Center for Supramolecular Chemistry & Catalysis and Department of Chemistry, College of Science, Shanghai University, 99 Shang-Da Road, Shanghai 200444, China.
Institute of Chemical Research of Catalonia (ICIQ), Avenida Països Catalans 16, 43007 Tarragona, Spain.
J Am Chem Soc. 2021 Aug 11;143(31):12397-12403. doi: 10.1021/jacs.1c06510. Epub 2021 Jul 30.
The cation-π interaction and the hydrophobic effect are important intermolecular forces in chemistry and play major roles in controlling recognition in biological systems. We compared their relative contributions to the binding of molecular "dumbbell" guests in synthetic container hosts in water. The guests offered direct, intramolecular competition between trimethylammonium groups, -N(CH), and -butyl groups, -C(CH), for the internal surfaces (aromatic panels) of the containers. In contrast with previous studies, the container molecules consistently preferred binding to the uncharged -butyl groups, regardless of the presence of anionic, cationic, or zwitterionic groups on the container peripheries. This preference is determined by solvation of the polar trimethylammonium group in water, which outcompetes the attraction between the positive charge and the π-surfaces in the container. The synthetic container complexes provide a direct measure of the relative strengths of cation-π interactions and desolvation in water. Interactions with the uncharged -butyl group are more than 12 kJ mol more favorable than the cation-π interactions with the trimethylammonium group in these cavitand complexes.
阳离子-π 相互作用和疏水作用是化学中重要的分子间作用力，在控制生物系统中的识别中起着重要作用。我们比较了它们在水相合成容器主体中对分子“哑铃”客体结合的相对贡献。客体提供了直接的、分子内竞争，即三甲铵基团 -N(CH₃)₃和 - 丁基基团 -C(CH₃)₃，用于容器的内部表面（芳香面板）。与以前的研究不同，无论容器外围是否存在阴离子、阳离子或两性离子基团，容器分子都一致优先与不带电的 - 丁基基团结合。这种偏好是由极性三甲铵基团在水中的溶剂化决定的，它与容器中正电荷和π 表面之间的吸引力相竞争。这些合成容器配合物提供了直接测量阳离子-π 相互作用和在水中去溶剂化的相对强度的方法。与不带电的 - 丁基基团的相互作用比在这些穴状配体配合物中与三甲铵基团的阳离子-π 相互作用有利超过 12 kJ mol。
