Supramolecular assemblies and polymer recognition based on polygonal and pillar-shaped macrocycles "pillar[n]arenes"

Macrocyclic compounds show highly symmetric structures, making them useful building blocks for the creation of various supramolecular assemblies. The properties of such supramolecular assemblies result from their shape, functionality, and structure. In 2008, we reported a new type of polygonal-shaped macrocycle termed "pillar[n]arenes". In this Focus Review, based on their polygonal structures, versatile functionality, and host-guest behavior, I present various pillar[n]arene-based supramolecular assemblies that have been investigated over the last 10 years in our group. Based on the versatile functionalization of pillar[n]arenes, continuous and length-controllable discrete one-dimensional channels, two-dimensional sheets, and three-dimensional vesicles have been produced. Bulk-state complexations using liquid and crystalline pillar[n]arenes are also discussed. The functionalization of pillar[n]arenes is also useful for creating functionalized crystals, and such crystals have shown guest-responsive changes in color, state, and water contact angle, as well as serving as reaction media for the spontaneous polymerization of cyclic monomers.