Pillar- and pillararene-based supramolecular assemblies built by using their cavity-size-dependent host–guest interactions
Pillar[n]arenes, which we first synthesized and named in 2008, are new pillar-shaped macrocyclic hosts. Pillar[n]arene homologues with n = 5–10 have already been synthesized, but the cyclic pentamers, i.e., pillararenes, and cyclic hexamers, i.e., pillararenes, have been most widely used because these can be obtained in good yields. To date, nearly all pillar[n]arene-based supramolecular assemblies have been constructed using pillar- and pillararene scaffolds. In this feature article, we describe supramolecular assemblies built using host–guest interactions depending on the cavity sizes of pillar- and pillararenes. We first discuss the effects of the type of substituents on the rims of pillar- and pillararenes on their solubilities, functionalities and host–guest properties. We then discuss supramolecular assemblies based on their host–guest properties and pillar-shaped architectures.