圆柱状有机超分子胶囊的侧壁功能化及其应用研究

Supramolecular capsule, which possesses an isolated cavity analogous to enzyme's binding pocket, can accelerate or even catalyze some organic reactions and stabilize reactive intermediates. It has been widely applied to the study of physical organic chemistry. However, most of capsular structures known to date are highly symmetric and short of functional groups in their inner cavity, which greatly limit their application scope. Thus, modification of the walls and functionalization of the cavity of supramolecular capsules may be the only way to expand their applications. Nevertheless, this will inevitably results in longer synthetic route and greater number of possible assembly isomers, remaining one of obstacles in the development of this field. In this project, we would like to modify the walls and cavity of a cylindrical hydrogen-bonded supramolecular capsule based on urea binding motif. The high thermal stability of this capsule will make it a good platform for us to explore the general strategy on modifying supramolecular capsule's walls and cavity. Various strategies, such as template effect, steric repulsion and self-sorting, will be harnessed to control the isomerism of supramolecular capsule. On the basis of the resulting modifiable capsule, we will further tailor the capsule's cavity according to need through introducing functional groups on the walls, to construct molecular devices and molecular flasks. According to the isolation and stabilization properties of the functionalized supramolecular capsule, we may be able to monitor the reactive intermediates of some organic reactions with the routine analytic tools, such as NMR, and unravel the underlying reaction mechamism.We believe the research results of this project will lay a solid foundation for expanding the application of supramolecular capsules.

超分子胶囊具有类似于酶的空腔结构，能够加速或催化有机反应、稳定反应中间体，被广泛应用于物理有机化学研究。目前的胶囊结构通常高度对称，空腔缺少功能基团，大大地限制了其应用范围。因此，胶囊的侧壁修饰与空腔功能化是扩展其应用的必由之路。然而这又将导致合成路线的加长和组装异构体数目的增加，成为该研究领域的难点。本项目拟以脲基圆柱状超分子胶囊为基础，对其侧壁和空腔进行修饰。我们拟利用该胶囊的稳定特性，总结修饰超分子胶囊侧壁和空腔的通用策略。采用模版效应、空间位阻和自分类等策略，来控制超分子胶囊的异构化。在此可修饰超分子胶囊的基础上，通过侧壁将功能基团引入到胶囊空腔内，实现对胶囊空腔的按需剪裁，制备分子器件和分子反应容器。我们拟进一步利用超分子胶囊的隔离效应和稳定作用，使用NMR等常规分析手段监测部分有机化学反应中间体，揭示相应的反应机理。我们相信本项目的研究将为扩展超分子胶囊的应用奠定坚实的基础。

酶的活性键合位点通常具有空腔，并且通常在其空腔内有功能性基团。空腔与功能性基团的协同作用使得酶能够高选择性、高效地执行催化反应。而人工受体的空腔内通常缺少功能性位点。在本项目申请书中，我们拟采用单侧壁修饰的穴状配体，来构建具有内功能性基团的分子胶囊。由于合成、分离以及结构的复杂性等不可控因素，我们并没有获得内修饰的分子胶囊。然而，我们利用萘基分子管实现了将空腔与功能性基团结合起来的目标。我们先后合成了空腔内具有脲、硫脲、酰胺等基团的内修饰分子管。研究发现含有脲或硫脲的分子管在非极性溶剂（氯仿）中对中性分子具有很强的键合能力，最大键合常数可达1000000 M-1。而水溶性酰胺基内修饰分子管甚至可以在水中利用氢键键合高度亲水的中性分子，最大键合常数可达10000 M-1，可用于地下水中的持久性污染物——1,4-二氧六环的荧光检测。在水中利用氢键进行分子识别是超分子化学界公认的难题！内修饰分子管为这一难题提供了一个解决思路。我们相信在设计人工受体时，空腔与功能性基团结合起来的思路将开辟新的超分子化学研究方向。