Intramolecularly Hydrogen-Bonded Aromatic Pentamers as Modularly Tunable Macrocyclic Receptors for Selective Recognition of Metal Ions

Despite the tremendous progress that has been made in macrocyclic chemistry since the discovery of corands, cryptands, and spherands more than four decades ago, macrocyclic systems possessing a high level of controllability in structural configuration concurrent with a systematic tunability in function are still very rare. Employing an inner design strategy to orient H-bonding forces toward a macrocyclic cavity interior while convergently aligning exchangeable ion-binding building blocks that dictate a near-identical backbone curvature, we demonstrate here a novel pentagonal framework that not only enables its variable interior cavity to be maintained at near-planarity but also allows its ion-binding potential to be highly tunable. The H-bonded macrocyclic pentamers thus produced have allowed a systematic and combinatorial evolution of ion-selective pentamers for preferential recognition of Cs+, K+, or Ag+ ions.尽管四十余年前冠醚（corands）、穴状配体（cryptands）与球穴配体（spherands）被发现以来，大环化学（macrocyclic chemistry）已取得长足进展，但兼具高度可控的结构构型与系统可调的功能特性的大环体系依然极为罕见。本研究采用内部设计策略，将氢键作用力（H-bonding forces）定向至大环空腔（macrocyclic cavity）内部，同时以收敛方式排布可交换的离子结合结构单元（ion-binding building blocks），这些单元可赋予骨架近乎一致的主链曲率；本文报道了一种新型五边形骨架（pentagonal framework），其不仅可使可变的内部空腔保持近乎平面的构型，还能实现离子结合潜能（ion-binding potential）的高度可调。由此制备得到的氢键合大环五聚体，可实现离子选择性五聚体（ion-selective pentamers）的系统组合演化，从而实现对Cs+、K+或Ag+离子的优先识别。