Noncovalently bound and mechanically interlocked systems using pillar[ n ]arenes.

Pillar[ n ]arenes are pillar-shaped macrocyclic compounds owing to the methylene bridges linking the para-positions of the units. Owing to their unique pillar-shaped structures, these compounds exhibit various excellent properties compared with other cyclic host molecules, such as versatile functionality using various organic synthesis techniques, substituent-dependent solubility, cavity-size-dependent host-guest properties in organic media, and unit rotation along with planar chiral inversion. These advantages have enabled the high-yield synthesis and rational design of pillar[ n ]arene-based mechanically interlocked molecules (MIMs). In particular, new types of pillar[ n ]arene-based MIMs that can dynamically convert between interlocked and unlocked states through unit rotation have been produced. The highly symmetrical pillar-shaped structures of pillar[ n ]arenes result in simple NMR spectra, which are useful for studying the motion of pillar[ n ]arene wheels in MIMs and creating sophisticated MIMs with higher-order structures. The creation and application of polymeric MIMs based on pillar[ n ]arenes is also discussed.