Clathrates

A clathrate is a chemical compound made up of a lattice that traps or contains molecules. The term clathrate is derived from the Latin clathratus (clatratus), which means "with bars, latticed." Most clathrate compounds are polymeric and fully engulf the guest molecule, but in current usage, clathrates also include host-guest complexes and inclusion compounds. Clathrates, according to IUPAC, are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules." The term refers to a variety of molecular hosts, including calixarenes and cyclodextrins, as well as some inorganic polymers such as zeolites. Clathrate hydrates are formed from organic hydrogen-bonded frameworks. These frameworks are made up of molecules that "self-associate" through numerous hydrogen-bonding interactions. Cavities such as dodecahedral, tetrakaidecahedral, and hexakaidecahedral cavities are frequent in clathrate crystal formations. Humphry Davy first found clathrate hydrates in 1810. P. Pfeiffer researched clathrates in 1927, while E. Hertel described "molecular compounds" as substances broken into separate components in solution or gas state using the mass action law in 1930. H. M. Powell studied the crystal structure of these substances and termed them clathrates in 1945.