Homocalixarenes

Abstract

Of all the macrocycles encountered in supramolecular chemistry, two are predominant: calixarenes and crown ethers. Conventionally, calixarenes are 2,6-metacyclophanes derived from phenols, with a single CH2 group separating each phenolic moiety (see Calixarenes: Synthesis and Historical Perspectives). It is possible to introduce variation into the calixarene framework by extending the bridge between phenols to create a range of "homocalixarenes." This bridge may consist solely of alkyl groups or may have heteroatoms, such as nitrogen or oxygen, incorporated in the chain. Introduction of heteroatoms has the additional interesting effect of combining crown ether (or azacrown ether) features with those of calixarenes. The potential of homocalixarenes and their derivatives to form a wide range of supramolecular complexes is therefore vast and as yet largely untapped.