Host-guest behavior of pillar[n]arene-based supramolecular assemblies

Pillar[n]arenes usually form 1:1 host-guest complexes with guest molecules. However, unique host-guest properties appear by the formation of new struc-tures, such as tubular dimers, nanotubes, boxes, and end-capped cavitands. In addition, crystalline pillar[5]arenes show unique host-guest properties, such as gate opening, encapsulation of a guest molecule by two pillar[5]arene wheels, and quantitative uptake of alkane guest molecules. Therefore, cooperative bind-ing of guest molecules to pillar[n]arene assemblies is the key to achieve unique host-guest behavior. Pillar[n]arenes show planar chirality owing to their shape, and thus coupling between the planar chirality and host-guest property enables planar chiral inversion, memory, and erasure. In this review, we discuss the diversity, functionality, and supramolecular chirality of host-guest pillar[n]arene assemblies.