Crown ethers

Abstract Crown ethers are perhaps the most widely used family of host compounds in supramolecular chemistry-the chemistry of the non-covalent bond. The fortuitous discovery of the macrocyclic polyethers by Pedersen in 1967 laid the foundation for an exhaustive study of their preparation and complexing abilities, primarily with metal cations but also with neutral and even anionic species.5 Moreover, the metal ions which are complexed by crown ethers can also be utilised as templates for their formation.