Alonso Mercedes, Woller Tatiana, Martín-Martínez Francisco J, Contreras-García Julia, Geerlings Paul, De Proft Frank
ALGC Research Group General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2 1050 Brussels (Belgium), Fax: (+32) 2-629-33-17.
Chemistry. 2014 Apr 22;20(17):4931-41. doi: 10.1002/chem.201400107. Epub 2014 Apr 1.
Noncovalent interactions involving aromatic rings, such as π-stacking and CH/π interactions, are central to many areas of modern chemistry. However, recent studies proved that aromaticity is not required for stacking interactions, since similar interaction energies were computed for several aromatic and aliphatic dimers. Herein, the nature and origin of π/π, σ/σ, and σ/π dispersion interactions has been investigated by using dispersion-corrected density functional theory, energy decomposition analysis, and the recently developed noncovalent interaction (NCI) method. Our analysis shows that π/π and σ/σ stacking interactions are equally important for the benzene and cyclohexane dimers, explaining why both compounds have similar boiling points. Also, similar dispersion forces are found in the benzene⋅⋅⋅methane and cyclohexane⋅⋅⋅methane complexes. However, for systems larger than naphthalene, there are enhanced stacking interactions in the aromatic dimers adopting a parallel-displaced configuration compared to the analogous saturated systems. Although dispersion plays a decisive role in stabilizing all the complexes, the origin of the π/π, σ/σ, and σ/π interactions is different. The NCI method reveals that the dispersion interactions between the hydrogen atoms are responsible for the surprisingly strong aliphatic interactions. Moreover, whereas σ/σ and σ/π interactions are local, the π/π stacking are inherently delocalized, which give rise to a non-additive effect. These new types of dispersion interactions between saturated groups can be exploited in the rational design of novel carbon materials.
涉及芳环的非共价相互作用，如π-堆积和CH/π相互作用，是现代化学许多领域的核心。然而，最近的研究证明堆积相互作用并不需要芳香性，因为对几种芳香族和脂肪族二聚体计算出了相似的相互作用能。在此，通过使用色散校正密度泛函理论、能量分解分析和最近开发的非共价相互作用（NCI）方法，研究了π/π、σ/σ和σ/π色散相互作用的本质和起源。我们的分析表明，π/π和σ/σ堆积相互作用对苯和环己烷二聚体同样重要，这解释了为什么这两种化合物具有相似的沸点。此外，在苯···甲烷和环己烷···甲烷络合物中也发现了类似的色散力。然而，对于大于萘的体系，与类似的饱和体系相比，采用平行错位构型的芳香族二聚体中存在增强的堆积相互作用。尽管色散在稳定所有络合物中起决定性作用，但π/π、σ/σ和σ/π相互作用的起源是不同的。NCI方法表明，氢原子之间的色散相互作用是脂肪族相互作用出奇强的原因。此外，虽然σ/σ和σ/π相互作用是局部的，但π/π堆积本质上是离域的，这会产生非加和效应。饱和基团之间的这些新型色散相互作用可用于新型碳材料的合理设计。
