Roos Goedele, Murray Jane S
Univ. Lille, CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F-59000 Lille, France.
Department of Chemistry, University of New Orleans, New Orleans, LA 70148, USA.
Phys Chem Chem Phys. 2024 Feb 28;26(9):7592-7601. doi: 10.1039/d3cp06005e.
We focus on intramolecular interactions, using the electrostatic potential plotted on iso-density surfaces to lead the way. We show that plotting the electrostatic potential on varying iso-density envelopes much closer to the nuclei than the commonly used 0.001 a.u. contour can reveal the driving forces for such interactions, whether they be stabilizing or destabilizing. Our approach involves optimizing the structures of molecules exhibiting intramolecular interactions and then finding the contour of the electronic density which allows the interacting atoms to be separated; we call this the nearly-touching contour. The electrostatic potential allows then to identify the intramolecular interactions as either attractive or repulsive. The discussed 1,5- and 1,6-intramolecular interactions in -bromophenol and -nitrophenol are attractive, while the interactions between terminal methyl hydrogens in diethyl disulfides (as shown recently) and those between the closest hydrogens in planar biphenyl and phenanthrene are clearly repulsive in nature. For the attractive 1,4-interactions in trinitromethane and chlorotrinitromethane, and the 1,3-S⋯N and the 1,4-Si⋯N interactions in the ClHSi(CH)NH series, the lack of (3,-1) bond critical points has often been cited as reason to not identify such interactions as attractive in nature. Here, by looking at the nearly-touching contours we see that bond critical points are neither necessary nor sufficient for attractive interactions, as others have pointed out, and in some instances also pointing to repulsive interactions, as the examples of planar biphenyl and phenanthrene discussed in this work show.
我们聚焦于分子内相互作用,利用绘制在等密度表面上的静电势来引领研究方向。我们表明,在比常用的0.001原子单位等值线更靠近原子核的不同等密度包络上绘制静电势,能够揭示此类相互作用的驱动力,无论它们是稳定的还是不稳定的。我们的方法包括优化表现出分子内相互作用的分子结构,然后找到能使相互作用原子分离的电子密度等值线;我们将其称为近接触等值线。静电势随后能将分子内相互作用识别为吸引性的或排斥性的。在对溴苯酚和对硝基苯酚中所讨论的1,5 - 和1,6 - 分子内相互作用是吸引性的,而二乙二硫醚中末端甲基氢之间的相互作用(如最近所显示的)以及平面联苯和菲中最接近的氢之间的相互作用在本质上显然是排斥性的。对于三硝基甲烷和氯代三硝基甲烷中的吸引性1,4 - 相互作用,以及ClHSi(CH)NH系列中的1,3 - S⋯N和1,4 - Si⋯N相互作用,常常有人以缺乏(3, -1)键临界点为由,认为不应将此类相互作用认定为本质上具有吸引力。在此,通过观察近接触等值线,我们发现正如其他人所指出的,键临界点对于吸引性相互作用既非必要条件也非充分条件,并且在某些情况下还指向排斥性相互作用,正如本文所讨论的平面联苯和菲的例子所示。