Chemistry of Azacalixarenes

Calixarenes constitute an important class of macrocyclic compounds in both fundamental research and application as a result of the versatile functions as a host molecule. In recent years, a variety of calixarene analogues involving heteroatoms as the bridging units have been reported because the replacement of the methylene bridges of calixarenes with heteroatoms can impart novel properties and functions to molecules. Of them, nitrogen-bridged calixarene analogues, simply called as azacalixarenes, have recently emerged as a new calixarene family. The diversity is limited yet, but interesting structure-property relationships based on the introduction of nitrogen atoms as the bridging units have thus far been disclosed. This review summarizes the current developments of the syntheses, complexation abilities, and oxidation behaviors of azacalixarenes.