Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, Zacatenco, Mexico City, 07360, Mexico.
Chemistry. 2019 Nov 7;25(62):14042-14047. doi: 10.1002/chem.201902735. Epub 2019 Oct 18.
The use of the electrostatic stoppers concept in the field of mechanically interlocked molecules is reported; these stoppers are chemically sensitive end groups on a linear guest molecule that allows for the conversion of a pseudo-rotaxane species into a rotaxane complex by a change in the medium acidity. The chemical stimulus causes the appearance of negative charges on both ends of the linear component, passing from cationic to anionic, and causing a significant ring-to-axle electrostatic repulsion. This phenomenon has two different and simultaneous effects: 1) destabilizes the complex as a consequence of confining an anionic ring into an anionic axle, and 2) increases the dissociation energy barrier, thus impeding ring extrusion. This newly formed metastable rotaxane species is resistant to solvent and temperature effects and performs as a two-state degenerated molecular shuttle in solution.
报告了静电塞在机械互锁分子领域的应用；这些塞是线性客体分子上的化学敏感端基，允许通过改变介质酸度将假轮烷物种转化为轮烷配合物。化学刺激导致线性组分两端出现负电荷，从阳离子变为阴离子，并导致环对轴的静电排斥显著增加。这种现象有两个不同且同时的效果：1）由于将阴离子环约束在阴离子轴内，使配合物不稳定，2）增加离解能垒，从而阻碍环的挤出。这种新形成的亚稳态轮烷物种对溶剂和温度效应具有抗性，并在溶液中作为两态简并分子梭发挥作用。
