Keshtkar Noushin, Loveday Oliver, Polo Víctor, Echeverría Jorge
Departamento de Química Física, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
Departament de Química Inorgànica i Orgànica and IQTC-UB, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Cryst Growth Des. 2023 Jun 22;23(7):5112-5116. doi: 10.1021/acs.cgd.3c00347. eCollection 2023 Jul 5.
Methyl groups bound to electronegative atoms, such as N or O, are recognized to participate in tetrel bonding as Lewis acids. On the other hand, the capability of methyl groups bound to electropositive atoms, such as B or Al, to act as Lewis bases has been recently reported. Herein, we analyze the combination of these two behaviors to establish attractive methyl···methyl interactions. We have explored the Cambridge Structural Database to find experimental examples of these dimethyl-bound systems, finding a significant degree of directionality in the relative disposition of the two methyl groups. Moreover, we have carried out a comprehensive computational analysis at the DFT level of the dimethyl interactions, including the natural bond orbital, energy decomposition analysis, and topological analysis of the electron density (QTAIM and NCI). The dimethyl interaction is characterized as weak yet attractive and based on electrostatics, with a non-negligible contribution from orbital charge transfer and polarization.
与电负性原子（如N或O）相连的甲基被认为作为路易斯酸参与四元键合。另一方面，最近有报道称与电正性原子（如B或Al）相连的甲基有作为路易斯碱的能力。在此，我们分析这两种行为的结合以建立有吸引力的甲基···甲基相互作用。我们在剑桥晶体结构数据库中进行了探索，以找到这些二甲基结合体系的实验实例，发现两个甲基的相对排布具有显著的方向性。此外，我们在密度泛函理论（DFT）水平上对二甲基相互作用进行了全面的计算分析，包括自然键轨道、能量分解分析以及电子密度的拓扑分析（QTAIM和NCI）。二甲基相互作用的特点是较弱但具有吸引力，且基于静电作用，轨道电荷转移和极化也有不可忽视的贡献。
