calixarenes: Originally macrocyclic compounds capable of assuming a basket (or 'calix') shaped conformation. They are formed from p-hydrocarbyl phenols and formaldehyde. The term now applies to a variety of derivatives by substitution of the hydrocarbon cyclo{oligo(1,3-phenylene)methylene}.[1]
A calixarene is a macrocycle or cyclic oligomer based on a methylene-linked phenols. With hydrophobic cavities that can hold smaller molecules or ions, calixarenes belong to the class of cavitands known in host–guest chemistry.[2]