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Sample records for lariat crown ethers

  1. Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

    PubMed Central

    Cho, Dae Won

    2014-01-01

    Summary In this review, we describe direct and indirect photochemical approaches that have been developed for the preparation of phthalimide- and naphthalimide-based, lariat-type crown ethers. The direct route utilizes a strategy in which nitrogen-linked side chains containing polyethoxy-tethered phthalimides and naphthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form macrocyclic ring systems. In contrast, the indirect route developed for the synthesis of lariat-type crown ethers employs sequences in which SET-promoted macrocyclization reactions of α-trialkylsilyl-terminated, polyethoxy-tethered phthalimides and naphthalimides are followed by a side chain introduction through substitution reactions at the amidol centers in the macrocyclic ethers. The combined observations made in these investigations demonstrate the unique features of SET-promoted photocyclization reactions that make them well-suited for the use in the synthesis of functionalized crown ethers. In addition, while some limitations exist for the general use of SET-photochemical reactions in large-scale organic synthesis, important characteristics of the photoinduced macrocyclization reactions make them applicable to unique situations in which high temporal and spatial control is required. PMID:24605169

  2. A highly K(+)-selective phenylaza-[18]crown-6-lariat-ether-based fluoroionophore and its application in the sensing of K+ ions with an optical sensor film and in cells.

    PubMed

    Ast, Sandra; Schwarze, Thomas; Müller, Holger; Sukhanov, Aleksey; Michaelis, Stefanie; Wegener, Joachim; Wolfbeis, Otto S; Körzdörfer, Thomas; Dürkop, Axel; Holdt, Hans-Jürgen

    2013-10-25

    Herein, we report the synthesis of two phenylaza-[18]crown-6 lariat ethers with a coumarin fluorophore (1 and 2) and we reveal that compound 1 is an excellent probe for K(+) ions under simulated physiological conditions. The presence of a 2-methoxyethoxy lariat group at the ortho position of the anilino moiety is crucial to the substantially increased stability of compounds 1 and 2 over their lariat-free phenylaza-[18]crown-6 ether analogues. Probe 1 shows a high K(+)/Na(+) selectivity and a 2.5-fold fluorescence enhancement was observed in the presence of 100 mM K(+) ions. A fluorescent membrane sensor, which was prepared by incorporating probe 1 into a hydrogel, showed a fully reversible response, a response time of 150 s, and a signal change of 7.8% per 1 mM K(+) within the range 1-10 mM K(+). The membrane was easily fabricated (only a single sensing layer on a solid polyester support), yet no leaching was observed. Moreover, compound 1 rapidly permeated into cells, was cytocompatible, and was suitable for the fluorescent imaging of K(+) ions on both the extracellular and intracellular levels. PMID:24105686

  3. Alkylated lariat ethers as solvent extraction reagents: Surveying the extraction of alkali metals by bis-t-octylbenzo-14-crown-4-acetic acid by use of potentiometric two-phase titration

    SciTech Connect

    Sachleben, R.A.; Moyer, B.A.; Case, F.I.; Garmon, S.A.

    1993-01-01

    Two-phase potentiometric titrimetry was used to survey the extraction of alkali metal cations from aqueous chloride solution by the lipophilic, ionizable lariat ether bis-(t-octylbenzo)-14-crown-4-acetic acid (BOB14C4AA) in o-xylene. Analysis of the data indicates that ion-exchange extraction by the crown-carboxylic acid at low loading (i.e., low conversion of BOB14C4AA to its salt form) is stronger for lithium ion than for the other alkali metals. Little or no selectivity occurs at high loadings. In comparison with the long-chain carboxylic acid 2-methyl-2-heptylnonanoic acid (HMHN), BOB14C4AA extracts lithium and sodium at significantly lower pH; in the loading range of 0.1 to 0.7, the pH shift is 1.4-1.8 pH units for sodium ion and 1.7-2.3 pH units for lithium ion. The titration data are interpreted in terms of aggregated organic-phase species. In the case of lithium extraction, clear evidence was found for a species in which neutral BOB14C4AA participates in the organic-phase complexation of the metal cation.

  4. Crown ethers in graphene

    SciTech Connect

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-13

    Crown ethers, introduced by Pedersen1, are at their most basic level neutral rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted special attention for their ability to selectively incorporate various atoms2 or molecules within the cavity formed by the ring3-6. This property has led to the use of crown ethers and their compounds in a wide range of chemical and biological applications7,8. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity9,10. In this Letter, we report atomic-resolution images of the same basic structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar and thus uniquely suited for the many applications that crown ethers are known for. First-principles calculations show that the close similarity of the structures seen in graphene with those of crown ether molecules also extends to their selectivity towards specific metal cations depending on the ring size. Atoms (or molecules) incorporated within the crown ethers in graphene offer a simple environment that can be easily and systematically probed and modeled. Thus, we expect that this discovery will introduce a new wave of investigations and applications of chemically functionalized graphene.

  5. Crown ethers in graphene

    DOE PAGESBeta

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-13

    Crown ethers, introduced by Pedersen1, are at their most basic level neutral rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted special attention for their ability to selectively incorporate various atoms2 or molecules within the cavity formed by the ring3-6. This property has led to the use of crown ethers and their compounds in a wide range of chemical and biological applications7,8. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity9,10. In this Letter, we report atomic-resolution images of the same basicmore » structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar and thus uniquely suited for the many applications that crown ethers are known for. First-principles calculations show that the close similarity of the structures seen in graphene with those of crown ether molecules also extends to their selectivity towards specific metal cations depending on the ring size. Atoms (or molecules) incorporated within the crown ethers in graphene offer a simple environment that can be easily and systematically probed and modeled. Thus, we expect that this discovery will introduce a new wave of investigations and applications of chemically functionalized graphene.« less

  6. Crown ethers in graphene

    NASA Astrophysics Data System (ADS)

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-01

    Crown ethers are at their most basic level rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted attention for their ability to selectively incorporate various atoms or molecules within the cavity formed by the ring. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity. Here we present atomic-resolution images of the same basic structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar. First-principles calculations show that the close similarity of the structures should also extend to their selectivity towards specific metal cations. Crown ethers in graphene offer a simple environment that can be systematically tested and modelled. Thus, we expect that our finding will introduce a new wave of investigations and applications of chemically functionalized graphene.

  7. Metal ion complexation by ionizable crown ethers. Progress report, January 1, 1991--December 31, 1993

    SciTech Connect

    Bartsch, R.A.

    1993-07-01

    Cyclic and acyclic polyether compounds with pendent carboxylic acid, phosphonic acid monoethyl ester, sulfonic acid, phosphinic acid and hydroxamic acid groups have been synthesized. The proton-ionizable polyethers can come with and without lipophilic groups. Two types of lipophilic di-ionizable lariat ethers have been prepared. Conformations of proton-ionizable lariat ethers have been probed. Competitive alkali metal cation transport by syn-(decyl)dibenzo-16-crown-5-oxyacetic acid and lipophilic proton-ionizable dibenzo lariat ethers in polymer-supported liquid membranes was studied. Complexation of alkali metal cations with ionized lariat ethers was studied. Condensation polymerization of cyclic and acyclic dibenzo polyethers containing pendent mono-ionizable groups with formaldehyde produces novel ion exchange resins with both ion exchange sites for metal ion complexation and polyether binding sites for metal ion recognition. Resins prepared from lariat ether dibenzo phosphonic acid monoethyl esters show strong sorption of divalent heavy metal cations with selectivity for Pb{sup 2+}.

  8. A schiff-base bibracchial lariat ether forming a cryptand-like cavity for lanthanide ions.

    PubMed

    González-Lorenzo, Marina; Platas-Iglesias, Carlos; Avecilla, Fernando; Geraldes, Carlos F G C; Imbert, Daniel; Bünzli, Jean-Claude G; de Blas, Andrés; Rodríguez-Blas, Teresa

    2003-10-20

    We report here a structural and photophysical study of lanthanide(III) complexes with the di-deprotonated form of the bibracchial lariat ether N,N'-bis(2-salicylaldiminobenzyl)-1,10-diaza-15-crown-5. The X-ray crystal structures of [Ce(L(2)-2H)](ClO(4)).0.5H(2)O (2) and [Sm(L(2)-2H)](ClO(4)).C(3)H(8)O (5b) show the metal ion being nine-coordinated and deeply buried in the cavity of the dianionic receptor. Thanks to the formation of a pseudomacrocycle through pi-pi interaction between one of the phenol rings and one of the benzyl rings, the complexes present a cryptand-like structure in the solid state. (1)H and (13)C NMR studies on the La(III) complex point that the solid state structure is essentially maintained in acetonitrile solution. High-resolution laser-excited emission spectra of the crystalline Eu(III) complex demonstrate the presence of several coordination sites arising from different conformations of the crown moiety. The ligand-to-Eu(III) energy transfer is relatively efficient at low temperature, but back transfer is implied in the deactivation process, especially at room temperature, because the ligand triplet state lies at very low energy. However, the low energy of the (3)pipi state provides an efficient conversion of the visible light absorbed into near-infrared light emitted by the Nd(III) ion. PMID:14552647

  9. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.

  10. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.O.; McBreen, J.

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI{sup +} ion in alkali metal batteries. 3 figs.

  11. "Crown Ether" Synthesis: An Organic Laboratory Experiment.

    ERIC Educational Resources Information Center

    Field, Kurt W.; And Others

    1979-01-01

    This experiment is designed to acquaint the student with a macromolecular synthesis of a crown ether type compound. The starting materials are readily available and the product, a cyclic polyether, belongs to a class of compounds that has aroused the interest of chemist and biologist alike. (Author/BB)

  12. Crown Ethers in Nonaqueous Electrolytes for Lithium/Air Batteries

    SciTech Connect

    Xu, Wu; Xiao, Jie; Wang, Deyu; Zhang, Jian; Zhang, Jiguang

    2010-02-04

    The effects of three crown ethers, 12-crown-4, 15-crown-5, and 18-crown-6, as additives and co-solvents in non-aqueous electrolytes on the cell performance of primary Li/air batteries operated in a dry air environment were investigated. Crown ethers have large effects on the discharge performance of non-aqueous electrolytes in Li/air batteries. A small amount (normally less than 10% by weight or volume in electrolytes) of 12-Crown-4 and 15-crown-5 reduces the battery performance and a minimum discharge capacity appears at the crown ether content of ca. 5% in the electrolytes. However, when the content increases to about 15%, both crown ethers improve the capacity of Li/air cells by about 28% and 16%, respectively. 15-Crown-5 based electrolytes even show a maximum discharge capacity in the crown ether content range from 10% to 15%. On the other hand, the increase of 18-crown-6 amount in the electrolytes continuously lowers of the cell performance. The different battery performances of these three crown ethers in electrolytes are explained by the combined effects from the electrolytes’ contact angle, oxygen solubility, viscosity, ionic conductivity, and the stability of complexes formed between crown ether molecules and lithium ions.

  13. Phosphorus-nitrogen compounds. Part 20: Fully substituted spiro-cyclotriphosphazenic lariat (PNP-pivot) ether derivatives

    NASA Astrophysics Data System (ADS)

    Okumuş, Aytuğ; Bilge, Selen; Kılıç, Zeynel; Öztürk, Aslı; Hökelek, Tuncer; Yılmaz, Filiz

    2010-08-01

    The condensation reactions of partly substituted spiro-cyclotriphosphazenic lariat (PNP-pivot) ethers, N 3P 3[( o-NHPhO) 2R]Cl 4 [where R = -CH 2CH 2- ( 1) and -CH 2CH 2OCH 2CH 2- ( 2)] with morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) produce fully substituted morpholino ( 3 and 4) and 1,4-dioxa-8-azaspiro[4,5]deca ( 5 and 6) phosphazenes. These are the new examples of the spiro-cyclophosphazenic lariat ether derivatives with N 2O x ( x = 2 and 3) donor type containing 11- and 14-membered macrocycles. The solid state structures of 3, 5 and 6 have been determined by X-ray diffraction techniques. Compound 3 has intermolecular N-H…O hydrogen bond, compound 5 has intra- and intermolecular N-H…O hydrogen bonds, while compound 6 has intramolecular N-H…O and O-H…N and intermolecular N-H…O and O-H…O hydrogen bonds. The correlations of the endocyclic ( α) and exocyclic ( α') NPN bond angles with δP spiro values are investigated. The structural investigations of 3- 6 have been verified by elemental analyses, MS, FTIR, 1H, 13C and 31P NMR, DEPT and HETCOR techniques.

  14. Supramolecular polymers constructed by crown ether-based molecular recognition.

    PubMed

    Zheng, Bo; Wang, Feng; Dong, Shengyi; Huang, Feihe

    2012-03-01

    Supramolecular polymers, polymeric systems beyond the molecule, have attracted more and more attention from scientists due to their applications in various fields, including stimuli-responsive materials, healable materials, and drug delivery. Due to their good selectivity and convenient enviro-responsiveness, crown ether-based molecular recognition motifs have been actively employed to fabricate supramolecular polymers with interesting properties and novel applications in recent years. In this tutorial review, we classify supramolecular polymers based on their differences in topology and cover recent advances in the marriage between crown ether-based molecular recognition and polymer science. PMID:22012256

  15. Extraction of actinides and nitric acid by crown ethers

    SciTech Connect

    Rozen, A.M.; Nikolotova, Z.I.; Kartasheva, N.A.; Luk'yanenko, N.G.; Bogatskii, A.V.

    1982-10-01

    This work studied the extraction of thorium nitrate, and an extraction isotherm of uranyl nitrate was obtained; the distribution of HNO/sub 3/ was studied over a wide range of acidity (up to 18M), which uses different concepts on the mechanism of the process. The extraction of Pu(VI) and Np(IV) was studied up to a 12 M acidity; two crown ethers had not previously been used for the extraction of the actinides. A quantitative description of the equilibria studied is given, and the influence of the structure of the ethers on the complex formation is discussed.

  16. Increasing the thermopower of crown-ether-bridged anthraquinones.

    PubMed

    Ismael, Ali K; Grace, Iain; Lambert, Colin J

    2015-11-01

    We investigate strategies for increasing the thermopower of crown-ether-bridged anthraquinones. The novel design feature of these molecules is the presence of either () crown-ether or () diaza-crown-ether bridges attached to the side of the current-carrying anthraquinone wire. The crown-ether side groups selectively bind alkali-metal cations and when combined with TCNE or TTF dopants, provide a large phase-space for optimising thermoelectric properties. We find that the optimum combination of cations and dopants depends on the temperature range of interest. The thermopowers of both and are negative and at room temperature are optimised by binding with TTF alone, achieving thermpowers of -600 μV K(-1) and -285 μV K(-1) respectively. At much lower temperatures, which are relevant to cascade coolers, we find that for , a combination of TTF and Na(+) yields a maximum thermopower of -710 μV K(-1) at 70 K, whereas a combination of TTF and Li(+) yields a maximum thermopower of -600 μV K(-1) at 90 K. For , we find that TTF doping yields a maximum thermopower of -800 μV K(-1) at 90 K, whereas at 50 K, the largest thermopower (of -600 μV K(-1)) is obtain by a combination TTF and K(+) doping. At room temperature, we obtain power factors of 73 μW m(-1) K(-2) for (in combination with TTF and Na(+)) and 90 μW m(-1) K(-2) for (with TTF). These are higher or comparable with reported power factors of other organic materials. PMID:26426840

  17. Secondary Li battery incorporating 12-Crown-4 ether

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, Ganesan (Inventor); Distefano, Salvador (Inventor)

    1992-01-01

    A rechargeable lithium battery which utilizes a polyethylene oxide (PEO) solid polymeric electrolyte complexed with a lithium salt is disclosed. The conductivity is increased an order of magnitude and interfacial charge transfer resistance is substantially decreased by incorporating a minor amount of 12-Crown-4 ether in the PEO-lithium salt solid electrolyte film. Batteries containing the improved electrolyte permit operation at a lower temperature with improved efficiency.

  18. Novel Ordered Crown Ether-Containing Polyimides for Ion Conduction

    NASA Technical Reports Server (NTRS)

    Irvin, Jennifer A.; Stasko, Daniel; Fallis, Stephen; Guenthner, Andrew J.; Webber, Cynthia; Blackwell, John; Chvalun, Sergei N.

    2003-01-01

    We report the synthesis and characterization of thermally-stable polyimides for use as battery and fuel cell electrolyte membranes. Dianhydrides used were 1,4,5,8- naphthalenetetracarboxylic dianhydride and/or 4,4'-(hexafluoroisopropylidene)diphthalic anhydride. Diamines used were anti-4,4-diaminodibenzo-l8-crown-6, 4,4'- diaminodibenzo-24-crown-8, 2,2-bis(4-aminophenyl)hexafluoropropane, and/or 2,5- diaminobenzenesulfonic acid. The polymers were characterized using electrochemical impedance spectroscopy (EIS), thermal analysis and X-ray diffraction. Polymers containing the hexafluoroisopropylidene (HFIP) group were soluble in common organic solvents, while polymers without the HFIP group were very poorly soluble. Sulfonation yields polymers that are sparingly soluble in aqueous base and/or methanol. Degree of sulfonation, determined by titration, was between one and three sulfonate groups per repeat unit. Proton conductivity was determined as a function of water content, with a maximum conductivity of l x 10(exp -2) per centimeter when fully hydrated. Crown ether-containing polymers exhibit a high degree of order that may be indicative of crown ether channel formation, which may facilitate Li(+) transport for use in battery membranes.

  19. On the radiation stability of crown ethers in ionic liquids.

    SciTech Connect

    Shkrob, I.; Marin, T.; Dietz, M.

    2011-04-14

    Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic nuclear waste streams. Room temperature ionic liquids (ILs) are presently being considered as replacements for traditional molecular solvents employed in such separations. It is desirable that the extraction efficacy obtained with such solvents should not deteriorate in the strong radiation fields generated by decaying radionuclides. This deterioration will depend on the extent of radiation damage to both the IL solvent and the CE solute. While radiation damage to ILs has been extensively studied, the issue of the radiation stability of crown ethers, particularly in an IL matrix, has not been adequately addressed. With this in mind, we have employed electron paramagnetic resonance (EPR) spectroscopy to study the formation of CE-related radicals in the radiolysis of selected CEs in ILs incorporating aromatic (imidazolium and pyridinium) cations. The crown ethers have been found to yield primarily hydrogen loss radicals, H atoms, and the formyl radical. In the low-dose regime, the relative yield of these radicals increases linearly with the mole fraction of the solute, suggesting negligible transfer of the excitation energy from the solvent to the solute; that is, the solvent has a 'radioprotective' effect. The damage to the CE in the loading region of practical interest is relatively low. Under such conditions, the main chemical pathway leading to decreased extraction performance is protonation of the macrocycle. At high radiation doses, sufficient to increase the acidity of the IL solvent significantly, such proton complexes compete with the solvent cations as electron traps. In this regime, the CEs will rapidly degrade as the result of H abstraction from the CE ring by the released H atoms. Thus, the radiation dose to which a CE/IL system is exposed must be maintained at a level sufficiently low to avoid this regime.

  20. Crown ether derivative assisted growth of oriented polyaniline nanotubes

    NASA Astrophysics Data System (ADS)

    Xia, Haibing; Cheng, Daming; Lam, Peisuan; Chan, Hardy Sze On

    2006-08-01

    We report a chemical route to synthesize oriented arrays of conducting polyaniline (PANI) nanotubes (60-150 nm in diameter and a few micrometres in length) by hydrogen-bonding directionality in the presence of a crown ether derivative (CE-SO3K) and ammonium persulfate (APS) in HCl solution. The morphology of the oriented PANI nanotubes was confirmed by SEM and TEM images. The effects of reaction conditions on the morphology of the resultant PANI nanostructures were studied. The chemical and electronic structures of the PANI nanotubes were also studied by FTIR and UV-vis spectrometry, respectively.

  1. Synthesis and fluorescence properties of divalent europium-poly(methacrylate containing crown ether structure) complexes

    SciTech Connect

    Higashiyama, N.; Nakamura, H.; Mishima, T.; Shiokawa, J.; Adachi, G. )

    1991-02-01

    This paper reports on divalent europium complexes with poly(methacrylate containing crown ether structure)s, poly(crown ether)s, prepared and their fluorescence properties studied. The polymers used were poly(15-crown-5-methyl methacrylate) (PMA15C5), copoly(15- crown-5-methyl methacrylate-X) (copoly(MA15C5-X)); (X = MMA, EMA, BMA, 2-methoxyethyl methacrylate (MAGI) 3,6,9,12,15- pentaoxahexadecyl methacrylate (MAG5)), poly(18-crown-6- methyl methacrylate) (PMA18C6), and copoly(18-crown-6-methyl methacrylate-MMA) (copoly(MA18C6-MMA)), which were obtained by bulk polymerization. The fluorescence properties of Eu{sup 2+} polymers activated by complexing Eu{sup 2+} ions with crown ether groups were measured in powder form. The Eu{sup 2+}-poly (crown ether)s irradiated by UV light generally gave blue bright emission in the region of 420-465 nm. It was Eu{sup 2+}-copoly(Ma15C5-X); (X = MMA, EMA, and MAG1) that showed the largest emission intensity among the Eu{sup 2+} polymers, and its emission intensity was ca. 20% of that for CaWO{sub 4}:Pb (NBS1026) whose quantum efficiency is about 76%. The intensities of emission for the Eu{sup 2+} polymers containing 15-crown-5 were much larger than that for the ones containing 18-crown-6.

  2. SOLUTION EFFECTS ON CESIUM COMPLEXATION WITH CALIXARENE CROWN ETHERS FROM LIQUID TO SUPERCRITICAL FLUIDS

    EPA Science Inventory

    Calixarene-crown ethers with rigid skeletons are superior to flexible crown ethers for separation of 137Cs from high level waste (HLW). However, this extraction methodology often requires undesirable solvents and the extraction efficiency is strongly dependent on the solvent pol...

  3. Construction of supramolecular organogels and hydrogels from crown ether based unsymmetric bolaamphiphiles.

    PubMed

    Gao, Lingyan; Xu, Donghua; Zheng, Bo

    2014-10-18

    A bolaamphiphilic low-molecular-weight gelator based on crown ether, which could self-assemble into organogels and hydrogels, was prepared. The contribution of each part of the structure to the gelation property was investigated by designing a series of analogues. A simple framework (crown ether-hydrophobic linkage-ammonium salt) was proposed. PMID:25174940

  4. Sorbents based on crown ethers: preparation and application for the sorption of strontium

    NASA Astrophysics Data System (ADS)

    Bezhin, N. A.; Dovhyi, I. I.

    2015-12-01

    The key approaches to the synthesis of crown ether-based sorbents, including immobilization both with and without covalent bonding, are reviewed. Examples of sorbent preparation using anodic oxidation, chemical modification of polymers, polycondensation reactions, chemical modification of inorganic supports and radiochemical synthesis for covalent bonding of crown ether moieties are considered. Immobilization methods without covalent bonding including support synthesis in the presence of crown ethers, impregnation of supports with a crown ether solution and the use of powdered crown ether as a sorbent are presented. The applications of sorbents for selective removal of strontium from solutions of radioactive waste and spent nuclear fuel, for radiochemical analysis (determination of strontium in water, soil and biological materials) and for separation of strontium and yttrium isotopes are discussed. The bibliography includes 114 references.

  5. Radium separation through complexation by aqueous crown ethers and ion exchange or solvent extraction

    SciTech Connect

    Chiarizia, R.; Dietz, M.L.; Horwitz, E.P.; Burnett, W.C.

    1997-11-01

    The effect of three water-soluble, unsubstituted crown ethers (15-crown-5 (15C5), 18-crown-6 (18C6) and 21-crown-7 (21C7)) on the uptake of Ca, Sr, Ba and Ra cations by a sulfonic acid cation exchange resin, and on the extraction of the same cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions has been investigated. The crown ethers enhance the sorption of the larger cations by the ion exchange resin, thereby improving the resin selectivity over calcium, a result of a synergistic interaction between the crown ether and the ionic functional groups of the resin. Similarly, the extraction of the larger alkaline earth cations into xylene by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group IIa cation separations have been obtained using each of the three crown ethers as the aqueous ligands and the sulfonic acid cation exchange resin. Even greater separation factors for the radium-calcium couple have been measured with the crown-ethers and HDNNS solutions in the solvent extraction mode. The application of the uptake and extraction results to the development of radium separation schemes is discussed and a possible flowchart for the determination of {sup 226}Ra/{sup 228}Ra in natural waters is presented.

  6. Iptycene-derived crown ether hosts for molecular recognition and self-assembly.

    PubMed

    Han, Ying; Meng, Zheng; Ma, Ying-Xian; Chen, Chuan-Feng

    2014-07-15

    CONSPECTUS: Synthetic macrocyclic hosts have played key roles in the development of host-guest chemistry. Crown ethers are a class of macrocyclic molecules with unique flexible structures. They have served as the first generation of synthetic hosts, and researchers have extensively studied them in molecular recognition. However, the flexible structures of simple crown ethers and their relatively limited modes of complexation with guests have limited the further applications of these molecules. In recent years, researchers have moved toward fabricating interlocking molecules, supramolecular polymers, and other assemblies with specific structures and properties. Therefore, researchers have developed more complex crown ether-based macrocyclic hosts with multicavity structures and multicomplexation modes that provide more diverse and sophisticated host-guest systems. In this Account, we summarize our research on the synthesis and characterization of iptycene-derived crown ether hosts, their use as host molecules, and their applications in self-assembled complexes. Iptycenes including triptycenes and pentiptycenes are a class of aromatic compounds with unique rigid three-dimensional structures. As a result, they are promising building blocks for the synthesis of novel macrocyclic hosts and the construction of novel self-assembled complexes with specific structures and properties. During the last several years, we have designed and synthesized a new class of iptycene-derived crown ether hosts including macrotricyclic polyethers, molecular tweezer-like hosts, and tritopic tris(crown ether) hosts, which are all composed of rigid iptycene building blocks linked by flexible crown ether chains. We have examined the complexation behavior of these hosts with different types of organic guest molecules. Unlike with conventional crown ethers, the combination of iptycene moieties and crown ether chains provides the iptycene-derived crown ether hosts with complexation properties

  7. Design and synthesis of redox-switched lariat ethers and their application for transport of alkali and alkaline-Earth metal cations across supported liquid membrane.

    PubMed

    Awasthy, Anubhuti; Bhatnagar, Mamta; Tomar, Jyoti; Sharma, Uma

    2006-01-01

    A new class of redox-switched anthraquinone derived lariat ethers 1-(1-anthraquinonyloxy) 3, 6, 9 trioxaundecane 11-ol (M(1)), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-ol (M(2)), 1-(1-anthraquinonyloxy) 3 oxapentane 5-ol (M(3)), 1-(1-anthraquinonyloxy) 3 oxapentane 5-butane (M(4)), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-methane (M(5)) and 1-(1-anthraquinonyloxy) 3 oxapentane 5-methane (M(6)) have been synthesized and characterized by spectral analysis. These ionophores were used in liquid membrane carrier facilitated transport of main group metal cations across supported liquid membrane (SLM). Cellulose nitrate membrane was used as membrane support. Effect of various parameters such as variation in concentration of metal as well as ionophore, effect of chain length and end group of ionophore have been studied. The sequence of metal ions transported by ionophore M(1) is Na(+) > Li(+) > K(+) > Ca(2+) > Mg(2+) and the order of metal ions transported by ionophores (M(2)-M(6)) is Li(+) > Na(+) > K(+) > Ca(2+) > Mg(2+). Ionophore M(1) is selective for Na(+), Li(+), and K(+) and ionophores (M(2)-M(6)) are selective for Li(+) and Na(+). PMID:17497021

  8. Methoxy-ether and crown-ether derivatives of tetrahomodioxa- and octahomotetraoxacalix[4]arenes.

    PubMed

    Masci, B; Saccheo, S; Fonsi, M; Varrone, M; Finelli, M; Nierlich, M; Thuéry, P

    2001-08-01

    Three methoxy-ether and one methoxy-ether/crown-ether derivatives of p-tert-butyltetrahomodioxa- and p-R-octahomotetraoxacalix[4]arenes (R = methyl, tert-butyl, H) have been investigated. The first three compounds, 7,15,21,27-tetra-tert-butyl-29,30,31,32-tetramethoxy-3,11-dioxapentacyclo[23.3.1.1(5,9).1(13,17).1(19,23)]ditriaconta-1(29),5,7,9(30),13,15,-17(31),19,21,23(32),25,27-dodecaene, C(50)H(68)O(6), 33,34,35,36-tetramethoxy-7,15,23,31-tetramethyl-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),21,23,25(36),29,31-dodecaene, C(40)H(48)O(8), and 7,23-di-tert-butyl-33,34,35,36-tetramethoxy-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),- 21,23,25(36),29,31-dodecaene, C(44)H(56)O(8), in the partial-cone or 1,2-alternate conformations, present the common feature of methoxy-ether self-inclusion, while the fourth, 42,43-dimethoxy-7,15,23,31-tetramethyl-3,11,19,27,34,37,40-heptaoxahexacyclo[15.15.9.1(5,9).1(21,25).0(13,41).0(29,33)]tritetraconta-5(42),6,8,13(41),14,16,21(43),22,24,29(33),30,32-dodecaene, C(42)H(50)O(9), adopts the 1,3-alternate conformation owing to the presence of a 1,3-polyether chain. PMID:11498633

  9. Development of the aza-crown ether metal complexes as artificial hydrolase.

    PubMed

    Yu, Lan; Li, Fang-zhen; Wu, Jiao-yi; Xie, Jia-qing; Li, Shuo

    2016-01-01

    Hydrolases play a crucial role in the biochemical process, which can catalyze the hydrolysis of various compounds like carboxylic esters, phosphoesters, amides, nucleic acids, peptides, and so on. The design of artificial hydrolases has attracted extensive attention due to their scientific significance and potential applications in the field of gene medicine and molecular biology. Numerous macrocyclic metal complexes have been used as artificial hydrolase in the catalytic hydrolysis of the organic substrate. Aza-crown ether for this comment is a special class of the macrocyclic ligand containing both the nitrogen atoms and oxygen atoms in the ring. The studies showed that the aza-crown complexes exhibited high activity of hydrolytic enzyme. However, the aza-crown ether metal complex as artificial hydrolase is still very limited because of its difficulty in synthesis. This review summarizes the development of the aza-crown ether metal complexes as the artificial hydrolase, including the synthesis and catalysis of the transition metal complexes and lanthanide metal complexes of aza-crown ethers. The purpose of this review is to highlight: (1) the relationship between the structure and hydrolytic activity of synthetic hydrolase; (2) the synergistic effect of metal sites and ligands in the course of organic compound hydrolysis; and (3) the design strategies of the aza-crown ethers as hydrolase. PMID:26460062

  10. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives.

    PubMed

    Chen, Teng-Hao; Schneemann, Andreas; Fischer, Roland A; Cohen, Seth M

    2016-02-21

    A series of unprecedented crown ether- and thiacrown ether-derivatized benzene dicarboxylic acid (H2bdc) ligands has been synthesized and incorporated into the prototypical isoreticular metal-organic framework (IRMOF) and UiO-66 materials. In the case of UiO-66, only MOFs comprised from a mixed-ligand composition, requiring both unsubstituted bdc and crown ether containing ligands, could be prepared. These are among the few ligand derivatives, and resulting MOFs, that incorporate a macrocyclic group directly on the bdc ligand, providing a new, modular platform for exploring new supramolecular and coordination chemistry within MOFs. PMID:26765588

  11. Reaction of a bituminous coal with the potassium-crown ether reagent

    SciTech Connect

    Huang, S.; Wood, K.; Narayan, R.

    1986-09-01

    In this paper, the authors report on the reaction of a bituminous coal with a powerful yet selective site-specific reagent, namely, potassium-crown ether operating at room temperature and atmospheric pressure. The potassium-crown ether reagent can generate a stable solution of electrons at room temperature and atmospheric pressure. The small size of the electron and its high reactivity permits it to diffuse into the macromolecular coal network and transfer onto the aromatic substrates in the coal. This results in the formation of aromatic radical anions or dianions which undergo cleavage reactions at ether and diaryl alkane linkages.

  12. Differential Self-Assembly of Novel Redox Crown Ethers

    NASA Astrophysics Data System (ADS)

    Merithew, Andrew William

    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

  13. Release of Lariat Peanut

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lariat is a high-oleic runner-type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) that has enhanced Sclerotinia blight and pod rot tolerance when compared to the cultivar Red River Runner. Lariat (experimental designation ARSOK-R35) is the result of a cross between cultivar Red River Ru...

  14. Metal ion complexation by ionizable crown ethers. Final report, January 1, 1988--June 30, 1994

    SciTech Connect

    Bartsch, R.A.

    1994-12-31

    During the report period a variety of new lipophilic ionizable crown ethers with pendent proton-ionizable groups has been synthesized. The ligands possess one or more ionizable group (carboxylic acid, phosphonic acid monoethyl ester, para-nitrophenol, phosphonic acid) attached to crown ether, monoazacrown ether or diazacrown ether frameworks. These novel chelating agents have either pendent or inward-facing proton-ionizable groups. Such lipophilic proton-ionizable crown ethers are designed for use in multiphase metal ion separations (solvent extraction, liquid membrane transport). In addition a series of proton-ionizable crown ethers without lipophilic groups was prepared to study how structural variations within the ligand influence metal ion complexation in homogeneous media as assessed by NMR spectroscopy or titration calorimetry. A third class of new metal ion-complexing agents is a series of lipophilic acyclic polyether dicarboxylic acids. Competitive solvent extractions of alkali metal and alkaline earth cations and of the mixed species have been conducted to reveal the influence of ring size, nature and attachment site of the lipophilic group, sidearm length, and proton-ionizable group identity and location upon the selectivity and efficiency of metal ion complexation. In addition to such studies of structural variation within the lipophilic proton-ionizable crown ether, the effect of changing the organic solvent and variation of the stripping conditions have been assessed. The influence of structural variations within lipophilic acyclic polyether dicarboxylic acids upon competitive solvent extraction of alkaline earth cations has been probed. Also a new chromogenic, di-ionizable crown ether with extremely high selectivity for Hg{sup 2+} has been discovered.

  15. Phase transition metal-crown ether coordination compounds tuned by metal ions.

    PubMed

    Ye, Qiong; Wang, Hui-Ting; Zhou, Lin; Kong, Li-Hui; Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi

    2016-01-21

    Two isostructural metal crown ether coordination compounds, (15-crown-5)(BiCl3) 1 and (15-crown-5)(SbCl3) 2, are discovered to show phase transitions above room temperature, where the phase transition temperature relates to the metal center. Compound 1 crystallizes in the chiral orthorhombic space group P212121 in the low temperature phase and undergoes a reversible phase transition around 365 K to crystallize in the polar orthorhombic space group Pna21 in the high temperature phase, accompanied by thermal and dielectric anomalies. The variable-temperature structure analyses of compound 1 show that the phase transition is rooted in the conformational change of the crown ether and the displacement of the Bi cation and Cl anion. PMID:26648559

  16. Stable Alkali-Metal Complexes of Hybrid Disila-Crown Ethers.

    PubMed

    Reuter, Kirsten; Buchner, Magnus R; Thiele, Günther; von Hänisch, Carsten

    2016-05-01

    The complexation ability of hybrid disilane and ethylene containing crown ether ring systems was analyzed using 1,2-disila[12]crown-4 (1), 1,2-disila[15]crown-5 (2), 1,2-disila[18]crown-6 (3), and 1,2,7,8-tetrasila[12]crown-4 (7). Alkali-metal complexes (Li(+), Na(+), K(+)) were obtained and analyzed via X-ray diffraction. The complex stability of [Li(1,2-disila[12]crown-4)](+) and [Li(1,2,7,8-tetrasila[12]crown-4)](+) was determined, in relation to the lithium complex of [12]crown-4, by density functional theory (DFT) calculations employing the BP86/def2-TZVP level of theory. In solution, the exchange of lithium cations between pure [12]crown-4 and hybrid [12]crown-4 is on even terms, as has been shown from the relative binding affinity of compounds 1 and 7 by means of dynamic proton nuclear magnetic resonance (NMR) spectroscopy. PMID:27082743

  17. Evaluation of polymer inclusion membranes containing crown ethers for selective cesium separation from nuclear waste solution.

    PubMed

    Mohapatra, P K; Lakshmi, D S; Bhattacharyya, A; Manchanda, V K

    2009-09-30

    Transport behaviour of (137)Cs from nitric acid feed was investigated using cellulose triacetate plasticized polymer inclusion membrane (PIM) containing several crown ether carriers viz. di-benzo-18-crown-6 (DB18C6), di-benzo-21-crown-7 (DB21C7) and di-tert-butylbenzo-18-crown-6 (DTBB18C6). The PIM was prepared from cellulose triacetate (CTA) with various crown ethers and plasticizers. DTBB18C6 and tri-n-butyl phosphate (TBP) were found to give higher transport rate for (137)Cs as compared to other carriers and plasticizers. Effect of crown ether concentration, nitric acid concentration, plasticizer and CTA concentration on the transport rate of Cs was also studied. The Cs selectivity with respect to various fission products obtained from an irradiated natural uranium target was found to be heavily dependent on the nature of the plasticizer. The present work shows that by choosing a proper plasticizer, one can get either good transport efficiency or selectivity. Though TBP plasticized membranes showed good transport efficiency, it displayed poor selectivities. On the other hand, an entirely opposite separation behaviour was observed with 2-nitrophenyloctylether (NPOE) plasticized membranes suggesting the possible application of the later membranes for the removal of bulk (137)Cs from the nuclear waste. The stability of the membrane was tested by carrying out transport runs for nearly 25 days. PMID:19398153

  18. Vertical ionisation potentials of a number of crown ethers from charge transfer bands of their EDA complexes

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sumanta; Sharma, Anubha; Nayak, Sandip K.; Mukherjee, Asok K.

    2002-11-01

    Vertical ionisation potentials ( IDv) of a number of crown ethers, viz. dibenzo-30-crown-10 (Crown 1), benzo-15-crown-5 (Crown 2), dibenzo-24-crown-8 (Crown 3), dicyclohexano-24-crown-8 (Crown 4) and 4'-nitrobenzo-15-crown-5 (Crown 5) are being reported for the first time from a study of EDA interaction of these crown ethers with a number of electron acceptors like C 60, C 70, o-chloranil, p-chloranil, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and pyromellitic diimide (PMD). The study has been carried out in CCl 4 medium by electronic absorption spectroscopy. Charge transfer (CT) absorption bands in the 360-900 nm range have been found in each case (excepting the 60 fullerene-Crown 4 system). The vertical ionisation potentials ( IDv) of all the crown ethers thus determined show a good correlation with those calculated by the semiempirical AM1 method. Of the six acceptors under study the vertical electron affinity of PMD was not found in the literature. This has also been determined from an analysis of the present hνCT data.

  19. Insights into the effects of 2:1 "sandwich-type" crown-ether/metal-ion complexes in responsive host-guest systems.

    PubMed

    Yu, Hai-Rong; Hu, Jia-Qi; Lu, Xiao-Hua; Ju, Xiao-Jie; Liu, Zhuang; Xie, Rui; Wang, Wei; Chu, Liang-Yin

    2015-01-29

    In-depth investigations of the specific ion-responsive characteristics based on 2:1 "sandwich" structures and effects of crown ether cavity sizes on the metal-ion/crown-ether complexation are systematically performed with a series of PNIPAM-based responsive copolymers containing similar contents of crown ether units with different cavity dimensions (12-crown-4 (12C4), 15-crown-5 (15C5), 18-crown-6 (18C6)). The lower critical solution temperature (LCST) values of copolymers in deionized water shift to lower temperatures gradually when the crown ether contents increase or the ring sizes decrease from 18C6 to 12C4. With increasing the concentrations of alkali metal ions (Na(+), K(+), Cs(+)) or the contents of pendent crown ether groups, the copolymers with different crown ether cavity sizes exhibit higher selectivity and sensitivity to corresponding cations. Importantly, the ion sensitivities of the copolymers in response to corresponding alkali metal ions increase dramatically with an increase in the crown ether cavity size. Interestingly, a linear relationship between the crown ether cavity size and the diameter of corresponding cation for the formation of stable 2:1 "sandwich" complexes is found for the first time, from which the size of metal ions or other guests that able to form 2:1 "sandwich" complexes with crown ethers can be deduced. The results in this work are valuable and useful for further developments and practical applications of various crown-ether-based smart materials. PMID:25562507

  20. Synthesis of ribo-hexopyranoside- and altrose-based azacrown ethers and their application in an asymmetric Michael addition.

    PubMed

    Rapi, Zsolt; Bakó, Péter; Keglevich, György; Szöllősy, Áron; Drahos, László; Hegedűs, László

    2013-01-10

    The synthesis of four new ribo-hexopyranoside-based chiral lariat ethers of monoaza-15-crown-5 type and two altropyranoside-based crown ethers were elaborated. Our syntheses utilized the regioselective ring opening of the oxiran moiety of the 2,3-anhydro sugars by nucleophilic reagents to afford the key intermediates. The reaction of methyl-2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside with ethanolamine is especially of interest to afford a 3-substituted altropyranoside. One of the ribo-hexopyranoside-based lariat ethers with a 4-methoxyphenyl substituent induced an enantioselectivity of 80% when used as catalyst in the Michael addition of diethyl acetamidomalonate to trans-β-nitrostyrene under phase transfer catalytic conditions. PMID:23220061

  1. Extractant composition including crown ether and calixarene extractants

    DOEpatents

    Meikrantz, David H.; Todd, Terry A.; Riddle, Catherine L.; Law, Jack D.; Peterman, Dean R.; Mincher, Bruce J.; McGrath, Christopher A.; Baker, John D.

    2009-04-28

    An extractant composition comprising a mixed extractant solvent consisting of calix[4] arene-bis-(tert-octylbenzo)-crown-6 ("BOBCalixC6"), 4',4',(5')-di-(t-butyldicyclo-hexano)-18-crown-6 ("DtBu18C6"), and at least one modifier dissolved in a diluent. The DtBu18C6 may be present at from approximately 0.01M to approximately 0.4M, such as at from approximately 0.086 M to approximately 0.108 M. The modifier may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol ("Cs-7SB") and may be present at from approximately 0.01M to approximately 0.8M. In one embodiment, the mixed extractant solvent includes approximately 0.15M DtBu18C6, approximately 0.007M BOBCalixC6, and approximately 0.75M Cs-7SB modifier dissolved in an isoparaffinic hydrocarbon diluent. The extractant composition further comprises an aqueous phase. The mixed extractant solvent may be used to remove cesium and strontium from the aqueous phase.

  2. Effects of Added Salts on Surface Tension and Aggregation of Crown Ether Surfactants.

    PubMed

    Suzuki, Maki; Fujio, Katsuhiko

    2016-01-01

    Two crown ether surfactants, dodecanoyloxymethyl- (C11Φ6) and octanoyloxymethyl-18-crown-6 (C7Φ6), were synthesized and the surface tension dependence on surfactant concentration of their aqueous solutions was measured both in the absence and presence of alkali chlorides to confirm the critical micelle concentration (CMC) is highest for the added cation that have an ionic diameter comparable to the hole size of the crown ether ring and that several break points on the surface tension vs. concentration curves occur for these crown ether surfactants. For C11Φ6 and C7Φ6, in the absence of salt, the surface tension vs. concentration curves had two break points. Using the solubilization of a water-insoluble dye as an indicator, we found that the break point at the higher concentration (m0) for C7Φ6 was due to micelle formation. Two break points were also observed for the aqueous solution of C11Φ6 in the presence of NaCl, KCl, RbCl, and CsCl salts at concentrations of 0.22 mol kg(-1) and for C7Φ6 with 0.22 mol kg(-1) KCl added. The CMC (m0) was found to be the highest for solutions containing K(+) salts because K(+) has an ionic diameter comparable to the hole size of 18-crown-6 ring. Furthermore, the CMC decreased as the ionic diameters of the added cations deviated from the hole size. The molecular areas at two break points, estimated by the Gibbs adsorption isotherm, except for that at the break point at mI of C7Φ6, were very small for an adsorbed monolayer. Further investigation is required to elucidate the reason for the break point at mI. PMID:26666275

  3. Reactivity of hydroxy- and aquo(hydroxy)-λ3-iodane-crown ether complexes.

    PubMed

    Miyamoto, Kazunori; Yokota, Yukie; Suefuji, Takashi; Yamaguchi, Kentaro; Ozawa, Tomoyuki; Ochiai, Masahito

    2014-04-25

    We have designed a series of hydroxy(aryl)-λ(3)-iodane-[18]crown-6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown-6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non-hygroscopic shelf-storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy-λ(3)-iodane-[18]crown-6 complexes serve as efficient progenitors for the synthesis of diaryl-, vinyl-, and alkynyl-λ(3)-iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases. PMID:24644216

  4. Improvement of Thiolate/Disulfide Mediated Dye-Sensitized Solar Cells through Supramolecular Lithium Cation Assembling of Crown Ether

    PubMed Central

    Liu, Linfeng; Li, Xiong; Chen, Jiangzhao; Rong, Yaoguang; Ku, Zhiliang; Han, Hongwei

    2013-01-01

    A supramolecular lithium cation assemblies of crown ether, [Li⊂12-crown-4]+, has been used to replace conventional tetraalkylammonium counterion in thiolate/disulfide (ET−/BET) mediated dye-sensitized solar cells (DSCs), which exhibit high stability and efficiency of 6.61% under 100 mW·cm−2 simulated sunlight illumination. PMID:23933601

  5. Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

    PubMed Central

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz; Riahi, Siavash

    2008-01-01

    Ionophore incorporated PVC membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. Potentiometric sensors have some outstanding advantages including simple design and operation, wide linear dynamic range, relatively fast response and rational selectivity. The vital component of such plasticized PVC members is the ionophore involved, defining the selectivity of the electrodes' complex formation. Molecular recognition causes the formation of many different supramolecules. Different types of supramolecules, like calixarenes, cyclodextrins and podands, have been used as a sensing material in the construction of ion selective sensors. Schiff's bases and crown ethers, which feature prominently in supramolecular chemistry, can be used as sensing materials in the construction of potentiometric ion selective electrodes. Up to now, more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anion complexes will be described. Liquid membrane sensors based on Schiff's bases and crown ethers will then be discussed.

  6. Intrinsic affinities of alkali cations for 15-crown-5 and 18-crown-6: Bond dissociation energies of gas-phase M{sup +}-crown ether complexes

    SciTech Connect

    More, M.B.; Ray, D.; Armentrout, P.B.

    1999-01-20

    Bond dissociation energies (BDEs) of M{sup +}[c-(C{sub 2}H{sub 4}O){sub 5}] and M{sup +}[c-(C{sub 2}H{sub 4}O){sub 6}] for M = Na, K, Rb, and Cs are reported. The BDEs are determined experimentally by analysis of the thresholds for collision-induced dissociation of the cation-crown ether complexes by xenon measured by using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissociation channel observed experimentally in endothermic loss of the ligand molecule. The cross section thresholds are interpreted to yield 0 and 298 K BDEs after accounting for the effects of multiple ion-molecule collisions, internal energy of the complexes, and unimolecular decay rates. For both 18-crown-6 and 15-crown-5, the BDEs decrease monotonically with increasing cation size. These results indicate that the intrinsic affinity of c-(C{sub 2}H{sub 4}O){sub 5} and c-(C{sub 2}H{sub 4}O){sub 6} for M{sup +} is determined principally by the charge density of the cation not by the ratio of the ionic radius to the cavity size. The BDEs reported here are in fair agreement with recent ab initio calculations at the MP2 level with 6-31+G* basis sets. The experimental values are systematically smaller than the computed values by 8 {+-} 2 kJ/mol per metal-oxygen interaction. The existence of less strongly bound isomers in the experimental apparatus for Rb{sup +}(15-crown-5) and Cs{sup +}(15-crown-5) appears likely, but their absence for Na{sup +} and K{sup +} complexes indicates interesting metal-dependent dynamics to the formation of such isomers.

  7. Conformation-Specific Electronic and Vibrational Spectroscopy of DIBENZO-15-CROWN-5 Ether in a Supersonic Jet.

    NASA Astrophysics Data System (ADS)

    Buchanan, Evan G.; Rodrigo, Chirantha P.; James, William H. James, III; Newby, Josh J.; Zwier, Timothy S.

    2009-06-01

    Crown ethers are oxygen containing cyclic structures noted for their ability to preferentially bind substrates such as ions and water. Despite the high symmetry inherent to the chemical structure, crown ethers are remarkably flexible, adapting their conformation to the substrate to which they are bound. As such, it is valuable to study the conformational preferences of the isolated crown ethers in the absence of any substrate. Here, we present the electronic and infrared spectroscopy of jet-cooled, isolated dibenzo-15-crown-5 ether (DB15C). By incorporating two phenyl rings into the crown, we are afforded the opportunity to explore the ultraviolet spectroscopy of both groups and the coupling between them. One-color resonant two-photon ionization, laser induced fluorescence, UV-UV holeburning, and resonant ion-dip infrared spectroscopies are used to provide conformation-specific electronic and infrared spectra of the three conformers. Additionally, single vibronic level dispersed fluorescence spectra provide evidence for the existence of close lying S_2 states in the two major conformers, located about 527 cm^{-1} above their S_1 counterparts. Based on a comparison with benzo-15-crown-5 ether, we surmise that the local conformation of the ethoxy groups about the two phenyl rings are different. Electronic energy transfer appears to be slow between these phenyl rings on the timescale of the excited state fluorescence. Finally, DFT and MP2 calculations will be presented as a basis for tentative structural assignments and provide insight into the excitonic coupling of the two chromophores.

  8. Solvent-Free Covalent Functionalization of Fullerene C60 and Pristine Multi-Walled Carbon Nanotubes with Crown Ethers.

    PubMed

    Henao-Holguín, Laura V; Meza-Laguna, Victor; Gromovoy, Taras Yu; Basiuk, Elena V; Rivera, Margarita; Basiuk, Vladimir A

    2016-06-01

    The goal of the present work was to test the feasibility of simple, one-step and solvent-free covalent functionalization of pristine multi-walled carbon nanotubes (MWNTs) and fullerene C60 (as a model system) with amino-substituted crown ethers, namely, 4'-aminobenzo-15-crown-5 and 4'-aminobenzo-1 8-crown-6. The attachment technique proposed is based on thermal instead of chemical activation, and can be considered as ecologically friendly. The suggested covalent binding mechanism is the nucleophilic addition of amino functionalities of crown ethers to the 6,6 bonds of pyracylene units in the case of C60, and to pentagonal (and probably other) defects of similar nature in the case of pristine MWNTs. The hybrids of crown ethers with MWNTs were characterized by means of scanning and transmission electron microscopy, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. The functionalized C60 samples were additionally studied by means of 13C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and laser desorption/ionization time-of-flight mass spectrometry. The approach proposed allows for a facile preparation of crown ether-functionalized pristine MWNTs without contamination with other chemical reagents, detergents and solvents, which is especially important for a vast variety of nanotube applications ranging from nanoelectronics to nanomedicine. PMID:27427687

  9. Highly selective methyl transfer from methylsilanes to phenylthallium(III) crown ether complexes

    SciTech Connect

    Kakiuchi, Fumitoshi; Furuta, Kiyonori; Murai, Shinji ); Kawasaki, Yoshikane )

    1993-01-01

    Reactions of (18-crown-6)phenylthallium(III) diperchlorate monohydrate (1a) with Me[sub 3]SiR (R = PhCH[sub 2], Et, Ph, CH[double bond]CH[sub 2], SiMe[sub 3], OSiMe[sub 3]) proceeded at 60[degrees]C to provide (18-crown-6)phenylmethylthallium(III) perchlorate (3) in good to excellent yields. Cleavage of the Me-Si bond in tetramethylsilane using 1a also occurred at 25[degrees]C, albeit for a long reaction time. The silicon-containing products of the reaction of 1a with benzyltrimethylsilane were siloxanes. Intramolecular trapping of the silyl fragments by a hydroxy group using (1,7-DTC)phenylthallium(III) bis(trifluoromethanesulfonate) (1b) was employed with trans-2-((trimethylsilyl)methyl)-1-cyclohexanol, affording a bicyclic silyl ether in 92% yield. 18 refs., 1 tab.

  10. A Ratiometric Luminescent Switch Based on Platinum Complexes Tethered to a Crown-Ether Scaffold.

    PubMed

    Sinn, Stephan; Biedermann, Frank; Vishe, Mahesh; Aliprandi, Alessandro; Besnard, Céline; Lacour, Jérôme; De Cola, Luisa

    2016-06-17

    A ratiometric chemosensor for potassium is reported, based on phosphorescent dinuclear cyclometalated Pt(II) complexes featuring a cis-crown ether as the cation-recognition unit. The metal complexes are blue luminescent in a non-aggregated state but become strongly orange emissive when in a close physical proximity, as is the case when the macrocycle is in the folded state. Upon binding of the cation, unfolding occurs, resulting in a pronounced change in the emission properties (e.g. emission wavelength), which can be used for ratiometric sensing applications. The reversibility of the binding was confirmed by competitive titration experiments with unsubstituted 18-crown-6; the system shows supramolecular switching behavior. PMID:26918952

  11. Studies of ion transport through a liquid membrane by using crown ethers

    SciTech Connect

    Gaikwad, A.G. , Trivandrum ); Noguchi, H.; Yoshio, Masaki )

    1991-01-01

    Studies on ion transport through a liquid membrane system composed of two extraction processes have been carried out. Kinetic models based on extraction processes with consideration of the controlled parameters were developed for mediated ion transport through liquid membranes, especially those using crown ethers as the ion carrier. A study of the concentration change in the receiving or source phase envisages the determination of the equilibrium constant by a kinetic method corresponding to the chemical reaction at the interface as well as the maximum initial flux through the membrane. The equilibrium constant values determined by the kinetic process were checked by the solvent extraction method.

  12. Complex formation of alkaline-earth cations with crown ethers and cryptands in methanol solutions

    SciTech Connect

    Buschman, H.J.

    1986-06-01

    The complexation of alkaline-earth cations by different crown ethers, azacrown ethers, and cryptands has been studied in methanol solutions by means of calorimetric and potentiometric titrations. The smallest monocyclic ligands examined from 2:1 complexes (ratio of ligand to cation) with cations which are too large to fit into the ligand cavity. With the smallest cryptand, only Sr/sup 2 +/ and Ba/sup 2 +/ ions are able to form exclusive complexes. In the case of the reaction of cryptand (211) with Ca/sup 2 +/, a separate estimation of stability constants for the formation of exclusive and inclusive complexes was possible for the first time. Higher values for stability constants are found for the reaction of alkaline-earth cations with cryptands compared to the reaction with alkali ions. This increase is only caused by favorable entropic contributions.

  13. Enantioseparations of primary amino compounds by high-performance liquid chromatography using chiral crown ether-based chiral stationary phase.

    PubMed

    Hyun, Myung Ho

    2013-01-01

    Liquid chromatographic resolution of racemic compounds containing a primary amino group has been known to be most successful when chiral crown ether-based chiral stationary phases (CSPs) are used. Among various crown ether-based CSPs, the stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel has been successfully applied in the resolution of various racemic compounds containing primary amino groups. In this chapter, the preparation of the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel and examples for the application to the enantioseparation of racemic compounds including α-amino acids, cyclic amines, amino alcohols, and chiral drugs are described. PMID:23283776

  14. Comparison of chiral separations of aminophosphonic acids and their aminocarboxylic acid analogs using a crown ether column.

    PubMed

    Barnhart, Wesley W; Xia, Xiaoyang; Jensen, Randy; Gahm, Kyung H

    2013-07-01

    Crown ethers are capable of complexing with primary amines and have been utilized in chromatography to separate amino acid racemates. This application has been extended to resolve (1-amino-1-phenylmethyl)phosphonic acid and (1-aminoethyl)phosphonic acid racemates, along with their aminocarboxylic acid analogs (2-phenylglycine and alanine, respectively), via a ChiroSil RCA crown ether based chiral stationary phase. Effects of the organic modifier, temperature, and acid type and concentration on retention and selectivity were also investigated. Trends in retention and selectivity varied between aminophosponic acids and their aminocarboxylic analogs. Computer modeling and (1)H NMR analyses were performed to potentially gain a better understanding of interactions of the aforementioned molecules with the ChiroSil RCA chiral stationary phase. Theoretical predictions of the most stable conformations for (R)- and (S)-enantiomers were compared to elution order; it was found that the elution order agreed with molecular modeling such that the longest retention correlated with the predicted most stable complex between the enantiomer and crown ether. (1)H NMR demonstrated interactions of aminophosphonic and aminocarboxylic racemates with (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid in solution and was utilized to determine enantiomeric excess of (1-amino-1-phenylmethyl)phosphonic acid after its enantioenrichment via crystallization through diastereomeric salt formation with the crown ether followed by filtration. PMID:23703726

  15. Alkali-Ion-Crown Ether in Art and Conservation: The Applied Bioinorganic Chemistry Approach

    PubMed Central

    Hilfrich, Uwe; Taylor, Harold; Weser, Ulrich

    2004-01-01

    Dried varnish is rich in many ester moieties, which may be broken down into small, soluble compounds by esterase activity or alkaline hydrolysis. Two methods for varnish removal have been developed, including the treatment of either lipase or RbOH / PEG-400 crown ether which allow aged oil varnishes or paint coverings to be removed or thinned. These techniques are designed to proceed in a controlled manner without damaging lower paint or base layers. Unfortunately, lipase did not react with the aged ester groups of dried linseed oil varnish. Surprisingly, the varnish came off in the presence of Tris buffer alone which, in addition, formed reactive metal complexes. A better choice was the use of high Mr alkali ion polyethylene glycol–400 (PEG-400) crown ether type chelates. PEG-400 complexes alkali ions including rubidium and other alkaliions impeding the diffusion of their basic counter ions into lower varnish or paint layers. Possible migration of alkali metal ions into the paint layer during alkaline varnish removal was determined by labelling the cleansing solutions with 86Rb. Fortunately, varnish is degraded on the surface only. Lower paint or varnish layers are not attacked even if chemically similar to the varnish or over painting to be removed as virtually no 86Rb was detected on the paint surface. PMID:18365066

  16. Photodissociation of protonated tryptophan and alteration of dissociation pathways by complexation with crown ether

    SciTech Connect

    Kadhane, Umesh; Andersen, Jens Ulrik; Ehlerding, Anneli; Hvelplund, Preben; Kirketerp, Maj-Britt S.; Lykkegaard, Morten Koecks; Nielsen, Steen Broendsted; Panja, Subhasis; Wyer, Jean Ann; Zettergren, Henning

    2008-11-14

    The behavior of protonated tryptophan (TrpH{sup +}) and its complex with 18-crown-6-ether (CE) after photoexcitation has been explored based on measurements of dissociation lifetimes, fragmentation channels, and absorption spectra using an electrostatic ion storage ring. A recent implementation of pulsed power supplies for the ring elements with microsecond response times allows us to identify the daughter ion fragment masses and to disentangle fragmentation that occurs from excited states immediately after photoexcitation from that occurring on a longer time scale of several microseconds to milliseconds. We find that attachment of crown ether significantly alters the dissociation channels since it renders the {pi}{sigma}*(NH{sub 3}) state inaccessible and hence prevents the N-H bond breakage which is an important fragmentation channel of TrpH{sup +}. As a result, on a long time scale (>10 {mu}s), photoexcited TrpH{sup +}(CE) decays exponentially whereas TrpH{sup +} displays a power-law decay. The only ions remaining in the latter case are Trp{sup +{center_dot}} radical cations with a broad internal energy distribution caused by the departing hydrogen. Large changes in the fragment branching ratios as functions of excitation wavelength between 210 and 290 nm were found for both TrpH{sup +} and TrpH{sup +}(CE)

  17. Liquid chromatographic resolution of mexiletine and its analogs on crown ether-based chiral stationary phases.

    PubMed

    Jin, Kab Bong; Kim, Hee Eun; Hyun, Myung Ho

    2014-05-01

    Mexiletine, an effective class IB antiarrhythmic agent, and its analogs were resolved on three different crown ether-based chiral stationary phases (CSPs), one (CSP 1) of which is based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid and the other two (CSP 2 and CSP 3) are based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. Mexiletine was resolved with a resolution (R(S)) of greater than 1.00 on CSP 1 and CSP 3 containing residual silanol group-protecting n-octyl groups on the silica surface, but with a resolution (R(S)) of less than 1.00 on CSP 2. The chromatographic behaviors for the resolution of mexiletine analogs containing a substituted phenyl group at the chiral center on the three CSPs were quite dependent on the phenoxy group of analytes. Namely, mexiletine analogs containing 2,6-dimethylphenoxy, 3,4-dimethylphenoxy, 3-methylphenoxy, 4-methylphenoxy, and a simple phenoxy group were resolved very well on the three CSPs even though the chiral recognition efficiencies vary with the CSPs. However, mexiletine analogs containing 2-methylphenoxy group were not resolved at all or only slightly resolved. Among the three CSPs, CSP 3 was found to show the highest chiral recognition efficiencies for the resolution of mexiletine and its analogs, especially in terms of resolution (R(S)). PMID:24677299

  18. pH-responsive supramolecular polymerization in aqueous media driven by electrostatic attraction-enhanced crown ether-based molecular recognition.

    PubMed

    Ji, Xiaofan; Zhu, Kelong; Yan, Xuzhou; Ma, Yingjie; Li, Jinying; Hu, Bingjie; Yu, Yihua; Huang, Feihe

    2012-07-26

    All the previously reported supramolecular polymers based on crown ether-based molecular recognition have been prepared in anhydrous organic solvents. This is mainly due to the weakness of crown ether-based molecular recognition in the presence of water. Here we report a linear supramolecular polymer constructed from a heteroditopic monomer in an aqueous medium driven by crown ether-based molecular recognition through the introduction of electrostatic attraction. In addition, the reversible transition between the linear supramolecular polymer and oligomers is achieved by adding acid and base. This study realizes the breakthrough of the solvent for supramolecular polymerization driven by crown ether-based molecular recognition from anhydrous organic solvents to aqueous media. It is helpful for achieving supramolecular polymerization driven by crown ether-based molecular recognition in a completely aqueous medium. PMID:22495805

  19. Rotamerism-driven large magnitude host-guest binding change in a crown ether derivatized pyridinium-phenolate series.

    PubMed

    Ay, Emel; Hobeika, Nelly; Chaumeil, Hélène; Tschamber, Théophile; Jin, Ming; Versace, Davy-Louis; Malval, Jean-Pierre

    2016-03-17

    Two TICTOID-based pyridinium-phenolates bearing a crown ether macrocycle have been designed for the complexation of a potassium cation. The nucleophilicity of the intraannular phenolate -O(-) function can be strongly modulated by biaryl twisting. Such a structure/electronic transduction effect gives rise to a host-guest binding change by more than two orders of magnitude. PMID:26948128

  20. Selective recognition and extraction of KBr via cooperative interactions with a urea functionalized crown ether dual-host.

    PubMed

    Akhuli, Bidyut; Ghosh, Pradyut

    2015-11-28

    Selective solid-liquid extraction of KBr is demonstrated for the first time with a crown ether based pentafluorophenyl urea functionalized dual-host receptor. (1)H-NMR and ITC studies have been carried out to illustrate the effect of cooperativity towards the recognition of alkali metal salts. PMID:26417887

  1. Coordination effect-regulated CO2 capture with an alkali metal onium salts/crown ether system

    SciTech Connect

    Yang, Zhen-Zhen; Jiang, Deen; Zhu, Xiang; Tian, Chengcheng; Brown, Suree; Do-Thanh, Chi-Linh; He, Liang-Nian; Dai, Sheng

    2014-01-01

    A coordination effect was employed to realize equimolar CO2 absorption, adopting easily synthesized amino group containing absorbents (alkali metal onium salts). The essence of our strategy was to increase the steric hindrance of cations so as to enhance a carbamic acid pathway for CO2 capture. Our easily synthesized alkali metal amino acid salts or phenolates were coordinated with crown ethers, in which highly sterically hindered cations were obtained through a strong coordination effect of crown ethers with alkali metal cations. For example, a CO2 capacity of 0.99 was attained by potassium prolinate/18-crown-6, being characterized by NMR, FT-IR, and quantum chemistry calculations to go through a carbamic acid formation pathway. The captured CO2 can be stripped under very mild conditions (50 degrees C, N-2). Thus, this protocol offers an alternative for the development of technological innovation towards efficient and low energy processes for carbon capture and sequestration.

  2. Aza-crown ether complex cation ionic liquids: preparation and applications in organic reactions.

    PubMed

    Song, Yingying; Cheng, Chen; Jing, Huanwang

    2014-09-26

    Aza-crown ether complex cation ionic liquids (aCECILs) were devised, fabricated, and characterized by using NMR spectroscopy, MS, thermogravimetric differential thermal analysis (TG-DTA), elemental analysis and physical properties. These new and room-temperature ILs were utilized as catalysts in various organic reactions, such as the cycloaddition reaction of CO2 to epoxides, esterification of acetic acid and alcohols, the condensation reaction of aniline and propylene carbonate, and Friedel-Crafts alkylation of indole with aldehydes were investigated carefully. In these reactions, the ionic liquid exhibited cooperative catalytic activity between the anion and cation. In addition, the aza-[18-C-6HK][HSO4]2 was the best acidic catalyst in the reactions of esterification and Friedel-Crafts alkylation under mild reaction conditions. PMID:25154312

  3. Recognition of silver cations by a cucurbit[8]uril-induced supramolecular crown ether.

    PubMed

    Geng, Qing-Xia; Wang, Fang; Cong, Hang; Tao, Zhu; Wei, Gang

    2016-02-28

    The host-guest interaction of cucurbit[8]uril (Q[8]) with a synthesized guest molecule, consisting of naphthalene and viologen moieties bridged by a carbon oxygen chain, was investigated by (1)H NMR and UV-Vis spectroscopy. The results indicated the formation of an inclusion complex in a ratio of 1 : 1 with a moderate association constant of Ka = (1.1 ± 0.2) × 10(6) L mol(-1). The formation of this special complex is driven by the markedly enhanced charge-transfer interaction between the electron-rich and electron-deficient guest molecule inside the hydrophobic cavity of Q[8], while the carbon oxygen chain stays outside of Q[8] to form a supramolecular crown ether. Screening of the metal cation substrate suggested that the inclusion complex recognizes Ag(+) ions with high selectivity, as shown by UV-Vis spectroscopy. PMID:26879150

  4. Probing Ternary Complex Equilibria of Crown Ether Ligands by Time-Resolved Fluorescence Spectroscopy

    PubMed Central

    2015-01-01

    Ternary complex formation with solvent molecules and other adventitious ligands may compromise the performance of metal-ion-selective fluorescent probes. As Ca(II) can accommodate more than 6 donors in the first coordination sphere, commonly used crown ether ligands are prone to ternary complex formation with this cation. The steric strain imposed by auxiliary ligands, however, may result in an ensemble of rapidly equilibrating coordination species with varying degrees of interaction between the cation and the specific donor atoms mediating the fluorescence response, thus diminishing the change in fluorescence properties upon Ca(II) binding. To explore the influence of ligand architecture on these equilibria, we tethered two structurally distinct aza-15-crown-5 ligands to pyrazoline fluorophores as reporters. Due to ultrafast photoinduced electron-transfer (PET) quenching of the fluorophore by the ligand moiety, the fluorescence decay profile directly reflects the species composition in the ground state. By adjusting the PET driving force through electronic tuning of the pyrazoline fluorophores, we were able to differentiate between species with only subtle variations in PET donor abilities. Concluding from a global analysis of the corresponding fluorescence decay profiles, the coordination species composition was indeed strongly dependent on the ligand architecture. Altogether, the combination of time-resolved fluorescence spectroscopy with selective tuning of the PET driving force represents an effective analytical tool to study dynamic coordination equilibria and thus to optimize ligand architectures for the design of high-contrast cation-responsive fluorescence switches. PMID:25313708

  5. Laser Spectroscopic Study of Cold Gas-Phase Host-Guest Complexes of Crown Ethers.

    PubMed

    Ebata, Takayuki; Inokuchi, Yoshiya

    2016-06-01

    The structure, molecular recognition, and inclusion effect on the photophysics of guest species are investigated for neutral and ionic cold host-guest complexes of crown ethers (CEs) in the gas phase. Here, the cold neutral host-guest complexes are produced by a supersonic expansion technique and the cold ionic complexes are generated by the combination of electrospray ionization (ESI) and a cryogenically cooled ion trap. The host species are 3n-crown-n (3nCn; n = 4, 5, 6, 8) and (di)benzo-3n-crown-n ((D)B3nCn; n = 4, 5, 6, 8). For neutral guests, we have chosen water and aromatic molecules, such as phenol and benzenediols, and as ionic species we have chosen alkali-metal ions (M(+) ). The electronic spectra and isomer-specific vibrational spectra for the complexes are observed with various laser spectroscopic methods: laser-induced fluorescence (LIF); ultraviolet-ultraviolet hole-burning (UV-UV HB); and IR-UV double resonance (IR-UV DR) spectroscopy. The obtained spectra are analyzed with the aid of quantum chemical calculations. We will discuss how the host and guest species change their flexible structures for forming best-fit stable complexes (induced fitting) and what kinds of interactions are operating for the stabilization of the complexes. For the alkali metal ion•CE complexes, we investigate the solvation effect by attaching water molecules. In addition to the ground-state stabilization problem, we will show that the complexation leads to a drastic effect on the excited-state electronic structure and dynamics of the guest species, which we call a "cage-like effect". PMID:27006080

  6. Calixarene crown ether solvent composition and use thereof for extraction of cesium from alkaline waste solutions

    DOEpatents

    Moyer, Bruce A.; Sachleben, Richard A.; Bonnesen, Peter V.; Presley, Derek J.

    2001-01-01

    A solvent composition and corresponding method for extracting cesium (Cs) from aqueous neutral and alkaline solutions containing Cs and perhaps other competing metal ions is described. The method entails contacting an aqueous Cs-containing solution with a solvent consisting of a specific class of lipophilic calix[4]arene-crown ether extractants dissolved in a hydrocarbon-based diluent containing a specific class of alkyl-aromatic ether alcohols as modifiers. The cesium values are subsequently recovered from the extractant, and the solvent subsequently recycled, by contacting the Cs-containing organic solution with an aqueous stripping solution. This combined extraction and stripping method is especially useful as a process for removal of the radionuclide cesium-137 from highly alkaline waste solutions which are also very concentrated in sodium and potassium. No pre-treatment of the waste solution is necessary, and the cesium can be recovered using a safe and inexpensive stripping process using water, dilute (millimolar) acid solutions, or dilute (millimolar) salt solutions. An important application for this invention would be treatment of alkaline nuclear tank wastes. Alternatively, the invention could be applied to decontamination of acidic reprocessing wastes containing cesium-137.

  7. Reaction of premium Wyodak subbituminous coal with potassium-crown ether reagent

    SciTech Connect

    Huang, S.L.; Narayan, R.

    1987-01-01

    Coal conversions typically involve reacting coal under severe conditions of temperature and pressure. As a result, bond cleavage is nonselective and often accompanied by retrogressive (bond forming) reactions. This has resulted in less than satisfactory results in deducing coal structure, coal behavior, and reactivity. Incorrect model of the basic structural units of the coal, and the nature of the linkages joining these units have been postulated. In our laboratory, we are studying the solubilization of coal at ambient temperatures and pressures using a site-specific reagent potassium-crown ether (K-CE), and the characterization of the soluble coal oligomer fragments. The small size and high reactivity of the solvated electrons generated by the K-CE reagent, promotes cleavage reactions at ether, ester, and diarylethane linkages, resulting in depolymerization and solubilization of coal. Reduction of aromatic rings to dihydro and tetrahydro analogs also occur. In this paper we report on the solubilization of a Wyodak premium subbituminous coal using K-CE reagent. The characterization of the solubilized coal fragments by IR, NMR, GPC, and microanalysis, is described.

  8. Theoretical study of the asymmetric phase-transfer mediated epoxidation of chalcone catalyzed by chiral crown ethers derived from monosaccharides

    NASA Astrophysics Data System (ADS)

    Makó, Attila; Menyhárd, Dóra K.; Bakó, Péter; Keglevich, György; Tőke, László

    2008-12-01

    The synthesis of a novel, optically active crown ether derived from α- D-altropyranoside is described. A significantly different asymmetric induction was generated by the α- D-glucopyranoside-, α- D-mannopyranoside- and α- D-altropyranoside-based chiral crown catalysts in the epoxidation of trans-chalcone with tert-butyl hydroperoxide under phase-transfer catalytic conditions. It was shown that absolute configuration of the crown-ring fused carbon atoms of the monosaccharides has a great impact on the enantioselectivity. The asymmetric induction could be well explained by considering the possible mechanistic pathway. Molecular modeling (MCMM) and subsequent DFT calculations - in accordance with the experimental results - indicate that the use of glucopyranoside-based catalyst 1 and that of mannopyranoside-based crown ether 2 results in the preferred formation of the opposite antipodes (2 R,3 S and 2 S,3 R, respectively) of the corresponding epoxyketone. At the same time, practically no asymmetric induction was proved if altropyranoside-based crown 3 is applied as the catalyst. The computational results are in qualitative agreement with the experimental data.

  9. SYNTHESIS OF NOVEL CROWN ETHERS BEARING THE exo-cis-2,3-NORBORNYL GROUP AS POTENTIAL Na+ AND K+ EXTRACTANTS

    SciTech Connect

    Robeson, R.M.; Bonnesen, P.

    2007-01-01

    The synthesis of a series of novel dinorbornyl-16-crown-5 and dinorbornyl-18-crown-6 ethers that incorporate the exo-cis-2,3-norbornyl moiety within the macrocycle framework is described. The key starting material for the crown ethers, exo-cis-2,3-norbornanediol, was successfully prepared on a large (>30g) scale in 88% yield from norbornylene by osmium tetroxide-catalyzed hydroxylation. The syn and anti isomers of the dinorbornyl-16-crown-5 ether family were prepared using diethylene glycol with ring closure achieved using a methallyl linkage. The isomers cis-syn-cis and cis-anti-cis di-norbornano-15-methyleno-16-crown-5 (6A and 6B) could be separated using column chromatography, and a single crystal of the syn isomer 6A suitable for X-ray crystal structure analysis was obtained, thereby confi rming the syn orientation. The syn and anti isomers of the dinorbornyl-18-crown-6 ether family were successfully prepared employing a different synthetic strategy, involving the potassium–templated cyclization of two bis-hydroxyethoxy-substituted exo-cis-2,3-norbornyl groups under high dilution conditions. Attempts to fully separate cis-syn-cis di-norbornano-18-crown-6 (10A) and cis-anti-cis di-norbornano-18-crown-6 (10B) from one another using column chromatography were unsuccessful. All intermediates and products were checked for purity using either thin layer chromatography or gas chromatography, and characterized by proton and carbon NMR. Crown ethers 6AB and 10AB are to our knowledge the fi rst crown ethers to incorporate the exo-cis-2,3-norbornyl moiety into the crown ring to be successfully synthesized and characterized.

  10. Enhanced performance in gas adsorption and Li ion batteries by docking Li(+) in a crown ether-based metal-organic framework.

    PubMed

    Bai, Linyi; Tu, Binbin; Qi, Yi; Gao, Qiang; Liu, Dong; Liu, Zhizhou; Zhao, Lingzhi; Li, Qiaowei; Zhao, Yanli

    2016-02-18

    Incorporating supramolecular interaction units, crown ether rings, into metal-organic frameworks enables the docking of metal ions through complexation for enhanced performance in H2 and CO2 adsorption and lithium ion batteries. PMID:26785426

  11. A responsive supramolecular metallogel constructed by coordination-driven self-assembly of a crown ether-based [3]pseudorotaxane and a diplatinum(II) acceptor.

    PubMed

    Xing, Hao; Wang, Hu; Yan, Xuzhou; Ji, Xiaofan

    2015-07-01

    Herein, a stimuli-responsive supramolecular metallogel was prepared by orthogonal coordination-driven self-assembly of a crown ether-based [3]pseudorotaxane and a 180° organic di-Pt(II) acceptor. PMID:26030667

  12. Alkaline-side extraction of technetium from tank waste using crown ethers and other extractants

    SciTech Connect

    Bonnesen, P.V.; Moyer, B.A.; Presley, D.J.; Armstrong, V.S.; Haverlock, T.J.; Counce, R.M.; Sachleben, R.A.

    1996-06-01

    The chemical development of a new crown-ether-based solvent-extraction process for the separation of (Tc) from alkaline tank-waste supernate is ready for counter-current testing. The process addresses a priority need in the proposed cleanup of Hanford and other tank wastes. This need has arisen from concerns due to the volatility of Tc during vitrification, as well as {sup 99}Tc`s long half-life and environmental mobility. The new process offers several key advantages that direct treatability--no adjustment of the waste composition is needed; economical stripping with water; high efficiency--few stages needed; non-RCRA chemicals--no generation of hazardous or mixed wastes; co-extraction of {sup 90}Sr; and optional concentration on a resin. A key concept advanced in this work entails the use of tandem techniques: solvent extraction offers high selectivity, while a subsequent column sorption process on the aqueous stripping solution serves to greatly concentrate the Tc. Optionally, the stripping solution can be evaporated to a small volume. Batch tests of the solvent-extraction and stripping components of the process have been conducted on actual melton Valley Storage Tank (MVST) waste as well as simulants of MVST and Hanford waste. The tandem process was demonstrated on MVST waste simulants using the three solvents that were selected the final candidates for the process. The solvents are 0.04 M bis-4,4{prime}(5{prime})[(tert-butyl)cyclohexano]-18-crown-6 (abbreviated di-t-BuCH18C6) in a 1:1 vol/vol blend of tributyl phosphate and Isopar{reg_sign} M (an isoparaffinic kerosene); 0.02 M di-t-BuCH18C6 in 2:1 vol/vol TBP/Isopar M and pure TBP. The process is now ready for counter-current testing on actual Hanford tank supernates.

  13. Separation of Long-Lived Fission Products Tc-99 and I-129 from Synthetic Effluents by Crown Ethers

    SciTech Connect

    Paviet-Hartmann, P.; Hartmann, T.

    2006-07-01

    To minimize significantly the radio-toxic inventory of nuclear geological repositories to come as well as to reduce the potential of radionuclides migration and to minimize long-term exposure, the concept of partitioning and transmutation (P/T) of nuclear waste is currently discussed. Transmutation offers the possibility to convert radio-toxic radionuclides with long half-lives into radionuclides of shorter half-lives, less toxic isotopes, or even into stable isotopes. Besides the most prominent isotopes of neptunium, plutonium, americium, and curium, the long-lived fission products Tc-99 and I-129 (half-lives of 2.13 x 10{sup 5} years, and 1.57 x 10{sup 7} years, respectively) are promising candidates for transmutation in order to prevent their migration from a nuclear repository. Partitioning and transmutation of the most radio-toxic radionuclides will not only minimize the nuclear waste load but most importantly will significantly reduce the long-term radio-toxic hazard of nuclear waste repositories to come. Prior to the deployment of partitioning and transmutation, selective extraction techniques are required to separate the radionuclides of concern. Since the discovery of crown ethers by C. Pedersen, various applications of crown ethers have drawn much attention. Although liquid-liquid extraction of alkali and alkali earth metals by crown ethers has been extensively studied, little data is available on the extraction of Tc-99 and I-129 by crown ethers. The methods developed herein for the specific extraction of Tc-99 and I-129 provide recommendations in support of their selectively extraction from liquid radioactive waste streams, mainly ILW. We report data on the solvent extraction of Tc-99 and I-129 from synthetic effluents by six crown ethers of varying cavity dimensions and derivatization. To satisfy the needs of new extractant systems we are demonstrating that crown ether (CE) based systems have the potential to serve as selective extractants for the

  14. Synthesis and Enantiomeric Recognition Studies of Optically Active Pyridino-Crown Ethers Containing an Anthracene Fluorophore Unit.

    PubMed

    Szemenyei, Balázs; Móczár, Ildikó; Pál, Dávid; Kocsis, Ivett; Baranyai, Péter; Huszthy, Péter

    2016-07-01

    Novel enantiopure pyridino-18-crown-6 ether-based sensor molecules containing an anthracene fluorophore unit were synthesized. Their enantiomeric recognition abilities toward the enantiomers of 1-phenylethylamine hydrogen perchlorate (PhEt), 1-(1-naphthyl)ethylamine hydrogen perchlorate (NapEt), phenylglycine methyl ester hydrogen perchlorate (PhgOMe), and phenylalanine methyl ester hydrogen perchlorate (PheOMe) were examined in acetonitrile using fluorescence spectroscopy. The sensor molecules showed appreciable enantiomeric recognition toward the enantiomers of NapEt, PhEt, and PhgOMe. The highest enantioselectivity was found in the case of crown ether containing isobutyl groups in the macroring and the enantiomers of NapEt. Chirality 28:562-568, 2016. © 2016 Wiley Periodicals, Inc. PMID:27349957

  15. Enantiomeric recognition of organic ammonium salts by chiral crown ethers based on the pyridino-18-crown-6 structure

    SciTech Connect

    Davidson, R.B.; Bradshaw, J.S.; Jones, B.A.; Dalley, N.K.; Christensen, J.J.; Izatt, R.M.

    1984-01-27

    Enantiomeric recognition by several chiral dimethyl-substituted macrocycles of the pyridino-18-crown-6 type for chiral organic ammonium salts has been studied by titration calorimetry in CH/sub 3/OH, temperature-dependent /sup 1/H NMR spectroscopy in CD/sub 2/CL/sub 2/, and selective crystallization. Results from the three procedures are consistent in demonstrating either host-guest recognition or nonrecognition in the systems investigated. Futhermore, enaniomeric recognition by one chiral host for a pair of chiral guests is correlated with X-ray crystallographic data for the same system. The chiral dimethyl-substituted ligands used in the study include three dimethyl diester pyridino-18-crown-6 ligands, dimethyl thiono diester pyridino-18-crown-6, and dimethyl-pyridino-18-crown-6 ligands. All of these ligands exhibited chiral recognition. Dimethylpyridino-18-crown-6 in complexation with (R)- and (S)-(..cap alpha..-(1-naphthyl)ethyl)ammonium perchlorate exhibited the largest ratio of ..delta..G/sub c/+ yet observed by the /sup 1/H NMR technique. A diphenyl-substituted diester pyridino-18-crown-6 where the phenyl substituents are in less rigid portion of the macrocycle failed to show chiral recognition.

  16. Separation of calcium-48 isotope by crown ether chromatography using ethanol/hydrochloric acid mixed solvent.

    PubMed

    Okumura, Shin; Umehara, Saori; Fujii, Yasuhiko; Nomura, Masao; Kaneshiki, Toshitaka; Ozawa, Masaki; Kishimoto, Tadafumi

    2015-10-01

    Benzo-18-crown-6 ether resin embedded in porous silica beads was synthesized and used as the packing material for chromatographic separation of (48)Ca isotope. The aim of the present work is to develop efficient isotope enrichment process for double β decay nuclide (48)Ca. To this end, ethanol/HCl mixed solvent was selected as the medium for the chromatographic separation. Adsorption of calcium on the resin was studied at different HCl concentrations and different ethanol mixing ratios in batch-wise experiments. A very interesting phenomenon was observed; Ca adsorption is controlled not by the overall HCl concentration of the mixed solvent, but by the initial concentration of added HCl solution. Calcium break-through chromatography experiments were conducted by using 75v/v% ethanol/25v/v% 8M HCl mixed solvent at different flow rates. The isotope separation coefficient between (48)Ca and (40)Ca was determined as 3.8×10(-3), which is larger than that of pure HCl solution system. Discussion is extended to the chromatographic HETP, height equivalent to a theoretical plate. PMID:26358563

  17. Halogen impact into new oxonium benzo-crown ether complexes with tetrachloro- and tetrabromoaurates(III).

    PubMed

    Pluzhnik-Gladyr, Sergei M; Kravtsov, Victor Ch; Fonari, Marina S; Kamalov, Gerbert L

    2014-05-21

    Five oxonium tetrahalogenaurate(III) (Hal = Cl, Br) benzo-crown ether (BCE) complexes are prepared and reported. The new compounds are [(H3O)(B18C6)(0.58)(4'-Cl-B18C6)0.42][AuCl4] 1, [(H3O)(B18C6)][AuCl4] 2, [(H3O)(4'-Br-B18C6)][AuCl4] 3, [(H3O)(4'-Br-B18C6)][AuBr4] 4, and [(H3O)(B18C6)][AuBr4] 5. The reaction medium, distinctive from the previously used aqua regia, allowed avoiding the unwanted nitration of initial macrocycles. The compositions and structures for 1, 3, 4, and 5 were proved by single crystal X-ray crystallography. The complete conversion of tetrachloroaurate(III) to the tetrabromoaurate(III) salts resulted in complex 4 isomorphous and isostructural to 3. All compounds form the laminated structures with alternation of cationic and anionic layers. The robustness of the anionic sheets is sustained by the halogen-halogen interactions and makes crucial impact on extraction of stoichiometric products in the case of tetrabromoaurate(III) salts. PMID:24671258

  18. Hydrogen-bonding interactions and protic equilibria in room-temperature ionic liquids containing crown ethers.

    SciTech Connect

    Marin, T.; Shkrob, I.; Dietz, M.

    2011-04-14

    Nuclear magnetic resonance (NMR) spectroscopy has been used to study hydrogen-bonding interactions between water, associated and dissociated acids (i.e., nitric and methanesulfonic acids), and the constituent ions of several water-immiscible room-temperature ionic liquids (ILs). In chloroform solutions also containing a crown ether (CE), water molecules strongly associate with the IL ions, and there is rapid proton exchange between these bound water molecules and hydronium associated with the CE. In neat ILs, the acids form clusters differing in their degree of association and ionization, and their interactions with the CEs are weak. The CE can either promote proton exchange between different clusters in IL solution when their association is weak or inhibit such exchange when the association is strong. Even strongly hydrophobic ILs are shown to readily extract nitric acid from aqueous solution, typically via the formation of a 1:1:1 {l_brace}H{sub 3}O{sup +} {center_dot} CE{r_brace}NO{sub 3}{sup -} complex. In contrast, the extraction of methanesulfonic acid is less extensive and proceeds mainly by IL cation-hydronium ion exchange. The relationship of these protic equilibria to the practical application of hydrophobic ILs (e.g., in spent nuclear fuel reprocessing) is discussed.

  19. Sodium ion-selective electrodes based on dibenzo-16-crown-5 compounds with pendent amide groups

    SciTech Connect

    Ohki, Akira; Maeda, Shigeru ); Lu, J.P.; Bartsch, R.A. )

    1994-05-15

    Potentiometric selectivities for alkali-metal cations of dibenzo-16-crown-5 compounds with amide-containing side arms attached to the central carbon atom of the three-carbon bridge have been determined in solvent polymeric membrane electrodes. The lariat ethers include N-alkyl- and N,N-dialkyl-sym-(R)-dibenzo-16-crown-5-oxyacetamides with R = hydrogen or an alkyl group. The presence of an alkyl group on the ring carbon which bears the amide-containing side arm markedly increases the Na[sup +]/K[sup +] selectivity of poly(vinyl chloride) matrix membrane electrodes with o-nitrophenyl octyl ether as the membrane solvent. Lariat ethers with a N,N-dipentyloxyacetamide group as the side arm and a geminal alkyl group of two or more carbon atoms exhibit high Na[sup +]K[sup +] selectivities (log K[sub Na,K][sup Pot] = [minus]2.1) with good selectivities for Na[sup +] over the other alkali-metal cations, H[sup +], NH[sub 4][sup +], and alkaline-earth-metal cations. 25 refs., 6 figs., 1 tab.

  20. Preparation and characterization of novel crown ether functionalized ionic liquid-based solid-phase microextraction coatings by sol-gel technology.

    PubMed

    Zhou, Xin; Xie, Peng-fei; Wang, Jiang; Zhang, Bei-bei; Liu, Ming-ming; Liu, Han-lan; Feng, Xiong-han

    2011-06-10

    A novel crown ether functionalized ionic liquid (IL), 1-allyl-3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium hexafluorophosphate was synthesized and used as selective stationary phase to prepare task-specific IL-based solid phase microextraction (SPME) fibers by sol-gel method and free radical cross-linking technology. The underlying mechanism of the sol-gel reaction was proposed and the successful chemical bonding of the crown ether functionalized IL to the formed hybrid organic-inorganic copolymer coating was confirmed by FT-IR spectroscopy. The performance of this in situ created crown ether functionalized IL-based SPME fibers, was investigated in detail. The coating has porous surface structure, stable performance in high temperature (to 340 °C) and in different solutions (water, organic solvent, acid and alkali), and good coating preparation reproducibility. In contrast to the sol-gel derived 1-allyl-3-methyl imidazolium hexafluorophosphate-based coating prepared in our previous work with the identical procedure, the extraction performance of this newly developed sol-gel crown ether functionalized IL-based coating was superior for alcohols, phthalate esters, phenolic environmental estrogens, fatty acids and aromatic amines due to the introduction of benzo-15-crown-5 functional group in IL structure. Moreover, it was shown to provide higher or comparable extraction efficiencies for most analytes studied than did the commercial PDMS, PDMS/DVB and PA fibers. PMID:21531419

  1. Enantiomer-selective ultraviolet photolysis of temperature-controlled protonated tryptophan on a chiral crown ether in the gas phase

    NASA Astrophysics Data System (ADS)

    Fujihara, Akimasa; Sato, Takashi; Hayakawa, Shigeo

    2014-08-01

    Enantiomer-selective ultraviolet photolysis of temperature-controlled protonated tryptophan (TrpH+) on the chiral crown ether, (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6TA), was examined using a tandem mass spectrometer containing a temperature-variable 22-pole ion trap. The spectra of D-TrpH+-(+)-18C6TA at 9-320 K showed that the loss of NH2CH2COOH due to Cαsbnd Cβ bond cleavage decreased gradually with increasing temperature. The spectrum at room temperature was similar to that of L-TrpH+-(+)-18C6TA, which showed no temperature dependence on photolysis. The chiral-specific photolysis of cold D-TrpH+-(+)-18C6TA was attributed to the structures involving the chiral-dependent interactions of the Cαsbnd H group of TrpH+ with the oxygen atoms of (+)-18C6TA.

  2. Solvent extraction of lanthanoid picrates with crown ethers: preferential sandwich complexation and unique cation selectivities

    SciTech Connect

    Nakagawa, K.; Okada, S.; Inoue, Y.; Tai, A.; Hakushi, T.

    1988-11-15

    Quantitative solvent extractions of aqueous lanthanoid picrates with 15-crown-5 and 18-crown-6 were conducted at low ionic strength in the absence of background salts. An overwhelming preference for the sandwich complexation and unique cation selectivities were observed. The peak extraction constants were found for samarium with 15-crown-5 (1:2 stoichiometry) and for cerium and praseodymium with 18-crown-6 (1:1 and 1:2 stoichiometries, respectively). The facile sandwich complexation and unique cation selectivities are interpreted in terms of the heavy hydration of lanthanoid ions of high charge density.

  3. 12-crown-4 ether-assisted enhancement of ionic conductivity and interfacial kinetics in polyethylene oxide electrolytes

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.

    1990-01-01

    The electrical and electrochemical properties of thin films of polyethylene oxide electrolytes with and without 12-crown-4 ether (12Cr4) are studied as a function of temperature and in the frequency regime from 100 kHz to 0.1 Hz. These measurements were made on electrolytes containing LiCF3SO3, LiBF4, or LiClO4 salts. At a given temperature, the bulk conductivity for a particular salt depends on the 12Cr4 concentration, reaching a maximum for a ratio of 12Cr4 to Li of 0.003.

  4. Water Ionic Liquid-Crown Ether System Controlling Morphologies and Sizes of Soluble Polypyrrole Nanostructures and Their Self-Assembly Behaviors in the System

    NASA Astrophysics Data System (ADS)

    Yavari, Issa; Kowsari, Elaheh

    The present study reports a novel chemical route to synthesize different sizes of conducting polypyrrol (ppy) nanoparticles by hydrogen-bonding directionality in the presence of a crown ether, ionic liquid ([octmim]Br, octhyl-methyl imidazulim bromide) and ammonium persulfate in HCl solution. The morphology of the nanoparticle of PPy was confirmed by SEM images. The effects of reaction conditions on the morphology of the resultant ppy nanostructures were studied. The conductivity of the product varied with the mass ratio of aniline monomer to crown ether and IL. The chemical and electronic structures of the ppy nanoparticle were also studied by FT-IR and UV-Vis spectrometry, respectively.

  5. A taco complex derived from a bis-crown ether capable of executing molecular logic operation through reversible complexation.

    PubMed

    Mandal, Amal Kumar; Das, Priyadip; Mahato, Prasenjit; Acharya, Suhash; Das, Amitava

    2012-08-17

    As learned from natural systems, self-assembly and self-sorting help in interconnecting different molecular logic gates and thus achieve high-level logic functions. In this context, demonstration of important logic operations using changes in optical responses due to the formation of molecular assemblies is even more desirable for the construction of a molecular computer. Synthesis of an appropriate divalent as well as a luminescent crown ether based host 1 and paraquat derivatives, 2(PF(6))(2) and 3(PF(6))(2), as guests helped in demonstrating a reversible [3](taco complex) (1·{2(PF(6))(2)}(2) or 1·{3(PF(6))(2)}(2)) formation in nonpolar solvent. Detailed (1)H NMR studies revealed that two paraquat units were bound cooperatively by the two crown units in 1. Because of preorganization, the flexible host molecule 1 adopts a folded conformation, where each of two paraquat units remain sandwiched between the two aromatic units of each folded crown ether moiety in 1. Disassembly of the "taco" complex in the presence of KPF(6) and reassembly on subsequent addition of DB18C6 was initially demonstrated by (1)H NMR spectral studies, which were subsequently corroborated through luminescence spectral studies. Further, luminescence spectral responses as output signals with appropriate and two independent molecular inputs could be correlated to demonstrate basic logic operation like OR and YES gates, while the results of the three molecular inputs could be utilized to demonstrate important logic operation like an INHIBIT gate. PMID:22834483

  6. Extraction of protactinium-233 and separation from thermal neutron-irradiated thorium-232 using crown ethers

    SciTech Connect

    Jalhoom, Moayyed G.; Mohammed, Dawood A.; Khalaf, Jumah S.

    2008-07-01

    A new method was developed for the extraction and separation of {sup 233}Pa from thermal neutron-irradiated {sup 232}Th. Solutions of Pa{sup 233} were prepared in LiCI-HCl solutions from which appreciable extraction was obtained using dibenzo-18-crown-6 in 1,2-dichloroethane. The effects of cavity size, substitutions on the crown ring, type of the organic solvent, and temperature on extraction are discussed. Very high separation factors were obtained for the pairs {sup 233}Pa/{sup 232}Th (>105), {sup 233}Pa/{sup 233}U (> 1000), and {sup 232}U/{sup 232}Th (>60). (authors)

  7. Crown-Ether Derived Graphene Hybrid Composite for Membrane-Free Potentiometric Sensing of Alkali Metal Ions.

    PubMed

    Olsen, Gunnar; Ulstrup, Jens; Chi, Qijin

    2016-01-13

    We report the design and synthesis of newly functionalized graphene hybrid material that can be used for selective membrane-free potentiometric detection of alkali metal ions, represented by potassium ions. Reduced graphene oxide (RGO) functionalized covalently by 18-crown[6] ether with a dense surface coverage is achieved by the introduction of a flexible linking molecule. The resulting hybrid composite is highly stable and is capable of detecting potassium ions down to micromolar ranges with a selectivity over other cations (including Ca(2+), Li(+), Na(+), NH4(+)) at concentrations up to 25 mM. This material can be combined further with disposable chips, demonstrating its promise as an effective ion-selective sensing component for practical applications. PMID:26703780

  8. Structure of hydrated clusters of dibenzo-18-crown-6-ether in a supersonic jet--encapsulation of water molecules in the crown cavity.

    PubMed

    Kusaka, Ryoji; Inokuchi, Yoshiya; Ebata, Takayuki

    2008-11-01

    The structure of dibenzo-18-crown-6-ether (DB18C6) and its hydrated clusters has been investigated in a supersonic jet. Two conformers of bare DB18C6 and six hydrated clusters (DB18C6-(H(2)O)(n)) were identified by laser-induced fluorescence, fluorescence-detected UV-UV hole-burning and IR-UV double-resonance spectroscopy. The IR-UV double resonance spectra were compared with the IR spectra obtained by quantum chemical calculations at the B3LYP/6-31+G* level. The two conformers of bare DB18C6 are assigned to "boat" and "chair I" forms, respectively, among which the boat form is dominant. All the six DB18C6-(H(2)O)(n) clusters with n = 1-4 have a boat conformation in the DB18C6 part. The water molecules form a variety of hydration networks in the boat-DB18C6 cavity. In DB18C6-(H(2)O)(1), a water molecule forms the bidentate hydrogen bond with the O atoms adjacent to the benzene rings. In this cluster, the water molecule is preferentially hydrogen bonded from the bottom of boat-DB18C6. In the larger clusters, the hydration networks are developed on the basis of the DB18C6-(H(2)O)(1) cluster. PMID:18936847

  9. Investigation of bis-crown ethers for ion-selective electrodes by FT-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Egyed, O.; Izvekov, V. P.; Toth, K.; Holly, S.; Pungor, E.

    1990-03-01

    The structure of bis-benzo-15-crown-5 derivatives containing nitro groups and urethane linkages has been studied by FT-IR spectroscopy, regarding especially the secondary bonds (H-bridges) of the chain connecting the two crow rings of the molecule. It was concluded that the formation of an ion trap stabilized by intramolecular cross H-bonds between urethane NH groups and O atoms is presumable.

  10. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data. PMID:22653895

  11. Metallosupramolecular poly[2]pseudorotaxane constructed by metal coordination and crown-ether-based molecular recognition.

    PubMed

    Wei, Peifa; Li, Jinying; Yan, Xuzhou; Zhou, Qizhong

    2014-01-01

    A novel bis(m-phenylene)-32-crown-10 derivative bearing two π-extended pyridyl groups was synthesized, and its host-guest complexation with a paraquat derivative to form a threaded [2]pseudorotaxane was studied. Subsequently, a poly[2]pseudorotaxane was constructed with a metallosupramolecular polymer backbone via metal coordination, which was comprehensively confirmed by the combination of (1)H NMR, (31)P{(1)H} NMR, DOSY NMR, DLS, and EDX techniques. PMID:24328434

  12. The interaction between ketamine and some crown ethers in common organic solvents studied by NMR: The effect of donating atoms and ligand structure

    NASA Astrophysics Data System (ADS)

    Chekin, Fereshteh; Bordbar, Maryam; Fathollahi, Yaghoub; Alizadeh, Naader

    2006-02-01

    1H NMR spectroscopy was used to investigate the stoichiometry and stability of the drug ketamine cation complexes with some crown ethers, such as 15-crown-5 (15C5), aza-15-crown-5 (A15C5), 18-crown-6 (18C6), aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6), dibenzyl-diaza-18-crown-6 (DBzDA18C6) and cryptant [2,2,2] (C222) in acetonitrile (AN), dimethylsulfoxide (DMSO) and methanol (MeOH) at 27 °C. In order to evaluate the formation constants of the ketamine cation complexes, the CH 3 protons chemical shift (on the nitrogen atom of ketamine) was measured as function of ligand/ketamine mole ratio. The formation constant of resulting complexes were calculated by the computer fitting of chemical shift versus mole ratio data to appropriate equations. A significant chemical shift variation was not observed for 15C5 and 18C6. The stoichiometry of the mono aza and diaza ligands are 1:1 and 1:2 (ligand/ketamine), respectively. In all of the solvents studied, DA18C6 formed more stable complexes than other ligands. The solvent effect on the stability of these complexes is discussed.

  13. Regioselective carbon-oxygen bond cleavage reactions of aromatic ethers and esters with potassium metal/18-crown-6/THF as the electron-transfer reagent

    SciTech Connect

    Fish, R.H.; Dupon, J.W.

    1988-10-28

    The facile carbon-oxygen bond cleavage reactions of a variety of aromatic ethers and esters were studied with an electron-transfer reagent that consisted of potassium metal and 18-crown-6 in tetrahydrofuran (THF). The relative rates of carbon-oxygen bond cleavage, with these aromatic ethers and esters under electron-transfer conditions, was studied in competition with the standard, diphenyl ether. The order of relative reactivities was as follows: phenyl 2-hydroxybenzoate (10) (>2.0); phenyl 2-methoxybenzoate (11) (>2.0); phenyl 4-methoxybenzoate (12) (>2.0); 2-methoxyphenyl benzoate (13) (>2.0); 4-methoxyphenyl benzoate (14) (>2.0); 4-hydroxyphenyl benzoate (15) (1.6); benzyl benzoate (9) (1.3); 4-methoxyphenyl phenyl ether (5) (1.15); phenyl benzoate (8) (1.04); diphenyl ether (1) (1.0); dibenzyl ether (2) (0.98); 2-methoxyphenyl phenyl ether (6) (0.97); benzyl phenyl ether (3) (0.96); phenethyl phenyl ether (7) (0.77); and 4-hydroxyphenyl phenyl ether (4) (<0.1). From these relative rates, it is clear that electron-donating groups increase the relative rates of C-O bond cleavage in aromatic esters. Conversely, a methoxyl group has no apparent effect on the relative rates of aromatic ether C-O bond cleavage, while a hydroxyl group dramatically decreases the rate. Proton donors, tert-butyl alcohol and hydroquinone, decreased the rate of diphenyl ether cleavage. The regioselectivity for C-O bond cleavage of esters 8-15, i.e., carbonyl-oxygen versus carboxyl-carbon cleavage, showed selective carbonyl-oxygen bond cleavage.

  14. Selective solid-phase extraction of catecholamines from plasma using nanofibers doped with crown ether and their quantitation by HPLC with electrochemical detection.

    PubMed

    Chen, LiQin; Zhu, XingHua; Shen, Jun; Zhang, WanQi

    2016-07-01

    A simple and convenient preparation method has been developed for polymeric crown ethers containing the dibenzo-18-crown-6 subunit and electrospun composite nanofibers composed of polymeric crown ethers with polystyrene (PCE-PS). Furthermore, this composite nanofiber was used as a sorbent for selective extraction of plasma catecholamines, viz. dopamine (DA), norepinephrine (NE), and epinephrine (E). After the protein deposition of the plasma sample, the supernatant was adjusted to neutral pH with buffer solution. Then, the mixture was loaded and pushed through a column packed with composite nanofiber sorbent, and the analytes were eluted with 50 μL of acetic acid. The effectiveness of the plasma sample cleanup method was verified by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The PCE-PS packed column may prove clinically useful, as it provides a convenient and selective method for evaluation of human plasma catecholamines. Graphical Abstract Scheme showing the selective packed fiber SPE of catecholamines from spiked plasma using nanofibers doped with ploymeric crown ether. PMID:27173391

  15. Cesium and strontium extraction using a mixed extractant solvent including crown ether and calixarene extractants

    DOEpatents

    Meikrantz, David H.; Todd, Terry A.; Riddle, Catherine L.; Law, Jack D.; Peterman, Dean R.; Mincher, Bruce J.; McGrath, Christopher A.; Baker, John D.

    2007-11-06

    A mixed extractant solvent including calix[4]arene-bis-(tert-octylbenzo)-crown-6 ("BOBCalixC6"), 4',4',(5')-di-(t-butyldicyclo-hexano)-18-crown-6 ("DtBu18C6"), and at least one modifier dissolved in a diluent. The mixed extractant solvent may be used to remove cesium and strontium from an acidic solution. The DtBu18C6 may be present from approximately 0.01 M to approximately 0.4M, such as from approximately 0.086 M to approximately 0.108 M. The modifier may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol ("Cs-7SB") and may be present from approximately 0.01M to approximately 0.8M. In one embodiment, the mixed extractant solvent includes approximately 0.15M DtBu18C6, approximately 0.007M BOBCalixC6, and approximately 0.75M Cs-7SB modifier dissolved in an isoparaffinic hydrocarbon diluent. The mixed extractant solvent may form an organic phase in an extraction system that also includes an aqueous phase. Methods of extracting cesium and strontium as well as strontium alone are also disclosed.

  16. Absolute configuration and predominant conformations of a chiral crown ether-based colorimetric sensor: a vibrational circular dichroism spectroscopy and DFT study of chiral recognition.

    PubMed

    Merten, Christian; Hyun, Myung Ho; Xu, Yunjie

    2013-05-01

    In the present work, we report a comprehensive vibrational circular dichroism (VCD) spectroscopic study of a chiral crown ether which features an axial chiral 3.3'-diphenyl-1,1'-binaphthyl group as chiral moiety. By comparing the experimental and calculated VCD spectra, we show that the presumably very flexible crown ether preferably adopts only one ring conformation. Conformational flexibility is observed in the 2,4-dinitrophenyl-diazophenol group, which was previously introduced for colorimetric detection of primary amines and amino alcohols (Cho et al., Chirality 2011;23:349-353). The VCD spectra of the host-guest complexes with phenyl glycinol (PG) and phenyl alaninol have been studied as well. Based on the spectra calculated, it is shown that the diastereomeric complexes in general can be differentiated using VCD spectroscopy. Furthermore, the experimental VCD spectra of the complexes of the host molecule with PG support the above finding. PMID:23620265

  17. The LArIAT Experiment at Fermilab

    NASA Astrophysics Data System (ADS)

    Nutini, Irene; LArIAT Collaboration

    2016-02-01

    The LArIAT experiment at Fermilab is part of the International Neutrino program recently approved in the US. LArIAT aims to measure the main features of charged particles interactions in argon in the energy range (0.2 - 2.0 GeV) corresponding to the energy spectrum of the same particles when produced in a neutrino-argon interaction (neutrino energies of few GeV) typical of the short- and long-baseline neutrino beams of the Neutrino Program. Data collected from the 1 st Run are being analyzed for both Physics studies and a technical characterization of the scintillation light collection system. Two analysis topics are reported: the method developed for charged pion cross section measurement, based on the specific features of the LArTPC, and the development and test of the LArIAT custom-designed cold front-end electronics for SiPM devices to collect LAr scintillation light.

  18. Two highly stable and selective solid phase microextraction fibers coated with crown ether functionalized ionic liquids by different sol-gel reaction approaches.

    PubMed

    Shu, Jianjun; Xie, Pengfei; Lin, Danni; Chen, Rongfeng; Wang, Jiang; Zhang, Beibei; Liu, Mingming; Liu, Hanlan; Liu, Fan

    2014-01-01

    In this work, two novel crown ether functionalized ionic liquid (FIL)-based solid phase microextraction (SPME) fibers were prepared by sol-gel technology using the synthesized 1-(trimethoxysily)propyl 3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium bis(trifluoromethanesulphonyl)imide ([TMSP(Benzo15C5)HIM][N(SO2CF3)2]) and 1-allyl-3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium bis(trifluoromethanesulphonyl)imide ([A(Benzo15C5)HIM][N(SO2CF3)2]) as selective stationary phases. Owing to the introduction of trimethoxysilypropyl to the imidazole cation, the [TMSP(Benzo15C5)HIM][N(SO2CF3)2] could be chemically bonded to the formed sol-gel silica substrate through the hydrolysis and polycondensation reaction. Similarly, the [A(Benzo15C5)HIM][N(SO2CF3)2] was able to participate in the formation of the organic-inorganic copolymer coatings through the free radical crosslinking reaction. These two fibers were determined to have "bubble-like" surface characteristics analogous to a previously prepared [A(Benzo15C5)HIM][PF6]-based fiber. Their thermal stabilities were much higher than that of the [A(Benzo15C5)HIM][PF6]-based coating. They were capable of withstanding temperatures as high as 400°C without evident loss of the crown ether FILs. They also had strong solvent, acid and alkali resistance, good coating preparation reproducibility and high selectivity for medium polar to polar compounds. The high selectivity of these two fibers could be attributed to the strong ion-dipole, hydrogen bonding and π-π interactions provided by the synergetic effect of ILs and benzo-15-crown-5 functionalities. Moreover, the selectivity of these two fibers was rather different although the structures of these two crown ether FILs were very similar. This is maybe because the relative contents of the crown ether FILs chemically bonded to the organic-inorganic copolymer coatings were quite different when prepared by different sol-gel reaction approaches. PMID:24331051

  19. High extraction efficiency fiber coated with calix[4] open-chain crown ether for solid-phase microextraction of polar aromatic and aliphatic compounds.

    PubMed

    Liu, Mingming; Zeng, Zhaorui; Lei, Yun; Li, Haibing

    2005-11-01

    The calix[4] open-chain crown ether, 5,11,17,23-tetra-tert-butyl-25,27-di(2-allyloxyethoxyl)-26,28-dihydroxycalix[4]arene was synthesized and used for preparation of solid-phase microextraction (SPME) fibers of enhanced extraction efficiency. The new SPME coating made from calix[4] open-chain crown ether and hydroxyl-terminated silicone oil was developed with the aid of vinyltriethoxylsilane as bridge using sol-gel method and cross-linking technology. The efficiency of the novel fiber in the extraction of polar aromatic and aliphatic compounds, such as phenols, alcohols, and volatile fatty acids, was also investigated. Due to the introduction of the polar open-chain crown ether in calix[4]arene molecules, the calix[4] open-chain crown ether fiber showed much better selectivity and sensitivity to these polar compounds in comparison with calix[4]arene fiber. It also had superior extraction efficiency when compared to commercial poly(dimethylsiloxane)-divinylbenzene and polyacrylate fibers. Parts per billion to parts per trillion level detection limits were achieved for most of the analytes through SPME in conjunction with GC and flame ionization detector. The linear ranges were two to four orders of magnitude, and the RSD values were below 7% for all analytes. The novel fiber was applied to determine volatile alcohols and fatty acids in wine samples. The volatile-free wine prepared in this work was used to assure similar chemical environment for analytes in both calibration solutions and in real wine samples, thus compensating for possible matrix interferences. The established internal standard method using 4-methyl-2-pentanol as internal standard showed satisfactory accuracy and precision. PMID:16342796

  20. A novel pentiptycene bis(crown ether)-based [2](2)rotaxane whose two DB24C8 rings act as flapping wings of a butterfly.

    PubMed

    Ma, Ying-Xian; Meng, Zheng; Chen, Chuan-Feng

    2014-04-01

    A novel [2](2)rotaxane based on pentiptycene-derived bis(crown ether) can be efficiently synthesized via a "click chemistry" method and the subsequent N-methylation. Due to the different affinities of DB24C8 with the ammonium and triazolium stations, the wing-flapping movement of the DB24C8 "wings" in the [2](2)rotaxane can be easily achieved by acid/base stimulus. PMID:24635015

  1. Ammonium-crown ether supramolecular cation-templated assembly of an unprecedented heterobicluster-metal coordination polymer with enhanced NLO properties.

    PubMed

    Zhang, Jinfang; Jia, Ding; Humphrey, Mark G; Meng, Suci; Zaworotko, Michael J; Cifuentes, Marie P; Zhang, Chi

    2016-03-01

    An ammonium-crown ether host-guest supramolecular cation-templated synthetic methodology has been developed to construct a structurally unprecedented heterobicluster-metal coordination polymer (HCM-CP 1) based on tetranuclear clusters [WS4Cu3](+) with different connection environments, pentanuclear clusters [WS4Cu4](2+), and Cu(+) building metal ions. HCM-CP 1 exhibits enhanced NLO properties, which may be ascribed to the incorporation of diverse building cluster components. PMID:26864604

  2. Discussion on the complexing ability of the uranyl ion with several crown ethers and cryptands in water and in propylene carbonate

    SciTech Connect

    Brighli, M.; Fux, P.; Lagrange, J.; Lagrange, P.

    1985-01-02

    Interactions of the uranyl ion (UO/sub 2//sup 2 +/) with some common crown ethers (12C4, 15C5, 18C6, DB-18C6) and cryptands (22,222) are investigated in aqueous and propylene carbonate (PC) solutions, I = 0.1 M ((TEA)ClO/sub 4/). Stability constants of the complexes formed are determined by potentiometric and spectrophotometric measurements. Discussions on the stability constants of the complexes allow us to postulate whether or not direct uranyl-macrocycle bonds are obtained. In PC solution, uranyl inner-sphere complexes with 18C6, DB-18C6, 22, and 222 are formed with the uranyl ion probably inside or partially enclosed in the ligand cavity. In aqueous media, complexation occurs only with crown ethers by formation of hydrogen bonds between hydrogen of water molecules of the hydrate shell of the uranyl ion and oxygen atoms of the crown ether (UO/sub 2//sup 2 +/ outer-sphere complexes). 31 references, 5 figures, 3 tables.

  3. A Highly K(+) -Selective Fluorescent Probe - Tuning the K(+) -Complex Stability and the K(+) /Na(+) Selectivity by Varying the Lariat-Alkoxy Unit of a Phenylaza[18]crown-6 Ionophore.

    PubMed

    Schwarze, Thomas; Schneider, Radu; Riemer, Janine; Holdt, Hans-Jürgen

    2016-01-01

    A desirable goal is to synthesize easily accessible and highly K(+) /Na(+) -selective fluoroionophores to monitor physiological K(+) levels in vitro and in vivo. Therefore, highly K(+) /Na(+) -selective ionophores have to be developed. Herein, we obtained in a sequence of only four synthetic steps a set of K(+) -responsive fluorescent probes 4, 5 and 6. In a systematic study, we investigated the influence of the alkoxy substitution in ortho position of the aniline moiety in π-conjugated aniline-1,2,3-triazole-coumarin-fluoroionophores 4, 5 and 6 [R=MeO (4), EtO (5) and iPrO (6)] towards the K(+) -complex stability and K(+) /Na(+) selectivity. The highest K(+) -complex stability showed fluoroionophore 4 with a dissociation constant Kd of 19 mm, but the Kd value increases to 31 mm in combined K(+) /Na(+) solutions, indicating a poor K(+) /Na(+) selectivity. By contrast, 6 showed even in the presence of competitive Na(+) ions equal Kd values (Kd (K+) =45 mm and Kd (K+/Na+) =45 mm) and equal K(+) -induced fluorescence enhancement factors (FEFs=2.3). Thus, the fluorescent probe 6 showed an outstanding K(+) /Na(+) selectivity and is a suitable fluorescent tool to measure physiological K(+) levels in the range of 10-80 mm in vitro. Further, the isopropoxy-substituted N-phenylaza[18]crown-6 ionophore in 6 is a highly K(+) -selective building block with a feasible synthetic route. PMID:26473334

  4. Effects of 12-Crown-4 ether on the ionic conductivity and electrode kinetics of electrolytes in polyethylene oxide

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.

    1990-01-01

    Results are described of investigations of the electrical and electrochemical properties of thin films of polyethylene oxide (PEO) electrolytes with and without 12-Crown-4 ether (12Cr4) as a function of temperature and in the frequency regime 100 kHz-0.1 Hz. These measurements were made for LiCF3SO3, LiBF4, and LiClO4 salts. At a given temperature, the bulk conductivity, sigma, (S/cm), for a particular salt, depends on the 12Cr4 concentration with sigma reaching a maximum at about 3 mM 12Cr4. Of the three salts studied, the sigma is the highest for PEO/LiBF4 with 3 mM 12Cr4. The ac and dc measurements yield a lower charge transfer resistance for 12Cr4-incorporated samples than for samples without. Plating/stripping of Li occurs at a potential closer to Li(+)/Li for 12Cr4 samples than those without. The conductivities of a thin (about 100 microns) and a thick (400 microns) films are similar.

  5. Spectroscopy, NMR and DFT studies on molecular recognition of crown ether bridged chiral heterotrinuclear salen Zn(II) complex

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Ruan, Wen-Juan; Chen, Jia-Mei; Zhang, Ying-Hui; Zhu, Zhi-Ang

    2005-12-01

    A barium-containing crown ether bridged chiral heterotrinuclear salen Zn(II) complex BaZn 2L(ClO 4) 2, where L is a folded dinuclear chiral ( R, R)-salen ligand, has been synthesized and characterized by elemental analysis, 1H NMR, UV-vis, IR, circular dichroism (CD) spectra, and mass spectra. As a folded dinuclear chiral host, its recognition with achiral guests (imidazole derivatives), rigid bidentate guest (1,4-diazobicyclo[2,2,2]octane, DABCO) and chiral guests (amino acid methyl esters) was investigated by means of UV-vis spectrophotometric titration, CD spectra. The association constants of D-amino acid methyl esters are found to be higher than those of their L-enantiomer. The sandwich-type binding of BaZn 2L(ClO 4) 2-DABCO supramolecular assembly was specially studied via 1H NMR titration and 1H ROESY. To understand the recognition on molecular level, density functional theory (DFT) calculations on B3LYP/LanL2DZ were performed on the minimal energy conformations of host, guests, and host-guest complexes. The minimal energy conformations were obtained by molecular mechanics (MM) optimization and molecular dynamics (MD) simulation. The results of single point energy, HOMO energy, and charges transfer were analyzed. The results of theoretical calculations are in good agreement with the experimental data.

  6. UV and IR Spectroscopy of Cold H2O(+)-Benzo-Crown Ether Complexes.

    PubMed

    Inokuchi, Yoshiya; Ebata, Takayuki; Rizzo, Thomas R

    2015-11-12

    The H2O(+) radical ion, produced in an electrospray ion source via charge transfer from Eu(3+), is encapsulated in benzo-15-crown-5 (B15C5) or benzo-18-crown-6 (B18C6). We measure UV photodissociation (UVPD) spectra of the (H2O·B15C5)(+) and (H2O·B18C6)(+) complexes in a cold, 22-pole ion trap. These complexes show sharp vibronic bands in the 35 700-37 600 cm(-1) region, similar to the case of neutral B15C5 or B18C6. These results indicate that the positive charge in the complexes is localized on H2O, giving the forms H2O(+)·B15C5 and H2O(+)·B18C6, in spite of the fact that the ionization energy of B15C5 and B18C6 is lower than that of H2O. The formation of the H2O(+) complexes and the suppression of the H3O(+) production through the reaction of H2O(+) and H2O can be attributed to the encapsulation of hydrated Eu(3+) clusters by B15C5 and B18C6. On the contrary, the main fragment ions subsequent to the UV excitation of these complexes are B15C5(+) and B18C6(+) radical ions; the charge transfer occurs from H2O(+) to B15C5 and B18C6 after the UV excitation. The position of the band origin for the H2O(+)·B18C6 complex (36323 cm(-1)) is almost the same as that for Rb(+)·B18C6 (36315 cm(-1)); the strength of the intermolecular interaction of H2O(+) with B18C6 is similar to that of Rb(+). The spectral features of the H2O(+)·B15C5 complex also resemble those of the Rb(+)·B15C5 ion. We measure IR-UV spectra of these complexes in the CH and OH stretching region. Four conformers are found for the H2O(+)·B15C5 complex, but there is one dominant form for the H2O(+)·B18C6 ion. This study demonstrates the production of radical ions by charge transfer from multivalent metal ions, their encapsulation by host molecules, and separate detection of their conformers by cold UV spectroscopy in the gas phase. PMID:26491792

  7. Design, synthesis, characterization, and OFET properties of amphiphilic heteroleptic tris(phthalocyaninato) europium(III) complexes. The effect of crown ether hydrophilic substituents.

    PubMed

    Gao, Yingning; Ma, Pan; Chen, Yanli; Zhang, Ying; Bian, Yongzhong; Li, Xiyou; Jiang, Jianzhuang; Ma, Changqin

    2009-01-01

    Two amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with hydrophilic crown ether heads and hydrophobic octyloxy tails [Pc(mCn)(4)]Eu[Pc(mCn)(4)]Eu[Pc(OC(8)H(17))(8)] [m = 12, n = 4, H(2)Pc(12C4)(4) = 2,3,9,10,16,17,23,24-tetrakis(12-crown-4)phthalocyanine; m = 18, n = 6, H(2)Pc(18C6)(4) = 2,3,9,10,16,17,23,24-tetrakis(18-crown-6)phthalocyanine; H(2)Pc(OC(8)H(17))(8) = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] (1, 2) were designed and prepared from the reaction between homoleptic bis(phthalocyaninato) europium compound [Pc(mCn)(4)]Eu[Pc(mCn)(4)] (m = 12, n = 4; m = 18, n = 6) and metal-free H(2)Pc(OC(8)H(17))(8) in the presence of Eu(acac)(3).H(2)O (Hacac = acetylacetone) in boiling 1,2,4-trichlorobenzene. These novel sandwich triple-decker complexes were characterized by a wide range of spectroscopic methods and electrochemically studied. With the help of the Langmuir-Blodgett technique, these typical amphiphilic triple-decker complexes were fabricated into organic field effect transistors (OFET) with top contact configuration on bare SiO(2)/Si substrate, hexamethyldisilazane-treated SiO(2)/Si substrate, and octadecyltrichlorosilane (OTS)-treated SiO(2)/Si substrate, respectively. The device performance is revealed to be dependent on the species of crown ether substituents and substrate surface treatment. OFETs fabricated from the triple decker with 12-crown-4 hydrophilic substituents, 1, allow the hole transfer in the direction parallel to the aromatic phthalocyanine rings. In contrast, the devices of a triple-decker compound containing 18-crown-6 as hydrophilic heads, 2, transfer holes in a direction along the long axis of the assembly composed of face-to-face aggregated triple-decker molecules, revealing the effect of molecular structure, specifically the crown ether substituents on the film structure and OFET functional properties. The carrier mobility for hole as high as 0.33 cm(2) V(-1) s(-1) and current modulation of 7.91 x 10

  8. Design and synthesis of the next generation of crown ethers for waste separations: An interlaboratory comprehensive proposal. 1997 annual progress report

    SciTech Connect

    Moyer, B.A.; Dietz, M.L.; Alexandratos, S.D.; Hay, B.P.

    1997-09-01

    'The purpose of this task is to undertake the design, synthesis, and characterization of the next generation of crown ethers for metal-ion separations applicable to the US Department of Energy''s (DOE''s) environmental needs. The general target problem is the removal of alkali and alkaline-earth metal contaminants from certain environmental and waste streams. Although not a radioactivity hazard, Li{sup +} ions leaching from burial sites containing more than 12 metric tons of lithium compounds contaminate the groundwater at the Oak Ridge Y-12 Plant and have raised noncompliance concerns because of the resultant toxicity to aquatic biota. A more highly visible problem has been treatment of high-level wastes stored in underground tanks at Oak Ridge National Laboratory (ORNL), Idaho National Engineering and Environmental Laboratory, and especially the Hanford Site. The fission products {sup 90}Sr and {sup 137}Cs have been explicitly targeted for removal by the following DOE programs: the Office of Environmental Management, the Office of Science and Technology, the Tank Waste Remediation System, the Tanks Focus Area, and the Efficient Separations and Processing Cross-Cutting Program. These seemingly ubiquitous fission products also appear in soil and groundwater at numerous DOE sites. In addition, radium has recently been named as a target contaminant at the Niagara Falls Storage Site. Unfortunately, the separations technologies needed to address these problems either do not exist or exhibit substantial deficiencies. Established techniques such as solvent extraction and ion exchange certainly have a strong role to play, especially as enhanced with the use of the new highly selective metal-ion hosts such as crown ethers and calixarenes. Recently applied results in the United States, France, Russia, and elsewhere have demonstrated the effective performance of crown ethers under realistic or actual process conditions for the removal of alkali and alkaline-earth metal ions

  9. Retention behavior of common mono- and divalent cations on calcinated silica gel columns in ion chromatography with conductimetric detection and the use of nitric acid, containing crown ethers, as eluents.

    PubMed

    Ohta, Kazutoku; Kusumoto, Keiji; Takao, Yasumasa; Towata, Atsuya; Kawakami, Shoji; Murase, Yoshio; Ohashi, Masayoshi

    2002-05-17

    Ion chromatographic behavior of common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) on columns packed with silica gels (Super Micro Bead Silica Gel B-5, SMBSG B-5) calcinated at 200, 400, 600, 800 and 1000 degrees C for 5 h was investigated using nitric acid containing crown ethers [18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane) and 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane)] as eluent. When using 0.5 mM HNO3 as the eluent, the calcination had almost no effect on the improvement of peak resolution between these mono- and divalent cations. In contrast, when using 0.5 mM HNO3 containing crown ethers as the eluent, with increasing the calcinating temperature, the amount of crown ethers adsorbed on the corresponding calcinated SMBSG B-5 silica gels columns increased and, as a consequence, peak resolution between these mono- and divalent cations was quite improved. Excellent simultaneous separation of these mono- and divalent cations was achieved on column (150x4.6 mm I.D.) packed with the SMBSG B-5 silica gel calcinated at 1000 degrees C by elution with 0.5 mM HNO3 containing either 1.0 mM 18-crown-6 or 5.0 mM 15-crown-5. PMID:12108647

  10. Ludwig-Soret effect of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol: Temperature, molecular weight, and hydrogen bond effect

    NASA Astrophysics Data System (ADS)

    Maeda, Kousaku; Shinyashiki, Naoki; Yagihara, Shin; Wiegand, Simone; Kita, Rio

    2015-09-01

    The thermal diffusion, also called the Ludwig-Soret effect, of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol is investigated as a function of temperature by thermal diffusion forced Rayleigh scattering. The Soret coefficient, ST, and the thermal diffusion coefficient, DT, show a linear temperature dependence for all studied compounds in the investigated temperature range. The magnitudes and the slopes of ST and DT vary with the chemical structure of the solute molecules. All studied molecules contain ether and/or hydroxyl groups, which can act as acceptor or donor to form hydrogen bonds, respectively. By introducing the number of donor and acceptor sites of each solute molecule, we can express their hydrogen bond capability. ST and DT can be described by an empirical equation depending on the difference of donor minus acceptor sites and the molecular weight of the solute molecule.

  11. Ludwig-Soret effect of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol: Temperature, molecular weight, and hydrogen bond effect.

    PubMed

    Maeda, Kousaku; Shinyashiki, Naoki; Yagihara, Shin; Wiegand, Simone; Kita, Rio

    2015-09-28

    The thermal diffusion, also called the Ludwig-Soret effect, of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol is investigated as a function of temperature by thermal diffusion forced Rayleigh scattering. The Soret coefficient, ST, and the thermal diffusion coefficient, DT, show a linear temperature dependence for all studied compounds in the investigated temperature range. The magnitudes and the slopes of ST and DT vary with the chemical structure of the solute molecules. All studied molecules contain ether and/or hydroxyl groups, which can act as acceptor or donor to form hydrogen bonds, respectively. By introducing the number of donor and acceptor sites of each solute molecule, we can express their hydrogen bond capability. ST and DT can be described by an empirical equation depending on the difference of donor minus acceptor sites and the molecular weight of the solute molecule. PMID:26429021

  12. Influence of temperature and crown ether complex formation on the charge partitioning between z and c fragments formed after electron capture by small peptide dications

    NASA Astrophysics Data System (ADS)

    Ehlerding, Anneli; Jensen, Camilla S.; Wyer, Jean A.; Holm, Anne I. S.; Jørgensen, Palle; Kadhane, Umesh; Larsen, Mikkel K.; Panja, Subhasis; Poully, Jean Christophe; Worm, Esben S.; Zettergren, Henning; Hvelplund, Preben; Brøndsted Nielsen, Steen

    2009-04-01

    Electron capture by peptide dications results in N-C[alpha] bond cleavage to give c+ and z or c and z+ fragments. In this work we have investigated how crown ether (18-crown-6 = CE) complex formation and a change in the internal energy affect the charge division between the z and c fragments. Both complex formation and a high temperature have the effect of breaking internal ionic hydrogen bonds. The crown ether complex also lowers the probability of internal proton transfer between the two fragments, and reduces the recombination energy of the charged group it targets. The systems under study were doubly protonated di- and tripeptides, [AK+2H]2+, [AR+2H]2+, [KK+2H]2+ and [GHK+2H]2+ (A = alanine, K = lysine, R = arginine, G = glycine and H = histidine). For crown ether complexes the formation of z+ ions was always preferred over c+ ions. In the case of [GHK+2H]2+, the bare ion dissociated into z2+ + c1 and z1 + c2+ from cleavage of the first and second N-C[alpha] bond, respectively, whereas z1+ fragment ions had higher yield than c2+ for [GHK+2H]2+(CE). The internal energy of the ions was changed by storing them in a 22-pole ion trap in which they were equilibrated to a temperature between -60 and 90 °C in collisions with helium gas. The average internal energy increased by about 0.4 eV from the lowest to the highest temperature for the dipeptides and 0.6 eV for the tripeptide. More fragmentation occurred at the higher temperature, as observed by an increase in the formation of b+ and y+ ions after breakage of the peptide bond of vibrationally hot even-electron cations and from secondary reactions of z+ radical cations within the time window of the experiment. However, the z+ to c+ partitioning was not found to depend significantly on temperature in the measured range. In addition the decay of [GHK+H]+/[GHK+2H]+ and [AK+H]+ formed after electron capture by [GHK+2H]2+ and [AK+2H]2+ was found to occur on a microsecond to millisecond timescale. The data are well

  13. Liquid chromatographic resolution of 3-amino-1,4-benzodiazepin-2-ones on crown ether-based chiral stationary phases.

    PubMed

    Park, Je Young; Jin, Kab Bong; Hyun, Myung Ho

    2012-05-01

    3-Amino-5-phenyl (or 5-methyl)-1,4-benzodiazepin-2-ones, which are chiral precursors of anti-respiratory syncytial virus active agents, were resolved on three different chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid or (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. Among the three CSPs, the CSP that is based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 and containing residual silanol group-protecting n-octyl groups on the silica surface was found to be most effective with the use of 80% ethanol in water containing perchloric acid (10 mM) and ammonium acetate (1.0 mM) as a mobile phase. The separation factors (α) and resolutions (R(S) ) were in the range of 1.90-3.21 and 2.79-5.96, respectively. From the relationship between the analyte structure and the chromatographic resolution behavior, the chiral recognition mechanism on the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was proposed to be different from that on the CSP based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. In addition, the chromatographic resolution behavior of the most effective CSP was investigated as a function of the composition of aqueous mobile phase containing organic and acidic modifier and ammonium acetate. PMID:22508444

  14. The influence of water-ethanol mixture on the thermodynamics of complex formation between 18-crown-6 ether and L-phenylalanine

    NASA Astrophysics Data System (ADS)

    Usacheva, T. R.; Sharnin, V. A.; Chernov, I. V.; Matteoli, E.; Terekhova, I. V.; Kumeev, R. S.

    2012-08-01

    The influence of water-ethanol mixture composition on the complex formation between 18-crown-6 ether and L-phenylalanine was studied by titration calorimetry at Т = 298.15 K. The standard thermodynamic parameters (ΔrGо, ΔrHо, ТΔrSо) of formation of [Phe18C6] molecular complex were calculated from data obtained by means of the microcalorimetric system TAM III (TA Instruments, USA) at X(EtOH) = 0.0/0.6 mol fraction. The stability of [Phe18C6] and the mechanism of complexation in water were investigated using the 1Н and 13С NMR spectroscopy. The increase of EtOH concentration results in an increase of the complex stability and of the exothermicity of complexation.

  15. A Focus on Triazolium as a Multipurpose Molecular Station for pH-Sensitive Interlocked Crown-Ether-Based Molecular Machines

    PubMed Central

    Coutrot, Frédéric

    2015-01-01

    The control of motion of one element with respect to others in an interlocked architecture allows for different co-conformational states of a molecule. This can result in variations of physical or chemical properties. The increase of knowledge in the field of molecular interactions led to the design, the synthesis, and the study of various systems of molecular machinery in a wide range of interlocked architectures. In this field, the discovery of new molecular stations for macrocycles is an attractive way to conceive original molecular machines. In the very recent past, the triazolium moiety proved to interact with crown ethers in interlocked molecules, so that it could be used as an ideal molecular station. It also served as a molecular barrier in order to lock interlaced structures or to compartmentalize interlocked molecular machines. This review describes the recently reported examples of pH-sensitive triazolium-containing molecular machines and their peculiar features. PMID:26491633

  16. A Focus on Triazolium as a Multipurpose Molecular Station for pH-Sensitive Interlocked Crown-Ether-Based Molecular Machines.

    PubMed

    Coutrot, Frédéric

    2015-10-01

    The control of motion of one element with respect to others in an interlocked architecture allows for different co-conformational states of a molecule. This can result in variations of physical or chemical properties. The increase of knowledge in the field of molecular interactions led to the design, the synthesis, and the study of various systems of molecular machinery in a wide range of interlocked architectures. In this field, the discovery of new molecular stations for macrocycles is an attractive way to conceive original molecular machines. In the very recent past, the triazolium moiety proved to interact with crown ethers in interlocked molecules, so that it could be used as an ideal molecular station. It also served as a molecular barrier in order to lock interlaced structures or to compartmentalize interlocked molecular machines. This review describes the recently reported examples of pH-sensitive triazolium-containing molecular machines and their peculiar features. PMID:26491633

  17. Direct stereochemical resolution of aspartame stereoisomers and their degradation products by high-performance liquid chromatography on a chiral crown ether based stationary phase.

    PubMed

    Motellier, S; Wainer, I W

    1990-09-21

    The direct stereochemical resolution of the four stereoisomers of aspartame (N-DL-alpha-aspartyl-DL-phenylalanine methyl ester) and their degradation products was achieved on a high-performance liquid chromatography chiral stationary phase based upon a chiral crown ether. The chromatographic conditions included a mobile phase composed of aqueous perchloric acid adjusted to a pH of 2.8 and modified with 1.5% of 2-propanol and a temperature gradient. The active L,L-isomer (sold under the brand name NutraSweet) was measured in a diet cola and coffee sweetened with NutraSweet. Degradation products of NutraSweet were also detected but no racemization of stereochemical contamination was observed. PMID:2150410

  18. Selective transport of Pb2+ and Cd2+ across a phospholipid bilayer by a cyclohexanemonocarboxylic acid-capped 15-crown-5 ether.

    PubMed

    Hamidinia, Shawn A; Steinbaugh, Gregory E; Erdahl, Warren L; Taylor, Richard W; Pfeiffer, Douglas R

    2006-03-01

    A cyclohexanemonocarboxylic acid-capped 15-crown-5 ether was synthesized and found to be effective as an ionophore for Pb2+ and Cd2+, transporting them across a phospholipid bilayer membrane. Transport studies were carried out using 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylcholine (POPC) vesicles containing the chelating indicator 2-([2-bis(carboxymethyl)amino-5-methylphenoxy]methyl)-6-methoxy-8-bis(carboxymethyl)aminoquinoline (Quin-2). Data obtained at pH 7.0 using this system, show that the synthetic ionophore transports divalent cations with the selectivity sequence Pb2+ > Cd2+ > Zn2+ > Mn2+ > Co2+ > Ni2+ > Ca2+ > Sr2+. Selectivity factors, based on the ratio of individual initial cation transport rates, are 280 (Pb2+/Ca2+), 62 (Pb2+/Zn2+), 68 (Cd2+/Ca2+), and 16 (Cd2+/Zn2+). Plots of log initial rate versus logM(n+) or log ionophore concentration suggest that Pb2+ and Cd2+ are transported primarily as a 1:1 cation-ionophore complex, but that complexes with other stoichiometries may also be present. The ionophore transports Pb2+ and Cd2+ by a predominantly electrogenic mechanism, based upon an enhanced rate of transport that is produced by agents which dissipate transmembrane potentials. The rate of Pb2+ transport shows a biphasic pH dependence with the maximum occurring at pH approximately 6.5. The high selectivity for Pb2+ and Cd2+ displayed by the cyclohexanecarboxylic acid-capped 15-crown-5 ether suggests potential applications of this ionophore for the treatment of Pb and Cd intoxication, and removal of these heavy metals from wastewater. PMID:16488017

  19. Structures of potassium calix[4]arene crown ether inclusion complexes and application in polymerization of rac-lactide.

    PubMed

    Li, Yingguo; Zhao, Hongwei; Mao, Xiaoyang; Pan, Xiaobo; Wu, Jincai

    2016-06-21

    Reaction of 1,3-dipropoxy-p-tert-butyl-calix[4]arene (L(1)H2) with KN(SiMe3)2 afforded a one-dimensional (1D) chain complex [K2L(1)]n (1). Upon reaction with 1 equivalent 18-crown-6, complex 1 can convert to complex [K2(18-crown-6)L(1)] (2) which possesses a sandwich structure. Treatment of two calix[4]arene-crown ligands of 1,3-dihydroxy-p-tert-butyl-calix[4]arene-crown-5 (L(2)H2) and 1,2-dihydroxy-p-tert-butyl-calix[4]arene-crown-5 (L(3)H2) with KN(SiMe3)2 gave the dinuclear complex [K2L(2)] (3) and the mononuclear complex [K(THF)L(3)H] (4), respectively. Complexes 1-4 were all characterized by single-crystal X-ray diffraction techniques. The variable temperature (1)H NMR spectrum indicates there is a quick rotation equilibrium of the two phenoxy groups in complex 3. In addition, complexes 1-4 have been tested for the ring-opening polymerization (ROP) of rac-lactide and the results showed that complexes 2 and 3 are highly active for the ROP of rac-lactide. The obtained polymers displayed low dispersity values (Đ) and the molecular weights are close to the calculated ones. Furthermore, complexes 2 and 3 show moderate isoselectivities of Pm = 0.67 and Pm = 0.73, respectively. PMID:27222057

  20. DFT-B3LYP study of interactions between host biphenyl-1-aza-18-crown-6 ether derivatives and guest Cd(2+): NBO, NEDA, and QTAIM analyses.

    PubMed

    Behjatmanesh-Ardakani, R; Pourroustaei-Ardakani, F; Taghdiri, M; Kotena, Zahrabatoul Mosapour

    2016-07-01

    This report present the results of natural energy decomposition analysis (NEDA), natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM) calculations of three derivatives of biphenyl-1-aza-18-crown-6 ether and their 1:1 complexes with Cd(2+). All calculations used the B3LYP density functional theory in combination with the 6-311G and WTBS basis sets for ligands and Cd(2+) ion, respectively. Ligands 1 and 3 have a single 1-aza-18-crown-6, substituent; ligand 2 has two such substituents. The results show that, in the optimized geometries of the complexes, the distance between N and Cd(2+) is greater than the distance between O and Cd(2+). NBO and QTAIM data confirm these results. There was no stabilization energy or bond critical point for N · · · Cd(2+) in NBO or QTAIM, respectively. Data show that the O · · · Cd(2+) interaction is a kind of closed shell interaction. The trend of the calculated stabilization energy was similar to the experimental data. Different contributions of interaction energies for complex formation were analyzed by NEDA, and the results show that the main component of the interactions is accounted for by polarization. PMID:27271162

  1. Chiral stationary phase covalently bound with a chiral pseudo-18-crown-6 ether for enantiomer separation of amino compounds using a normal mobile phase.

    PubMed

    Hirose, Keiji; Yongzhu, Jin; Nakamura, Takashi; Nishioka, Ryota; Ueshige, Tetsuro; Tobe, Yoshito

    2005-03-01

    In order to apply the excellent chiral recognition ability of chiral pseudo-18-crown-6 ethers that we developed to chiral separation, we prepared a chiral stationary phase (CSP) by immobilizing a chiral pseudo-18-crown-6-type host on 3-aminopropyl silica gel. A chiral column was prepared by the slurry-packing method in a stainless steel HPLC column. A liquid chromatography system using this CSP combined with the detection by mass spectrometry was used for enantiomer separation of amino compounds. A normal mobile phase can be used on this CSP as opposed to conventional dynamic coating-type CSPs. Enantiomers of 18 common natural amino acids were efficiently separated. The chiral separation observed for amino acid methyl esters, amino alcohols, and lipophilic amines was fair using this HPLC system. In view of the correlation between the enantiomer selectivity observed in chromatography and the complexion in solution, the chiral recognition in host-guest interactions might contribute to this enantiomer separation. PMID:15704196

  2. Extraction of Cesium by a Calix[4]arene-Crown-6 Ether Bearing a Pendant amine Group

    SciTech Connect

    Harmon, Ben; Ensor, Dale; Delmau, Laetitia Helene; Moyer, Bruce A

    2007-01-01

    The goal of this work was to evaluate the role of the amino group of 5-aminomethylcalix[4]arene-[bis-4-(2-ethylhexyl)benzo-crown-6] (AMBEHB) in the extraction of cesium from acidic and basic mixtures of sodium nitrate and other concentrated salts. The extraction of cesium from nitrate media was measured as a function of extractant concentration, nitrate concentration, cesium concentration, and pH over the range 1-13. The initial studies showed a moderate decrease in the extraction of cesium in acidic media, which indicated the binding of cesium by the calixarene-crown was weakened by the protonation of the amine group. The results also indicated that a 1:1:1 Cs-ligand-nitrate complex is formed in the organic phase. To further evaluate AMBEHB, the empirical data were mathematically modeled to determine the formation constants of the complexes formed in the organic phase. The resulting formation constants showed that the attachment of the amine group to the calixarene-crown molecule reduced the binding stability for the cesium ion upon contact with an acidic solution. This supports the hypothesis of charge repulsion as the basis for more efficient stripping of cesium via pH-switching.

  3. Supramolecular Alternating Polymer from Crown Ether and Pillar[5]arene-Based Double Molecular Recognition for Preparation of Hierarchical Materials.

    PubMed

    Li, Hui; Fan, Xiaodong; Qi, Miao; Yang, Zhen; Zhang, Haitao; Tian, Wei

    2016-01-01

    A novel supramolecular alternating polymer is constructed based on double molecular recognition events of benzo-21-crown-7 with a secondary ammonium salt and of pillar[5]arene with a neutral guest. The resulting polymer is utilized to prepare hierarchical materials with different dimensionalities for the first time. These materials included zero-dimensional spherical aggregates, one-dimensional nanofibers, two-dimensional microstructured films, and three-dimensional ordered glue. This development will be helpful for designing and preparing supramolecular hierarchical materials with different dimensionalities. PMID:26555439

  4. Ab initio and density functional theoretical design and screening of model crown ether based ligand (host) for extraction of lithium metal ion (guest): effect of donor and electronic induction.

    PubMed

    Boda, Anil; Ali, Sk Musharaf; Rao, Hanmanth; Ghosh, Sandip K

    2012-08-01

    The structures, energetic and thermodynamic parameters of model crown ethers with different donor, cavity and electron donating/ withdrawing functional group have been determined with ab initio MP2 and density functional theory in gas and solvent phase. The calculated values of binding energy/ enthalpy for lithium ion complexation are marginally higher for hard donor based aza and oxa crown compared to soft donor based thia and phospha crown. The calculated values of binding enthalpy for lithium metal ion with 12C4 at MP2 level of theory is in good agreement with the available experimental result. The binding energy is altered due to the inductive effect imparted by the electron donating/ withdrawing group in crown ether, which is well correlated with the values of electron transfer. The role of entropy for extraction of hydrated lithium metal ion by different donor and functional group based ligand has been demonstrated. The HOMO-LUMO gap is decreased and dipole moment of the ligand is increased from gas phase to organic phase because of the dielectric constant of the solvent. The gas phase binding energy is reduced in solvent phase as the solvent molecules weaken the metal-ligand binding. The theoretical values of extraction energy for LiCl salt from aqueous solution in different organic solvent is validated by the experimental trend. The study presented here should contribute to the design of model host ligand and screening of solvent for metal ion recognition and thus can contribute in planning the experiments. PMID:22318713

  5. A novel fluorescent probe for Cr(3+) based on rhodamine-crown ether conjugate and its application to drinking water examination and bioimaging.

    PubMed

    Diao, Quanping; Ma, Pinyi; Lv, Linlin; Li, Tiechun; Wang, Xinghua; Song, Daqian

    2016-03-01

    A trivalent chromium (Cr(3+)) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine-crown ether conjugate. This probe displayed a favorable selectivity for Cr(3+) over a range of other common metal ions in DMF/H2O (3:7, v/v; PBS buffer 50 mmol L(-1); pH=6.8) solution, leading to prominent fluorescence "OFF-ON" switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L(-1) (S/N=3). The binding ratio of RhC-Cr(3+) complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr(3+) in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L(-1), and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr(3+) in living cells with a fluorescence enhancement signal. PMID:26641281

  6. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodong; Lei, Ming; Zhou, Yi; Song, Bo; Li, Yongfang

    2015-08-01

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH3NH3PbI3-XClX. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (Jsc). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  7. A novel fluorescent probe for Cr3 + based on rhodamine-crown ether conjugate and its application to drinking water examination and bioimaging

    NASA Astrophysics Data System (ADS)

    Diao, Quanping; Ma, Pinyi; Lv, Linlin; Li, Tiechun; Wang, Xinghua; Song, Daqian

    2016-03-01

    A trivalent chromium (Cr3 +) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine-crown ether conjugate. This probe displayed a favorable selectivity for Cr3 + over a range of other common metal ions in DMF/H2O (3:7, v/v; PBS buffer 50 mmol L- 1; pH = 6.8) solution, leading to prominent fluorescence "OFF-ON" switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L- 1 (S/N = 3). The binding ratio of RhC-Cr3 + complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr3 + in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L- 1, and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr3 + in living cells with a fluorescence enhancement signal.

  8. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    SciTech Connect

    Liu, Xiaodong; Zhou, Yi E-mail: songbo@suda.edu.cn Song, Bo E-mail: songbo@suda.edu.cn; Lei, Ming; Li, Yongfang E-mail: songbo@suda.edu.cn

    2015-08-10

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH{sub 3}NH{sub 3}PbI{sub 3−X}Cl{sub X}. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (J{sub sc}). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  9. Comparison of polarimetry and crown ether-based HPLC chiral stationary phase method to determine (L)-amino acid optical purity.

    PubMed

    Lee, Mee Sung; Khan, F Nawaz; Shin, Sung Chul; Jeong, Euh Duck; Kim, Hae Gyeong; Kim, Mi Jin; Cho, Yoon Jae; Cha, Jae-Young; Hyun, Myung Ho; Jin, Jong Sung

    2012-11-15

    Although various pharmacopoeias provide titration methods to assay (L)-amino acid content, none of these methods distinguish between (L)- and (D)-amino acids and do not consider the presence of enantiomeric impurities. Consequently, these methods are limited in scope to describe the relationship between content and specific rotation, [α]. In this study, the US Pharmacopoeia method was compared with the crown ether-based high performance liquid chromatographic (HPLC) chiral stationary phase (CSP) method to determine (L)-amino acid content and specific rotation. The (L)-amino acid content specified by the US Pharmacopoeia method was not consistent with the specific rotation in the presence of enantiomeric impurities, whereas the HPLC-CSP method was very effective for determining the (L)-amino acid content and the optical purity. The other advantage is that the HPLC-CSP method requires amino acid samples of quite low concentration (as low as 1 μg/mL), whereas the pharmacopoeia method requires higher concentrations (20-110 mg/mL). PMID:22868097

  10. ACE applied to the quantitative characterization of benzo-18-crown-6-ether binding with alkali metal ions in a methanol-water solvent system.

    PubMed

    Ehala, Sille; Makrlík, Emanuel; Toman, Petr; Kasicka, Václav

    2010-01-01

    ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo-18-crown-6-ether (B18C6) and several alkali metal ions, Li(+), Na(+), K(+), Rb(+) and Cs(+), in a mixed binary solvent system, methanol-water (50/50 v/v). The apparent binding (stability) constants (K(b)) of B18C6-alkali metal ion complexes in the hydro-organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25 degrees C, and the constant ionic strength, 10 mM. In the 50% v/v methanol-water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log K(b)=2.89+/-0.17), the weakest complex with cesium ion (log K(b)=2.04+/-0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol-water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water. PMID:20108263

  11. Muon Charge Sign Determination in LArIAT

    NASA Astrophysics Data System (ADS)

    Soubasis, Brandon; LArIAT Collaboration

    2016-03-01

    LArTPC In A Test beam experiment (LArIAT) at the Fermilab aims to calibrate and characterize liquid argon time projection chambers with a beam of charges particles. Liquid Argon Time Projection Chamber (LArTPC) are ideal neutrino detectors which has full 3D-imaging and particle Identification (PID) capability. Processes for which the μ undergoes capture vs. decay in LArIAT TPC for sign-determination (without magnetic field) is one area of studies we are currently interested in. Systematic study of the processes following μ- capture in argon have never been performed and LArTPC sign-determination capability has never been explored. Statistical analysis on topological criteria can be used to determine the sign of a particle's charge (without magnetic field). LArIAT test beam with selectable polarity will provide data for direct measurement of the sign separation efficiency (and purity) for muons.

  12. Liquid chromatographic resolution of amino acid esters of acyclovir including racemic valacyclovir on crown ether-based chiral stationary phases.

    PubMed

    Ahn, Seong Ae; Hyun, Myung Ho

    2015-03-01

    Valacyclovir, a potential prodrug for the treatment of patients with herpes simplex and herpes zoster, and its analogs were resolved on two chiral stationary phases (CSPs) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 covalently bonded to silica gel. In order to find out an appropriate mobile phase condition, various mobile phases consisting of various organic modifiers in water containing various acidic modifiers were applied to the resolution of valacyclovir and its analogs. When 30% acetonitrile in water containing any of 0.05 M, 0.10 M, or 0.15 M perchloric acid was used as a mobile phase, valacyclovir and its analogs were resolved quite well on the two CSPs with the separation factors (α) in the range of 2.49 ~ 6.35 and resolutions (RS ) in the range of 2.95 ~ 12.21. Between the two CSPs, the CSP containing residual silanol protecting n-octyl groups on the silica surface was found to be better than the CSP containing residual silanol groups. PMID:25626672

  13. Dethreading of a Photoactive Azobenzene-Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation.

    PubMed

    Tabacchi, Gloria; Silvi, Serena; Venturi, Margherita; Credi, Alberto; Fois, Ettore

    2016-06-17

    Pseudorotaxanes formed by a dibenzo[24]crown-8 ring (R) and a dialkylammonium axle bearing either two E- or two Z-azobenzene units (EE-A or ZZ-A) revealed useful for the construction of light-powered molecular machines and motors, as they provide the opportunity of photocontrolling self-assembly/disassembly processes. The potential energies profiles for the dethreading of these complexes have been investigated by adopting a combination of first-principles molecular dynamics, metadynamics and quantum-chemical geometry optimization approaches. While the dethreading of the EE-A axle is associated with a monotonic energy increase, for that of the ZZ-A axle a transition state and an intermediate structure, in which the components are still threaded together, are found. The rate determining step for the dethreading of the ZZ axle has a higher energy barrier than that of the EE axle, in agreement with the experimental kinetic data. Moreover, the results suggest that the elliptic shape of the ring cavity is important for discriminating between the E and Z terminal azobenzene during dethreading. PMID:26918775

  14. Alkaline-Side Extraction of Cesium from Savannah River Tank Waste Using a Calixarene-Crown Ether Extractant

    SciTech Connect

    Bonnesen, P.V.; Delmau, L.H.; Haverlock, T.J.; Moyer, B.A.

    1998-12-01

    Results are presented supporting the viability of the alkaline-side CSEX process as a potential replacement for the In-Tank Precipitation process for removal of cesium from aqueous high-level waste (HLW) at the Savannah River Site (SRS). Under funding from the USDOE Efficient Separations and Crosscutting program, a flowsheet was suggested in early June of 1998, and in the following four months, this flowsheet underwent extensive testing, both in batch tests at ORNL and ANL and in two centrifugal-contactor tests at ANL. To carry out these tests, the initial ESP funding was augmented by direct funds from Westinghouse Savannah River Corporation. The flowsheet employed a solvent containing a calixarene-crown hybrid compound called BoBCalixC6 that was invented at ORNL and can now be obtained commercially for government use from IBC Advanced Technologies. This special extractant is so powerful and selective that it can be used at only 0.01 M, compensating for its expense, but a modifier is required for use in an aliphatic diluent, primarily to increase the cesium distribution ratio D{sub Cs} in extraction. The modifier selected is a relatively economical fluorinated alcohol called Cs3, invented at ORNL and so far available. only from ORNL. For the flowsheet, the modifier is used at 0.2 M in the branched aliphatic kerosene Isopar{reg_sign} L. Testing at ORNL and ANL involved simulants of the SRS HLW. After extraction of the Cs from the waste simulant, the solvent is scrubbed with 0.05 M HNO{sub 3} and stripped with a solution comprised of 0.0005 M HNO{sub 3} and 0.0001 M CsNO{sub 3}. The selection of these conditions is justified in this report, both on the basis of experimental data and underlying theory.

  15. Synergistic adsorption of heavy metal ions and organic pollutants by supramolecular polysaccharide composite materials from cellulose, chitosan and crown ether

    PubMed Central

    Mututuvari, Tamutsiwa M.; Tran, Chieu D.

    2013-01-01

    We have developed a simple one-step method to synthesize novel supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS) and benzo-15-crown 5 (B15C5). Butylmethylimidazolium chloride [BMIm+Cl−], an ionic liquid (IL), was used as a sole solvent for dissolution and preparation of the composites. Since majority of [BMIm+Cl−] used was recovered for reuse, the method is recyclable. The [CEL/CS + B15C5] composites obtained retain properties of their components, namely superior mechanical strength (from CEL), excellent adsorption capability for heavy metal ions and organic pollutants (from B15C5 and CS). More importantly, the [CEL/CS + B15C5] composites exhibit truly supramolecular properties. By itself CS, CEL and B15C5 can effectively adsorb Cd2+, Zn2+ and 2,4,5-trichlorophenol. However, adsorption capability of the composite was substantially and synergistically enhanced by adding B15C5 to either CEL and/or CS. That is, the adsorption capacity (qe values) for Cd2+ and Zn2+ by [CS + B15C5], [CEL + B15C5] and [CEL + CS + B15C5] composites are much higher than combined qe values of individual CS, CEL and B15C5 composites. It seems that B15C5 synergistically interact with CS (or CEL) to form more stable complexes with Cd2+ (or Zn2+), and as a consequence, the [CS + B15C5] (or the [CEL + B15C5]) composite can adsorb relatively larger amount Cd2+ (or Zn2+). Moreover, the pollutants adsorbed on the composites can be quantitatively desorbed to enable the [CS + CEL + B15C5] composites to be reused with similar adsorption efficiency. PMID:24333678

  16. Supramolecular Dimerization and [2 + 2] Photocycloaddition Reactions of Crown Ether Styryl Dyes Containing a Tethered Ammonium Group: Structure-Property Relationships.

    PubMed

    Ushakov, Evgeny N; Vedernikov, Artem I; Lobova, Natalia A; Dmitrieva, Svetlana N; Kuz'mina, Lyudmila G; Moiseeva, Anna A; Howard, Judith A K; Alfimov, Michael V; Gromov, Sergey P

    2015-12-31

    Molecular self-assembly is an effective strategy for controlling the [2 + 2] photocycloaddition reaction of olefins. The geometrical properties of supramolecular assemblies are proven to have a critical effect on the efficiency and selectivity of this photoreaction both in the solid state and in solution, but the role of other factors remains poorly understood. Convenient supramolecular systems to study the structure-property relationships are pseudocyclic dimers spontaneously formed by styryl dyes containing a crown ether moiety and a remote ammonium group. New dyes of this type were synthesized to investigate the effects of structural and electronic factors on the quantitative characteristics of supramolecular dimerization and [2 + 2] photocycloaddition in solution. Variable structural parameters for the styryl dyes were the size and structure of macrocyclic moiety, the nature of heteroaromatic residue, and the length of the ammonioalkyl group attached to this residue. Quantum chemical calculations of the pseudocyclic dimers were performed in order to interpret the relationships between the structure of the ammonium dyes and the efficiency of the supramolecular photoreaction. One of the dimeric complexes was obtained in the crystalline state and studied by X-ray diffraction. The results obtained demonstrate that the photocycloaddition in the pseudocyclic dimers can be dramatically affected by the electronic structure of the styryl moieties, as dependent on the electron-donating ability of the substituents on the benzene ring, and by the conformational flexibility of the pseudocycle, which determines the mobility of the olefinic bonds. The significance of electronic factors is highlighted by the fact that the photocycloaddition quantum yield in geometrically similar dimeric structures varies from ≤10(-4) to 0.38. The latter value is unusually high for olefins in solution. PMID:26650887

  17. New NO donor ligands and complexes containing furfuryl or crown ether moiety: Syntheses, crystal structures and tautomerism in ortho-hydroxy substituted compounds as studied by UV-vis spectrophotometry

    NASA Astrophysics Data System (ADS)

    Şahin, Duygu; Koçoğlu, Serhat; Şener, Öznur; Şenol, Cemal; Dal, Hakan; Hökelek, Tuncer; Hayvalı, Zeliha

    2015-12-01

    NO donor ligands were prepared by the condensation of methoxy substituted salicylaldehyde with 5-methylfurfurylamine (1 and 2) and 4‧-aminobenzo-15-crown 5 (3-5). New crown ether ligands of Schiff base type (3-5) containing recognition sites for alkali metal and transition guest cations. Ni(II) complexes (1a-5a) have been synthesized with bidentate NO donor Schiff base ligands (1-5) with Ni(CH3COO)2.·4H2O. Monotopic crystalline 1:1 (Na+:ligand) sodium complexes (3b-5b) of the crown ether ligands were also prepared. Schiff bases (1-5) and complexes (1a-5a, 3b-5b) were characterized by elemental analyses, FT-IR, 1H-, 13C-NMR and mass spectroscopies. The crystal structures of 1, 1a and 2 were verified by X-ray diffraction analysis. The tautomeric equilibria (phenol-imine, O-H⋯N and keto-amine, O⋯H-N forms) have been systematically studied by using UV-vis spectrophotometry for the o-hydroxy substituted compounds (1-5). The UV-visible spectra of these ligands (1-5) were recorded and commented in polar, non-polar, acidic and basic media.

  18. Optical and electrochemical properties of heteroditopic ion receptors derived from crown ether-based calix[4]arene with amido-anthraquinone pendants.

    PubMed

    Chailap, Benjamat; Tuntulani, Thawatchai

    2012-05-14

    Two heteroditopic receptors based on a calix[4]arene crown ether containing amidoanthraquinone pendants in cone and 1,3-alternate conformations (1 and 2, respectively) were synthesized. Photophysical properties of 1 and 2 were studied by UV-vis and fluorescence spectrophotometry in dried CH(3)CN. Both 1 and 2 showed the highest sensitivity towards F(-) through the appearance of a new charge transfer band at 500 nm and the enhancement of the emission spectra at λ(em) = 542 nm and 528 nm respectively. Interestingly, in the presence of K(+), the fluorescence intensity of 1 at 542 nm increased around 2 fold compared to that in the absence of K(+) upon addition of F(-), while this phenomenon was not observed in the case of receptor 2. Cyclic voltammograms of receptors 1 and 2 showed two consecutive one-electron reversible waves in 40% v/v CH(3)CN in CH(2)Cl(2), corresponding to two single-electron reductions to give mono- and dianions species at E(1/2)I = -1.21 V and E(1/2)II = -1.66 V as well as E(1/2)I = -1.25 V and E(1/2)II = -1.71 V, respectively. H(2)PO(4)(-) gave remarkable potential shifts (ca. 200 mV) of the second reduction waves (E(1/2)II) of both free 1 and 2. In the presence of K(+), only receptor 1 gave remarkable potential shifts in its redox wave II upon adding F(-) and AcO(-). Therefore, receptors 1 and 2 exhibited dual sensing modes by fluorescence spectrophotometry and cyclic voltammetry. The topology of ligands also played an important role in cooperative binding properties of heteroditopic receptor 1 possessing a closer distance between a cation and an anion binding. On the other hand, the two ion binding sites of receptor 2 were separated by a longer distance and did not support the cooperative binding. This resulted in the abstraction of K(+) from receptor 2 upon addition of anions. PMID:22469902

  19. Scintillation light detection system in LArIAT

    NASA Astrophysics Data System (ADS)

    Kryczynski, P.

    2016-02-01

    The LArIAT experiment is currently taking data at Fermilab using a Liquid Argon TPC, with the aim of studying particle interactions and characterizing detector response for neutrino detectors using argon. In parallel, it serves as a test-bench to develop and evaluate the performance of the simulation, reconstruction, and analysis software used in LAr neutrino experiments. LArIAT also takes advantage of the scintillating capabilities of liquid argon and will evaluate the feasibility of using the light signal to determine calorimetric information and particle identification. To test this possibility, a scintillation light detection system consisting of high Quantum Efficiency (QE) PMT and Silicon Photomultiplier (SiPM) devices is installed in the cryostat, viewing the interior of the TPC. Light collection efficiency is maximized by means of lining the walls with reflector foils covered by a wavelength shifter layer. Collecting the light reflected at the boundaries of the active volume greatly improves also the uniformity of the light yield. Presented here are initial results of the LArIAT light detection system calibration together with the preliminary results of the dedicated simulation and its application in future LAr TPC experiments

  20. Cowboy Fluid Mechanics: Lariat Modes of a Viscous Rope

    NASA Astrophysics Data System (ADS)

    Ribe, Neil; Badr, Sarah; Morris, Stephen

    2009-11-01

    A thin filament of viscous fluid falling onto a surface winds itself into a helical coil whose angular frequency of rotation φ depends on the fall height H, the flow rate, and the fluid properties. We have studied a novel variant of this phenomenon in which the nozzle ejecting the fluid rotates about a vertical axis at a constant rate φ. In laboratory experiments using viscous corn syrup, we observe that the filament coils in the normal way when φφ. However, when φ φ and H is sufficiently large, a new ``lariat'' mode appears in which the filament is thrown outward in the form of a spiral of large diameter (up to tens of cm) rotating at a rate 0.9φ. The transition between the coiling and lariat modes is hysteretic with respect to variations in φ. In addition to the laboratory experiments, we will also present preliminary results of numerical calculations of the lariat mode based on a ``slender body'' model for a viscous filament with inertia.

  1. Crown ether-modified electrodes for the simultaneous stripping voltammetric determination of Cd(II), Pb(II) and Cu(II).

    PubMed

    Serrano, Núria; González-Calabuig, Andreu; del Valle, Manel

    2015-06-01

    This work describes the immobilization of 4-carboxybenzo-18-crown-6 (CB-18-crown-6) and 4-carboxybenzo-15-crown-5 (CB-15-crown-5) assisted by lysine on aryl diazonium salt monolayers anchored to the surface of graphite-epoxy composite electrodes (GEC), and their use for the simultaneous determination of Cd(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetry (DPASV). These modified electrodes display a good repeatability and reproducibility with detection and quantification limits at levels of µg L(-1) (ppb), confirming their suitability for the determination of Cd(II), Pb(II) and Cu(II) ions in environmental samples. The overlapped nature of the multimetal stripping measurements was resolved by employing the two-sensor array CB-15-crown-5-GEC and CB-18-crown-6-GEC, since the metal complex selectivity exhibited by the considered ligands could add some discrimination power. For the processing of the voltammograms, Discrete Wavelet Transform and Causal Index were selected as preprocessing tools for data compression coupled with an artificial neural network for the modeling of the obtained responses, allowing the resolution of mixtures of these metals with good prediction of their concentrations (correlation with expected values for an external test subset better than 0.942). PMID:25863381

  2. Studies of a pyridino-crown ether-based chiral stationary phase on the enantioseparation of biogenic chiral aralkylamines and α-amino acid esters by high-performance liquid chromatography.

    PubMed

    Lévai, Sándor; Németh, Tamás; Fődi, Tamás; Kupai, József; Tóth, Tünde; Huszthy, Péter; Balogh, György Tibor

    2015-11-10

    This paper reports the enantioseparation ability of a pyridino-18-crown-6 ether-based chiral stationary phase [(S,S)-CSP-1]. The enantiomeric discrimination of chiral stationary phase (S,S)-CSP-1 was evaluated by HPLC using the mixtures of enantiomers of various protonated primary aralkylamines [1-phenylethylamine hydrogen perchlorate (PEA), 2,3-dihydro-1H-inden-1-amine (1-aminoindan), 2,2'-(1,2-diaminoethane-1,2-diyl) diphenol (HPEN)] and perchlorate salts of α-amino acid esters [alanine benzyl ester (Ala-OBn), phenylalanine benzyl ester (Phe-OBn), phenylalanine methyl ester (Phe-OMe), phenylglycine methyl ester (PhGly-OMe), glutamic acid dibenzyl ester (Glu-diOBn), and valine benzyl ester (Val-OBn)]. The best enantioseparation was achieved in the case of PEA. The high enantioselectivity was rationalized by the strong π-π interaction of the extended π system of the aryl-substituted pyridine unit. PMID:26218505

  3. Widespread alternative and aberrant splicing revealed by lariat sequencing

    PubMed Central

    Stepankiw, Nicholas; Raghavan, Madhura; Fogarty, Elizabeth A.; Grimson, Andrew; Pleiss, Jeffrey A.

    2015-01-01

    Alternative splicing is an important and ancient feature of eukaryotic gene structure, the existence of which has likely facilitated eukaryotic proteome expansions. Here, we have used intron lariat sequencing to generate a comprehensive profile of splicing events in Schizosaccharomyces pombe, amongst the simplest organisms that possess mammalian-like splice site degeneracy. We reveal an unprecedented level of alternative splicing, including alternative splice site selection for over half of all annotated introns, hundreds of novel exon-skipping events, and thousands of novel introns. Moreover, the frequency of these events is far higher than previous estimates, with alternative splice sites on average activated at ∼3% the rate of canonical sites. Although a subset of alternative sites are conserved in related species, implying functional potential, the majority are not detectably conserved. Interestingly, the rate of aberrant splicing is inversely related to expression level, with lowly expressed genes more prone to erroneous splicing. Although we validate many events with RNAseq, the proportion of alternative splicing discovered with lariat sequencing is far greater, a difference we attribute to preferential decay of aberrantly spliced transcripts. Together, these data suggest the spliceosome possesses far lower fidelity than previously appreciated, highlighting the potential contributions of alternative splicing in generating novel gene structures. PMID:26261211

  4. Absorption and biotransformation of polybrominated diphenyl ethers DE-71 and DE-79 in chicken (Gallus gallus), mallard (Anas platyrhynchos), American kestrel (Falco sparverius) and black-crowned night-heron (Nycticorax nycticorax) eggs

    USGS Publications Warehouse

    McKernan, Moira A.; Rattner, Barnett A.; Hatfield, Jeff S.; Hale, Robert C.; Ottinger, Mary Ann

    2010-01-01

    We recently reported that air cell administration of penta-brominated diphenyl ether (penta-BDE; DE-71) evokes biochemical and immunologic effects in chicken (Gallus gallus) embryos at very low doses, and impairs pipping (i.e., stage immediately prior to hatching) and hatching success at 1.8 ug g-1 egg (actual dose absorbed) in American kestrels (Falco sparverius). I n the present study, absorption of polybrominated diphenyl ether (PBDE) congeners was measured following air cell administration of a penta-BDE mixture (11.1 ug DE-71 g-1 egg) or an octa-brominated diphenyl ether mixture (octa-BDE; DE-79; 15.4 ug DE-79 g-1 egg). Uptake of PBDE congeners was measured at 24 h post-injection, midway through incubation, and at pipping in chicken, mallard (Anas platyrhynchos), and American kestrel egg contents, and at the end of incubation in black-crowned night-heron (Nycticorax nycticorax) egg contents. Absorption of penta-BDE and octa-BDE from the air cell into egg contents occurred throughout incubation; at pipping, up to 29.6% of penta-BDE was absorbed, but only 1.40-6.48% of octa-BDE was absorbed. Higher brominated congeners appeared to be absorbed more slowly than lower brominated congeners, and uptake rate was inversely proportional to the log Kow of predominant BDE congeners. Six congeners or co-eluting pairs of congeners were detected in penta-BDE-treated eggs that were not found in the dosing solution suggesting debromination in the developing embryo, extraembryonic membranes, and possibly even in the air cell membrane. This study demonstrates the importance of determining the fraction of xenobiotic absorbed into the egg following air cell administration for estimation of the lowest-observed-effect level.

  5. Supramolecular side-chain poly[2]pseudorotaxanes formed by orthogonal coordination-driven self-assembly and crown-ether-based host-guest interactions.

    PubMed

    Xing, Hao; Wei, Peifa; Yan, Xuzhou

    2014-06-01

    The themes of coordination-driven self-assembly, host-guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]pseudorotaxanes. Specifically, a bis(p-phenylene)-34-crown-10 derivative 1 bearing two pyridyl groups polymerizes into a side-chain poly[2]pseudorotaxane upon the addition of di-Pt(II) acceptor 4 in the presence of paraquat. Interestingly, by adding a competitive guest 3, the poly[2]pseudorotaxane can realize a conversion in one pot. PMID:24819441

  6. The effect of ring size variation on the structure and stability of lanthanide(III) complexes with crown ethers containing picolinate pendants.

    PubMed

    Roca-Sabio, Adrián; Mato-Iglesias, Marta; Esteban-Gómez, David; de Blas, Andrés; Rodríguez-Blas, Teresa; Platas-Iglesias, Carlos

    2011-01-14

    The coordination properties of the macrocyclic receptor N,N'-bis[(6-carboxy-2-pyridyl)methylene]-1,10-diaza-15-crown-5 (H(2)bp15c5) towards the lanthanide ions are reported. Thermodynamic stability constants were determined by pH-potentiometric titration at 25 °C in 0.1 M KCl. A smooth decrease in complex stability is observed upon decreasing the ionic radius of the Ln(III) ion from La [log K(LaL) = 12.52(2)] to Lu [log K(LuL) = 10.03(6)]. Luminescence lifetime measurements recorded on solutions of the Eu(III) and Tb(III) complexes confirm the absence of inner-sphere water molecules in these complexes. (1)H and (13)C NMR spectra of the complexes formed with the diamagnetic La(III) metal ion were obtained in D(2)O solution and assigned with the aid of HSQC and HMBC 2D heteronuclear experiments, as well as standard 2D homonuclear COSY and NOESY spectra. The (1)H NMR spectra of the paramagnetic Ce(III), Eu(III) and Yb(III) complex suggest nonadentate binding of the ligand to the metal ion. The syn conformation of the ligand in [Ln(bp15c5)](+) complexes implies the occurrence of two helicities, one associated with the layout of the picolinate pendant arms (absolute configuration Δ or Λ), and the other to the five five-membered chelate rings formed by the binding of the crown moiety (absolute configuration δ or λ). A detailed conformational analysis performed with the aid of DFT calculations (B3LYP model) indicates that the complexes adopt a Λ(λδ)(δδλ) [or Δ(δλ)(λλδ)] conformation in aqueous solution. Our calculations show that the interaction between the Ln(III) ion and several donor atoms of the crown moiety is weakened as the ionic radius of the metal ion decreases, in line with the decrease of complex stability observed on proceeding to the right across the lanthanide series. PMID:21116555

  7. Crown Gall

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown gall disease occurs on diverse dicotyledonous and gymnospermous plant species worldwide. Reports of crown gall on hop date back to at least 1929, and the disease has been reported from most countries where hop is or has been grown commercially. The epidemiology of the causal bacterium, Agrob...

  8. Crown gall

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown gall is uncommon in alfalfa. The disease has been reported from alfalfa stands in the Imperial Valley of California, but rare infected plants can be found occasionally in other parts of the U.S. Symptoms: The galls or tumor-like overgrowths form on the crown branches at or slightly below t...

  9. A homolog of lariat-debranching enzyme modulates turnover of branched RNA

    PubMed Central

    Garrey, Stephen M.; Katolik, Adam; Prekeris, Mantas; Li, Xueni; York, Kerri; Bernards, Sarah; Fields, Stanley; Zhao, Rui; Damha, Masad J.; Hesselberth, Jay R.

    2014-01-01

    Turnover of the branched RNA intermediates and products of pre-mRNA splicing is mediated by the lariat-debranching enzyme Dbr1. We characterized a homolog of Dbr1 from Saccharomyces cerevisiae, Drn1/Ygr093w, that has a pseudo-metallophosphodiesterase domain with primary sequence homology to Dbr1 but lacks essential active site residues found in Dbr1. Whereas loss of Dbr1 results in lariat-introns failing broadly to turnover, loss of Drn1 causes low levels of lariat-intron accumulation. Conserved residues in the Drn1 C-terminal CwfJ domains, which are not present in Dbr1, are required for efficient intron turnover. Drn1 interacts with Dbr1, components of the Nineteen Complex, U2 snRNA, branched intermediates, and products of splicing. Drn1 enhances debranching catalyzed by Dbr1 in vitro, but does so without significantly improving the affinity of Dbr1 for branched RNA. Splicing carried out in in vitro extracts in the absence of Drn1 results in an accumulation of branched splicing intermediates and products released from the spliceosome, likely due to less active debranching, as well as the promiscuous release of cleaved 5′-exon. Drn1 enhances Dbr1-mediated turnover of lariat-intermediates and lariat-intron products, indicating that branched RNA turnover is regulated at multiple steps during splicing. PMID:24919400

  10. Dental crowns

    MedlinePlus

    ... cover a tooth Replace a misshapen tooth or dental implant Correct a misaligned tooth Talk to your dentist ... the tooth pulled and replaced with a tooth implant. Your crown could chip or crack: If you grind your teeth or clench your jaw, you may need to ...

  11. Crown wart

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown wart has been found widely distributed in Australia, New Zealand, and European countries. It has been recorded sporadically in India (Punjab), South Africa, South America (Ecuador, Chile, Peru), Panama, Mexico, and Canada (British Columbia). In the United States, it has been found more frequ...

  12. Alkali-metal ion coordination in uranyl(VI) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li(+)-, Na(+)- and K(+)-uranyl(VI)-peroxide-carbonate systems.

    PubMed

    Zanonato, Pier Luigi; Szabó, Zoltán; Vallet, Valerie; Di Bernardo, Plinio; Grenthe, Ingmar

    2015-10-01

    The constitution and equilibrium constants of ternary uranyl(vi) peroxide carbonate complexes [(UO2)p(O2)q(CO3)r](2(p-q-r)) have been determined at 0 °C in 0.50 M MNO3, M = Li, K, and TMA (tetramethyl ammonium), ionic media using potentiometric and spectrophotometric data; (17)O NMR data were used to determine the number of complexes present. The formation of cyclic oligomers, "[(UO2)(O2)(CO3)]n", n = 4, 5, 6, with different stoichiometries depending on the ionic medium used, suggests that Li(+), Na(+), K(+) and TMA ions act as templates for the formation of uranyl peroxide rings where the uranyl-units are linked by μ-η(2)-η(2) bridged peroxide-ions. The templating effect is due to the coordination of the M(+)-ions to the uranyl oxygen atoms, where the coordination of Li(+) results in the formation of Li[(UO2)(O2)(CO3)]4(7-), Na(+) and K(+) in the formation of Na/K[(UO2)(O2)(CO3)]5(9-) complexes, while the large tetramethyl ammonium ion promotes the formation of two oligomers, TMA[(UO2)(O2)(CO3)]5(9-) and TMA[(UO2)(O2)(CO3)]6(11-). The NMR spectra demonstrate that the coordination of Na(+) in the five- and six-membered oligomers is significantly stronger than that of TMA(+); these observations suggest that the templating effect is similar to the one observed in the synthesis of crown-ethers. The NMR experiments also demonstrate that the exchange between TMA[(UO2)(O2)(CO3)]5(9-) and TMA[(UO2)(O2)(CO3)]6(11-) is slow on the (17)O chemical shift time-scale, while the exchange between TMA[(UO2)(O2)(CO3)]6(11-) and Na[(UO2)(O2)(CO3)]6(11-) is fast. There was no indication of the presence of large clusters of the type identified by Burns and Nyman (M. Nyman and P. C. Burns, Chem. Soc. Rev., 2012, 41, 7314-7367) and possible reasons for this and the implications for the synthesis of large clusters are briefly discussed. PMID:26331776

  13. Application of lariat lock catch knot suture in the achilles tendon rupture

    PubMed Central

    Wang, Baocang; Feng, Xiaona; Yan, Ming; Wang, Hui; Li, Yong

    2015-01-01

    The aim of this study was to summarize the clinical experience of repairing the Achilles tendon rupture by lariat lock catch knot suture. Between January 2011 and February, 2014, 32 cases of the Achilles tendon rupture were treated by lariat lock catch knot suture. There were 26 males and 6 females, with the average age of 39 years (range 17-53 years), including 13 left knees and 19 right knees. 29 wounds healed by first intention, and 3 cases who were performed local flap transfer due to necrosis of skin were healed by second intention. Thirty-two cases were followed up 10-25 months (13 months on average). No re-rupture of Achilles tendon or deep infection occurred during follow-up period. According to Arner-Lindholm assessment standard, the results were excellent in 19 cases and good in 13 cases, the excellent and good rate was 100%. Lariat lock catch knot suture is a safe and effective method for repairing Achilles tendon. PMID:26770612

  14. Speciation of a group I intron into a lariat capping ribozyme

    PubMed Central

    Meyer, Mélanie; Nielsen, Henrik; Oliéric, Vincent; Roblin, Pierre; Johansen, Steinar D.; Westhof, Eric; Masquida, Benoît

    2014-01-01

    The lariat-capping (LC) ribozyme is a natural ribozyme isolated from eukaryotic microorganisms. Despite apparent structural similarity to group I introns, the LC ribozyme catalyzes cleavage by a 2′,5′ branching reaction, leaving the 3′ product with a 3-nt lariat cap that functionally substitutes for a conventional mRNA cap in the downstream pre-mRNA encoding a homing endonuclease. We describe the crystal structures of the precleavage and postcleavage LC ribozymes, which suggest that structural features inherited from group I ribozymes have undergone speciation due to profound changes in molecular selection pressure, ultimately giving rise to an original branching ribozyme family. The structures elucidate the role of key elements that regulate the activity of the LC ribozyme by conformational switching and suggest a mechanism by which the signal for branching is transmitted to the catalytic core. The structures also show how conserved interactions twist residues, forming the lariat to join chemical groups involved in branching. PMID:24821772

  15. Crystal structure of the inverse crown ether tetra­kis­[μ2-bis­(tri­methyl­sil­yl)amido]-μ4-oxido-dicobalt(II)disodium, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O)

    PubMed Central

    Hansen, Christopher B.; Filatov, Alexander S.; Hillhouse, Gregory L.

    2016-01-01

    The title compound, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O), (I), represents a new entry in the class of inverse crown ethers. In the mol­ecule, each Co atom is formally in the oxidation state +II. The structure contains one half of a unique mol­ecule per asymmetric unit with the central μ4-oxido ligand residing on an inversion center, leading to a planar coordination to the Na and Co atoms. In the crystal, bulky tri­methyl­silyl substituents prevent additional inter­actions with cobalt. However, weak inter­molecular Na⋯H3C—Si inter­actions form an infinite chain along [010]. The structure is isotypic with its Mg, Mn and Zn analogues. PMID:27308041

  16. Crystal structure of the inverse crown ether tetra-kis-[μ2-bis-(tri-methyl-sil-yl)amido]-μ4-oxido-dicobalt(II)disodium, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O).

    PubMed

    Hansen, Christopher B; Filatov, Alexander S; Hillhouse, Gregory L

    2016-06-01

    The title compound, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O), (I), represents a new entry in the class of inverse crown ethers. In the mol-ecule, each Co atom is formally in the oxidation state +II. The structure contains one half of a unique mol-ecule per asymmetric unit with the central μ4-oxido ligand residing on an inversion center, leading to a planar coordination to the Na and Co atoms. In the crystal, bulky tri-methyl-silyl substituents prevent additional inter-actions with cobalt. However, weak inter-molecular Na⋯H3C-Si inter-actions form an infinite chain along [010]. The structure is isotypic with its Mg, Mn and Zn analogues. PMID:27308041

  17. An Improved Method for the Separation of Lead-210 from Ra-DEF for Radioactive Equilibrium Experiments: Microscale Liquid-Liquid Extraction Using a Polymer-Supported Crown Ether

    NASA Astrophysics Data System (ADS)

    Dietz, Mark L.; Horwitz, E. Philip

    1996-02-01

    A novel extraction chromatographic material, comprised of a solution of a lead-selective macrocyclic polyether (di-t-butylcyclohexano-18-crown-6) in isodecanol sorbed on an inert polymeric support, is shown to provide a rapid and simple means for the separation of lead-210 from its daughter products for subsequent radiochemical experimentation.

  18. Two-state model based on electron-transfer reactivity changes to quantify the noncovalent interaction between Co(NH3)5Cl2+ and 18-crown-6 ether: the effect of second-sphere coordination on electron-transfer processes.

    PubMed

    Borreguero, M; Prado-Gotor, R

    2008-04-01

    The electron-transfer reaction between [Fe(CN)6]4- and [CoCl(NH3)5]2+ was studied in the presence of 18-crown-6 ether (18C6) in different reaction media constituted by water and acetonitrile as organic cosolvent at 298.2 K. The results corresponding to this reaction show a clear influence of 18C6 on the kinetics: a positive catalytic effect. Trends in the observed reactivity are explained by a change in the degree of association of one of the reactants (the cobalt complex) with the 18C6. This association is governed by an equilibrium constant that depends on the dielectric constant of the medium. The results show an increase of the rate constants for the electron-transfer process as the 18-crown-ether concentration increases and an increase of the binding free energy of the cobalt complex to the 18C6 when the electrostatic field of the medium becomes weaker. An analysis of the experimental data allows not only the reactivity changes associated with adducts formation processes for an electron-transfer reaction but also information on the binding free energy of the cobalt complex to the 18C6 to be obtained, which can be quantified by using a two-state model. We have found a good correlation between the energy of binding and the Kosower's Z-value. The influence of the 18C6 in the intramolecular electron transfer in the binuclear complex [Fe(CN)5pzCo(NH3)5] has been also investigated. PMID:18311956

  19. Molecular characterization of a new member of the lariat capping twin-ribozyme introns

    PubMed Central

    2014-01-01

    Background Twin-ribozyme introns represent a complex class of mobile group I introns that harbour a lariat capping (LC) ribozyme and a homing endonuclease gene embedded in a conventional self-splicing group I ribozyme (GIR2). Twin-ribozyme introns have so far been confined to nucleolar DNA in Naegleria amoeboflagellates and the myxomycete Didymium iridis. Results We characterize structural organization, catalytic properties and molecular evolution of a new twin-ribozyme intron in Allovahlkampfia (Heterolobosea). The intron contains two ribozyme domains with different functions in ribosomal RNA splicing and homing endonuclease mRNA maturation. We found Allovahlkampfia GIR2 to be a typical group IC1 splicing ribozyme responsible for addition of the exogenous guanosine cofactor (exoG), exon ligation and circularization of intron RNA. The Allovahlkampfia LC ribozyme, by contrast, represents an efficient self-cleaving ribozyme that generates a small 2′,5′ lariat cap at the 5′ end of the homing endonuclease mRNA, and thus contributes to intron mobility. Conclusions The discovery of a twin-ribozyme intron in a member of Heterolobosea expands the distribution pattern of LC ribozymes. We identify a putative regulatory RNA element (AP2.1) in the Allovahlkampfia LC ribozyme that involves homing endonuclease mRNA coding sequences as an important structural component. PMID:25342998

  20. Structural basis of lariat RNA recognition by the intron debranching enzyme Dbr1.

    PubMed

    Montemayor, Eric J; Katolik, Adam; Clark, Nathaniel E; Taylor, Alexander B; Schuermann, Jonathan P; Combs, D Joshua; Johnsson, Richard; Holloway, Stephen P; Stevens, Scott W; Damha, Masad J; Hart, P John

    2014-01-01

    The enzymatic processing of cellular RNA molecules requires selective recognition of unique chemical and topological features. The unusual 2',5'-phosphodiester linkages in RNA lariats produced by the spliceosome must be hydrolyzed by the intron debranching enzyme (Dbr1) before they can be metabolized or processed into essential cellular factors, such as snoRNA and miRNA. Dbr1 is also involved in the propagation of retrotransposons and retroviruses, although the precise role played by the enzyme in these processes is poorly understood. Here, we report the first structures of Dbr1 alone and in complex with several synthetic RNA compounds that mimic the branchpoint in lariat RNA. The structures, together with functional data on Dbr1 variants, reveal the molecular basis for 2',5'-phosphodiester recognition and explain why the enzyme lacks activity toward 3',5'-phosphodiester linkages. The findings illuminate structure/function relationships in a unique enzyme that is central to eukaryotic RNA metabolism and set the stage for the rational design of inhibitors that may represent novel therapeutic agents to treat retroviral infections and neurodegenerative disease. PMID:25123664

  1. A group III twintron encoding a maturase-like gene excises through lariat intermediates.

    PubMed Central

    Copertino, D W; Hall, E T; Van Hook, F W; Jenkins, K P; Hallick, R B

    1994-01-01

    The 1605 bp intron 4 of the Euglena gracilis chloroplast psbC gene was characterized as a group III twintron composed of an internal 1503 nt group III intron with an open reading frame of 1374 nt (ycf13, 458 amino acids), and an external group III intron of 102 nt. Twintron excision proceeds by a sequential splicing pathway. The splicing of the internal and external group III introns occurs via lariat intermediates. Branch sites were mapped by primer extension RNA sequencing. The unpaired adenosines in domains VI of the internal and external introns are covalently linked to the 5' nucleotide of the intron via 2'-5' phosphodiester bonds. This bond is susceptible to hydrolysis by the debranching activity of the HeLa nuclear S100 fraction. The internal intron and presumptive ycf13 mRNA accumulates primarily as a linear RNA, although a lariat precursor can also be detected. The ycf13 gene encodes a maturase-like protein that may be involved in group III intron metabolism. Images PMID:7512259

  2. Using 15-crown-5, 18-crown-6 and dicyclohexano-18-crown-6 for Am, Ce, Eu and Cm extraction from acid solutions

    SciTech Connect

    Romanovski, V.V.; Proyaev, V.V.; Wester, D.W.

    1994-08-01

    The extraction from nitric acid of Am, Eu, Ce, Cm(III) tracers by 15-crown-5 (15C5), 18-crown-6 (18C6), dicyclohexano-18-crown-6 (DCH18C6) as well as mixtures of crown ethers and chlorinated cobalt dicarbollide (ChCoD) in nitrobenzene solutions has been investigated. It was revealed that 18C6 is selective for Ce, Am and Cm compared with Eu. The addition of 18C6 to a solution of ChCoD allows Am and Cm to be separated from lanthanides by using this extractant more efficiently. The separation factors of Ce, Am, Cm and Eu are increased as a function of the ionic strength of the aqueous phase for extraction by mixtures of 18C6 and ChCoD and of DCH18C6 and ChCoD.

  3. Light-based triggering and reconstruction of Michel electrons in LArIAT

    NASA Astrophysics Data System (ADS)

    Foreman, W.

    2016-01-01

    The LArIAT Experiment aims to calibrate the liquid argon time projection chamber (LArTPC) using a beam of charged particles at the Fermilab Test Beam Facility. It is equipped with a novel scintillation light readout system using PMTs and custom SiPM preamplifier boards to detect light from reflector foils coated with wavelength-shifting TPB. A trigger on delayed secondary flashes of light captures events containing stopping cosmic muons together with the Michel electrons coming from their subsequent decay. This dedicated Michel trigger supplies an abundant sample of low-energy electrons throughout the detector's active volume, providing opportunities to study the combined calorimetric capabilities of the light system and the TPC. Preliminary results using scintillation light to study properties of the Michel electron sample are presented.

  4. Non-coding RNA generated following lariat-debranching mediates targeting of AID to DNA

    PubMed Central

    Zheng, Simin; Vuong, Bao Q.; Vaidyanathan, Bharat; Lin, Jia-Yu; Huang, Feng-Ting; Chaudhuri, Jayanta

    2015-01-01

    SUMMARY Transcription through immunoglobulin switch (S) regions is essential for class switch recombination (CSR) but no molecular function of the transcripts has been described. Likewise, recruitment of activation-induced cytidine deaminase (AID) to S regions is critical for CSR; however, the underlying mechanism has not been fully elucidated. Here, we demonstrate that intronic switch RNA acts in trans to target AID to S region DNA. AID binds directly to switch RNA through G-quadruplexes formed by the RNA molecules. Disruption of this interaction by mutation of a key residue in the putative RNA-binding domain of AID impairs recruitment of AID to S region DNA, thereby abolishing CSR. Additionally, inhibition of RNA lariat processing leads to loss of AID localization to S regions and compromises CSR; both defects can be rescued by exogenous expression of switch transcripts in a sequence-specific manner. These studies uncover an RNA-mediated mechanism of targeting AID to DNA. PMID:25957684

  5. MnBr₂/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield.

    PubMed

    Hausmann, David; Kuzmanoski, Ana; Feldmann, Claus

    2016-04-21

    The reaction of manganese(ii) bromide and the crown ether 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] under mild conditions (80-130 °C) resulted in the formation of three different coordination compounds: MnBr2(18-crown-6) (), Mn3Br6(18-crown-6)2 () and Mn3Br6(18-crown-6) (). In general, the local coordination and the crystal structure of all compounds are driven by the mismatch between the small radius of the Mn(2+) cation (83 pm) and the ring opening of 18-crown-6 as a chelating ligand (about 300 pm). This improper situation leads to different types of coordination and bonding. MnBr2(18-crown-6) represents a molecular compound with Mn(2+) coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3Br6(18-crown-6)2 falls into a [MnBr(18-crown-6)](+) cation - with Mn(2+) coordinated by six oxygen atoms and Br - and a [MnBr(18-crown-6)MnBr4](-) anion. In this anion, Mn(2+) is coordinated by five oxygen atoms of the crown ether as well as by two bromine atoms, one of them bridging to an isolated (MnBr4) tetrahedron. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged [Mn2(18-crown-6)(MnBr6)] chain. Herein, 18-crown-6 is exocyclically coordinated by two Mn(2+) cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3Br6(18-crown-6)) and 98% (Mn3Br6(18-crown-6)2). The excellent quantum yield of Mn3Br6(18-crown-6)2 and its differentiation from MnBr2(18-crown-6) and Mn3Br6(18-crown-6) can be directly correlated to the local coordination. PMID:26956783

  6. The Influence of Crown Ether and Alcohol on Unsaturation and Molar Mass of Poly(propylene oxide)s Prepared by Use of Potassium t-Butoxide: Reinvestigation of Chain Transfer Reactions

    PubMed Central

    Jurek-Suliga, Justyna; Skrzeczyna, Kinga; Gabor, Jadwiga; Łężniak, Marta

    2016-01-01

    Potassium t-butoxide dissolved in tetrahydrofuran effectively initiates homogeneous polymerization of propylene oxide at room temperature. Unsaturation and molar mass (Mn) of the polymers prepared depend on the presence of additives, such as macrocyclic ligand 18-crown-6 (L) and t-butanol. Application of the ligand alone results in distinct increase of unsaturation and decrease of Mn, whereas use of t-BuOH leads to simultaneous decrease of unsaturation and Mn. Activation of t-BuOK/t-BuOH system with the ligand causes further decrease of unsaturation, that is, from 12.0 to 3.5 mol % for OK/OH (1/3) and OK/OH/L (1/3/2) systems, respectively. Unexpectedly, Mn of the polymers obtained does not practically change (~4800). This result differs from that reported earlier for neat PO polymerization initiated potassium 1-methoxy-2-propoxide/1-methoxy-2-propanol, in which in the presence of the same ligand Mn increases to ~12 400 for the same ratio of reagents. The mechanism of studied processes was discussed. PMID:27528874

  7. Pentabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Pentabromodiphenyl ether ; CASRN 32534 - 81 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncar

  8. Hexabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Hexabromodiphenyl ether ; CASRN 36483 - 60 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  9. Ethyl ether

    Integrated Risk Information System (IRIS)

    Ethyl ether ; CASRN 60 - 29 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  10. Tetrabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Tetrabromodiphenyl ether ; CASRN 40088 - 47 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncar

  11. Nonabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Nonabromodiphenyl ether ; CASRN 63936 - 56 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  12. Tribromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Tribromodiphenyl ether ; CASRN 49690 - 94 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  13. Octabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Octabromodiphenyl ether ; CASRN 32536 - 52 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  14. The acrylic jacket crown.

    PubMed

    Bell, A M

    1975-04-01

    An attempt has been made to cover briefly the many applications of the acrylic jacket crown. It is readily understandable that this type of restoration has many shortcomings but at the same time it has many useful and important applications in dentistry when properly employed. It is hoped that the specialist and generalist alike will have found some new and useful applications of the acrylic jacket crown. PMID:1090464

  15. A lariat-functionalized copper(II) diimine-dioxime complex.

    PubMed

    Kiani, Salma; Staples, Richard J; Packard, Alan B

    2002-12-01

    The dimeric title copper(II) complex, diaqua-1kappaO,2kappaO-bis[3,9-dimethyl-6-(2-pyridylmethyl)-4,8-diazaundeca-3,8-diene-2,10-dione dioximato(1-)]-1k(4)N(2),N(4),N(8),N(10);1:2kappa(5)O(2):N(2),N(4),N(8),N(10)-dicopper(II) diperchlorate, [Cu(2)(C(17)H(24)N(5)O(2))(2)](ClO(4))(2), crystallizes with one Cu atom in a square-pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water molecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) A] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water molecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to Cu(II). PMID:12466608

  16. Circular RNA biogenesis can proceed through an exon-containing lariat precursor

    PubMed Central

    Barrett, Steven P; Wang, Peter L; Salzman, Julia

    2015-01-01

    Pervasive expression of circular RNA is a recently discovered feature of eukaryotic gene expression programs, yet its function remains largely unknown. The presumed biogenesis of these RNAs involves a non-canonical ‘backsplicing’ event. Recent studies in mammalian cell culture posit that backsplicing is facilitated by inverted repeats flanking the circularized exon(s). Although such sequence elements are common in mammals, they are rare in lower eukaryotes, making current models insufficient to describe circularization. Through systematic splice site mutagenesis and the identification of splicing intermediates, we show that circular RNA in Schizosaccharomyces pombe is generated through an exon-containing lariat precursor. Furthermore, we have performed high-throughput and comprehensive mutagenesis of a circle-forming exon, which enabled us to discover a systematic effect of exon length on RNA circularization. Our results uncover a mechanism for circular RNA biogenesis that may account for circularization in genes that lack noticeable flanking intronic secondary structure. DOI: http://dx.doi.org/10.7554/eLife.07540.001 PMID:26057830

  17. A lariat-functionalized copper(II) diimine—dioxime complex

    PubMed Central

    Kiani, Salma; Staples, Richard J.; Packard, Alan B.

    2013-01-01

    The dimeric title copper(II) complex, diaqua-1κO,2κO-bis[3,9-dimethyl-6-(2-pyridylmethyl)-4,8-diazaundeca-3,8-diene-2,10-dione dioximato(1–)]-1k4N2,N4,N8,N10;1:2κ5O2:N2,-N4,N8,N10-dicopper(II) diperchlorate, [Cu2(C17H24N5O2)2]-(ClO4)2, crystallizes with one Cu atom in a square-pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water molecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) Å] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water molecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to CuII. PMID:12466608

  18. A Rolling Circle Replication Mechanism Produces Multimeric Lariats of Mitochondrial DNA in Caenorhabditis elegans

    PubMed Central

    Lewis, Samantha C.; Joers, Priit; Willcox, Smaranda; Griffith, Jack D.; Jacobs, Howard T.; Hyman, Bradley C.

    2015-01-01

    Mitochondrial DNA (mtDNA) encodes respiratory complex subunits essential to almost all eukaryotes; hence respiratory competence requires faithful duplication of this molecule. However, the mechanism(s) of its synthesis remain hotly debated. Here we have developed Caenorhabditis elegans as a convenient animal model for the study of metazoan mtDNA synthesis. We demonstrate that C. elegans mtDNA replicates exclusively by a phage-like mechanism, in which multimeric molecules are synthesized from a circular template. In contrast to previous mammalian studies, we found that mtDNA synthesis in the C. elegans gonad produces branched-circular lariat structures with multimeric DNA tails; we were able to detect multimers up to four mtDNA genome unit lengths. Further, we did not detect elongation from a displacement-loop or analogue of 7S DNA, suggesting a clear difference from human mtDNA in regard to the site(s) of replication initiation. We also identified cruciform mtDNA species that are sensitive to cleavage by the resolvase RusA; we suggest these four-way junctions may have a role in concatemer-to-monomer resolution. Overall these results indicate that mtDNA synthesis in C. elegans does not conform to any previously documented metazoan mtDNA replication mechanism, but instead are strongly suggestive of rolling circle replication, as employed by bacteriophages. As several components of the metazoan mitochondrial DNA replisome are likely phage-derived, these findings raise the possibility that the rolling circle mtDNA replication mechanism may be ancestral among metazoans. PMID:25693201

  19. Stability constants and thermodynamic data for complexes of 12-crown-4 with alkali metal and alkaline-earth cations in methanol solutions

    SciTech Connect

    Buschmann, H.

    1987-03-01

    The formation of 1:1- and 2:1-complexes of the crown ether 12C4 with mono- and bivalent cations was studied in methanol solutions by calorimetric, potentiometric and conductometric titrations. It is shown that not all donor atoms of the ligand 12C4 take part in complex formation. The accuracy of the three experimental methods are checked by comparing the results for the complexation of alkali ions with crown ether 18C6.

  20. A ferric-cyanide-bridged one-dimensional dirhodium complex with (18-crown-6)potassium cations.

    PubMed

    Kim, Y; Kim, S J; Nam, W

    2001-03-01

    The crystal structure of the title compound, catena-poly[bis[aqua(18-crown-6)potassium] diaqua(18-crown-6)potassium [[tetra-mu-benzoato-2:3 kappa(8)O:O'-mu-cyano-1:2 kappa(2)C:N-tetracyano-1 kappa C-irondirhodium(Rh-Rh)]-mu-cyano-1 kappa C:3' kappa N] octahydrate], [K(18-crown-6)(H(2)O)](2)[K(18-crown-6)(H(2)O)(2)][FeRh(2)(C(7)H(5)O(2))(4)(CN)(6)] x 8H(2)O, where (18-crown-6) is 1,4,7,10,13,16-hexaoxacyclooctadecane (C(12)H(24)O(6)), has been determined. Ferric cyanides connect the dirhodium units to form a one-dimensional chain compound. [K(18-crown-6-ether)(H(2)O)(2)] cations (with inversion symmetry) and [K(18-crown-6-ether)(H(2)O)] cations (in general positions) are located between the chains. PMID:11250572

  1. Bisthioxanthylidene biscrown ethers as potential stereodivergent chiral ligands.

    PubMed

    Geertsema, Edzard M; Schoevaars, Anne Marie; Meetsma, Auke; Feringa, Ben L

    2006-11-21

    The concept of bisthioxanthylidene biscrown ethers as potential stereodivergent chiral ligands in asymmetric synthesis is introduced. Substituted bisthioxanthylidenes may be chiral and can exist as stable enantiomers due to their folded structure. As a result, both a right-handed helix (P) and left-handed helix (M) are present in this type of molecule. This offers the unique possibility to construct two crown ether moieties, attached to the same molecule, of which one exhibits (P)-helicity and the other (M)-helicity. When the crown ether moieties differ in size they can be complexed selectively with a base containing a cation of appropriate diameter. In this manner the (P)-helix and the (M)-helix can be activated selectively to serve as a chiral environment for base catalyzed asymmetric synthesis. Thus, we envisioned the new concept of a single chiral ligand to separately synthesize two enantiomers of a chiral product just by varying the added base. For this purpose, four new bisthioxanthylidene monocrown ethers and two new bisthioxanthylidene biscrown ethers were synthesized. Two biscrowns and two monocrowns were separated into their respective enantiomers (HPLC) and optical data (UV and CD) were collected to ensure stability of enantiomers at ambient temperatures. Ion complexation of one mono- and two biscrown ethers with potassium and sodium cations was investigated. PMID:17312964

  2. All-ceramic crowns.

    PubMed

    Lehner, C R; Schärer, P

    1992-06-01

    Despite the good appearance and biocompatibility of dental porcelains, failures are still of considerable concern because of some limited properties common to all-ceramic crown systems. As in the years before, pertinent scientific articles published between November 1990 and December 1991 focused on strengthening mechanisms and compared fracture toughness for different ceramic systems by using various test methods. Some evaluated the clinical implications thereon for seating and loading crowns and measured wear against different ceramic surface conditions. Recently introduced with pleasing aesthetic qualities, IPS-Empress (Ivoclar, Schaan, Liechtenstein), a new European leucite-reinforced glass-ceramic, has finally drawn attention in some journals and has been reviewed with promising in vitro test results. Using a simple press-molding technique, well-fitting crowns, inlays, and veneers can be fabricated without an additional ceramming procedure. Again, only long-term clinical trials will validate achievements compared with other all-ceramic systems and with well-established metal ceramics. PMID:1325848

  3. Poly(arylene ether)s containing pendent ethynyl groups

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Jensen, Brian J. (Inventor)

    1996-01-01

    Poly(arylene ether)s containing pendent ethynyl and substituted ethynyl groups and poly(arylene ether) copolymers containing pendent ethynyl and substituted ethynyl groups are readily prepared from bisphenols containing ethynyl and substituted ethynyl groups. The resulting polymers are cured up to 350.degree. C. to provide crosslinked poly(arylene ether)s with good solvent resistance, high strength and modulus.

  4. An electrochemical investigation of the effect of macrocycle ring size on the binding of di- and trivalent lanthanide cations by 12-crown-4,4-tert-butylbenzo-15-crown-5, and dibenzo-30-crown-10 in propylene carbonate

    SciTech Connect

    Massaux, J.; Desreux, J.F.

    1982-06-02

    The complexation in anhydrous proplene carbonate of the lanthanide ions by various macrocylic polyethers featuring from four to ten oxygen atoms has been investigated by a competitive potentiometric technique with lead(II) or thallium(I) as auxilliary ions. The stability of the complexes appears to depend primarily on the relative sizes of the metal ions and of the internal cavity of each macrocycle. It depends also on the rigidity of the ligands and is influenced by solvation effects. The small ligands 12-crown-4 (1) and 15-crown-5 (2) exhibit a similar behavior: they form 1:2 lanthanide complexes, the stability of which decreases with decreasing ionic radius despite the higher charge density of the metal ions. The presence of an electron-withdrawing phenyl group, as in 4-tert-butylbenzo-15-crown-5 (3), leads to a strong reduction of the stability constants. A maximum stability of 1:1 complexes of 3 is found at Nd(III) while a marked minimum is observed at Gd(III) in the complexation curve of dibenzo-30-crown-10 (5). Divalent samarium and ytterbium are more strongly coordinated than the corresponding trivalent ions by the crown ethers 1-5. The larger divalent ions fit better into the internal cavity of 5 and they form stable 1:2 sandwich complexes with 1 and 3. The properties of the complexes described in the present work are completely different from those reported so far in the case of noncylic ligands.

  5. Raman spectra and conformations of dibenzo- and dicyclohexano-18-crown-6

    NASA Astrophysics Data System (ADS)

    Takeuchi, Hideo; Arai, Takaki; Harada, Issei

    1990-06-01

    Conformations of dibenzo-18-crown-6 (DBC), dicyclohexano-18-crown-6 (DCC) and their alkali cation complexes in the solid state and in solution have been investigated by Raman spectroscopy. The Raman spectra were analysed by using the relationships between Raman frequencies and conformations previously found for unsubstituted crown ethers. DBC takes a conformation, ( tCttGttG't) 2, with gauche ( G) or gauche' ( G') 2CH 2 bonds, trans ( t) CO bonds and cis ( C) OCCO linkages at the benzene rings, when it complexes with a cation in the solid state and in solution. Uncomplexed DBC adopts another conformation in the solid state, which contains both the trans and gauche conformations about the CH 2CH 2 and CO bonds. In solution, uncomplexed DBC exists as a mixture of conformers including the two conformers described above. Vibrational couplings between the oxyethylene and cyclohexane rings are strong in DCC and its strength depends on the crown conformation. The cation-bound crown rings of DCC isomers A and B in solution predominantly take the same conformation, ( tG'ttGt) 3, found for the crystalline isomer B-NaBr complex. A metastable conformer containing trans CH 2CH 2 bonding is found for the Na + complexes of both isomers in solution. Uncomplexed DCC adopts different crown ring conformations in isomers A and B in the solid state and diverse conformational states in solution.

  6. Synthesis and Cytotoxicity of Silicon and Germanium Containing Pyridine Oxime O-Ethers

    PubMed Central

    Abele, Edgars; Abele, Ramona; Arsenyan, Pavel; Shestakova, Irina; Kanepe, Iveta; Antonenko, Inga; Popelis, Juris; Lukevics, Edmunds

    2003-01-01

    Silicon and germanium containing pyridine aldoxime, ketoxime and amidoxime O-ethers have been prepared using phase transfer catalytic systems oxime alkyl halide solid KOH 18-crown-6 benzene and oxime alkyl halide solid K2CO3 or Cs2CO3 18-crown-6 toluene. Cytotoxic activity of silicon and germanium containing pyridine oxime O-ethers was tested in vitro on two monolayer tumor cell lines: MG- 22A (mouse hepatoma) and HT-1080 (human fibrosarcoma). O-[3-Yriethylsilylpropyl]- and O-[3-(1-methyl- 1-silacyclopentyl)propyl] oximes of pyridine aldehydes and ketones exhibit high cytotoxicity. Presence of methyl group in the pyridine ring considerably decreased activity of amidoxime O-ethers. Oxime ethers containing two elements are essentially inactive. For 2-acetylpyridine oxime ethers the activity increases in order of alkyl substituents: Et3GeCH2CH2SiMe2CH2 < Et3SiCH2CH2CH2 < (CH2)4SiCH2CH2CH2. Cytotoxicity of ketoxime O-ethers is considerably lower in comparison with aldoxime O-ethers. PMID:18365061

  7. Halogen derivatives of benzo- and dibenzocrown ethers: synthesis, structure, properties and application

    NASA Astrophysics Data System (ADS)

    Pluzhnik-Gladyr, S. M.

    2016-02-01

    Methods of synthesis of halogenated benzo- and dibenzocrown ether derivatives are surveyed: halogenation of benzo- and dibenzocrown ethers with molecular halogens, N-halosuccinimides in the solid phase and different media (water, ethanol, halohydrocarbons) and hypohalites in water, as well as the 'assembly' method. Reactions of these compounds are considered: synthesis of phosphorus-containing crown ethers, organometallic synthesis, the Heck and Sonogashira reactions, synthesis of acetylene derivatives and other reactions. Special attention is focused on the complexing properties of halogenated benzocrown ethers with respect to ionic guests and neutral organic molecules. The possibility of synthesis of complexes of such compounds in the solid phase is demonstrated. The extraction and sorption properties of halogenated benzo- and dibenzocrown ethers are considered. Examples of practical use of these compounds are presented. The bibliography includes 203 references.

  8. Removal of failed crown and bridge

    PubMed Central

    Rahul, G R.; Poduval, Soorya T.; Shetty, Karunakar

    2012-01-01

    Crown and bridge have life span of many years but they fail for a number of reasons. Over the years, many devices have been designed to remove crowns and bridges from abutment teeth. While the removal of temporary crowns and bridges is usually very straightforward, the removal of a definitive cast crown with unknown cement is more challenging. Removal is often by destructive means. There are a number of circumstances, however, in which conservative disassembly would aid the practitioner in completing restorative/endodontic procedures. There are different mechanisms available to remove a failed crown or bridge. But there is no information published about the classification of available systems for crown and bridge removal. So it is logical to classify these systems into different groups which can help a clinician in choosing a particular type of system depending upon the clinical situation. The aim of this article is to provide a classification for various crown and bridge removal systems; describe how a number of systems work; and when and why they might be used. A PubMed search of English literature was conducted up to January 2010 using the terms: Crown and bridge removal, Crown and bridge disassembly, Crown and bridge failure. Additionally, the bibliographies of 3 previous reviews, their cross references as well as articles published in various journals like International Endodontic Journal, Journal of Endodontics and were manually searched. Key words:Crown and bridge removal, Crown and bridge disassembly, Crown and bridge failure. PMID:24558549

  9. Coibamide A, a natural lariat depsipeptide, inhibits VEGFA/VEGFR2 expression and suppresses tumor growth in glioblastoma xenografts.

    PubMed

    Serrill, Jeffrey D; Wan, Xuemei; Hau, Andrew M; Jang, Hyo Sang; Coleman, Daniel J; Indra, Arup K; Alani, Adam W G; McPhail, Kerry L; Ishmael, Jane E

    2016-02-01

    Coibamide A is a cytotoxic lariat depsipeptide isolated from a rare cyanobacterium found within the marine reserve of Coiba National Park, Panama. Earlier testing of coibamide A in the National Cancer Institute in vitro 60 human tumor cell line panel (NCI-60) revealed potent anti-proliferative activity and a unique selectivity profile, potentially reflecting a new target or mechanism of action. In the present study we evaluated the antitumor activity of coibamide A in several functional cell-based assays and in vivo. U87-MG and SF-295 glioblastoma cells showed reduced migratory and invasive capacity and underwent G1 cell cycle arrest as, likely indirect, consequences of treatment. Coibamide A inhibited extracellular VEGFA secreted from U87-MG glioblastoma and MDA-MB-231 breast cancer cells with low nM potency, attenuated proliferation and migration of normal human umbilical vein endothelial cells (HUVECs) and selectively decreased expression of vascular endothelial growth factor receptor 2 (VEGFR2). We report that coibamide A retains potent antitumor properties in a nude mouse xenograft model of glioblastoma; established subcutaneous U87-MG tumors failed to grow for up to 28 days in response to 0.3 mg/Kg doses of coibamide A. However, the natural product was also associated with varied patterns of weight loss and thus targeted delivery and/or medicinal chemistry approaches will almost certainly be required to improve the toxicity profile of this unusual macrocycle. Finally, similarities between coibamide A- and apratoxin A-induced changes in cell morphology, decreases in VEGFR2 expression and macroautophagy signaling in HUVECs raise the possibility that both cyanobacterial natural products share a common mechanism of action. PMID:26563191

  10. Development of HPLC Chiral Stationary Phases Based on (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid and Their Applications.

    PubMed

    Hyun, Myung Ho

    2015-09-01

    Crown ether-based chiral stationary phases (CSPs) have been known to be useful for the resolution of racemic primary amino compounds. In particular, CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid have been reported to be useful for the resolution of secondary amino compounds as well as primary amino compounds. In this article, the process of developing various CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to improve the chiral recognition efficiency and/or the stability of the CSPs and their applications to the resolution of various primary and nonprimary amino compounds are reviewed. PMID:26237013

  11. INTRAVENOUS ETHER ANESTHESIA

    PubMed Central

    Eger, Edmond I.; Johnson, Edward A.

    1963-01-01

    From a study of intravenous ether anesthesia, it was concluded that ether diluted to a 5 per cent solution in 5 per cent dextrose and water may be used to induce and maintain a smooth and easily controlled anesthetic state similar to that obtained with inhalation ether but without the dependence of the latter technique on ventilation. Cough and laryngospasm were absent. Adequate spontaneous respiration can be maintained with this technique. The technique is particularly useful in endoscopy during which the airway is often not available for anesthetic administration. PMID:14051486

  12. Genotoxicity of glycol ethers.

    PubMed Central

    McGregor, D B

    1984-01-01

    The genetic toxicology of glycol ethers is reviewed. Ethylene glycol monomethyl ether (EGME) and diglyme have been more extensively studied than other members of this series. Most results indicate a lack of genotoxic potential, but certain tests have yielded positive responses with certain compounds. Ethylene glycol monoethyl ether (EGEE) induced sister chromatid exchanges and chromosomal aberrations in cultured cells. Both EGME and diglyme induced mouse sperm head morphological changes, male rat weak dominant lethal mutations and marked, but reversible, loss of male rat fertility. PMID:6541999

  13. Vinyl ether silicones

    SciTech Connect

    Herzig, C.; Dauth, J.; Deubzer, B.; Weis, J.

    1995-12-01

    Siloxanes with vinyl ether groups are prepared by hydrosilylation reaction of dihydrosiloxanes with divinyl ethers in excess. Different stoichiometry, produces linear copolymers of different viscosities and double bond concentrations always with an active vinyl ether group at each chain end. Polymerisations triggered by UV light were done with mixtures of these compounds and a series of onium salts. Very fast cure is observed even with low doses at 290 nm. V.E. silicones are found to cure essentially quantitative. The comparison with other highly reactive cationic monomers revealed that compounds are among the fastest curing prepolymers in cationic chemistry.

  14. Catalytic oxidation of dimethyl ether

    DOEpatents

    Zelenay, Piotr; Wu, Gang; Johnston, Christina M.; Li, Qing

    2016-05-10

    A composition for oxidizing dimethyl ether includes an alloy supported on carbon, the alloy being of platinum, ruthenium, and palladium. A process for oxidizing dimethyl ether involves exposing dimethyl ether to a carbon-supported alloy of platinum, ruthenium, and palladium under conditions sufficient to electrochemically oxidize the dimethyl ether.

  15. A surprising host-guest relationship between 1,2-dichloroethane and the cesium complex of tetrabenzo-24-crown-8

    SciTech Connect

    Levitskaia, T.G.; Bryan, J.C.; Sachleben, R.A.; Lamb, J.D.; Moyer, B.A.

    2000-02-02

    The structure of the complex [Cs(tetrabenzo-24-crown-8)(1,2-dichloroethane){sub 2}](NO{sub 3}){sm{underscore}bullet}H{sub 2}O was shown by X-ray crystallography to involve an unprecedented bidentate coordination of two 1,2-dichloroethane solvent molecules to the Cs{sup +} cation via the four chlorine atoms. The coordination of the solvent molecules occurs within two clefts between facing benzo groups, one pair of benzo groups related to the other pair by an improper noncrystallographic 90{degree} rotation. Resembling the seam on a tennis ball, the crown ether envelops the metal cation within a cagelike arrangement of eight crown ether oxygen atoms. Good geometric and electronic complimentarily characterizes the apparent host-guest relationship between the cleft environment and the solvent molecules. The complete encapsulation of the cation by the crown ether and two solvent molecules explains well the speciation behavior observed in liquid-liquid extraction of CsNO{sub 3} or CsClO{sub 4} from aqueous solution to 1,2-dichloroethane solutions of the alkylated analogues 4,4{double{underscore}prime}- or 4,5{double{underscore}prime}-bis(tert-octylbenzo)dibenzo-24-crown-8. In the extraction process studied at 25 C, simple 1:1 metal/crown complexes form in the solvent phase, as modeled by the program SXLSQI. The complex cation and counteranion are present both as ion-pairs, postulated to be ligand-separated ion-pairs as suggested by the crystal structure, and as dissociated ions. In agreement with a theoretical treatment of ion-pairing, the ion-pairs possess unusually low stability and exhibit no discrimination between the anions, largely ascribed to the large effective radius of the complex metal cation. Values of log K{sub f} corresponding to the formation of the complex cations Cs[bis(tert-octylbenzo)-dibenzo-24-crown-8]{sup +} in 1,2-dichloroethane at 25 C average 10.5 {+-} 0.2 for both positional isomers of the crown ether and for their 3:2 mixture. Overall, these

  16. Conformation-Specific Infrared and Ultraviolet Spectroscopy of DIBENZO-15-CROWN-5-(H2O)1-CLUSTER: Reshaping a Binding Pocket

    NASA Astrophysics Data System (ADS)

    Buchanan, Evan G.; Rodrigo, Chirantha P.; Gutberlet, Anna K.; Zwier, Timothy S.

    2010-06-01

    Crown ethers are oxygen containing macrocycles noted for their ability to preferentially bind substrates such as ions and water. Despite the high symmetry inherent to the chemical structure, crown ethers are remarkably flexible, adapting their conformation to the substrate to which they are bound. Here, we present the conformational preferences of the singly hydrated dibenzo-15-crown-5 ether (DB15C) complex formed and cooled in a supersonic jet. The resonance enhanced two-photon ionization, UV-UV Hole-burning, and resonant ion-dip infrared spectra lead to the identification of a single DB15C-(H2O)1 conformer with the water doubly hydrogen bonded to the crown. Single vibronic level dispersed fluorescence identified both electronic origins and the coupling between the two chromophores. Finally, infrared population transfer spectroscopy is used to study the monomer conformer populations formed by infrared photodissocation of the complex via the water OH stretch transitions, providing unique insight to the energy flow between water and crown.

  17. Pd-catalyzed amination in the synthesis of a new family of macropolycyclic compounds comprising diazacrown ether moieties.

    PubMed

    Yakushev, Alexei A; Chernichenko, Nataliya M; Anokhin, Maxim V; Averin, Alexei D; Buryak, Alexei K; Denat, Franck; Beletskaya, Irina P

    2014-01-01

    N,N'-bis(bromobenzyl) and N,N'-bis(halopyridinyl) derivatives of diaza-12-crown-4, diaza-15-crown-5 and diaza-18-crown-6 ethers were synthesized in high yields. The Pd-catalyzed macrocyclization reactions of these compounds were carried out using a variety of polyamines and oxadiamines were carried out to give novel macrobicyclic and macrotricyclic compounds of the cryptand type. The dependence of the yields of macropolycycles on the nature of the starting diazacrown derivatives and polyamines was established. Generally N,N'-bis(3-bromobenzyl)-substituted diazacrown ethers and oxadiamines provided better yields of the target products. The highest yield of the macrobicyclic products reached 57%. PMID:24434669

  18. Synthesis and characterization of a chiral, aza-15-crown-5-functionalized ferrocenyldiphosphine ligand for asymmetric catalysis

    SciTech Connect

    Landis, C.R.; Sawyer, R.A.; Somsook, E.

    2000-03-20

    A chiral ferrocenyldiphosphine ligand that is functionalized with an aza crown ether, (S)-1-[(R)-1{prime},2-bis(diphenylphosphino)ferroceny]ethyl-1-aza-2,3-benzo-15-crown-5(1), has been synthesized. Both the resolved and racemic ligands react rapidly with Pt(II) precursors to form stable metal-ligand adducts; the complexes PtMeI(rac-1) and PtMe{sub 2}(rac-1) have been characterized crystallographically. Reaction of rac-1 with [Rh(NBD){sub 2}]OTf yields [Rh(NBD)(rac-1)]OTf. The three-dimensional solution structure of [Rh(NBD)(rac-1)]OTf has been determined by NOESY experiments and analysis using the two-dimensional conformer population analysis algorithm (2DCPA). The NOESY data reveal rapid, pairwise chemical exchange between vinyl protons. The complex [Rh(NBD)(rac-1)]OTf is a catalyst precursor for hydrogenation reactions. However, the authors demonstrate that the liability of the aza crown ether may limit the ability of these catalysts to control selectivity via secondary interactions.

  19. Marginal accuracy of temporary composite crowns.

    PubMed

    Tjan, A H; Tjan, A H; Grant, B E

    1987-10-01

    An in vitro study was conducted to quantitatively compare the marginal adaptation of temporary crowns made from Protemp material with those made from Scutan, Provisional, and Trim materials. A direct technique was used to make temporary restorations on prepared teeth with an impression as a matrix. Protem, Trim, and Provisional materials produced temporary crowns of comparable accuracy. Crowns made from Scutan material had open margins. PMID:2959770

  20. Triethylene glycol monoethyl ether

    Integrated Risk Information System (IRIS)

    Triethylene glycol monoethyl ether ; CASRN 112 - 50 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  1. Triethylene glycol monobutyl ether

    Integrated Risk Information System (IRIS)

    Triethylene glycol monobutyl ether ; CASRN 143 - 22 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  2. Propylene glycol monoethyl ether

    Integrated Risk Information System (IRIS)

    Propylene glycol monoethyl ether ; CASRN 52125 - 53 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  3. p-Bromodiphenyl ether

    Integrated Risk Information System (IRIS)

    p - Bromodiphenyl ether ; CASRN 101 - 55 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  4. Chloromethyl methyl ether (CMME)

    Integrated Risk Information System (IRIS)

    Chloromethyl methyl ether ( CMME ) ; CASRN 107 - 30 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  5. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, J.V.

    1996-10-22

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of the above formula together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  6. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  7. Glycol Ethers As Groundwater Contaminants

    NASA Astrophysics Data System (ADS)

    Ross, Benjamin; Johannson, Gunnar; Foster, Gregory D.; Eckel, William P.

    1992-01-01

    Ether derivatives of dihydroxy alcohols, which are formed from ethylene or propylene, comprise an important group of groundwater contaminants known as glycol ethers. Compounds in this group are used as solvents, cleaning agents, and emulsifiers in many chemical products and manufacturing operations. Glycol ethers have been associated with a variety of toxic effects, and some compounds in the group are relatively potent teratogens. The limited information available suggests that glycol ethers are contaminants in groundwater, especially in anaerobic plumes emanating from disposal of mixed industrial and household waste. Most methods used to analyze groundwater samples cannot adequately detect μg/? (ppb) concentrations of glycol ethers, and the existing methods perform worst for the most widely used and toxic species. A new method capable of analyzing μg/? concentrations of glycol ethers was recently developed, and its use is recommended for groundwater samples where glycol ethers are likely to be present.

  8. Pipe weld crown removal device

    SciTech Connect

    Sword, C.K.; Sette, P.J.

    1992-11-24

    A device is provided for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of the weld, a plurality of grinding wheels, supported by the cage assembly for grinding down the crown of the weld, and a plurality of support shafts, each extending longitudinally along the joined pipe sections, parallel thereto, for individually mounting respective grinding wheels. Each end of the support shafts is mounted for rotation in a bearing assembly housed within a radially directed opening in a corresponding one of the cage rings so as to provide radial movement of the associated shaft, and thus of the associated grinding wheel, towards and away from the weld. A first drive sprocket provides rotation of the cage assembly around the pipe sections while a second drive unit, driven by a common motor, provides rotation of the grinding wheels. 2 figs.

  9. Pipe weld crown removal device

    SciTech Connect

    Sword, C.K.; Sette, P.J.

    1991-12-31

    This invention is comprised of a device that provides for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of the weld, a plurality of grinding wheels, supported by the cage assembly for grinding down the crown of the weld, and a plurality of support shafts, each extending longitudinally along the joined pipe sections, parallel thereto, for individually mounting respective grinding wheels. Each end of the support shafts is mounted for rotation in a bearing assembly housed within a radially directed opening in a corresponding one of the cage rings so as to provide radial movement of the associated shaft, and thus of the associated grinding wheel, towards and away from the weld. A first drive sprocket provides rotation of the cage assembly around the pipe sections while a second drive unit, driven by a common motor, provides rotation of the grinding wheels.

  10. Pipe weld crown removal device

    DOEpatents

    Sword, Charles K.; Sette, Primo J.

    1992-01-01

    A device is provided for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of the weld, a plurality of grinding wheels, supported by the cage assembly for grinding down the crown of the weld, and a plurality of support shafts, each extending longitudinally along the joined pipe sections, parallel thereto, for individually mounting respective grinding wheels. Each end of the support shafts is mounted for rotation in a bearing assembly housed within a radially directed opening in a corresponding one of the cage rings so as to provide radial movement of the associated shaft, and thus of the associated grinding wheel, towards and away from the weld. A first drive sprocket provides rotation of the cage assembly around the pipe sections while a second drive unit, driven by a common motor, provides rotation of the grinding wheels.

  11. Sclerotinia stem and crown rot of chickpea

    Technology Transfer Automated Retrieval System (TEKTRAN)

    White mold of chickpea is caused by three soil borne fungi Sclerotinia sclerotiorum, S. minor and S. trifoliorum, causing either stem rot and crown rot. Stem infection, usually above ground and initiated by ascospores through carpogenic germination of scleroia produces stem rot, whereas crown infe...

  12. Developmental toxicity of diphenyl ether herbicides in nestling American kestrels.

    PubMed

    Hoffman, D J; Spann, J W; LeCaptain, L J; Bunck, C M; Rattner, B A

    1991-11-01

    Beginning the day after hatching, American kestrel (Falco sparverius) nestlings were orally dosed for 10 consecutive days with 5 microliters/g of corn oil (controls) or one of the diphenyl ether herbicides (nitrofen, bifenox, or oxyfluorfen) at concentrations of 10, 50, 250, or 500 mg/kg in corn oil. At 500 mg/kg, nitrofen resulted in complete nestling mortality, bifenox in high (66%) mortality, and oxyfluorfen in no mortality. Nitrofen at 250 mg/kg reduced nestling growth as reflected by decreased body weight, crown-rump length, and bone lengths including humerus, radius-ulna, femur, and tibiotarsus. Bifenox at 250 mg/kg had less effect on growth than nitrofen, but crown-rump, humerus, radius-ulna, and femur were significantly shorter than controls. Liver weight as a percent of body weight increased with 50 and 250 mg/kg nitrofen. Other manifestations of impending hepatotoxicity following nitrofen ingestion included increased hepatic GSH peroxidase activity in all nitrofen-treated groups, and increased plasma enzyme activities for ALT, AST, and LDH-L in the 250-mg/kg group. Bifenox ingestion resulted in increased hepatic GSH peroxidase activity in the 50- and 250-mg/kg groups. Nitrofen exposure also resulted in an increase in total plasma thyroxine (T4) concentration. These findings suggest that altricial nestlings are more sensitive to diphenyl ether herbicides than young or adult birds of precocial species. PMID:1942122

  13. Colour measurements of all ceramic crown systems.

    PubMed

    Rosenstiel, S F; Porter, S S; Johnston, W M

    1989-09-01

    The objectives of this study were: (i) to determine variability among colour parameters of five different ceramic crown systems; and (ii) to measure the effect of using coloured luting agents on restoration colour. The crown systems studied were Cerestore, Dicor, Hi-Ceram, Renaissance, and Vitadur-N. Five crowns for each system were made according to manufacturer's instructions with the same nominal shade (Vita Lumin Vacuum A2) to fit an Ivorine central incisor tooth. Restoration thickness was adjusted to within +/- 0.1 mm (+/- 0.05 mm in the mid-facial area where colour measurements were to be made) with the aid of a dial calliper prior to glazing or, in the case of Dicor, surface staining. Where a core was part of the system this was fabricated to the minimum recommended thickness. The crowns were cemented using luting agents of five different colours in a randomly chosen sequence. The colour of each restoration/cement combination was measured three times using a small-area colorimeter (Minolta CR-121). The variance of each colour parameter (L*, a*, b*) was statistically compared for each crown system using an analysis of variance procedure, as was the effect of the cement. Observed differences were related to visual perception by using the colour difference formula. There were statistically significant differences among the variances of the crown systems and the cements, with significant interactions between crown systems and direction of colour and between cement and direction of colour. Restorations made with different ceramic crown systems had noticeably different colour despite having the same nominal shade. Changing the shade of the luting agent had a perceivable effect on Dicor crowns and, to a lesser extent, on Vitadur-N crowns but not on the other systems due, presumably, to the opacity of their core materials. PMID:2809851

  14. Conformational effect of dicyclo-hexano-18-crown-6 on isotopic fractionation of zinc: DFT approach

    SciTech Connect

    Boda, A.; Singha Deb, A. K.; Ali, Sk. M.; Shenoy, K. T.; Ghosh, S. K.

    2014-04-24

    Generalized gradient approximated BP86 density functional employing triple zeta valence plus polarization (TZVP) basis set has been used to compute the reduced partition function ratio and isotopic separation factor for zinc isotopes. The isotopic separation factor was found to be in good agreement with the experimental results. The isotopic separation factor was found to depend on the conformation of the crown ether ligand. The trans-trans conformation shows the highest fractionation compared to cis-cis conformer. The present theoretical results can thus be used to plan the isotope separation experiments.

  15. Bacterial degradation of glycol ethers.

    PubMed

    Kawai, F

    1995-12-01

    Assimilation of ethyleneglycol (EG) ethers by polyethyleneglycol-utilizing bacteria was examined. Ethyleneglycol ether-utilizing bacteria were also isolated from soil and activated sludge samples by enrichment-culture techniques. Three strains (4-5-3, EC 1-2-1 and MC 2-2-1) were selected and characterized as Pseudomonas sp. 4-5-3, Xanthobacter autotrophicus, and an unidentified gram-negative, non-spore-forming rod respectively. Their growth characteristics were examined: Pseudomonas sp. 4-5-3 assimilated EG (diethyleneglycol, DEG) monomethyl, monoethyl and monobutyl ethers, DEG, propanol and butanol. X. autotrophicus EC 1-2-1 grew well on EG monoethyl and monobutyl ethers, EG and primary alcohols (C1-C4), and slightly on EG monomethyl ether. The strain MC 2-2-1 grew on EG monomethyl ether, EG, primary alcohols (C1-C4), and 1,2-propyleneglycol (PG). The mixed culture of Pseudomonas sp. 4-5-3 and X. autotrophicus EC 1-2-1 showed better growth and improved degradation than respective single cultures towards EG monomethyl, monoethyl or monobutyl ethers. Intact cells of Pseudomonas sp. 4-5-3 degraded various kinds of monoalkyl ethers, which cannot be assimilated by the strain. Metabolic products were characterized from reaction supernatants of intact cells of Pseudomonas sp. 4-5-3 with EG or DEG monoethyl ethers: they were analyzed by thin-layer chromatography and GC-MS and found to be ethoxyacetic acid and ethoxyglycoxyacetic acid. Also, PG monoalkyl ethers (C1-C4), dipropyleneglycol monoethyl and monomethyl ethers and tripropyleneglycol monomethyl ether were assimilated by polypropyleneglycol-utilizing Corynebacterium sp. 7. PMID:8597556

  16. Synthesis and Characterization of Macrocyclic Polyether N,N'-Diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6.

    PubMed

    Toeri, Julius; Laborie, Marie-Pierre

    2016-01-01

    In this study an efficient and direct production procedure for a macrocyclic polyether N,N'-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 from the reaction of catechol and N,N-bis(2-chloroethyl)prop-2-en-1-amine in n-butanol in the presence of a strong base is reported. The synthesis involves a two-step addition of sodium hydroxide to enhance the cyclization process, and at the end of the reaction, the reaction mixture is neutralized and the solvent replaced with water in-situ through distillation to afford a relatively pure precipitate that is easily recrystallized from acetone. The yield of the macrocycle was 36%-45% and could be scaled-up to one-mole quantities. The structure and purity of this compound was verified on the basis of elemental analysis, IR, UV-Vis, ¹H-, (13)C-NMR, 2D-NMR, mass spectroscopy, and thermal analysis. The white crystalline compound has a sharp melting point of 124 °C and a crystallization temperature of 81.4 °C determined by differential scanning calorimetry. Our motivation behind the synthesis of the bibracchial lariat azacrown polyether ligand was to examine its possible applications in ion-selective polymer-supported materials. PMID:26840284

  17. Developmental toxicity of diphenyl ether herbicides in birds

    USGS Publications Warehouse

    Hoffman, D.J.; Rattner, B.A.; Bunck, C.M.

    1991-01-01

    Diphenyl ether herblcldes, includlng nitrofen, have been identified as mammalian teratogens and cause perinatal mortality. American kestrel (Falco sparverius) nestlings were orally dosed for 10 days w1th 5 ul/g of corn oil (controls) or one of the diphenyl ether herbicides (nitrofen, bifenox, or oxyfluorofen). At 500 mg/kg, nitrofen resulted in complete mortality, bifenox in high (66%) mortality, and oxyfluorofen in no mortality. Nitrofen, at 250 mg/kg, reduced nestling growth, as reflected by decreased body weight and bone length. Bifenox at 250 mg/kg had less effect on growth than nitrofen but crown rump, humerus, radiusulna and femur lengths were significantly less than controls. Liver welght (percent of body welght) increased with 50 mg/kg nitrofen. Other manifestations of hepatotoxicity following nitrofen ingestion included increased hepatic GSH peroxidase activity with 0 mg/kg nitrofen, and increased plasma enzyme activities for ALT, AST. and LDHL with 250 mg/kg. Blfenox lngestion (50 mg/kg) resulted in increased hepatlc GSH peroxidase activity. Nitrofen exposure increased total plasma thyroxlne (T4) concentratlon. These findings suggest that altricial nestllng kestrels are more sensitive to diphenyl ether herbicides than precocial young or adult birds.

  18. Poly(arylene ether)s That Resist Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul; Smith, Joseph G., Jr.

    1994-01-01

    Novel poly(arylene ether)s containing phosphine oxide (PAEPO's) made via aromatic nucleophilic displacement reactions of activated aromatic dihalides (or, in some cases, activated aromatic dinitro compounds) with new bisphenol monomers containing phosphine oxide. Exhibited favorable combination of physical and mechanical properties and resistance to monatomic oxygen in oxygen plasma environment. Useful as adhesives, coatings, films, membranes, moldings, and composite matrices.

  19. Ether and Relativity

    NASA Astrophysics Data System (ADS)

    Farhoudi, Mehrdad; Yousefian, Maysam

    2016-05-01

    We consider one of the fundamental debates in performing the relativity theory, namely, the ether and the relativity points of view, in a way to aid the learning of the subjects. In addition, we present our views and prospects while describing the issues that being accessible to many physicists and allowing broader views. Also, we very briefly review the two almost recent observations of the Webb redshift and the ultra high energy cosmic rays, and the modified relativity models that have been presented to justify them, wherein we express that these justifications have not been performed via a single model with a single mechanism.

  20. Induction of Crown Gall on Carrot Slices.

    ERIC Educational Resources Information Center

    Babich, H.; Fox, K. D.

    1998-01-01

    Argues that the transfer of plasmid from a bacterium to a plant cell has received little attention. Presents an experiment for studying this type of genetic transformation using the causative agent of crown gall, a malignant plant tumor. (DDR)

  1. Analysis of geophysical logs from six boreholes at Lariat Gulch, former U.S. Air Force site PJKS, Jefferson County, Colorado

    USGS Publications Warehouse

    Paillet, Frederick L.; Hodges, Richard E.; Corland, Barbara S.

    2002-01-01

    This report presents and describes geophysical logs for six boreholes in Lariat Gulch, a topographic gulch at the former U.S. Air Force site PJKS in Jefferson County near Denver, Colorado. Geophysical logs include gamma, normal resistivity, fluid-column temperature and resistivity, caliper, televiewer, and heat-pulse flowmeter. These logs were run in two boreholes penetrating only the Fountain Formation of Pennsylvanian and Permian age (logged to depths of about 65 and 570 feet) and in four boreholes (logged to depths of about 342 to 742 feet) penetrating mostly the Fountain Formation and terminating in Precambrian crystalline rock, which underlies the Fountain Formation. Data from the logs were used to identify fractures and bedding planes and to locate the contact between the two formations. The logs indicated few fractures in the boreholes and gave no indication of higher transmissivity in the contact zone between the two formations. Transmissivities for all fractures in each borehole were estimated to be less than 2 feet squared per day.

  2. Allene ether Nazarov cyclization.

    PubMed

    Tius, Marcus A

    2014-05-01

    The ease of synthesis and the exceptional reactivity of alkoxyallenes has led to their use in a large number of highly diverse applications. This Report describes their use in various versions of the allene ether Nazarov cyclization. Following a brief introduction to the Nazarov cyclization (Section 1), the oxidative cyclization of vinyl alkoxyallenes is discussed first (Section 2). Nazarov cyclizations of α-alkoxyallenyl vinyl ketones and of α-alkoxyallenyl vinyl tertiary carbinols are covered (Section 3). The discovery and the subsequent rational design of acetals that serve as chiral auxiliaries on the allene in highly enantioselective Nazarov cyclizations is explained (Section 4). Interrupted Nazarov cyclizations of alkoxyallenes that are generated in situ from the isomerization of propargyl ethers on solid supports are discussed, including the evolution of a highly diastereoselective, chiral auxiliary controlled version of the reaction. Some applications of the methodology to natural products total synthesis have been included so as to provide the reader with benchmarks with which to judge the utility of the methodology. PMID:24196585

  3. Selective extraction of cesium from acidic nitrate solutions with didodecylnaphthalenesulfonic acid synergized with bis(tert-butylbenzo)-21-crown-7

    SciTech Connect

    McDowell, W.J.; Case, G.N. ); McDonough, J.A.; Bartsch, R.A. )

    1992-12-01

    The behavior of other crown ether-synergized sulfonic acid extraction systems suggested that the title system would be selective for cesium. Synthesis of the new lipophilic crown ether, bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7), allowed testing of this hypothesis. Under nonloading conditions, the distribution coefficient for cesium between a toluene solution 0.025 M in didodecylnaphthalenesulfonic acid (HDDNS) and D(tBB)21C7 and an aqueous phase 0.1 M in nitric acid is 100 with separation factors of 1.2 from rubidium, 5.6 from potassium, and 294 from sodium. Under loading and competitive extraction conditions, the distribution coefficients were lower (5 for cesium), but the separation factors remained in the same order and of useful magnitude, 1.5 from rubidium, 6.4 from potassium, and 192 from sodium. Increasing the concentrations of D(tBB)21C7 and HDDNS in the organic phase gives higher distribution coefficients for cesium as did lower aqueous acid concentrations. 23 refs., 8 figs., 1 tab.

  4. Crown cover chart for oak savannas. Forest Service technical brief

    SciTech Connect

    Law, J.R.; Johnson, P.S.; Houf, G.

    1994-07-01

    Although oak savannas have been defined in many ways, they are characterized by scattered trees, largely comprised of oaks, and a sparse ground layer rich in grasses and forbs. The crown cover chart can be used to estimate the crown cover of trees as a percent of total area. Potential applications of the chart include monitoring changes in savanna crown cover, determining needed reductions in crown cover, and defining the savanna state. in restoring savannas that have grown into closed canopy stands, one can use the chart to estimate initial crown cover before restoration work is begun and again after crown cover has been reduced.

  5. Functionalization of poly(aryl ether ether ketone)

    SciTech Connect

    Wang, Fei; Roovers, J.

    1993-12-31

    Bromomethyl and dibromomethyl substituted poly(aryl ether ether ketone) have been prepared from methyl poly(aryl ether ether ketone) by bromination with bromine. These brominated polymers are intermediates that can be further functionalized by: hydrolysis, oxidation, substitution etc. A series of new functionalized PEEK polymers has been prepared. The functional group includes -CH{sub 2}OH, -CH{sub 2}OCH{sub 3}, -CHO, -COOH, -COOCH{sub 3}, -CH{sub 2}CN, -CH{sub 2}COOH, -CH{sub 2}OCOCH{sub 3}, -CH{sub 2}N{sup +}H(CH{sub 2}CH{sub 3}){sub 2}Br{sup {minus}}, -CH{sub 2}N(CH{sub 2}CH{sub 3}){sub 2}, -CH{sub 2}N{sup +}H(CH{sub 2}CH{sub 3}){sub 3}Br{sup {minus}}.

  6. Polyarylene Ethers with Improved Properties

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor); Jensen, B. J. (Inventor); Havens, S. J. (Inventor)

    1986-01-01

    This invention relates to novel polyarylene ethers which possess the combination of high strength, toughness, and high use temperature with ease of extrusion and formation into complex objects. These polyarylene ethers are suitable for use in adhesives, coatings, films, membranes, and composite matrices. The polyarylene ethers of this invention are the polycondensation products from the reaction of either 1,3-bis (4-chloro or fluorobenzoyl) benzene with any one of the following bisphenolic compounds: bis (3-hydroxyphenyl) methane; bis (4-hydroxyphenyl) methane; 1,1-dimethyl-bis (4-hydroxyphenyl)methane, or 9,9-bis (4-hydroxyphenyl) fluorene. Random and block copolymers are also comprehended.

  7. Imide/Arylene Ether Copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Hergenrother, Paul M.; Bass, Robert G.

    1991-01-01

    New imide/arylene ether copolymers prepared by reacting anhydride-terminated poly(amic acids) with amine-terminated poly(arylene ethers) in polar aprotic solvents. Each resulting copolymer may have one glass-transition temperature or two, depending on chemical structure and/or compatibility of block units. Most of copolymers form tough, solvent-resistant films with high tensile properties. Films cast from solution tough and flexible, and exhibit useful thermal and mechanical properties. Potentially useful as moldings, adhesives, or composite matrices. Because of flexible arylene ether blocks, these copolymers easier to process than polyimides.

  8. Complexation of Donor-Acceptor Substituted Aza-Crowns with Alkali and Alkaline Earth Metal Cations. Charge Transfer and Recoordination in Excited State.

    PubMed

    Volchkov, Valery V; Gostev, Fedor E; Shelaev, Ivan V; Nadtochenko, Viktor A; Dmitrieva, Svetlana N; Gromov, Sergey P; Alfimov, Mikhail V; Melnikov, Mikhail Ya

    2016-03-01

    Complexation between two aza-15-crown-5 ethers bearing electron donor and acceptor fragments and alkali and alkaline earth perchlorates has been studied using absorption, steady-state fluorescence and femtosecond transient absorption spectroscopy. The spectral-luminescent parameters, the stability and dissociation constants of the complexes were calculated. The intramolecular charge transfer reaction takes place both in the excited state of the crowns and their complexes 1:1; the latter is subjected to photorecoordination resulting in a weakening or a complete disruption of coordination bond between nitrogen atom and metal cation, disposed within a cavity of the crown. The compounds investigated can be viewed as novel optical molecular sensors for alkali and alkaline-earth metal cations. The photoejection of a metal cation into the bulk was not observed. PMID:26670689

  9. Rearrangements of Cycloalkenyl Aryl Ethers.

    PubMed

    Törincsi, Mercedesz; Nagy, Melinda; Bihari, Tamás; Stirling, András; Kolonits, Pál; Novak, Lajos

    2016-01-01

    Rearrangement reactions of cycloalkenyl phenol and naphthyl ethers and the acid-catalyzed cyclization of the resulting product were investigated. Claisen rearrangement afforded 2-substituted phenol and naphthol derivatives. Combined Claisen and Cope rearrangement resulted in the formation of 4-substituted phenol and naphthol derivatives. In the case of cycloocthylphenyl ether the consecutive Claisen and Cope rearrangements were followed by an alkyl migration. The mechanism of this novel rearrangement reaction is also discussed. PMID:27104504

  10. Imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1992-01-01

    Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

  11. 9. VIEW OF CROWN POINT LOOKING NORTH. VISTA HOUSE, UPPER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. VIEW OF CROWN POINT LOOKING NORTH. VISTA HOUSE, UPPER RETAINING WALL, FLAG POLE AND PARKING LOT IN VIEW. - Historic Columbia River Highway, Crown Point, East of Corbett, Troutdale, Multnomah County, OR

  12. 11. DETAIL VIEW LOOKING EAST OF MASONRY RAILING AT CROWN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. DETAIL VIEW LOOKING EAST OF MASONRY RAILING AT CROWN POINT. ASHLAR EXAMPLE ON LEFT. RANDOM RUBBLE ON RIGHT. BEACON ROCK IN DISTANCE. - Historic Columbia River Highway, Crown Point, East of Corbett, Troutdale, Multnomah County, OR

  13. Castable glass ceramic crowns and their reaction to endodontic therapy.

    PubMed

    Cohen, B D; Wallace, J A

    1991-07-01

    The purpose of this investigation was to determine how castable glass (Dicor) crowns would react to both cold testing and endodontic access intervention. Full crown preparations were made on six extracted maxillary teeth. The teeth were then forwarded to Dentsply International, York, Pa. Six castable glass crowns were fabricated to fit these teeth and returned to us. Subsequently the teeth were dried and the crowns were cemented. Scanning electron micrographs of the cemented crowns were made, and endodontic access openings were drilled. The teeth were also cold tested with standard methods. The teeth were then again subjected to scanning electron microscopy to determine any changes the crowns might have undergone. One crown cracked around the gingival collar as scanning electron microscopy was performed. The other crowns did not exhibit any problems such as cracking or crazing from either the access openings or the cold testing. PMID:1891229

  14. Space, Time, Ether, and Kant

    NASA Astrophysics Data System (ADS)

    Wong, Wing-Chun Godwin

    This dissertation focused on Kant's conception of physical matter in the Opus postumum. In this work, Kant postulates the existence of an ether which fills the whole of space and time with its moving forces. Kant's arguments for the existence of an ether in the so-called Ubergang have been acutely criticized by commentators. Guyer, for instance, thinks that Kant pushes the technique of transcendental deduction too far in trying to deduce the empirical ether. In defense of Kant, I held that it is not the actual existence of the empirical ether, but the concept of the ether as a space-time filler that is subject to a transcendental deduction. I suggested that Kant is doing three things in the Ubergang: First, he deduces the pure concept of a space-time filler as a conceptual hybrid of the transcendental object and permanent substance to replace the category of substance in the Critique. Then he tries to prove the existence of such a space-time filler as a reworking of the First Analogy. Finally, he takes into consideration the empirical determinations of the ether by adding the concept of moving forces to the space -time filler. In reconstructing Kant's proofs, I pointed out that Kant is absolutely committed to the impossibility of action-at-a-distance. If we add this new principle of no-action-at-a-distance to the Third Analogy, the existence of a space-time filler follows. I argued with textual evidence that Kant's conception of ether satisfies the basic structure of a field: (1) the ether is a material continuum; (2) a physical quantity is definable on each point in the continuum; and (3) the ether provides a medium to support the continuous transmission of action. The thrust of Kant's conception of ether is to provide a holistic ontology for the transition to physics, which can best be understood from a field-theoretical point of view. This is the main thesis I attempted to establish in this dissertation.

  15. 28. Photocopy of Crown Roller Mill illustration; originally published in ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. Photocopy of Crown Roller Mill illustration; originally published in The Crown Roller Mill, Northwestern Miller 9 (May 21, 1880): 321; SHOWING WEST SIDE, LOOKING EAST - Crown Roller Mill, 105 Fifth Avenue, South, West Side Milling District, Minneapolis, Hennepin County, MN

  16. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  17. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  18. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  19. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  20. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  1. Ionizable calixarene-crown ethers with high selectivity for radium over light alkaline earth metal ions

    SciTech Connect

    Chen, X.; Ji, M.; Fisher, D.R.; Wai, C.M.

    1999-11-15

    {alpha} particle emitters are of increasing interest as the radionuclide attached to monoclonal antibodies of other targeting mechanisms for applications in cell-directed therapy of cancer. {alpha} particles are more effective than {beta}{sup {minus}} particles for cell-killing and promise a more effective treatment of cancer than other forms of radiation. This is because {alpha} particles have high initial energy (4--8 MeV), short path lengths (40--80 {micro}m, or several cell diameters), and consequently greater energy dissipation per unit length. Cell-directed immunotherapy can help improve irradiation of tumor cells while sparing normal tissues. The success of this approach will require effective chemistry for attaching the radionuclide to the antibody. Therefore, a concerted effort has been directed toward the design of chelating agents capable of holding the desired {alpha}-emitting radionuclide, both selectively and with high stability, to the antibody.

  2. Sulfonimide-containing poly(arylene ether)s and poly(arylene ether sulfone)s, methods for producing the same, and uses thereof

    DOEpatents

    Hofmann, Michael A.

    2006-11-14

    The present invention is directed to sulfonimide-containing polymers, specifically sulfonimide-containing poly(arylene ether)s and sulfonimide-containing poly(arylene ether sulfone)s, and processes for making the sulfonimide-containing poly(arylene ether)s and sulfonimide-containing poly(arylene ether sulfone)s, for use conductive membranes and fuel cells.

  3. Aspergillosis in a red-crowned crane

    USGS Publications Warehouse

    Stroud, R.K.; Duncan, R.M.

    1983-01-01

    An unusual form of pulmonary aspergillosis in a red-crowned crane (Grus japonensis) is described in this report. The major lesion is unique because it closely resembles a lesion referred to as an aspergilloma. An aspergilloma is a single large granulomatous lesion that resembles a tumor and is caused by fungi of the genus Aspergillus.

  4. Cementing porcelain-fused-to-metal crowns.

    PubMed

    Vadachkoria, D

    2009-12-01

    The clinical success of fixed prosthodontic restorations can be complex and involve multifaceted procedures. Preparation design, oral hygiene/micro flora, mechanical forces, and restorative materials are only a few of the factors which contribute to overall success. One key factor to success is choosing the proper cement. Popular use of cements for PFM crowns has shifted from zinc phosphate and glass ionomer cements to resin-reinforced glass ionomer, or RRGI, cements. This change has been rapid and profound. Dental cements have always been less than ideal materials, but this is shift to the relatively new RRGI category justified. Resin-reinforced glass ionomer (RRGI) cements appear to be better than zinc phosphate and glass ionomer cements when placing porcelain-to-metal crowns. RRGI cements, such as RelyX Luting, Fuji Plus and Vitremer Luting Cement, satisfy more of the ideal characteristics of PFM cementation than any other previous cement. Expansion of all three cements has not caused any apparent problems with the cements when used with PFM or metal crowns, but these cements, however, should be avoided when cementing all-ceramic crowns. PMID:20090144

  5. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  6. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  7. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  8. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  9. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  10. Cerec anterior crowns: restorative options with monolithic ceramic materials.

    PubMed

    Reich, Sven; Fiedlar, Kurt

    2013-01-01

    The aim of this article is to discuss the different types of monolithic ceramic crowns that can be placed on anterior teeth with existing shoulder preparations. Anterior crowns were indicated for the teeth 12 to 22 in the present case. The patient, a 65-year-old male, had received all-ceramic crowns 20 years earlier, which had started to develop cracks and palatal fractures over the last few years. The patient's teeth were prepared and four sets of crowns were fabricated using different monolithic ceramic materials: IPS e.max CAD, Cerec Blocs C In, VITABLOCS Real Life, and ENAMIC. Both shade characterization and crystallization firing were performed on the monolithic lithium disilicate glass ceramic crowns. The silicate ceramic crowns received glaze firing alone. The crowns made of hybrid ceramic (ENAMIC) were treated with a polymer sealant. PMID:24555406