Design and Application of Multifunctional Ligands

Abstract

Calixarene is a macrocycle or cyclic oligomer based on a hydroxyl alkylation product of phenols and aldehydes1. The word calixarene is derived from calix or chalice since they resemble a pot and from the word arene that refers to the aromatic building block. Calixarenes have hydrophobic cavities that can hold smaller molecules or ions and belong to the class of cavitands known as host-guest chemistry. In 1940s Zinke and Ziegler2 discovered base-induced reaction of p-alkylphenols with formaldehyde, which yields cyclic oligomers. Then, synthesis of major cyclic oligomers was reported3 comprising original Zinke mixture in good and reproducible yields3. Calixarenes can be used as ion sensitive electrodes or sensors4, optical sensors5, chiral recognition devices for solid phase extraction, as a stationary phase and modifiers6. Synthesis, properties and applications of calixarenes is the subject of several books7-12 and reviews13-17. Different structures and properties of calixarene resulted in many studies18-20. The calixarenes are classified in the following categories.