Calixarenes
Calixarenes
Calixarenes are macrocyclic oligomers, formed from phenol-formaldehyde condensation. They are sparingly soluble and high melting solids. They have chemical and thermal stability. The number [n] enclosed in brackets, which separates calix and arene, indicates the number of aromatic ring units in the macrocycle, for example, calix[4]arene, calix[6]arene and calix[8]arene.
They act as host molecules as they possess cavities. The shape of calixarenes is like a cup or a bucket with a defined upper and lower rim along with a central annulus. Both the upper and lower rims can be tailor made to provide highly preorganized structures. They have the ability to bind to a variety of ions and find applications as ion sensors. The aromatic rings of calixarenes rotate and produce different conformations. These conformations play a critical role in various properties such as the selectivity of the calixarene to complex with a specific species. Calixarenes are known as synthetic molecular baskets and have numerous applications as surfactants, chemoreceptors, catalysis, host-guest chemistry, enzyme mimetics, ion-sensitive electrodes, non-linear optics, drug recognition, drug delivery, and nanotechnology.
