美国北卡罗来纳大学格林斯伯勒分校Yirong Mo团队报道了关于类电荷封闭壳层离子间π-π堆积的亚稳态。相关研究成果发表在2023年12月28日出版的国际学术期刊《结构化学》。

平面型阳离子或阴离子可以在晶体或溶液中形成堆叠，如先前的研究所示，周围或环境在其中起着决定性作用。然而，如果去除环境的约束，这些违反直觉的相互作用是否具有任何固有的稳定性或是完全排斥的，目前尚不清楚。

该文中，研究人员用实验研究探索了类电荷封闭壳层离子之间π-π堆积的固有稳定性。固有的亚稳态通过特征局部极小值和阻止其离解的过渡态来确定，并通过从头算分子动力学（AIMD）模拟进行验证。基于块局域波函数方法（BLW-ED）的能量分解方法解释了所涉及的相互作用的本质。

与传统的中性π-π堆叠相互作用一样，电子关联是最具吸引力的能量成分。但它被所有二聚化模式的净电荷之间的库仑排斥所推翻，导致阳离子或阴离子之间的整体排斥相互作用。在降低密度梯度分析中也观察到范德华相互作用的贡献。通过考察单个物理因素对井深的贡献，阐明了亚稳态的起源。固有的亚稳态源于电子相关性，由于离子之间从过渡态到相应的最小值的重叠增强，电子相关性显著增加。

附：英文原文

Title: On the metastability of π-π stacking between closed-shell ions of like charges

Author: Jiayao Li, Xinru Peng, Shiwei Yin, Changwei Wang, Yirong Mo

Issue&Volume: 2023-12-28

Abstract: Planar cations or anions can form stacks in crystals or solutions, where the surrounding or environment plays a decisive role as demonstrated in previous studies. However, it remains unclear whether these counterintuitive interactions possess any inherent stability or are thoroughly repulsive if the constraint of environment is removed. In this work, we explored the inherent stability of π-π stacking between closed-shell ions of like charges with prototypes derived from experimental studies. The inherent metastability was identified by the characteristic local minima and the transition states preventing their dissociation and verified by ab initio molecular dynamics (AIMD) simulations. The nature of involved interactions was deciphered with the energy decomposition approach based on the block-localized wavefunction method (BLW-ED). Like the conventional neutral π-π stacking interactions, electron correlation is the most attractive energy component. But it is overturned by the Coulombic repulsion between net charges for all modes of dimerization, resulting in the overall repulsive inter-cation or anion interactions. Contributions from van der Waals interactions were also observed in the reduced density gradient analysis. The origin of the metastability was elucidated by examining the contributions of individual physical factors to the well-depths. The inherent metastability originates from the electron correlation, which dramatically increases due to the enhanced overlap between ions from a transition state to its corresponding minimum.

DOI: 10.1016/j.cjsc.2023.100213

Source: http://cjsc.ac.cn/cms/issues/551