Term: cryptand
https://doi.org/10.1351/goldbook.C01426

Definition:
A molecular entity comprising a cyclic or polycyclic assembly of binding sites that contains three or more binding sites held together by covalent bonds, and which defines a molecular cavity in such a way as to bind (and thus 'hide' in the cavity) another molecular entity, the guest (a cation, an anion or a neutral species), more strongly than do the separate parts of the assembly (at the same total concentration of binding sites). The adduct thus formed is called a 'cryptate'. The term is usually restricted to bicyclic or oligocyclic molecular entities. Example: C01426.png Corresponding monocyclic ligand assemblies crowns are sometimes included in this group, if they can be considered to define a cavity in which a guest can hide. The terms 'podand' and 'spherand' are used for certain specific ligand assemblies. Coplanar cyclic polydentate ligands, such as porphyrins, are not normally regarded as cryptands. 

Related Terms:
1) host (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.H02859).
2) molecular entity (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.M03986).
3) binding sites (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.B00649).
4) covalent bonds (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.C01384).
5) adduct (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.A00138).
6) crowns (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.C01421).
7) guest (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.G02711).
8) cation (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.C00907).
9) anion (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.A00358).
10) ligands (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.L03518).
11) porphyrins (<em>in biotechnology</em>) (http://doi.org/10.1351/goldbook.P04765).

Image: Not defined (https://goldbook.iupac.org/img/inline/C01426.png) 

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1102 (https://doi.org/10.1351/pac199466051077)

Citation: 'cryptand' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.C01426

License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.

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