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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Understanding of assembly phenomena by aromatic-aromatic interactions: Benzene dimer and the substituted systems
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Understanding of assembly phenomena by aromatic-aromatic interactions: Benzene dimer and the substituted systems

机译：通过芳香-芳香相互作用了解组装现象：苯二聚体和取代的体系

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Interactions involving aromatic rings are important in molecular/biomolecular assembly and engineering. As a consequence, there have been a number of investigations on dimers involving benzene or other substituted pi systems. In this Feature Article, we examine the relevance of the magnitudes of their attractive and repulsive interaction energy components in governing the geometries of several pi-pi systems. The geometries and the associated binding energies were evaluated at the complete basis set (CBS) limit of coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] using a least biased scheme for the given data set. The results for the benzene dimer indicate that the floppy T-shaped structure (center-to-center distance: 4.96 angstrom, with an axial benzene off-centered above the facial benzene) is isoenergetic in zero-point-energy (ZPE) corrected binding energy (D-0) to the displaced-stacked structure (vertical interplanar distance: 3.54 angstrom). However, the T-shaped structure is likely to be slightly more stable (D-0 approximate to 2.4-2.5 kcal/mol) if quadruple excitations are included in the coupled cluster calculations. The presence of substituents on the aromatic ring, irrespective of their electron withdrawing or donating nature, leads to an increase in the binding energy, and the displaced-stacked conformations are more stabilized than the T-shaped conformers. This explains the wide prevalence of displaced stacked structures in organic crystals. Despite that the dispersion energy is dominating, the substituent as well as the conformational effects are correlated to the electrostatic interaction. This electrostatic origin implies that the substituent effect would be reduced in polar solution, but important in apolar media, in particular, for assembling processes.
机译：涉及芳环的相互作用在分子/生物分子组装和工程中很重要。结果，已经对涉及苯或其他取代的pi系统的二聚体进行了许多研究。在这篇专题文章中，我们研究了它们吸引和排斥的相互作用能分量的大小与控制几个pi-pi系统的几何形状的相关性。使用给定的数据集的最小偏差方案，在单，双和扰动三重激发[CCSD（T）]的耦合簇理论的完整基集（CBS）极限下，评估了几何形状和相关的结合能。苯二聚体的结果表明，松散的T形结构（中心距：4.96埃，轴向苯偏心于面部苯上方）在零点能量（ZPE）校正的结合中是等能量的能量（D-0）到位移堆叠结构（垂直平面间距：3.54埃）。但是，如果在耦合簇计算中包括四重激发，则T形结构可能会稍微更稳定（D-0大约为2.4-2.5 kcal / mol）。芳环上取代基的存在，无论其吸电子或供电子的性质如何，都会导致结合能的增加，并且与T形构象体相比，取代堆叠构象更稳定。这解释了有机晶体中置换堆叠结构的广泛流行。尽管分散能占主导，但是取代基以及构象效应与静电相互作用相关。这种静电起因意味着在极性溶液中取代基的作用会降低，但在非极性介质中尤其重要，特别是对于组装过程。

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