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.