Pillar[n]arenes: Easy-to-Make Pillar-Shaped Macrocyclic Hosts for Supramolecular Chemistry

Abstract

In 2008, we reported the discovery of new pillar-shaped macrocyclic hosts, known as “pillar[n]arenes”. Today, 8 years after our initial report, pillar[n]arenes are recognized as key players in supramolecular chemistry because of their many unique advantages, including their facile synthesis, unique pillar-shaped structure, versatile functionality, interesting host-guest properties and original supramolecular assembly characteristics. In this chapter, we have provided a brief discussion of the synthesis of pillar[n]arenes. We also discuss why cyclic pentamers (i.e., pillar[5]arenes) and cyclic hexamers (i.e., pillar[6]arenes) are selectively obtained in high yields under optimized conditions, and describe the difficulties associated with the synthesis of higher pillar[n]arene homologs (n > 7). Second, we have provided some discussion of the different methods available for the functionalization of pillar[n]arenes. Third, we have discussed the unique pillar-shaped structure of pillar[n]arenes and compared it with the structures of several other typical host molecules. We have also provided a brief description of the unique host-guest properties of pillar[n]arenes in terms of their pillar-shaped structures. Finally, we have provided several examples of one-, two- and three-dimensional supramolecular assemblies constructed from pillar[n]arenes.