関: crown ether、cryptand

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Structure of 2.2.2-Cryptand encapsulating a potassium cation (purple). At crystalline state, obtained with an X-ray diffraction.^[1]

2.2.2-Cryptand

Cryptands are a family of synthetic bi- and polycyclic multidentate ligands for a variety of cations.^[2] The Nobel Prize for Chemistry in 1987 was given to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen for their efforts in discovering and determining uses of cryptands and crown ethers, thus launching the now flourishing field of supramolecular chemistry.^[3] The term cryptand implies that this ligand binds substrates in a crypt, interring the guest as in a burial. These molecules are three-dimensional analogues of crown ethers but are more selective and complex the guest ions more strongly. The resulting complexes are lipophilic.

Structure

The most common and most important cryptand is N[CH₂CH₂OCH₂CH₂OCH₂CH₂]₃N; the formal IUPAC (International Union of Pure and Applied Chemistry) name for this compound is 1,10-diaza-4,7,13,16,21,24-hexaoxabicyclo[8.8.8]hexacosane. This compound is termed [2.2.2]cryptand where the numbers indicate the number of ether oxygen atoms (and hence binding sites) in each of the three bridges between the amine nitrogen "caps". Many cryptands are commercially available under the tradename "Kryptofix."^[4] All-amine cryptands exhibit particularly high affinity for alkali metal cations, which has allowed the isolation of salts of K⁺.^[5]

Properties

The 3-dimensional interior cavity of a cryptand provides a binding site - or nook - for "guest" ions. The complex between the cationic guest and the cryptand is called a cryptate. Cryptands form complexes with many "hard cations" including NH₄⁺, lanthanoids, alkali metals, and alkaline earth metals. In contrast to crown ethers, cryptands bind the guest ions using both nitrogen and oxygen donors. This three-dimensional encapsulation mode confers some size-selectivity, enabling discrimination among alkali metal cations (e.g. Na⁺ vs. K⁺).

Uses

Cryptands are more expensive and difficult to prepare, but offer much better selectivity and strength of binding^[6] than other complexants for alkali metals, such as crown ethers. They are able to bind otherwise insoluble salts into organic solvents. They can also be used as phase transfer catalysts by transferring ions from one phase to another.^[7] Cryptands enabled the synthesis of the alkalides and electrides. They have also been used in the crystallization of Zintl ions such as Sn₉⁴⁻.

References

^ Alberto, R.; Ortner, K.; Wheatley, N.; Schibli, R.; Schubiger, A. P. (2001). "Synthesis and properties of boranocarbonate: a convenient in situ CO source for the aqueous preparation of [^99mTc(OH₂)₃(CO)₃]⁺". J. Am. Chem. Soc. 121 (13): 3135–3136. doi:10.1021/ja003932b.
^ von Zelewsky, A. Stereochemistry of Coordination Compounds; John Wiley: Chichester, 1995. ISBN 0-471-95057-2.
^ Lehn, J. M. Supramolecular Chemistry: Concepts and Perspectives; VCH: Weinhiem, 1995.
^ 23978-09-8
^ Kim, J.; Ichimura, A. S.; Huang, R. H.; Redko, M.; Phillips, R. C.; Jackson, J. E.; Dye, J. L. (1999). "Crystalline Salts of Na⁻ and K⁻ (Alkalides) that Are Stable at Room Temperature". J. Am. Chem. Soc. 121 (45): 10666–10667. doi:10.1021/ja992667v.
^ Dietrich, B. "Cryptands" in Comprehensive Supramolecular Chemistry; Gokel, G. W. Ed; Elsevier: Oxford, 1996; Vol. 1, pp 153–211. ISBN 0-08-040610-6.
^ Landini, D.; Maia, A.; Montanari, F.; Tundo, P. (1979). "Lipophilic [2.2.2] cryptands as phase-transfer catalysts. Activation and nucleophilicity of anions in aqueous-organic thirteen-phase systems and in organic solvents of low polarity". J. Am. Chem. Soc. 101 (10): 2526–2530. doi:10.1021/ja00504a004.

General reading

IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "cryptand".
Lee, J.D. (1991). Concise Inorganic Chemistry (4th ed.). New York: Chapman & Hall. pp. 306–08 & 353. ISBN 0-412-40290-4.
K. E. Krakowiak, J. S. Bradshaw, H.-Y. An and R. M. Izatt (1993). "Simple methods for the preparation of cryptands". Pure Appl. Chem. 65 (3): 511–514. doi:10.1351/pac199365030511.

English Journal

Towards libraries of luminescent lanthanide complexes and labels from generic synthons.

Starck M, Kadjane P, Bois E, Darbouret B, Incamps A, Ziessel R, Charbonniere LJ.SourceLaboratoire de Chimie Organique et Spectroscopie Avancees, UMR 7515 CNRS, ECPM, 25 rue Becquerel, 67087 Strasbourg Cedex 02 (France).
Chemistry (Weinheim an der Bergstrasse, Germany).Chemistry.2011 Aug 8;17(33):9164-79. doi: 10.1002/chem.201100390. Epub 2011 Jul 1.
A synthetic approach is developed to obtain families of luminescent lanthanide complexes and markers from a generic family of precursors built from nonadentate coordination sites. The syntheses of the precursors, based on a directed regioselective nucleophilic aromatic substitution on polyfluoropyri
PMID 21726007

Soluble urokinase plasminogen activator receptor (suPAR) for assessment of disease severity in ventilator-associated pneumonia and sepsis.

Savva A, Raftogiannis M, Baziaka F, Routsi C, Antonopoulou A, Koutoukas P, Tsaganos T, Kotanidou A, Apostolidou E, Giamarellos-Bourboulis EJ, Dimopoulos G.Source4th Department of Internal Medicine, ATTIKON University Hospital, 1 Rimini Str, 12462 Athens, Greece.
The Journal of infection.J Infect.2011 Aug 3. [Epub ahead of print]
Urokinase plasminogen activator (uPAR) is a receptor mainly expressed on peripheral blood mononuclear cells and neutrophils. The role of its soluble form, namely suPAR, as a predictor of sepsis outcome in a homogenous cohort of 180 septic patients, was investigated. Blood from 180 patients with vent
PMID 21839112

Japanese Journal

Novel properties of cooperative dinuclear zinc(II) ions. The selective recognition of phosphomonesters and their P-O ester bondcleavage by a new dinuclear zinc(II) cryptate

KOIKE T.
J. Am. Chem. Soc. 118, 3091-3099, 1996
NAID 80008925780

クリプタンド-ジチゾン系によるアンモニウムイオンの抽出光度定量

川本博,石田亘,角田欣一,赤岩英夫
分析化学 41(6), 281-283, 1992-06-05
… Cryptand(2.2.2), to form ammonium cryptate which is quantitatively extracted into chloroform as vermilion complex with dithizone. …
NAID 110002906417