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Encyclopedia of Physical Science and Technology EN007G-334 June 30, 2001 15:23

Inclusion (Clathrate)

Compounds

Jerry L. Atwood

University of Alabama

I. Historical Perspectives
II. Inorganic Hosts
III. Organic Hosts
IV. Biochemical Relationships

GLOSSARY INCLUSION COMPOUNDS are those formed between
two substances that are intimately linked, but not with co-
Calixarene Cyclic oligomer made by the base-catalyzed valent bonds. One substance is designated as the host and
condensation of a phenol and formaldehyde. the other as the guest. The original designation, clathrates,
Clathrate Inclusioncompoundinwhichtheguestiscom- was used to describe the situation in which the guest was
pletely surrounded by the host. completely encapsulated by the host. The field has ex-
Crown ether Macrocyclic polyether so called because of panded vastly since the initial elucidation of the clathrate
its appearance in molecular models. structures in the late 1940s.
Cyclodextrin One of a family of cyclic oligosaccharides
produced by the enzymatic degradation of starch.
Guest Molecule or ion that is held within a molecule (or I. HISTORICAL PERSPECTIVES
ion) or within a host lattice without the formation of a
covalent bond. The concept of inclusion is as old as humankind. The
Host Molecule, ion, or lattice capable of entrapping other hand is capable of a variable assortment of inclusions,
molecules or ions (guests). and many analogies are appropriate. The first verified
Inclusion compound Arrangement of two substances examples of inclusion compounds date from the early
that are intimately linked, but not with covalent bonds. 1800s. It is instructive to list the dates of record for the
Intercalation Reaction of a guest molecule (or ion) with preparation of inclusion compounds of various types: the
a layered host lattice. chlorine clathrate hydrate by Faraday in 1823, graphite
Zeolites Extensive group of porous tectosilicates. intercalates in 1841, the β-quinol H 2 S clathrate in 1849,

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