Cryptophanes are a class of organic supramolecular compounds studied and synthesized primarily for

molecular encapsulation A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

and recognition. One possible noteworthy application of cryptophanes is encapsulation and storage of

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

gas for potential use in

fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen fuel, hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most bat ...

automobiles. Cryptophanes can also serve as containers in which organic chemists can carry out reactions that would otherwise be difficult to run under normal conditions. Due to their unique

molecular recognition Supramolecular chemistry refers to the branch of chemistry concerning Chemical species, chemical systems composed of a integer, discrete number of molecules. The strength of the forces responsible for spatial organization of the system range from w ...

properties, cryptophanes also hold great promise as a potentially new way to study the binding of organic molecules with substrates, particularly as pertaining to biological and

biochemical Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, ...

applications.

Discovery

Cryptophanes were discovered by André Collet and Jacqueline Gabard in 1981 when these researchers created, using template-directed synthesis, the first cryptophane, now known as cryptophane-A.

Structure

Cryptophane cages are formed by two cup-shaped .1.1��ortho cyclophane units (see cyclotriveratrylene), connected by three bridges (denoted ''Y''). There are also choices of the peripheral substitutes ''R1'' and ''R2'' attached to the aromatic rings of the units. Most cryptophanes exhibit two

diastereomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have di ...

ic forms (''syn'' and ''anti''), distinguished by their

symmetry Symmetry () in everyday life refers to a sense of harmonious and beautiful proportion and balance. In mathematics, the term has a more precise definition and is usually used to refer to an object that is Invariant (mathematics), invariant und ...

type. This general scheme offers a variety of choices (''Y'', ''R1'', ''R2'', and symmetry type) by which the shape, volume and chemical properties of the generally hydrophobic pocket inside the cage can be modified, making cryptophanes suitable for encapsulating many types of small molecules and even chemical reactions.

General classification

Depending on their structure, cryptophane cages are classified according to the following table.

References

{{Reflist Supramolecular chemistry Hydrogen Cyclophanes