk1, Steve Scheiner2, Wiktor Zierkiewicz1
1Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370, Wrocław, Poland.
概括
甲基组可以形成弱吸引力相互作用,称为四键,即使存在排斥力. 计算化学揭示了加强这些C-C键的因素,为分子相互作用提供了洞察力.
科学领域:
- 计算化学的计算化学
- 量子化学 是一个量子化学.
- 超分子化学 超分子化学
背景情况:
- 研究了在同质体中具有甲基组相互作用的晶体结构.
- 利用了分子中的原子量子理论 (QTAIM),非共价相互作用 (NCI) 和自然键轨道 (NBO) 分析.
- 观察到建议的有吸引力的相互作用和计算的负面相互作用能量之间的差异.
研究的目的:
- 通过密度函数理论 (DFT) 计算,检查甲基组相互相互作用的能力.
- 为了探索同位体中C⋅⋅⋅C四键的性质和强度.
- 确定影响介甲基键强化的因素.
主要方法:
- 在一系列 (CH3PnHCH3) 2同极体上进行了DFT计算,改变了Pn原子 (N,P,As,Sb).
- 分析了C⋅⋅⋅C四结的物种的相互作用能量.
- 研究了取电子和电子捐赠替代剂对键强度的影响.
主要成果:
- 对于C⋅⋅⋅C四键的计算相互作用能量最初很低 (<1kcal/mol).
- 当碳原子被更重的四元素所取代时,相互作用能量显著增加 (高达~3kcal/mol).
- 不对称的替代 (捐赠者-接受者) 强化了C⋅⋅⋅C的甲基间键.
- 观测到吸引力,尽管 σ-洞之间的coulombic排斥.
结论:
- 甲基可以参与四结合,虽然通常很弱.
- 较重的四原子和不对称的替代增强了C⋅⋅⋅C的键强度.
- 应谨慎解释QTAIM,NCI和NBO分析,因为它们可能表明只存在排斥潜力的联系.
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