Cryptophane

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Cryptophanes are a family of organic molecules that form hollow cages capable of trapping small molecules inside. They are studied for molecular encapsulation and recognition, with potential uses in storing hydrogen gas for fuel-cell vehicles. They also can act as tiny reaction vessels where certain chemical processes can run inside the cage. Because of their unique ways of recognizing guest molecules, cryptophanes hold promise for studying how organic substances bind to other molecules, with possible biological and biochemical applications.

Cryptophanes were discovered in 1981 by André Collet and Jacqueline Gabard, who created the first one, cryptophane-A, using template-directed synthesis. A cryptophane cage is built from two cup-shaped units called [1.1.1]–orthocyclophane, connected by three bridges (Y) and bearing substituents R1 and R2 on the aromatic rings. Most cryptophanes exist as two diastereomers (syn and anti) due to symmetry. By choosing different Y bridges, R1 and R2 groups, and symmetry, chemists can tailor the cage’s shape, size, and interior properties to fit various small molecules or to host chemical reactions inside. They are classified by their structural features reflecting these building blocks and symmetry.