Gil Diego M, Echeverría Jorge, Alvarez Santiago
Departament de Química Inorgànica i Orgànica and Institut de Química Teòrica i Computacional IQTC-UB, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Inorg Chem. 2022 Jun 20;61(24):9082-9095. doi: 10.1021/acs.inorgchem.2c00600. Epub 2022 Jun 6.
The degree of interpenetration of the van der Waals crusts of two atoms, represented by a penetration index, is defined to better quantify the meaning of the nonbonding contact distances between two atoms, which should allow us to compare different atom pairs on the same footing. The structural trends of the intermolecular contacts between the tetramethylammonium cation (TMA) and halogen atoms are reviewed, and a computational study of model X···TMA ion pairs (X = F, Cl, Br, I, Au) is presented. The results disclose two energy minima, in each of which the anion simultaneously interacts with three hydrogen atoms. The bonding mechanisms in the two cases are discussed based on the results of the tools of the trade that provide a consistent picture in which a distribution of charges significantly varies not only around each different atom but is also strongly dependent on the distance to the central N atom. This behavior, together with some non-negligible covalent character of the interionic interaction, is not predicted from a single-molecular electrostatic potential map of the TMA cation.
用穿透指数表示的两个原子范德华壳层的相互穿透程度，其定义是为了更好地量化两个原子间非键接触距离的意义，这应使我们能够在相同基础上比较不同的原子对。本文综述了四甲基铵阳离子（TMA）与卤素原子间分子间接触的结构趋势，并给出了X···TMA离子对模型（X = F、Cl、Br、I、Au）的计算研究。结果揭示了两个能量最小值，在每个最小值中阴离子同时与三个氢原子相互作用。基于常用工具的结果讨论了两种情况下的键合机制，这些结果提供了一个一致的图景，其中电荷分布不仅在每个不同原子周围有显著变化，而且还强烈依赖于到中心N原子的距离。这种行为，连同离子间相互作用的一些不可忽略的共价性质，无法从TMA阳离子的单分子静电势图预测出来。
