関: cryptand、cryptate

WordNet

put an enamel cover on; "crown my teeth"
the upper branches and leaves of a tree or other plant (同)treetop
an English coin worth 5 shillings
the center of a cambered road (同)crest
(dentistry) dental appliance consisting of an artificial crown for a broken or decayed tooth; "tomorrow my dentist will fit me for a crown" (同)crownwork, jacket, jacket crown, cap
an ornamental jeweled headdress signifying sovereignty (同)diadem
a wreath or garland worn on the head to signify victory
the part of a hat (the vertex) that covers the crown of the head
the part of a tooth above the gum that is covered with enamel
invest with regal power; enthrone; "The prince was crowned in Westminster Abbey" (同)coronate
be the culminating event; "The speech crowned the meeting" (同)top
form the topmost part of; "A weather vane crowns the building"
utter shrill sounds; "The cocks crowed all morning"
black birds having a raucous call
the cry of a cock (or an imitation of it)
express pleasure verbally; "She crowed with joy"
any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom
a colorless volatile highly inflammable liquid formerly used as an inhalation anesthetic (同)ethoxyethane, divinyl ether, vinyl_ether, diethyl_ether, ethyl_ether
a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves (同)aether
representing a level of the highest possible achievement or attainment; "the crowning accomplishment of his career"
forming or providing a crown or summit; "the crowning star on a Christmas tree"; "her hair was her crowning glory"
provided with or as if with a crown or a crown as specified; often used in combination; "a high-crowned hat"; "an orange-crowned bird"; "a crowned signet ring"
having an (artificial) crown on a tooth; "had many crowned teeth"

PrepTutorEJDIC

〈C〉(王位の象徴として国王･王妃などがかぶる)王冠・《the~,[the]C-》『王位』,統治権;君主,王,女王 / 〈C〉(古代・中世で国王などから優者に与えられる)(…の)花冠,頭飾り《+『of』+『名』》;(一般に勝利の栄冠 / 《the~》(…の)絶頂,極致,きわみ《+『of』+『名』》 / 〈C〉(頭・帽子・山・アーチなどの)最も高い部分,頂(いただき) / 〈C〉歯冠;人工歯冠 / 〈C〉《英》クラウン紙幣(英国の旧銀貨);(一般に)王冠をデザインに使った貨幣 / …‘の'頭に王冠をのせる,'を'王位につける / (栄冠・賞を)…‘に'授ける《+『名』+『with』+『名』》 / 〈物が〉…‘の'頂部[てっぺん]をおおっている / 《『crown』+『名』+『名』》(…として)…'を'認める / (…を)…‘に'歯冠をかぶせる《+『名』+『with』+『名』》
『カラス』 / =crowbar
《単位形で》おんどりのかん高い鳴き声 / 〈娩〉《通例単数形で》キャッキャッという赤ん坊の笑い声 / 〈おんどりが〉ときを告げる / 〈赤ん坊が〉キャッキャッと笑う / (一般に)〈人が〉誇らしげに歓声をあげる
エーテル(麻酔などに用いる) / (またaether)《詩》天空,青空
この上ない,無上の

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2018/10/11 17:55:12」(JST)

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18-crown-6 coordinating a potassium ion

Crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are cyclic oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., –CH₂CH₂O–. Important members of this series are the tetramer (n = 4), the pentamer (n = 5), and the hexamer (n = 6). The term "crown" refers to the resemblance between the structure of a crown ether bound to a cation, and a crown sitting on a person's head. The first number in a crown ether's name refers to the number of atoms in the cycle, and the second number refers to the number of those atoms that are oxygen. Crown ethers are much broader than the oligomers of ethylene oxide; an important group are derived from catechol.

Crown ethers strongly bind certain cations, forming complexes. The oxygen atoms are well situated to coordinate with a cation located at the interior of the ring, whereas the exterior of the ring is hydrophobic. The resulting cations often form salts that are soluble in nonpolar solvents, and for this reason crown ethers are useful in phase transfer catalysis. The denticity of the polyether influences the affinity of the crown ether for various cations. For example, 18-crown-6 has high affinity for potassium cation, 15-crown-5 for sodium cation, and 12-crown-4 for lithium cation. The high affinity of 18-crown-6 for potassium ions contributes to its toxicity. Crown ethers are not the only macrocyclic ligands that have affinity for the potassium cation. Ionophores such as valinomycin also display a marked preference for the potassium cation over other cations.

Crown ethers have been shown to coordinate to Lewis acids through electrostatic, σ-hole (see halogen bond) interactions, between the Lewis basic oxygen atoms of the crown ether and the electrophilic Lewis acid center.^[1]^[2]

Structures of common crown ethers: 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6, and diaza-18-crown-6

History

In 1967, Charles Pedersen, who was a chemist working at DuPont, discovered a simple method of synthesizing a crown ether when he was trying to prepare a complexing agent for divalent cations.^[3]^[4] His strategy entailed linking two catecholate groups through one hydroxyl on each molecule. This linking defines a polydentate ligand that could partially envelop the cation and, by ionization of the phenolic hydroxyls, neutralize the bound dication. He was surprised to isolate a by-product that strongly complexed potassium cations. Citing earlier work on the dissolution of potassium in 16-crown-4,^[5]^[6] he realized that the cyclic polyethers represented a new class of complexing agents that were capable of binding alkali metal cations. He proceeded to report systematic studies of the synthesis and binding properties of crown ethers in a seminal series of papers. The fields of organic synthesis, phase transfer catalysts, and other emerging disciplines benefited from the discovery of crown ethers. Pedersen particularly popularized the dibenzo crown ethers.^[7]

Catenane derived from cyclobis(paraquat-p-phenylene)(a cyclophane with two viologen units) and a cyclic polyether (bis(para-phenylene-34-crown-10)). Carbon atoms of the two rotaxane components are colored green and purple. Otherwise, O = red, N = blue. H atoms are omitted.^[8] The second of Nobel Prizes in Chemistry involving crown ethers was awarded for the design and synthesis of molecular machines. Many of these "machines" incorporate crown ethers as essential design components.

Pedersen shared the 1987 Nobel Prize in Chemistry for the discovery of the synthetic routes to, and binding properties of, crown ethers.

Affinity for cations

Apart from its high affinity for potassium cations, 18-crown-6 can also bind to protonated amines and form very stable complexes in both solution and the gas phase. Some amino acids, such as lysine, contain a primary amine on their side chains. Those protonated amino groups can bind to the cavity of 18-crown-6 and form stable complexes in the gas phase. Hydrogen-bonds are formed between the three hydrogen atoms of protonated amines and three oxygen atoms of 18-crown-6. These hydrogen-bonds make the complex a stable adduct. By incorporating luminescent substituents into their backbone, these compounds have proved to be sensitive ion probes, as changes in the absorption or fluorescence of the photoactive groups can be measured for very low concentrations of metal present.^[9] Some attractive examples include macrocycles, incorporating oxygen and/or nitrogen donors, that are attached to polyaromatic species such as anthracenes (via the 9 and/or 10 positions)^[10] or naphthalenes (via the 2 and 3 positions).^[11]

Azacrowns

21- and 18-membered diazacrown ether derivatives exhibit excellent calcium and magnesium selectivities and are widely used in ion-selective electrodes.^[12] Some or all of the oxygen atoms in crown ethers can be replaced by nitrogens to form cryptands. A well-known tetrazacrown is cyclen in which there are no oxygens.^[13]

Lariat crown ethers have sidearms that can augment complexation of cation. The lariat is typically attached to an amine centre in an azacrown.^[14]

References

^ Marczenko, K. M.; Mercier, H. P. A.; Schrobilgen, G. J. "A Stable Crown-Ether Complex with a Noble-gas Compound". Angew. Chem. Int. Ed. doi:10.1002/anie.201806640.
^ Lipkowski, J.; Fonari, M. S.; Kravtsov, V. C.; Simonov, Y. A.; Ganin, E. V.; Gemboldt, V. O. (1996). J. Chem. Crystallogr. 26: 823. Missing or empty |title= (help)
^ Pedersen, C. J. (1967). "Cyclic polyethers and their complexes with metal salts". Journal of the American Chemical Society. 89 (26): 7017–7036. doi:10.1021/ja01002a035.
^ Pedersen, C. J. (1967). "Cyclic polyethers and their complexes with metal salts". Journal of the American Chemical Society. 89 (10): 2495–2496. doi:10.1021/ja00986a052.
^ GB 785229, Stewart, D. G.; D. Y. Waddan & E. T. Borrows,
^ Down, J. L.; Lewis, J.; Moore, B.; Wilkinson, G. (1959). "761. The solubility of alkali metals in ethers". Journal of the Chemical Society: 3767. doi:10.1039/jr9590003767.
^ Pedersen, Charles J. (1988). "Macrocyclic Polyethers: Dibenzo-18-Crown-6 Polyether and Dicyclohexyl-18-Crown-6 Polyether". Organic Syntheses.; Collective Volume, 6, p. 395
^ Ashton, P. R.; Goodnow, T. T.; Kaifer, A. E.; Reddington, M. V.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Vicent, C.; Williams, D. J. (1989). "A [2] Catenane Made to Order". Angewandte Chemie International Edition in English. 28: 1396–1399. doi:10.1002/anie.198913961.
^ Fabbrizzi, L.; Francese, G.; Licchelli, M.; Pallavicini, P.; Perotti, A.; Poggi, A.; Sacchi, D.; Taglietti, A. (1997). Desvergne, J. P.; Czarnik, A. W., eds. Chemosensors of Ion and Molecule Recognition. NATO ASI Series C. 492. Dordrecht: Kluwer Academic Publishers. p. 75.
^ Bouas-Laurent, H.; Desvergne, J. P.; Fages, F.; Marsau, P. (1993). A. W., Czarnik, ed. Fluorescent Chemosensors for Ion and Molecule Recognition. ACS Symposium Series 538. Washington, DC: American Chemical Society. p. 59.
^ Sharghi, Hashem; Ebrahimpourmoghaddam, Sakineh (2008). "A Convenient and Efficient Method for the Preparation of Unique Fluorophores of Lariat Naphtho-Aza-Crown Ethers". Helvetica Chimica Acta. 91 (7): 1363–1373. doi:10.1002/hlca.200890148.
^ Suzuki, K.; Watanabe, K.; Matsumoto, Y.; Kobayashi, M.; Sato, S.; Siswanta, D.; Hisamoto, H. (1995). "Design and Synthesis of Calcium and Magnesium Ionophores Based on Double-Armed Diazacrown Ether Compounds and Their Application to an Ion Sensing Component for an Ion-Selective Electrode". Anal. Chem. 67 (2): 324–334. doi:10.1021/ac00098a016.
^ Gatto, Vincent J.; Miller, Steven R.; Gokel, George W. (1988). "4,13-Diaza-18-Crown-6". Organic Syntheses.; Collective Volume, 8, p. 152
^ Gokel, G. W.; Barbour, L. J.; Ferdani, R.; Hu, J. (2002). "Lariat Ether Receptor Systems Show Experimental Evidence for Alkali Metal Cation Interactions". Acc. Chem. Res. 35: 878–886. doi:10.1021/ar000093p.

External links

Pedersen, Charles (1987). "Nobel Lecture" (PDF). Nobel Prize.
Molecular crown

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Peterson SM1, Helm ML, Appel AM.
Dalton transactions (Cambridge, England : 2003).Dalton Trans.2015 Jan 14;44(2):747-752. Epub 2014 Nov 12.
A binucleating ligand has been prepared that contains an SCS pincer and three oxygen donor atoms in a partial crown ether loop. To enable metalation with Ni0, a bromoarene precursor was used and resulted in the formation of a nickel-bromide complex in the SCS pincer portion of the ligand. Reaction o
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Long-lived charge separation in a rigid pentiptycene bis(crown ether)-Li(+)@C60 host-guest complex.

Supur M1, Kawashima Y, Ma YX, Ohkubo K, Chen CF, Fukuzumi S.
Chemical communications (Cambridge, England).Chem Commun (Camb).2014 Dec 25;50(99):15796-8. doi: 10.1039/c4cc07795d. Epub 2014 Nov 5.
We report long-lived charge separation in a highly rigid host-guest complex of pentiptycene bis(crown ether) and Li(+)@C60, in which the pentiptycene framework is actively involved as an electron donor in a photoinduced electron-transfer process to the excited states of Li(+)@C60 through a rigid dis
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Crown ethers attenuate aggregation of amyloid beta of Alzheimer's disease.

Tian Y1, Zhang X, Li Y, Shoup TM, Teng X, Elmaleh DR, Moore A, Ran C.
Chemical communications (Cambridge, England).Chem Commun (Camb).2014 Dec 25;50(99):15792-5. doi: 10.1039/c4cc06029f. Epub 2014 Nov 5.
In this report, we reasoned that non-covalent modification of amyloid beta (Aβ) by crown ethers could inhibit its aggregation. We demonstrated that PiB-C, a conjugate PiB and crown ether, could significantly reduce the aggregation in vitro. Additionally, two-photon imaging showed that PiB-C could e
PMID 25372154

Japanese Journal

Ion Sensing by Charge Transfer Absorption Variations of Benzocrown-Bipyridinium Conjugates with an Alkyl Chain

KUWABARA Tetsuo,SATAKE Ryota,GUO Haocheng
Analytical Sciences 31(1), 23-27, 2015-01
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Synthesis of MDI and PCL-diol-based polyurethanes containing [2] and [3]rotaxanes and their properties

Murakami Hiroto,Nishiide Ryuta,Ohira Shinji,Ogata Akiko
Polymer 55(24), 6239-6244, 2014-11-18
… We have successfully synthesized novel polyurethanes where PU1 contains a [3]rotaxane that consists of N-3,5-di-tert-butylbenzyl-N-3-hydroxypropylammonium hexafluorophosphate (AOH1) and N,N′-Dimethyl-N,N′-bis(dibenzo-24-crown-8)-terephthalamide (BisC) as well as PU2 contains a [2]rotaxane that consists of AOH1 and dibenzo-24-crown-8 ether. …
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