WordNet

designating or relating to a compound in which one component is physically enclosed within the crystal structure of another
the relation of comprising something; "he admired the inclusion of so many ideas in such a short work" (同)comprehension
the state of being included
the act of including

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/03 15:11:16」(JST)

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A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word clathrate is derived from the Latin clatratus meaning with bars or a lattice.^[1] Traditionally, clathrate compounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host-guest complexes and inclusion compounds.^[2] According to IUPAC, clathrates are "Inclusion compounds in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules."^[3]

Structure of the 3:1 inclusion complex of urea and 1,6-dichlorohexane. The framework is composed of molecules of urea that are linked by hydrogen bonds, leaving approximately hexagonal channels into which align the molecules of the chlorocarbon. Color scheme: oxygen is red, nitrogen is blue, chlorine is green.^[4]

Occurrence and scope

Traditionally clathrate compounds refer to polymeric hosts containing molecular guests. More recently, the term refers to many molecular hosts, including calixarenes and cyclodextrins and even some inorganic polymers such as zeolites. The natural silica clathrate mineral, chibaite was recently described from Japan.

Many clathrates are derived from an organic hydrogen-bonded frameworks. These frameworks are prepared from molecules that "self-associate" by multiple hydrogen-bonding interactions. The most famous clathrates are methane clathrates where the hydrogen-bonded framework is contributed by water and the guest molecules are methane. Large amounts of methane naturally frozen in this form exist both in permafrost formations and under the ocean sea-bed.^[5] Other hydrogen-bonded networks are derived from hydroquinone, urea, and thiourea. A much studied host molecule is Dianin's compound.

Space filling model of β-cyclodextrin, a host that forms clathrate complexes by inserting the guest into the "donut hole."

Hofmann compounds are coordination polymers with the formula Ni(CN)₄Ni(NH₃)₂. These materials crystallize with small aromatic guests (benzene, certain xylenes), and this selectivity has been exploited commercially for the separation of these hydrocarbons.^[2] Metal organic frameworks (MOFs) form clathrates.

Example of MOF-5, the cavity for the guests is indicated by the yellow sphere.

Photolytically-sensitive caged compounds have been examined as containers for releasing a drug or reagent.^[6]

History

Clathrate hydrates were discovered in 1810 by Humphry Davy.^[7] Clathrates were studied by P. Pfeiffer in 1927 and in 1930, E. Hertel defined "molecular compounds" as substances decomposed into individual components following the mass action law in solution or gas state. In 1945, H. M. Powell analyzed the crystal structure of these compounds and named them clathrates.

Related materials

Inclusion compounds are often molecules, whereas clathrates are typically polymeric. Intercalation compounds are not 3-dimensional, unlike clathrate compounds.

References

^ Latin dictionary
^ ^a ^b J. L. Atwood "Inclusion Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a14_119
^ http://goldbook.iupac.org/C01097.html
^ Hollingsworth, U.Werner-Zwanziger; Brown, J.D.Chaney; Huffman, K.D.M.Harris (1999). "Spring-Loading at the Molecular Level: Relaxation of Guest-Induced Strain in Channel Inclusion Compounds". J. Am. Chem. Soc 121: 9732. doi:10.1021/ja9919534.
^ Pearce, Fred (27 June 2009). "Ice on fire: The next fossil fuel". New Scientist. pp. 30–33. Retrieved 2009-07-05.
^ Ellis-Davies, Graham C. R. (July 2007). "Caged compounds: photorelease technology for control of cellular chemistry and physiology". Nature Methods 4 (8): 619–28. doi:10.1038/nmeth1072. PMID 17664946.
^ Ellen Thomas (November 2004). "Clathrates: little known components of the global carbon cycle". Wesleyan University. Retrieved 13 December 2007.

English Journal

Structural Collapse of the Hydroquinone-Formic Acid Clathrate: A Pressure-Medium-Dependent Phase Transition.

Eikeland E1, Thomsen MK1, Madsen SR1, Overgaard J1, Spackman MA2, Iversen BB3.
Chemistry (Weinheim an der Bergstrasse, Germany).Chemistry.2016 Feb 16. doi: 10.1002/chem.201504908. [Epub ahead of print]
The energy landscape governing a new pressure-induced phase transition in the hydroquinone-formic acid clathrate is reported in which the host structure collapses, opening up the cavity channels within which the guest molecules migrate and order. The reversible isosymmetric phase transition causes s
PMID 26879515

Dynamic free energy surfaces for sodium diffusion in type II silicon clathrates.

Slingsby JG1, Rorrer NA1, Krishna L2, Toberer ES2, Koh CA1, Maupin CM1.
Physical chemistry chemical physics : PCCP.Phys Chem Chem Phys.2016 Feb 10;18(7):5121-8. doi: 10.1039/c5cp06066d.
Earth abundant semiconducting type II Si clathrates have attracted attention as photovoltaic materials due to their wide band gaps. To realize the semiconducting properties of these materials, guest species that arise during the synthesis process must be completely evacuated from the host cage struc
PMID 26658349

Lattice constants and expansivities of gas hydrates from 10 K up to the stability limit.

Hansen TC1, Falenty A2, Kuhs WF2.
The Journal of chemical physics.J Chem Phys.2016 Feb 7;144(5):054301. doi: 10.1063/1.4940729.
The lattice constants of hydrogenated and deuterated CH4-, CO2-, Xe- (clathrate structure type I) and N2-hydrates (clathrate structure type II) from 10 K up to the stability limit were established in neutron- and synchrotron diffraction experiments and were used to derive the related thermal expansi
PMID 26851915

Japanese Journal

火星のメタン (特集火星探査計画における地質学者への期待)

石丸亮,小松吾郎,松井孝典
地質学雑誌 118(10), 664-674, 2012-10
NAID 40019477387

Structures and Low-Energy Excitations of Amorphous Gas Hydrates

Kikuchi Tatsuya,Inamura Yasuhiro,Onoda-Yamamuro Noriko,Yamamuro Osamu
J Phys Soc Jpn 81(9), 094604-094604-5, 2012-09-15
… We have prepared amorphous clathrate hydrates of Ar, CD4, Xe, and SF6 by depositing mixed vapors of water and guest molecules on a substrate at ca. …
NAID 150000103205