Pillararenes: Easy-to-Make and Versatile Receptors for Supramolecular Chemistry

Abstract

In 2008, we reported a new class of macrocyclic hosts named “pillararenes”. Pillararenes have repeating units connected by methylene bridges at the para-position, and thus they have a unique symmetrical pillar architecture differing from the basket-shaped structure of meta-bridged calixarenes. Synthesis of pillararenes is easy-to-make. They can be synthesized in high yield by reacting commercially available reagents. The reaction was completed in 3 minutes. Pillararenes also show versatile functionality similar to cyclodextrins. Based on the various synthetic approaches, position-selective mono-, di-, tetra-, penta- and per-functionalization of pillararenes can be achieved. Pillararenes can capture electron accepting guest molecules within their cavity similarly to cucurbiturils. Because of their unique pillar-shaped architectures, high yield synthesis, outstanding host-guest properties, planar chirality and functionality, pillararenes are useful platform to construct various supramolecules including rotaxanes, catenanes, supramolecular polymers and sensors.