Electrostatics does not dictate the slip-stacked arrangement of aromatic π–π interactions,Chemical Science

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Electrostatics does not dictate the slip-stacked arrangement of aromatic π–π interactions
Chemical Science ( IF 7.6 ) Pub Date : 2020-06-05 , DOI: 10.1039/d0sc02667k
Kevin Carter-Fenk _{1,

2,

3,

4} , John M. Herbert _{1,

2,

3,

4}

Affiliation

Benzene dimer has long been an archetype for π-stacking. According to the Hunter–Sanders model, quadrupolar electrostatics favors an edge-to-face CH⋯π geometry but competes with London dispersion that favors cofacial π-stacking, with a compromise “slip-stacked” structure emerging as the minimum-energy geometry. This model is based on classical electrostatics, however, and neglects charge penetration. A fully quantum-mechanical analysis, presented here, demonstrates that electrostatics actually exerts very little influence on the conformational landscape of (C₆H₆)₂. Electrostatics also cannot explain the slip-stacked arrangement of C₆H₆⋯C₆F₆, where the sign of the quadrupolar interaction is reversed. Instead, the slip-stacked geometry emerges in both systems due to competition between dispersion and Pauli repulsion, with electrostatics as an ambivalent spectator. This revised interpretation helps to rationalize the persistence of offset π-stacking in larger polycyclic aromatic hydrocarbons and across the highly varied electrostatic environments that characterize π–π interactions in proteins.

中文翻译：

静电不会决定芳族π-π相互作用的滑动堆积排列

苯二聚体一直是π堆积的原型。根据Hunter-Sanders模型，四极静电学倾向于边对面的CH⋯π几何形状，但是与伦敦分散相竞争，后者有利于界面π堆叠，而折衷的“滑移堆叠”结构则成为最小能量几何。但是，该模型基于经典静电学，忽略了电荷渗透。此处提供的完全量子力学分析表明，静电实际上对（C ₆ H ₆）₂的构象态几乎没有影响。静电学也无法解释C ₆ H ₆ ⋯C ₆ F _6的粉滑堆积排列，其中四极相互作用的符号相反。取而代之的是，由于色散和保利斥力之间的竞争，在两个系统中都出现了滑动堆叠的几何形状，其中静电是矛盾的旁观者。修改后的解释有助于合理化较大的多环芳烃中以及在表征蛋白质中π-π相互作用的高度变化的静电环境中存在的偏移π堆积的持久性。

更新日期：2020-07-08

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