Pillar[6]arenes: From preparation, host-guest property to self-assembly and applications

Pillar[n]arenes primarily comprise pillar[5]arenes and pillar[6]arenes, which belong to the new class of supramolecular macrocyclic hosts. Pillar[n]arenes have aroused wide attention because of their highly rigid and symmetrical architectures, controllable cavity size, and wide applications in a wide variety of areas. Although pillar[6]arene is difficult to synthesize, numerous studies have been conducted on it. In this review, the strategies to synthesize and functionalize pillar[6]arenes are investigated systematically. In addition, their host-guest properties in organic solvents and in aqueous solution are described. Moreover, pillar[6]arenes applied in different fields (e.g., molecular recognition, drug release, cancer therapy, and gas separation) are clarified. Hopefully, this study is capable of arousing more attention from increasing scientists to study large-cavity pillar[n]arenes.