# Cryptophane

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{{Short description|Class of organic compounds}}
[[Image:Cryptophane general structure.gif|250px|thumb|General structure of cryptophanes: ''syn'' and ''anti'' [diastereomer](/source/diastereomer)ic forms]]

'''Cryptophanes''' are a class of [organic](/source/Organic_compound) [supramolecular compound](/source/supramolecular_assembly)s studied and synthesized primarily for [molecular encapsulation](/source/molecular_encapsulation) and recognition. One possible noteworthy application of cryptophanes is encapsulation and storage of [hydrogen](/source/hydrogen) gas for potential use in [fuel cell](/source/fuel_cell) automobiles. Cryptophanes can also serve as containers in which organic chemists can carry out [reactions](/source/Chemical_reaction) that would otherwise be difficult to run under normal conditions. Due to their unique [molecular recognition](/source/molecular_recognition) 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](/source/biochemical) applications.<ref>Palaniappan, K. K.; Francis, M. B.; Pines, A.; Wemmer, D. E. Molecular sensing using hyperpolarized xenon NMR spectroscopy. Isr. J. Chem. 2014, 54, 104−112.</ref>

==Discovery==
Cryptophanes were discovered by [André Collet](/source/Andr%C3%A9_Collet) and Jacqueline Gabard in 1981<ref>{{
cite journal 
|author1=Gabard, J. |author2=Collet, A. | title = Synthesis of a (''D''<sub>3</sub>)-bis(cyclotriveratrylenyl) macrocage by stereospecific replication of a (''C''<sub>3</sub>)-subunit
| year = 1981
| publisher = [Royal Society of Chemistry](/source/Royal_Society_of_Chemistry)
| journal = Journal of the Chemical Society, Chemical Communications
| issue = 21
| pages = 1137–1139
| doi = 10.1039/C39810001137}}</ref> 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 <nowiki>[1.1.1]–</nowiki>ortho[cyclophane](/source/cyclophane) units (see [cyclotriveratrylene](/source/cyclotriveratrylene)),<ref name=Homan04>{{
Cite book
| last = Holman
| first = K. Travis
| contribution = Cryptophanes: Molecular Containers
| title = Encyclopedia of Supramolecular Chemistry
| editor = Atwood, J. L. |editor2=Steed, J. W.
| pages = 340–348
| publisher = [CRC Press](/source/CRC_Press)
| year = 2004
| doi = 10.1081/E-ESMC 
| doi-broken-date = 11 July 2025
| isbn = 0-8247-4723-2
}}</ref> 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](/source/diastereomer)ic forms (''syn'' and ''anti''), distinguished by their [symmetry](/source/symmetry) 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.<ref name=Homan04/>
{|class="wikitable" style="text-align: left;" 
|+  '''Classification of known cryptophane structures'''
! colspan="3" | '''Structure''' || colspan="2" | '''Name''' || 
|-
! Bridges ''Y'' || align="center" | ''R1'' || align="center" | ''R2'' || &nbsp;''anti''&nbsp; || &nbsp;''syn''&nbsp; || described in 
|-
| 3 × O(CX<sub>2</sub>)<sub>2</sub>O, where X is [H](/source/Hydrogen) or [D](/source/Deuterium) || OCX<sub>3</sub> || OCX<sub>3</sub> || align="center" | '''A''' ||  ||  Brotin ''et al.''<ref>{{cite journal |last1=Brotin |first1=Thierry |last2=Devic |first2=Thomas |last3=Lesage |first3=Anne |author-link3=Anne Lesage |last4=Emsley |first4=Lyndon |author-link4=Lyndon Emsley |last5=Collet |first5=André |date=March 2001 |title=Synthesis of deuterium-labeled cryptophane-A and investigation of Xe@Cryptophane complexation dynamics by 1D-EXSY NMR experiments |journal=Chemistry: A European Journal |volume=7 |issue=7 |pages=1561–1573 |doi=10.1002/1521-3765(20010401)7:7<1561::AID-CHEM1561>3.0.CO;2-9|pmid=11330913 }}</ref>
|-
| 3 × O(CX<sub>2</sub>)<sub>2</sub>O || OCH<sub>2</sub>CO<sub>2</sub>H || OCH<sub>2</sub>CO<sub>2</sub>H || align="center" | '''A3''' ||  ||  
|-
| 3 × O(CX<sub>2</sub>)<sub>2</sub>O || OCH<sub>3</sub> || H || align="center" | '''C''' || align="center" | '''D''' || 
|-
| 3 × O(CH<sub>2</sub>)<sub>3</sub>O || OCH<sub>3</sub> || OCH<sub>3</sub> || align="center" | '''E''' || align="center" | '''F'''|| 
|-
| 3 × O(CH<sub>2</sub>)<sub>3</sub>O || OCH<sub>2</sub>CO<sub>2</sub>H || OCH<sub>2</sub>CO<sub>2</sub>H || align="center" | '''E3''' ||  ||  
|-
| 3 × O(CH<sub>2</sub>)<sub>5</sub>O || OCH<sub>3</sub> || OCH<sub>3</sub> ||  align="center" |'''O''' || align="center" | '''P''' ||  
|-
| 3 × O(CH<sub>2</sub>)<sub>5</sub>O || OCH<sub>2</sub>CO<sub>2</sub>H || OCH<sub>2</sub>CO<sub>2</sub>H || align="center" | '''O3''' ||  ||  
|-
| 3 × OCH<sub>2</sub>C≡CC≡CH<sub>2</sub>O || CH<sub>3</sub> || CH<sub>3</sub> || align="center" | '''''γ''''' (gamma) || '''''δ''''' (delta)|| 
|-
| 2 × O(CH<sub>2</sub>)<sub>2</sub>O, 1 × O(CH<sub>2</sub>)<sub>3</sub>O || OCH<sub>3</sub> || OCH<sub>3</sub> || align="center" | '''223''' ||  ||  
|-
| 2 × O(CH<sub>2</sub>)<sub>3</sub>O, 1 × O(CH<sub>2</sub>)<sub>2</sub>O || OCH<sub>3</sub> || OCH<sub>3</sub>||  align="center" |'''233''' ||  ||  
|-
| 2 × O(CH<sub>2</sub>)<sub>2</sub>O, 1 × O(CH<sub>2</sub>)<sub>4</sub>O || OCH<sub>3</sub> || OCH<sub>3</sub> || align="center" | '''224''' ||  ||  
|}

==References==
{{Reflist}}

Category:Supramolecular chemistry
Category:Hydrogen
Category:Cyclophanes

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Adapted from the Wikipedia article [Cryptophane](https://en.wikipedia.org/wiki/Cryptophane) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Cryptophane?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.