Bibliografías temáticas / Crown ethers

Literatura académica sobre el tema "Crown ethers"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 31 de julio de 2024

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Artículos de revistas sobre el tema "Crown ethers"

1

Mao, Hua, John B. Thorne, Jennifer S. Pharr y Robert E. Gawley. "Effect of crown ether ring size on binding and fluorescence response to saxitoxin in anthracylmethyl monoazacrown ether chemosensors". Canadian Journal of Chemistry 84, n.º 10 (1 de octubre de 2006): 1273–79. http://dx.doi.org/10.1139/v06-093.

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Convenient macrocyclization synthetic routes for the preparation of different-sized monoaza anthracylmethyl crown ether chemosensors (15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, and 27-crown-9) are described. Evaluation of these crowns as chemosensors for saxitoxin revealed that the larger crowns have moderately higher binding constants, with the 27-crown-9 chemosensor having the largest binding constant (2.29 × 105 (mol/L)–1). Fluorescence enhancements of 100% were observed at saxitoxin concentrations of 5 µmol/L, which is close to the detection limit in mouse bioassay.Key words: anthracene, crown ethers, saxitoxin, paralytic shellfish poison (PSP), binding constants; chemosensors.
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2

Pranowo, Harno Dwi y Chairil Anwar. "INTERACTION BETWEEN Li+ CATION WITH CROWN ETHERS OF Bz15C5, DBz16C5 AND DBz18C6: MOLECULAR MODELING BASE ON MNDO/d SEMIEMPIRICAL METHOD". Indonesian Journal of Chemistry 3, n.º 1 (7 de junio de 2010): 55–66. http://dx.doi.org/10.22146/ijc.21906.

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The aim of this research is to find information about the substituent effect to the structure of crown ether benzo-15-crown-5 (Bz15C5), dibenzo-16-crown-5 (DBz16C5) and dibenzo-18-crown-6 (DBz18C6), and also crown ether selectivity to coordinate a Li+ metal cation. The presence of substituent could change the conformations flexibility of crown ether during interact with metal cation. In this research semi empirical MNDO/d method was used for calculations. Firstly, geometry optimization was conducted to crown ethers structure using MNDO/d methods. The next steps were running the geometry optimization of complexes between cation Li+ with crown ethers. Data were produced from these calculation are the parameter of crown ether structures, structures of the complexes, and the binding energy of the cation-crown ethers. The presence of electron-withdrawing substituents decreased the binding energy while that of electron-donating one increase the binding energy (value of ΔE more negative). The substituents which are increase the degree of symmetry of the cation-crown ether complexes could give the increase of crown ether selectivity to bind the cation. Selectivity of crown ether to bind the cation depends on the structural match between ionic radii of crown ether cavity (the ion-cavity size concept). Bz15C5 what has higher selectivity to bind Li+ than DBz16C5 and DBz18C6. Keywords: selectivity, crown ether, MNDO/d.
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3

Fronczek, Frank R., Richard D. Gandour, Thomas M. Fyles, Philippa J. Hocking, Susan J. McDermid y P. Daniel Wotton. "Polycarboxylate crown ethers from meso-tartaric acid". Canadian Journal of Chemistry 69, n.º 1 (1 de enero de 1991): 12–19. http://dx.doi.org/10.1139/v91-003.

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The synthesis of crown ethers derived from meso-tartaric acid was investigated. The sodium salt of the bis(dimethylamide) of meso-tartaric acid reacted with diethylene glycol ditosylate to give a mixture of 18-crown-6 tetraamide and 27-crown-9 hexaamide crown ethers. The 2R,3S,11S,12R 18-crown-6 isomer crystallized in triclinic space group [Formula: see text] (a = 7.557(2), b = 8.866(2), c = 10.4133(13) Å, α = 94.13(2), β = 95.86(2), γ = 99.26(2)°, R = 0.040 for 2090 observed of 3129 unique reflections). The structures of the remaining products were then assigned from the NMR spectra. The solution conformations of the amide crown ethers were examined by NMR, and provide a rationale for the product distribution obtained. One of the 18-crown-6 isomers and a mixture of the two 27-crown-9 isomers were hydrolyzed to the respective crown ether carboxylic acids, and the stability constants for complexation of cations were determined by potentiometric titration. The meso tetra- and hexacarboxylates are remarkably nonselective and inefficient cation complexing agents, compared to related crown ethers from R,R-(+)-tartaric acid, due to the unfavorable conformational control exerted by the tartaro units. Key words: crown ether synthesis, complexation, crown ether conformation, meso-tartaric acid, crystal structure.
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4

Lu, Zhongyuan, Benjamin A. Jackson y Evangelos Miliordos. "Ab Initio Calculations on the Ground and Excited Electronic States of Thorium–Ammonia, Thorium–Aza-Crown, and Thorium–Crown Ether Complexes". Molecules 28, n.º 12 (12 de junio de 2023): 4712. http://dx.doi.org/10.3390/molecules28124712.

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Positively charged metal–ammonia complexes are known to host peripheral, diffuse electrons around their molecular skeleton. The resulting neutral species form materials known as expanded or liquid metals. Alkali, alkaline earth, and transition metals have been investigated previously in experimental and theoretical studies of both the gas and condensed phase. This work is the first ab initio exploration of an f-block metal–ammonia complex. The ground and excited states are calculated for Th0–3+ complexes with ammonia, crown ethers, and aza-crown ethers. For Th3+ complexes, the one valence electron Th populates the metal’s 6d or 7f orbitals. For Th0–2+, the additional electrons prefer occupation of the outer s- and p-type orbitals of the complex, except Th(NH3)10, which uniquely places all four electrons in outer orbitals of the complex. Although thorium coordinates up to ten ammonia ligands, octa-coordinated complexes are more stable. Crown ether complexes have a similar electronic spectrum to ammonia complexes, but excitations of electrons in the outer orbitals of the complex are higher in energy. Aza-crown ethers disfavor the orbitals perpendicular to the crowns, attributed to the N-H bonds pointing along the plane of the crowns.
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5

Zimnicka, Magdalena M. "Crown ethers as shift reagents in peptide epimer differentiation –conclusions from examination of ac-(H)FRW-NH2 petide sequences". International Journal for Ion Mobility Spectrometry 23, n.º 2 (octubre de 2020): 177–88. http://dx.doi.org/10.1007/s12127-020-00271-2.

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Abstract Crown ethers with different ring sizes and substituents (18-crown-6, dibenzo-18-crown-6, dicyclohexano-18-crown-6, a chiral tetracarboxylic acid-18-crown-6 ether, dibenzo-21-crown-7, and dibenzo-30-crown-10) were evaluated as shift reagents to differentiate epimeric model peptides (tri-and tetrapeptides) using ion mobility mass spectrometry (IM-MS). The stable associates of peptide epimers with crown ethers were detected and examined using traveling-wave ion mobility time-of-flight mass spectrometer (Synapt G2-S HDMS) equipped with an electrospray ion source. The overall decrease of the epimer separation upon crown ether complexation was observed. The increase of the effectiveness of the microsolvation of a basic moiety - guanidine or ammonium group in the peptide had no or little effect on the epimer discrimination. Any increase of the epimer separation, which referred to the specific association mode between crown substituents and a given peptide sequence, was drastically reduced for the longer peptide sequence (tetrapeptide). The obtained results suggest that the application of the crown ethers as shift reagents in ion mobility mass spectrometry is limited to the formation of complexes differing in stoichiometry rather than it refers to a specific coordination mode between a crown ether and a peptide molecule.
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6

Szemenyei, Balázs, Balázs Novotny, Sarolta Zsolnai, Zsombor Miskolczy, László Biczók, Attila Takács, László Kollár, László Drahos, Ildikó Móczár y Péter Huszthy. "Push or Pull for a Better Selectivity? A Study on the Electronic Effects of Substituents of the Pyridine Ring on the Enantiomeric Recognition of Chiral Pyridino-18-Crown-6 Ethers". Symmetry 12, n.º 11 (30 de octubre de 2020): 1795. http://dx.doi.org/10.3390/sym12111795.

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Seven dimethyl-substituted optically active pyridino-18-crown-6 ethers containing various substituents at position 4 of the pyridine ring were studied with regards to the electron-donating and -withdrawing effects of substituents on enantiomeric recognition. In order to compile this set of compounds, we prepared four novel pyridino-18-crown-6 ethers, including an intermediate of a new synthetic route for a formerly reported crown ether. The discriminating ability of these pyridino-crown ethers with C2-symmetry toward the enantiomers of protonated primary amines was examined by isothermal titration calorimetry.
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7

Anantanarayan, Ashok y Thomas M. Fyles. "Polycarboxylate diaza crown ethers derived from R,R-(+)-tartaric acid: synthesis and complexation of metal ions". Canadian Journal of Chemistry 68, n.º 8 (1 de agosto de 1990): 1338–51. http://dx.doi.org/10.1139/v90-206.

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The synthesis and complexation properties of polycarboxylate diaza crown ethers based on R,R-(+)-tartaric acid are described. Cesium carbonate mediated macrocyclization of a bis-tosylamide precursor with a bis-tosylate precursor provided the protected crown ethers. Photochemical deprotection of the tosylamides and hydrolysis of the carboxamides yielded dicarboxylic and tetracarboxylic acid derivatives of 1,10-diaza-18-crown-6. N-Methylenecarboxylate (N-acetate) derivatives were prepared by N-alkylation with bromoacetic acid. The synthetic and purification procedures developed provide samples of the ligands in a metal-free form. Acidity and stability constants for complexation of alkali metal, alkaline earth, late- and post-transition metal cations were determined by potentiometric titration. The ligands form complexes which show enhancement of stability by charge–charge and chelate interaction with the carboxylates. In comparison with crown ether polycarboxylates these aza crown ethers showed a selectivity for softer metal ions relative to alkali and alkaline earth metal ions. N-Methylenecarboxylate chelate ligands were found to bind almost all types of metal ions, due to a highly co-operative array of charge–charge, chelate and crown ether interactions. Keywords: aza crown ether synthesis, tartaric acid, potentiometric titration, cation complexation, aminocarboxylate complexone.
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8

Esseffar, M'hamed, Mohamed El Mouhtadi, José-Luis M. Abboud, José Elguero y Daniel Liotard. "Étude théorique (AM1) de l'affinité protonique des polyéthers cycliques (éthers couronnes) et non cycliques (glymes)". Canadian Journal of Chemistry 69, n.º 12 (1 de diciembre de 1991): 1970–75. http://dx.doi.org/10.1139/v91-283.

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Semi-empirical calculations at the AM1 level have been used to study the proton affinity (PA) of polyether compounds (dioxane, glymes, and crown ethers). The calculated values, although systematically lower than the experimental ones, are linearly correlated with eight experimental PA's (r = 0.993). Taking into account the considerable conformational changes that take place upon protonation, the result is highly satisfactory and provides an estimate of proton affinity for 9-ether-crown-3 (206.5 kcal mol−1) and glyme-5 (231.1 kcal mol−1). Moreover, this work provides a rationale for the fact that, for the same number of oxygen atoms, glymes are more basic than crown ethers. For the crown ethers, the proton affinity depends on angular strain in the base and on intramolecular hydrogen bonds in the cation. Key words: protonation, reactivity, glymes, crown ethers, coordination.
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9

Oh, Young-Ho, Ju Gyeong Jeong, Dong Wook Kim y Sungyul Lee. "Nucleophilic Reactions Using Alkali Metal Fluorides Activated by Crown Ethers and Derivatives". Catalysts 13, n.º 3 (27 de febrero de 2023): 479. http://dx.doi.org/10.3390/catal13030479.

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We review crown ether-facilitated nucleophilic reactions using metal salts, presenting the studies using kinetic measurements and quantum chemical methods. We focus on the mechanistic features, specifically on the contact ion-pair (CIP) mechanism of metal salts for nucleophilic processes promoted by crown ethers and derivatives. Experimental verification of the CIP form of the metal salt CsF complexed with [18-Crown-6] by H-NMR spectroscopy is described. The use of chiral crown ethers and derivatives for enantioselective nucleophilic processes is also discussed.
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Inoue, Yoshihisa, Hiroya Harino, Toshiyo Nakazato, Noriaki Koseki y Tadao Hakushi. "Unsaturated crown ethers. 3. Syntheses of stilbeno crown ethers". Journal of Organic Chemistry 50, n.º 25 (diciembre de 1985): 5151–56. http://dx.doi.org/10.1021/jo00225a035.

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Tesis sobre el tema "Crown ethers"

1

Huang, Zilin. "Synthesis and Complexation Studies of Novel Functionalized Crown Ethers and Azacrown Ethers". Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5593/.

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Novel cage-functionalized azacrown ethers, i.e. 51, 52, 53, 55, 57, 61 and 62, which have various crown cavity and different number of nitrogen atoms incorporated, have been prepared. X-ray structures of 53, 55 and 57 have been obtained for the study of the crown topological structure. The complexation properties of crown 51, 52, 57, 61 and 62 have been evaluated via alkali metal picrate extraction, silver picrate extraction and ESI-MS study. The novel cage-fuctionalized azacrown ethers generally exhibit high avidity and selectivity towards Ag+ versus alkali metal ions and some transition metals i.e. Cu2+, Mn2+, Zn2+, Ni2+ and Pb2+. Crown 61 displays significant avidity and selectivity toward K+ in alkali metal picrate extraction experiments vis-à-vis the remaining alkali metal picrates. Three types of ditopic ion-exchange receptors for sodium hydroxide extraction study have been designed. All of the crown ether molecules have proper cavity for selective sodium complexation and have weakly acidic ionizable alcohols for sodium-proton exchange under strongly basic conditions. Crown 80 and 81 were synthesized; key intermediates for the synthesis of crown 82, 83 and 84 have been prepared. The preparation of 99 afforded an unexpected crown 103. The preparation of 109 had been attempted, but could not be successfully isolated. Four novel cage-functionalized calix[4]arene crown-5, i.e. 113-116, have been synthesized. The structures of 113 and 116 have been established by X-ray crystal structural analysis and NMR spectral analysis. The complexation properties of the four ionic receptors have been studied via alkali metal picrate extraction experiments. Crown 115 and 116 display more than modest avidity toward alkali metal ions and are most selective toward K+ vis-à-vis 113 and 114.
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2

Owens, K. A. "Polycyclic crown ethers incorporating cyclophane units". Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370864.

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Wilson, Mark James. "Activity relationships for aromatic crown ethers". Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249872.

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Huang, Zilin. "Synthesis and Properties of Novel Cage-Annulated Crown Ethers". Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc5523/.

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Three cage-functionalized polyoxacrown ethers (9, 10 and 12) and four novel cage-functionalized polyoxamonoazacrown ethers (18, 20, 25 and 29) that contain 3,5-disubstituted-4-oxahexacyclo[5.4.0.02,6.03,10.05,9.08,11]dodecane ("oxahexacyclic") moiety have been synthesized and their respective alkali metal picrate extraction profiles along with that of three analogues 13, 14 and 21 have been obtained. The observed avidities and selectivities of the host molecules toward complexation and transport of alkali metal picrates can be related to the size and shape of their respective macrocyclic cavity and the number of donor atoms. The effect of N-alkyl substitution on the complexation properties of azacrown ethers has been studied. The avidity of N-Et azacrown ethers toward complexation with alkali metal cations is generally higher than that of the corresponding non-N-alkylated hosts. However, the presence of an N-Et group appears to have a negligible effect upon their relative selectivities in their regards. The effect of pH on extraction process was studied; it was thereby determined that the alkali metal picrate extraction experiments are best performed at high pH (ca. 11-12).
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Denike, John Kane Carleton University Dissertation Chemistry. "The synthesis and complexation of bis-crown ethers and polymers bearing pendant crown ethers and the study of molecular motion of crown ethers in solids using solid state 2H NMR". Ottawa, 1992.

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Ji, Mingzhe. "Explorations with optically active, cage-annulated crown ethers". Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4207/.

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A variety of optically active macrocyclic crown ethers that serve as "host" systems that are capable of differentiating between enantiomeric "guest" molecules during host-guest complexation have been prepared via incorporation of chiral elements into the crown ring skeleton. The ability of these crown ethers to recognize the enantiomers of guest salts, i.e., (+) a-methyl benzylamine and to transport them enantioselectively in W-tube transport experiments were studied. The ability of these crown ethers to perform as chiral catalysts in an enantioselective Michael addition was studied. The extent of asymmetric induction, expressed in terms of the enantiomeric excess (%ee), was monitored by measuring the optical rotation of the product and comparing to the literature value.
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Merithew, Andrew William. "Differential Self-Assembly of Novel Redox Crown Ethers". Thesis, University of California, Santa Barbara, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3645672.

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Retinal prosthesis relies on the stimulation of living nerve tissue behind the rods and cones of the eye. The current state of the art relies on electrodes controlled by cameras which directly stimulate the nerve tissue to elicit a response to an image. These types of retinal implants have allowed for short-term crude vision in patients but have had limited long term success due to external battery packs and electroplating of the implanted electrodes.

Ionic stimulation is one of the principle mechanisms that sensory neurons utilize in the generation of an action potential. In a complex transduction pathway, ionic gradients are constantly altered inside the neuron by voltage sensors or mechanically controlled gates embedded in the neuronal cell membrane; responsible for the open and close state of these ion channels.

It has been demonstrated that local concentration increases of K + by direct injection proximal to the nerve can elicit nerve firing at a concentration of 15-20 mM (3-4X normal concentration) increase in K + concentration. As part of a larger concept of integrating biotechnology with nanofabrication, the materials for the development of potassium selective sequestration/storage and delivery were developed in the form of a redox-gated K+ selective crown ether.

The structure of the anthraquinone-based crown was deduced by computational simulation and stoichiometry of the complex confirmed by mass spec. along with 2D diffusion NMR techniques. In this instance, the stoichiometry could be controlled by the addition of different salts to give a 1:1 complex with large, aromatic anions and a 2:1 complex with smaller anions such as triflate. The synthesis of the molecule was optimized by computational modeling and simulations of transport through an artificial membrane. The selectivity of the architecture developed was specific for K+ over Na+, the other major ionic species present in the blood. The mechanism influencing the self-assembly of this class of compounds has much to do with the breakage of intramolecular π-stacking interactions and the formation of stronger intermolecular π-stacking interactions.

Finally, the transport of K+ through nanoporous membranes and single nanopores with novel PEG-type polymeric dispersions is demonstrated. This thesis concludes with future work toward developing more advanced transporters and proposes novel uses for anthraquinone-appended polymers as proton exchange membranes and DNA-base pair interchelators.

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8

D'Souza, Lawrence Joseph. "Bile Acid Based Molecular Tweezers And Crown Ethers". Thesis, Indian Institute of Science, 1995. https://etd.iisc.ac.in/handle/2005/114.

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Chapter 1. Introduction to Molecular Tweezers Whitlock and Zimmerman developed a class of molecular hosts, popularly known as molecular tweezers, which sandwich aromatic guests by ii=ii interaction. Chapter 1 summarizes molecular tweezers of various kinds which have recently been synthesized. Chapter 2. Design and synthesis of "Bile Acid-Based Molecular Tweezers" Bile acids have a rigid backbone, and the array of hydroxyl groups separated by 5-7 A provides opportunities for the attachment of binding surfaces such as two extended chromophoric units.
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D'Souza, Lawrence Joseph. "Bile Acid Based Molecular Tweezers And Crown Ethers". Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/114.

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Chapter 1. Introduction to Molecular Tweezers Whitlock and Zimmerman developed a class of molecular hosts, popularly known as molecular tweezers, which sandwich aromatic guests by ii=ii interaction. Chapter 1 summarizes molecular tweezers of various kinds which have recently been synthesized. Chapter 2. Design and synthesis of "Bile Acid-Based Molecular Tweezers" Bile acids have a rigid backbone, and the array of hydroxyl groups separated by 5-7 A provides opportunities for the attachment of binding surfaces such as two extended chromophoric units.
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Landry, Denis Joseph Carleton University Dissertation Chemistry. "Approaches to the synthesis and sterochemical analysis of aza crown ethers". Ottawa, 1989.

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Libros sobre el tema "Crown ethers"

1

E, Weber, Patai Saul y Rappoport Zvi, eds. Crown ethers and analogs. Chichester: Wiley, 1989.

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Michio, Hiraoka, ed. Crown ethers and analogous compounds. Amsterdam: Elsevier, 1992.

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Michio, Hiraoka, ed. Crown ethers and analogous components. Amsterdam: Elsevier, 1992.

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Weber, Edwin, John L. Toner, Israel Goldberg, Fritz Vgtle, Dale A. Laidler, J. Fraser Stoddart, Richard A. Bartsch y Charles L. Liotta, eds. Crown Ethers and Analogs (1989). Chichester, UK: John Wiley & Sons, Inc., 1989. http://dx.doi.org/10.1002/9780470772232.

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Robinson, Peter Mark. Crown ethers incorporating stable carbocations. Manchester: University of Manchester, 1994.

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Mooney, Nichola Jane. Crown ethers incorporating 1,8-dioxyxanthyl residues. Manchester: University of Manchester, 1996.

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Nesterov, S. V. Dicyclohexanocrown ethers: From synthesis to radiochemical applications. New York: Nova Science Publishers, 2011.

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Bradshaw, J. S. Aza-crown macrocycles. New York: Wiley, 1993.

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1926-, Izatt Reed McNeil y Bradshaw J. S, eds. The Pedersen memorial issue. Dordrecht: Kluwer Academic Publishers, 1992.

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Mooney, Nichola Jane. Synthesis and properties of crown ethers incorporating Xanthene residues. Manchester: University of Manchester, 1993.

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Capítulos de libros sobre el tema "Crown ethers"

1

Mohapatra, P. K. "Crown Ethers". En Encyclopedia of Membranes, 488–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-44324-8_162.

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Mohapatra, P. K. "Crown Ethers". En Encyclopedia of Membranes, 1–2. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-40872-4_162-4.

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Fedorova, Olga, Yuri Fedorov y Vladimir Lokshin. "Photochromic Crown Ethers". En Photon-Working Switches, 345–61. Tokyo: Springer Japan, 2017. http://dx.doi.org/10.1007/978-4-431-56544-4_17.

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Stoddart, J. Fraser. "Chiral Crown Ethers". En Topics in Stereochemistry, 207–88. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470147269.ch3.

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Kaller, Martin y Sabine Laschat. "Liquid Crystalline Crown Ethers". En Topics in Current Chemistry, 109–92. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/128_2011_211.

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Takata, Toshikazu y Hiromitsu Sogawa. "Crown Ethers-Based Supramolecular Polymers". En Encyclopedia of Polymeric Nanomaterials, 1–6. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-36199-9_96-1.

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Botti, P., H. L. Ball, P. Lucietto, M. Pinori y P. Mascagni. "Crown ethers and peptide synthesis". En Peptides 1994, 147–48. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-1468-4_56.

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Takata, Toshikazu y Hiromitsu Sogawa. "Crown Ethers-Based Supramolecular Polymers". En Encyclopedia of Polymeric Nanomaterials, 505–10. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-29648-2_96.

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Chen, Ling y Yu Liu. "Water-Soluble Aromatic Crown Ethers". En Handbook of Macrocyclic Supramolecular Assembly, 3–26. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-2686-2_2.

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Fu, Hong-Guang, Yong Chen y Yu Liu. "Polypseudorotaxanes Constructed by Crown Ethers". En Handbook of Macrocyclic Supramolecular Assembly, 27–47. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-2686-2_3.

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Actas de conferencias sobre el tema "Crown ethers"

1

El-Azhary, A. A., N. Al-Jallal, A. Al-Kahtani, N. Al-Badri, K. Al-Farhan y M. Al-Qunaibit. "Structure of crown ethers". En THEORY AND APPLICATIONS IN COMPUTATIONAL CHEMISTRY: THE FIRST DECADE OF THE SECOND MILLENNIUM: International Congress TACC-2012. AIP, 2012. http://dx.doi.org/10.1063/1.4730663.

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Vazirova, Leyla y Govhar Abbasova. "Sorbents Based on Iron Oxide Nanoparticles for Release of Tetracyclines for Water Treatment". En 2nd International Scientific-Practical Conference "Machine Building and Energy: New Concepts and Technologies". Switzerland: Trans Tech Publications Ltd, 2024. http://dx.doi.org/10.4028/p-sh9pfn.

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The aim of the research was to establish and produce unfamiliar magnetic absorbents based on a commonly accessible specimen containing crown ethers via iron nanoparticles (magnetite), investigation their structural, magnetic, and absorbance properties, and analyze the possible utilization of these sorbents for the sorption and accumulation of tetracyclines. New crown complexes with biological prop ethers have been created, and the structure of the produced crown complexes has been determined using elemental analysis data from studies of these samples' IR, mass, and NMR spectra. According to the contact duration between the phases, the pH and solution's composition, the structure of tetracyclines, and their concentration, an organized research of the sorption of tetracycline on a magnetic composite with crown ethers was conducted as a component of the study. Crown ethers and Fe3O4 (CE@Fe3O4NPs) nanoparticles were produced under certain conditions, and the composites' magnetic and structural characteristics were evaluated. Tetracyclines were evaluated for their ability to bind to the nanostructures produced by CE@Fe3O4 NPs. These structures have no negative effects and remain safe for consumption. Crown ethers are currently produced using novel techniques, and new magnetic sorbents made with crown ethers and Fe3O4 nanoparticles have also been developed. It has been shown that magnetic sorbents composed of Fe3O4 nanoparticles and crown ethers have superparamagnetic characteristics. The research in consideration identifies and discusses the characteristics of tetracyclines' sorption behavior. There are several methods for concentrating tetracyclines for sorption onto a magnetic sorbent using Fe3O4 nanoparticles and crown ethers from aqueous solutions. Our research has demonstrated, using the example of produced CE@Fe3O4 NPs nanostructures, that mixing the nanotechnological approach with the methods of supramolecular chemistry offers a large adsorption effectiveness.
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3

Birck, Jean Louis, Julien Bouchez, Akanksha Praharaj, Mathieu Dellinger y Samia Zrig. "Li separation from natural samples using crown-ethers." En Goldschmidt2023. France: European Association of Geochemistry, 2023. http://dx.doi.org/10.7185/gold2023.18705.

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Lopez, Juan, Susana Blanco, Melanie Schnell y Cristobal Perez. "CHARACTERIZATION OF MICROSOLVATED CROWN ETHERS FROM BROADBAND ROTATIONAL SPECTROSCOPY". En 71st International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2016. http://dx.doi.org/10.15278/isms.2016.ti05.

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Chang, S. H., T. J. Ka, J. Y. Kim, A. S. Yeon, H. H. Nam y G. S. Che. "Syntheses of new Bis-crown ethers based on siloxane". En International Conference on Science and Technology of Synthetic Metals. IEEE, 1994. http://dx.doi.org/10.1109/stsm.1994.835746.

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Trisca-Rusu, C., A. C. Nechifor, S. I. Voicu y G. Nechifor. "Covalently immobilized crown ethers onto polysulfone membranes as materials for sensors". En 2010 International Semiconductor Conference (CAS 2010). IEEE, 2010. http://dx.doi.org/10.1109/smicnd.2010.5649081.

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Nakamura, T., K. Honda, A. E. Underhill, A. T. Coomber y R. H. Friend. "Ni(dmit)/sub 2/ salts of group-i-cation-including crown ethers". En International Conference on Science and Technology of Synthetic Metals. IEEE, 1994. http://dx.doi.org/10.1109/stsm.1994.835469.

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Kim, Sun-Ju y Ji-Youn Seo. "Interfacial engineering through lead binding using crown ethers in perovskite solar cells". En International Conference on Hybrid and Organic Photovoltaics. València: FUNDACIO DE LA COMUNITAT VALENCIANA SCITO, 2024. http://dx.doi.org/10.29363/nanoge.hopv.2024.195.

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Guseva, E. V., Z. Z. Idiiatullova y L. F. Davletshina. "The study of ligand properties of crown ethers (18-crown-6 and dibenzo-18-crown-6) when interacting with RhCl3 • nH2O in aprotic and proton solvents". En ТЕНДЕНЦИИ РАЗВИТИЯ НАУКИ И ОБРАЗОВАНИЯ. НИЦ «Л-Журнал», 2019. http://dx.doi.org/10.18411/lj-03-2019-130.

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Paviet-Hartmann, Patricia, Ana Nunez Gomez-Aleixandre, Joshua Pak, Amparo Glez Espartero, Frederic Poineau, Amber Wright, Edward Mausolf y Kenneth R. Czerwinski. "Extraction of Technetium as [Tc(II)(NO)(AHA)2H2O]+ Species in the UREX Process". En 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75509.

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As it is envisioned today, the first segment of the UREX+ process uses low nitric acid concentrations for U(VI) extraction where pertechnetate anion, TcO4−, can be co-extracted with the uranyl and nitrate into TBP-hydrocarbon solutions. A reductant complexant, acetohydroxamic acid (AHA) is added to the process through the scrub to limit the extractability of plutonium and neptunium. Recent work performed in our laboratory (Ref. 1) demonstrated that TcO4− undergoes reductive nitrosylation by AHA under a variety of conditions. The resulting divalent technetium is complexed by AHA to form the pseudo-octahedral trans-aquonitrosyl-(diacetohydroxamic)-technetium(II) complex ([Tc(II)(NO)(AHA)2H2O]+). In this paper, we are reporting the extraction of [Tc(II)(NO)(AHA)2H2O]+ complex by new designed macrocompounds as well as commercially available crown ethers from 18-crown-6 to 24-crown-8 in ring size and of varying derivatization. Several organic diluents with different dielectric constants are used to enhance the distribution coefficient of technetium (II). The experimental efforts are focused on determining the best extraction conditions by varying the macrocomponds nature and concentration, and the organic phase composition.
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Informes sobre el tema "Crown ethers"

1

Bartsch, R. Metal ion complexation by ionizable crown ethers. Office of Scientific and Technical Information (OSTI), septiembre de 1989. http://dx.doi.org/10.2172/5483625.

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Bartsch, R. Metal ion complexation by ionizable crown ethers. Office of Scientific and Technical Information (OSTI), junio de 1990. http://dx.doi.org/10.2172/6737356.

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Chien M. Wai, Anne Rustenholtz, Shaofen Wang, Su-Chen Lee, Jamie Herman y Richard A. Porter. Solvent Effects on Cesium Complexation with Crown Ethers from Liquid to Supercritical Fluids. Office of Scientific and Technical Information (OSTI), marzo de 2004. http://dx.doi.org/10.2172/822406.

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Chiarizia, R., M. L. Dietz, E. P. Horwitz y W. C. Burnett. Radium separation through complexation by aqueous crown ethers and ion exchange or solvent extraction. Office of Scientific and Technical Information (OSTI), noviembre de 1997. http://dx.doi.org/10.2172/554809.

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Eyring, Edward M. y Sergio Petrucci. Rates and Mechanisms of Complexation Reactions of Cations with Crown Ethers and Related Macrocycles. Fort Belvoir, VA: Defense Technical Information Center, enero de 1989. http://dx.doi.org/10.21236/ada203436.

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Wai, Chien M. y Clem Yonker. Solution Effects on Cesium Complexation with Calixarene - Crown Ethers from Liquid to Supercritical Fluids. Office of Scientific and Technical Information (OSTI), junio de 1999. http://dx.doi.org/10.2172/833192.

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Bonnesen, P. V., B. A. Moyer, D. J. Presley, V. S. Armstrong, T. J. Haverlock, R. M. Counce y R. A. Sachleben. Alkaline-side extraction of technetium from tank waste using crown ethers and other extractants. Office of Scientific and Technical Information (OSTI), junio de 1996. http://dx.doi.org/10.2172/257317.

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Bartsch, R. A. Metal ion complexation by ionizable crown ethers. Final report, January 1, 1988--June 30, 1994. Office of Scientific and Technical Information (OSTI), diciembre de 1994. http://dx.doi.org/10.2172/392788.

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Bartsch, R. A. Metal ion complexation by ionizable crown ethers. Progress report, January 1, 1991--December 31, 1993. Office of Scientific and Technical Information (OSTI), julio de 1993. http://dx.doi.org/10.2172/10134650.

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Bonnesen, P. V., D. J. Presley, T. J. Haverlock y B. A. Moyer. Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers. Office of Scientific and Technical Information (OSTI), julio de 1995. http://dx.doi.org/10.2172/86950.

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