Patyal Ameevardhan Singh, Howe Joshua D
Department of Chemical Engineering, Texas Tech University, P.O. Box 43121, Lubbock, TX - 79409-3121, United States.
J Phys Chem C Nanomater Interfaces. 2025 Jan 30;129(4):2090-2101. doi: 10.1021/acs.jpcc.4c05974. Epub 2025 Jan 15.
Pillar[n]arenes have garnered popularity due to their unique pillar-shaped structure, which results in hydrophobic cavities. These cavities facilitate the formation of inclusion complexes with guest molecules through non-covalent interactions such as π - π stacking, hydrogen bonding, and van der Waals interactions. Such host-guest interactions enable diverse functionalities in pillar[n]arenes, including molecule recognition, self-assembly, and encapsulation. Nevertheless, it is important to note that the host-guest properties of pillar[n]arenes can be influenced by conformational changes, primarily driven by the rotation of hydroquinone units about their methylene bridge axis. These structural changes can lead to variations in underlying non-covalent and steric interactions, impacting the overall stability of the host-guest system and potentially leading to selective uptake of guest molecules. Additionally, due to relative energy differences, we expect a distribution of pillar[n]arene conformations at thermal equilibrium. In this work, we employ density functional theory (DFT) to evaluate ground state electronic structures of pillar[n]arene conformations across pillar[n]arenes of various sizes and functionalizations. We have aimed to explore the impact of dispersion interactions, hydrogen bonding, and steric interactions on the overall energetics of pillar[n]arene conformations and determine the dominant conformation at 298 K using a Boltzmann-weighted distribution. The relative strengths of hydrogen bonds across various pillar[n]arene conformations have been examined using Bader's QTAIM topological analysis. Furthermore, we have also assessed the solvation of pillar[n]arenes in water using an implicit solvent model that unveils quantitative distinctions in hydrogen bonding and relative dispersion contributions among various pillar[n]arene conformations. Finally, pillar[n]arene conformations with more complex functional groups such as primary amine, alkyl bromide and carboxylic acid, have been studied to evaluate the interplay between underlying interactions such as hydrogen bonding, dispersion, and steric interactions, and their collective impact on the structure and energetics of pillar[n]arene conformations.
柱[n]芳烃因其独特的柱状结构而受到关注，该结构会形成疏水腔。这些空腔通过π - π堆积、氢键和范德华相互作用等非共价相互作用促进与客体分子形成包合物。这种主客体相互作用使柱[n]芳烃具有多种功能，包括分子识别、自组装和包封。然而，需要注意的是，柱[n]芳烃的主客体性质会受到构象变化的影响，主要是由对苯二酚单元围绕其亚甲基桥轴的旋转驱动的。这些结构变化会导致潜在的非共价和空间相互作用发生变化，影响主客体系统的整体稳定性，并可能导致客体分子的选择性摄取。此外，由于相对能量差异，我们预计在热平衡时柱[n]芳烃构象会有分布。在这项工作中，我们采用密度泛函理论（DFT）来评估各种尺寸和功能化的柱[n]芳烃构象的基态电子结构。我们旨在探索色散相互作用、氢键和空间相互作用对柱[n]芳烃构象整体能量学的影响，并使用玻尔兹曼加权分布确定298 K时的主要构象。使用巴德的QTAIM拓扑分析研究了各种柱[n]芳烃构象中氢键的相对强度。此外，我们还使用隐式溶剂模型评估了柱[n]芳烃在水中的溶剂化作用，该模型揭示了各种柱[n]芳烃构象之间氢键和相对色散贡献的定量差异。最后，研究了具有更复杂官能团（如伯胺、烷基溴和羧酸）的柱[n]芳烃构象，以评估氢键、色散和空间相互作用等潜在相互作用之间的相互作用，以及它们对柱[n]芳烃构象的结构和能量学的综合影响。
