Calixarenes, new selective molecular receptors

Calixarenes are easily amenable to chemical modifications, e.g. derivatization of the phenolic hydrogen atoms or substitution at the para-positions, which can be operated separately or combined. They thus assume the role of platforms supporting arrays of functional groups able to act as ligating sites and resulting in a great variety of receptors displaying specific complexing abilities. A selection of examples are presented with the aim of illustrating the different factors of their ionic recognition properties and their already existing applications in the field of chemical sensors.