- Effects of complexation with 18-crown-6 on the hypernucleofugality of phenyl-λ3-iodanyl groups. Synthesis of vinyl- λ3-iodane·18-crown-6 complex
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(Chemical Equation Presented) 4-tert-Butyl-1-cyclohexenyl(phenyl) (tetrafluoroborato)-λ3-iodane forms a discrete supramolecular complex by the reaction with 18-crown-6. Solvolysis of the cyclohexenyl- λ3-iodane in the presence of 18-crown-6 indicates that the complexation with 18-crown-6 tends to decrease the leaving group ability of hypervalent phenyl-λ3-iodanyl groups.
- Ochiai, Masahito,Suefuji, Takashi,Miyamoto, Kazunori,Shiro, Motoo
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- N,N'-BIS(SUBSTITUTED)-4,13-DIAZA-18-CROWN-6 DERIVATIVES HAVING PI-DONOR-GROUP-SIDEARMS: CORRELATION OF THERMODINAMICS AND SOLID STATE STRUCTURES
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Solution thermodynamic data and solid state structure information are used to show that a series of N,N'-bis(substituted)-4,13-diaza-18-crown-6 (BiBLE) derivatives which lack oxygen or nitrogen donor groups in the sidearms do not utilize the sidearms for binding but show considerable variation in their binding constants.
- Arnold, Kristin A.,Viscariello, Anthony M.,Kim, MinSook,Gandour, Richard D.,Fronczek, Frank R.,Gokel, George W.
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- A Facile Synthesis of Hexa- and Octaethylene Glycols
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One-pot syntheses of hexa- and octaethylene glycol are achieved by the reaction of tri- or tetraethylene glycol with tosyl chloride in the presence of an appropriate base followed by a Williamson-type condensation reaction.
- Nakatsuji, Yohji,Kameda, Nobuko,Okahara, Mitsuo
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- STUDIES OF CROWN ETHER COMPLEXES; ARYLDIAZONIUM ION COMPLEXES
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DNMR studies show that for complexation of aryldiazonium salts 21-crown-7 is the preferred host.
- Krane, Jostein,Skjetne, Tore
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- The Complexation of Alkaline Cations by Crown Ethers and Cryptand in Acetone
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Stability constants and thermodynamic values for the complex formation of alkali ions by crown ethers, diaza crown ethers and cryptands have been measured by means of potentiometric and calorimetric titrations in acetone as solvent.The interactions between the ligands and solvent molecules play an important role for the complex formation.Cryptands form the most stable complexes with alkali ions if inclusion complexes are formed.Even in the case that the salts are not completely dissociated in acetone the presence of ion pairs does not influence the calculated values of the stability constants.
- Buschmann, H.-J.,Cleve, E.,Schollmeyer, E.
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- Facile and rapid synthesis of some crown ethers under microwave irradiation
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A series of crown ethers were synthesized from the reaction of 1,8-dichloro-3,6-dioxaoctane with the appropriate hydroxy compound under microwave irradiation in short times and high yields. Copyright Taylor & Francis Group, LLC.
- Ziafati, Ahmad,Sabzevari, Omolbanin,Heravi, Majid M.
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- Lithium-7 Nuclear Magnetic Resonance and Calorimetric Study of Lithium Crown Complexes in Various Solvents
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Lithium-7 NMR studies have been carried out on lithium ion complexes with crown ethers 12C4, 15C5, and 18C6 in water and in several nonaqueous solvents.In all cases the exchange between the free and complexed lithium ion was fast on the NMR time scale, and a single, population average, resonance was observed.Both 1:1 and 2:1 (sandwich) complexes were observed between lithium ion and 12C4 in nitromethane solution.The stability of the complexes varied very significantly with the solvent.With the exception of pyridine, the stability varies inversely with the Gutmann donor numbers of the solvent.In general, the stability order of the complexes was found to be 15C5*Li+ > 12C4*Li+ >18C6*Li+.Calorimetric studies on thse complexes show that, in most cases, the complex are both enthalpy and entropy stabilized.
- Smetana, Alfred J.,Popov, Alexander I.
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- Properties and applications of cryptand-22 surfactant for ion transport and ion extraction
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A non-ionic cryptand-22 surfactant consisting of a macrocyclic cryptand-22 polar head and a long paraffinic chain (C10H21-Cryptand-22) was synthesized and characterized. The critical micellar concentration (CMC) of the cryptand surfactant in ROH/H2O mixed solvent was determined by the pyrene fluorescence probe method. In general, the cmc of the cryptand surfactant increased upon decreasing the polarity of the surfactant solution. The cryptand surfactant also can behave as a pseudo cationic surfactant by protonation of cryptand-22 or complexation with metal ions. Effects of protonation and metal ions on the cmc of the cryptand surfactant were investigated. A preliminary application of the cryptand surfactant as an ion-transport carrier for metal ions, e.g., Li+, Na+, K+ and Sr2+, through an organic liquid-membrane was studied. The transport ability of the cryptand surfactant for these metal ions was in the order: K+ ≥ Na+ > Li+ > Sr2+. A comparison of the ion-transport ability of the cryptand surfactant with other macrocyclic polyethers, e.g., dibenzo-18-crown-6, 18-crown-6 and benzo-15-crown-5, was studied and discussed. Among these macrocyclic polyethers, the cryptand surfactant was the best ion-transport carrier for Na+, Li+ and Sr2+ ions. Furthermore, a foam extraction system using the cryptand surfactant to extract the cupric ion was also investigated.
- Hwang, Wen-Yu,Shih, Jeng-Shong
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- TEMPLATE EFFECTS. 7. LARGE UNSUBSTITUTED CROWN ETHERS FROM POLYETHYLENE GLYCOLS: FORMATION, ANALYSIS, AND PURIFICATION
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Through the reaction of polyethylene glycols with tosyl chloride and heterogeneous KOH in dioxane not only coronands from crown-4 to crown-8 can be obtained but also larger homologues.A systematic investigation has shown that: i) crown-9 and crown-10 can be formed from nona- and deca-ethylene glycol, respectively, and isolated in pure form; ii) the whole series of polyethylene glycols from tri- to deca-ethylene glycol yields not only the corresponding crown ethers but also higher cyclooligomers that can be analyzed up to about crown-20 by glc: in particular crown-12 and crown-16 were obtained from tetraethylene glycol and purified by column chromatography on cellulose; iii) the reaction, as applied to commercial mixtures of polyethylene glycols (from PEG 200 to PEG 1000), gives fairly high yields of crown ethers also in the region of large ring sizes.The contribution of the template effect of K(+) ion and the cyclooligomerization reactions for the various ring sizes are discussed.
- Vitali, Chiara Antonini,Masci, Bernardo
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- Reactivity with electrophiles of imido groups supported on trinuclear titanium systems
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Several trinuclear titanium complexes bearing amido μ-NHR, imido μ-NR, and nitrido μn-N ligands have been prepared by reaction of [{Ti(η5-C5Me5)(μ-NH)} 3(μ3-N)] (1) with 1 equiv of electrophilic reagents ROTf (R = H, Me, SiMe3; OTf = OSO2CF3). Treatment of 1 with triflic acid or methyl triflate in toluene at room temperature affords the precipitation of compounds [Ti3(η 5-C5Me5)3(μ3-N) (μ-NH)2(μ-NH2)(OTf)] (2) or [Ti3(η 5-C5Me5)3(μ3-N) (μ-NH)(μ-NH2)(μ-NMe)(OTf)] (3). Complexes 2 and 3 exhibit a fluxional behavior in solution consisting of proton exchange between μ-NH2 and μ-NH groups, assisted by the triflato ligand, as could be inferred from a dynamic NMR spectroscopy study. Monitoring by NMR spectroscopy the reaction course of 1 with MeOTf allows the characterization of the methylamido intermediate [Ti3(η5-C 5Me5)3(μ3-N)(μ-NH) 2(μ-NHMe)(OTf)] (4), which readily rearranges to give 3 by a proton migration from the NHMe amido group to the NH imido ligands. The treatment of 1 with 1 equiv of Me3SiOTf produces the stable ionic complex [Ti3(η5-C5Me5) 3(μ3-N)(μ-NH)2(μ-NHSiMe 3)][OTf] (5) with a disposition of the nitrogen ligands similar to that of 4. Complex 5 reacts with 1 equiv of [K{N(SiMe3)2}] at room temperature to give [Ti3(η5-C 5Me5)3(μ3-N)(μ-N)(μ-NH) (μ-NHSiMe3)] (6), which at 85 C rearranges to the trimethylsilylimido derivative [Ti3(η5-C 5Me5)3(μ3-N)(μ-NH) 2(μ-NSiMe3)] (7). Treatment of 7 with [K{N(SiMe 3)2}] affords the potassium derivative [K{(μ3-N)(μ3-NH)(μ3-NSiMe 3)Ti3(η5-C5Me5) 3(μ3-N)}] (8), which upon addition of 18-crown-6 leads to the ion pair [K(18-crown-6)][Ti3(η5-C 5Me5)3(μ3-N)(μ-N)(μ-NH) (μ-NSiMe3)] (9). The X-ray crystal structures of 2, 5, 6, and 8 have been determined.
- Caballo, Jorge,Gonzalez-Moreiras, Mariano,Mena, Miguel,Perez-Redondo, Adrian,Yelamos, Carlos
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- Synthesis and Characterization of Large (30-60-Membered) Aliphatic Crown Ethers
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We report a new synthetic approach to large (30-72 membered) crown ethers based on isolation of the small and large cyclic polyethers made by combination of 1 mol or 2 mol each, respectively, of oligo(ethylene glycol)s and oligo(ethylene glycol) ditosylates.The advantages of this approach are the use of readily available glycols as starting materials and the ability to optimize the procedure for selective production of either macrocycle, producing yields superior or comparable to previous methods.At higher reaction temperatures the large crown ether is preferentially formed.This approach has been used to produce the crown ethers on 100-g scales.Purification was achieved by a combination of filtration through silica gel, treatment with a polymeric acid chloride, and recrystallization techniques, avoiding standard column chromatography.The pure crown ethers, 60-crown-20, 48-crown-16, 42-crown-14, 36-crown-12, and 30-crown-10, were characterized by melting points, 1H- and 13C-NMR, elemental analysis, and/or MS, GC-MS, and TGA-MS.Melting points were as much as 26 deg C higher than previously reported for these crown ethers.All the aliphatic crown ethers larger than 18-crown-6 decompose upon heating in air at ca. 200 deg C.
- Gibson, Harry W.,Bheda, Mukesh C.,Engen, Paul,Shen, Ya Xi,Sze, Jean,et al.
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- Preparation of Macrocyclic Polyether-Thiono Diester and -Thiono Tetraester Ligands Containing either the Pyridine Subcyclic Unit or the Oxalyl Moiety, Their Complexes, and Their Reductive Desulfurization to Crown Ethers
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The preparation of seven new macrocyclic polyether-thiono diesters and one new macrocyclic polyether-thiono tetraester is reported.The new macrocyclic compounds containing a pyridine subcyclic unit formed complexes with metal and alkylammonium salts.Complex formation by some of these ligands was shown by variable-temperature 1H NMR spectroscopy and by cation transport through a CHCl3 membrane.All of the thiono compounds were reductively desulfurized to form the corresponding crown ethers.
- Jones, Brian A.,Bradshaw, Jerald S.,Brown, Philip R.,Christensen, James J.,Izatt, Reed M.
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- The Reduction of Crown Lactones to Crown Ethers
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Crown lactones may be reduced to crown ethers using lithium aluminium hydride.
- Ager, David J.,Sutherland, O.
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- Temperature-dependent IR spectroscopic and structural study of 18-crown-6 chelating ligand in the complexation with sodium surfactant salts and potassium picrate
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18-crown-6 ether (18C6) complexes with the following anionic surfactants: sodium n-dodecylsulfate (18C6-NaDS), sodium 4-(1-pentylheptyl)benzenesulfonate (18C6-NaDBS); and potassium picrate (18C6-KP) were synthesized and studied in terms of their thermal and structural properties. Physico-chemical properties of new solid 1:1 coordination complexes were characterized by infrared (IR) spectroscopy, thermogravimetry and differential thermal analysis, differential scanning calorimetry, X-ray diffraction and microscopic observations. The strength of coordination between Na+ and oxygen atoms of 18C6 ligand does not depend on anionic part of the surfactant, as established by thermodynamical parameters obtained by temperature-dependent IR spectroscopy. Each of these complexes exhibit different kinds of endothermic transitions in heating scan. Diffraction maxima obtained by SAXS and WAXS, refer the behavior of the compounds 18C6-NaDS and 18C6-NaDBS as smectic liquid crystalline. Distortion of 18C6-NaDS and 18C6-KP complexes occurs in two steps. Temperature of the decomplexation of solid crystal complex 18C6-KP is considerably higher than of mesophase complexes, 18C6-NaDS, and 18C6-NaDBS. The structural and liquid crystalline properties of novel 18-crown-ether complexes are function of anionic molecule geometry, type of chosen cation (Na+, K +), as well as architecture of self-organized aggregates. A good combination of crown ether unit and amphiphile may provide a possibility for preparing new functionalized materials, opening the research field of ion complexation and of host-guest type behavior.
- Mihelj, Tea,Toma?i?, Vlasta,Bili?kov, Nikola,Liu, Feng
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- The Synthesis of Unsubstituted Crown Ethers by the Reaction of Oligoethylene Glycols with Arenesulfonyl or Alkanesulfonyl Chlorides
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A new facile method of synthesizing crown ethers from oligoethylene glycols by treating them with arenesulfonyl or alkanesulfonyl chlorides in the presence of alkali metal hydroxide or alkoxide was described. 15-Crown-5 and 21-crown-7 were synthesized from pentaethylene glycol and heptaethylene glycol respectively in good yields, while 18-crown-6 was obtained from both hexaethylene glycol and triethylene glycol.Although the main product was 24-crown-8 in the reaction of tetraethylene glycol/TsCl/Na(K)OH in dioxane, 12-crown-4 was obtained in a moderate yield from the reaction of tetraethylene glycol/benzenesulfonyl chloride/t-BuOLi in t-BuOH.Furthermore, the analogous treatment of PEG 200 afforded a mixture of 15-, 18-, 21- and 24-crown ethers.The reaction conditions were investigated, and the scope of the reaction was discussed.
- Kuo, Ping-Lin,Kawamura, Norio,Miki, Masaki,Okahara, Mitsuo
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- Synthesis and molecular structures of novel isopropyl-substituted oligosilanes
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The cyclotetrasilane [(i-Pr)2Si]4 reacts with K in benzene in the presence of 18-crown-6 to give the 1,4-dipotassio compound K[(i-Pr)2Si]4K (1). The reaction of 1 with (i-Pr)2SiCl2 and Me3SiCl leads to the formation of the sterically crowded oligosilanes, [(i-Pr)2Si]5 (2) and Me3Si[(i-Pr)2Si]4SiMe3 (3), respectively. The molecular structures of the resulting oligosilanes, 2 and 3, display some unusual features.
- Tanaka, Ryoji,Unno, Masafumi,Matsumoto, Hideyuki
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- Preparation and Characterisation of Anionic Bis(cyclopentadienyl)niobium Complexes: Molecular Structure of
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The reaction between and LiBu, LiBu-1,4,7,10-tetraoxacyclododecane (12-crown-4), NaH-1,4,7,10,13-pentaoxacyclopentadecane (15-crown-5), KH-1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6), or NaNH2 gives M (M = Li, 1; or N
- Green, Malcolm L. H.,Hughes, Andrew K.,Mountford, Philip
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- Synthetic method 18- crown ether -6 (by machine translation)
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The preparation 18 - comprises the steps that the reaction time of the product, is less 10h, than, preferably, or more; purity, the product purity, yields, or more and.% or less of the crude product; is purified, times, of the crude product purification . The present invention provides the,product purification method of the product . The present invention provides a process, for producing 35% -crown ether crude by adding, to the crude potassium hydroxide 99.8% by adding, into the crude, product of the present invention at a reaction time of 20h, or more 5h; and less, % by weight of the, crude, product of tetrahydrofuran 15h of the, present invention in the crude product purification by, using acetonitrile in a mixed ;step method. (by machine translation)
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Paragraph 0021; 0024-0037
(2020/05/29)
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- Preparation method of 18-crown-6
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The invention discloses a preparation method of 18-crown-6. The method comprises the following steps of: under the stirring condition, adding a protonated solvent into a reaction flask filled with triethylene glycol and potassium hydroxide; then dropwise adding paratoluensulfonyl chloride into the reaction flask, controlling a reaction temperature to be within a range of 30 to 80 DEG C and controlling reaction time to be within a range of 2 to 6h; adding a separating agent into solution obtained after reaction for separating a potassium p-toluenesulfonate by-product, controlling a reaction temperature to be within a range of 70 to 100 DEG C, and controlling reaction time to be within a range of 3 to 6h; carrying out filtering, concentration and vacuum distillation on the obtained solution,washing distillate with distilled water, carrying out standing layering, settling lower solution by centrifugal separation, and drying sediments, so as to obtain the 18-crown-6. The preparation method disclosed by the invention is simple; when a high reaction rate and a high reactant conversion rate are ensured, the subsequent separation operation is also simplified, subsequent processing links are reduced, and purity of the final product is ensured.
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Paragraph 0022-0045
(2020/02/17)
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- A 18 - crown ether -6 synthetic method (by machine translation)
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The invention discloses a 18 - crown ether - 6 synthesis approach, the method is: in industrial microwave reactor is sequentially added in 1 to [...] alcohol methyl benzene sulfonic acid, 1.01 - 1.5 [...] of dihydric alcohol, 2 - 20 mol of alkali, 0 - 10 molar parts of solvent, for 0 °C -40 °C reaction under 10 minutes to 5 hours, after the reaction, and then after removing salt separation, extraction, evaporate the solvent, the crude product is distilled under reduced pressure, get the 18 - crown - 6. The technique has the room temperature, the reaction time of the ultra-short, and labor, high yield, water can be adopted as the solvent characteristics, is suitable for industrial production, can greatly reduce cost, energy-saving, and improves productivity, there is a significant economic benefits. (by machine translation)
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Paragraph 0028; 0029
(2018/09/11)
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- Hypervalent phenyl-λ3-iodane-mediated para-selective aromatic fluorination of 3-phenylpropyl ethers
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Exposure of 3-phenylpropyl ethers to an activated iodosylbenzene monomer·18-crown-6 complex [PhI(OH)BF4·18C6] in the presence of BF3-Et2O and water results in the para-selective monofluorination of benzene ring via neighboring alkoxy group participation and directly affords 3-(4-fluorophenyl)propyl ethers regioselectively in good yields.
- Saito, Motomichi,Miyamoto, Kazunori,Ochiai, Masahito
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supporting information; experimental part
p. 3410 - 3412
(2011/05/03)
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- Organic hole transporting and blue light emitting electroluminescent materials
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A tertiary amine imparted quaterphenyl compound represented by the following formula: where R1and R2, which can be different or the same, are hydrogen, C1-C5alkyl, or C6-C12aryl, and R3is hydrogen, C1-C5alkyl, a vinyl group, or an aryl vinyl group. The tertiary amine-imparted quaterphenyl compound exhibits good blue light luminescence and hole-transportability, and can be used in forming a hole-transporting layer, a blue light emitting layer, or a combined hole-transporting and light emitting layer of a light emitting organic electroluminescent device. Examples of the quaterphenyl compounds include N-quaterphenyl-4-yl-N,N-diphenylamine, N-(4′-(1,1-diphenylvinyl)quaterphenyl-4-yl)-N-phenyl-N-(m-tolyl)amine, or N-quaterphenyl-4-yl-N-phenyl-N-(m-tolyl)amine.
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- Thermodynamics of intermolecular interactions between saccharides and 18-crown-6 in water
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The intermolecular complexes of D-galactose, D-maltose, sucrose and raffinose with 18-crown-6 were found to be entropy stabilised.
- Parfenyuk, Elena V.,Davydova, Olga I.,Lebedeva, Nataliya Sh.,Agafonov, Alexander V.
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- NMR spectra of guest-host complexes of boron and silicon fluorides with crown ethers in nonaqueous solutions
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19F, 11B, and 29Si NMR spectroscopy was used to examine the behavior of the guest-host complexes (BF3·H2O) 2·18-crown-6·2H2O, (BF3·H2O)2·DCH-6B,
- Gel'mbol'dt,Selig,Ganin,Fonar',Ennan
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p. 150 - 151
(2008/10/08)
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- Thermodynamic study of some pyridinium ion derivatives with 18-crown-6, aza-18-crown-6 and 1,10-diaza-18-crown-6 in acetonitrile
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The complexation between the salts of protonated of pyridine, 2-methyl pyridine, 2,4-dimethyl pyridine and 2,4,6-trimethyl pyridine and macrocyclic ligands 18-crown-6, aza-18-crown-6 and 1,10-diaza-18-crown-6 have been studied conductometrically in acetonitrile at different temperature. Formation constants of the resulting 1:1 complexes were determined by the computer fitting of the molar conductance-mole ratio data. The stability of complexes decrease in the sequence: 1,10-diaza-18-crown-6 > aza-18-crown-6 > 18-crown-6. The enthalpy and entropy of complexation were determined from the temperature dependence of the formation constants. In all cases, the complexes were enthalpy stabilized, but entropy destabilized.
- Ganjali,Khoshdan,Hashemi,Seiyed Sajjadi
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p. 1389 - 1398
(2007/10/03)
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- Conductance study of binding of some Rb+ and Cs+ ions by macrocyclic polyethers in acetonitrile solution
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A conductance study of the interaction between Rb+ and Cs+ ions and 18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6), dibenzo-24-crown-8 (DB24C8), and dibenzo-30-crown-10 (DB30C10) in acetonitrile solution has been carried out at various temperatures. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data and found to vary in the order DC18C6 > 18C6 > DB30C10 > DB18C6 ~ DB24C8 for Rb+ ion and DC18C6 > 18C6 > DB30C10 ~ DB24C8 > DB18C6 for Cs+ ion. The enthalpy and entropy of complexation were determined from the temperature dependence of the formation constants. The complexes with the 18-crowns are both enthalpy and entropy stabilized while, in the case of large crown ethers, the corresponding complexes are enthalpy stabilized but entropy destabilized.
- Shamsipur, Mojtaba,Saeidi, Mahboubeh
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p. 1187 - 1198
(2007/10/03)
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- The association of an ionic surfactants with β-cyclodextrin. An isothermal titration calorimeter study
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The association of a series of anionic surfactants (CnH2n+1SO4Na, n = 6, 8, 10, 12, 14) with β-cyclodextrin was studied by means of the isothermal titration calorimeter (i.t.c.) at T = 298.15 K. For these types of inclusion complexes, the results agreed well with a 1:1 association mode. Apparent values for the association constants, and changes in the standard molar Gibbs energies, enthalpies, and entropies were derived for the association process. The results indicated that the association of surfactants with β-cyclodextrin is characterized by both favourable enthalpy and favourable entropy changes. The results also demonstrated that the longer the alkyl chain of the anionic surfactant, the greater the association constant with β-cyclodextrin.
- Eli, Wumanjiang,Chen, Wenhai,Xue, Qunji
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p. 1283 - 1296
(2007/10/03)
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- Constants of Complex Formation of Na+ and K+ Ions with 18-Crown-6 in Water-Acetonitrile Mixtures
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Constants of complex formation of Na+ and K+ ions with 18-crown-6 in water-acetonitrile mixtures (20, 40, and 60 wt %) were measured by the method of electromotive forces of voltaic cells without transport. Thermodynamic functions of complex formation were calculated. The enthropy and enthalpy of complex formation between M+ and 18-crown-6 were analyzed.
- El'tsov,Yurchenko,Bondarev
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p. 535 - 538
(2007/10/03)
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- The macrobicyclic cryptate effect in the gas phase
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The alkali cation (Li+, Na+, K+, Rb+, and Cs+) binding properties of cryptands [2.1.1], [2.2.1], and [2.2.2] were investigated under solvent-free, gas-phase conditions using Fourier transform ion cyclotron resonance mass spectrometry. The alkali cations serve as size probes for the cryptand cavities. All three cryptands readily form 1:1 alkali cation complexes. Ligand-metal (2:1) complexes of [2.1.1] with K+, Rb+, and Cs+, and of [2.2.1] with Rb+ and Cs+ were observed, but no 2:1 complexes of [2.2.2] were seen, consistent with formation of 'inclusive' rather than 'exclusive' complexes when the binding cavity of the ligand is large enough to accommodate the metal cation. Kinetics for 2:1 ligand-metal complexation, as well as molecular mechanics calculations and cation transfer equilibrium constant measurements, lead to estimates of the radii of the cation binding cavities of the cryptands under gas-phase conditions: [2.1.1], 1.25 ?; [2.2.1], 1.50 ?; [2.2.2], 1.65 ?. Cation transfer equilibrium studies comparing cryptands with crown ethers having the same number of donor atoms reveal that the cryptands have higher affinities than crowns for cations small enough to enter the cavity of the cryptand, while the crowns have the higher affinity for cations too large to enter the cryptand cavity. The results are interpreted in terms of the macrobicyclic cryptate effect: for cations small enough to fit inside the cryptand, the three-dimensional preorganization of the ligand leads to stronger binding than is possible for a floppier, pseudo-two-dimensional crown ether. The loss of binding by one ether oxygen which occurs as metal size increases for a given cryptand is worth approximately 25 kJ mol-1, and accounts for the higher cation affinities of the crowns for the larger metals. The Li+ affinity of 1,10-diaza-18-crown-6 is ~1 kJ mol-1 higher than that of 18-crown-6, while the latter has lower affinity than the former for all of the larger alkali cations (about 7 kJ mol-1 lower for Na+, and about 15 kJ mol-1 lower for K+, Rb+, and Cs+). The equilibrium measurements also allow the determination of relative free energies of cation binding for a number of crown ethers and cryptands. Molecular mechanics modeling with the AMBER force field is generally consistent with the experiments.
- Chen, Qizhu,Cannell, Kevin,Nicoll, Jeremy,Dearden, David V.
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p. 6335 - 6344
(2007/10/03)
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- Hydrogenolysis and One-Electron Reduction of Alkoxy Sulfones
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The readily available 1-t-butoxyalkyl sulfones were converted by hydride reduction into alkyl t-butyl ethers.Reductive coupling with sodium metal or amalgam in an aprotic solvent led to glycol bis-1,2-O-t-butyl ethers.Polyethers such as 18-crown-6 can be synthesized by this procedure.
- Julia, Marc,Uguen, Daniel,Zhang, Da
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p. 279 - 290
(2007/10/02)
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- Macrocyclic chemistry in the gas phase: intrinsic cation affinities and complexation rates for alkali metal cation complexes of crown ethers and glymes
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Reactions of 12-crown-4, 15-crown-5, 18-crown-6, and 21-crown-7, as well as the acyclic analogs triglyme, tetraglyme, and penta(ethylene glycol), with Li+, Na+, K+, Rb+, and Cs+, are observed and characterized using Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS) and tandem quadrupole mass spectrometry in the gas phase to obtain information on intrinsic host-guest interactions in the absence of the complicating effects of solvation. Radiatively stabilized attachment of the cations to the ligands is a rapid process, with rates in some cases a factor of 2 or more times the Langevin collision rate. The attachment efficiencies increase linearly with cation charge density, suggesting that attachment involves charge-induced rearrangement of the ligands to adopt favorable binding conformations. Attachment is more efficient, and more strongly dependent on charge density, for the cyclic ligands than for their acyclic counterparts. Metal-ligand undergo reaction with a second ligand to form 1:2 metal-ligand complexes, or "sandwiches". The efficiencies of crown sandwich formation are strongly dependent on the ratio of cation radius to binding cavity radius; when the ratio is than one, the efficiencies are too low to measure, but they become measurable at a ratio of 1:1 and increase by about 4 orders of magnitude as the ratio incrrases to about 1.25:1, At higher ratio values, efficiencies fall off slowly, probably due to decreasing cation density. The relative cation affinities of the various ligands are compared both collision-induced dissociation "kinetic" methods, with the tandem quadrupole, and using "bracketing" cation reactions in the FTICR. The tandem quadrupole results are in some cases dependent on the means of producing the 1;2 metal-ligand complexes, and in some cases they do not agree with the FTICR results. The two methods are compared and reasons for the discrepancies are discussed. We favor the FTICR results, which indicate that proton and alkali cation affinities increase with an increase in the number of oxygen donor atoms in the crowns. Equilibria observed in metal exchange reactions between 18-crown-6 and 21-crown-7 were found to always lie on the side of the cation bound to the larger ligand, but K+ has the smallest equilibrium constant of any of the alkali metals, reflecting the excellent size match between K+ and 18-crown-6.
- Chu, In-Hou,Zhang, Hong,Dearden, David V.
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p. 5736 - 5744
(2007/10/02)
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- Role of the macrocyclic polyether in the synthesis of N-alkylcarbamate ester from primary amines, CO2 and alkyl halides in the presence of crown-ethers
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Primary amines, RNH2 1, and CO2 easily afford monoalkylammonium N-alkylcarbamates, [RNH3][O2CNHR] 2, that have been reacted with alkyl halides, R'X, in the presence of crown-ethers to give organic carbamates in good yield. We report here the synthesis and spectroscopic characterization of some alkylammonium carbamates 2, where R - benzyl 2a, allyl 2b, ter-butyl 2c, cyclohexyl 2d, and discuss their stability in solution and the conditions in which they can react with alkyl halides to give organic carbamates, RNHC(O)OR'. The role played by the macrocyclic ligand in modifying the reactivity of monoalkylammonium carbamates 2 towards R'X has been rationalized and the influence of parameters such as solvent, temperature and CO2 pressure on the yield and selectivity of the process leading to organic carbamates has been also settled.
- Aresta,Quaranta
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p. 1515 - 1530
(2007/10/02)
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- Effect of an ortho-Substituent on the Decomposition of Crown Ether Complexed Arenediazonium Ions in 1,2-Dichloroethane
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The effect of an o-substituent (CH3, C2H5 and COCH3) on the complexation and the kinetics of thermal decomposition of arenediazonium tetrafluoroborates in the presence of crown ethers (15-crown-5, 18-crown-6 and 21-crown-7) and the effect of temperature on the decomposition of the complexed ions were studied by UV spectrophotometry in 1,2-dichloroethane.Solid 1:1 complexes were prepared and analyzed (by IR spectroscopy and by decomposition temperature).In the solid state, none of the arenediazonium ions is stabilized by complexation with crown ethers.In solution they form at most very weak charge-transfer complexes with 15-crown-5 but stronger insertion-type complexes with the larger 18-crown-6 and 21-crown-7 molecules (except for the o-acetyl-substituted ion, which is destabilized with increasing and ).The values of the complexation equilibrium constant K and the stabilization ability of the complexation are largest for 21-crown-7, and are much smaller than the corresponding values for the complexation of p- or m-substituted arenediazonium ions with the same complexing agents: e.i. there are clear ortho-effects due to the steric hindrance for the complexation.The values of the activation parameters ΔH and ΔS for the thermal decomposition of the complexed ions are large and positive (largest for 21-crown-7) and suggest an isokinetic relationship for each ion.The complexation in solution causes a hypsochromic shift in the UV spectrum of the arenediazonium ion which is proportional to the strength of the complexation.
- Kuokkanen, Toivo,Slotte, Thomas,Virtanen, Vesa
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p. 674 - 680
(2007/10/02)
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- An Unusual Reduction of Ethylene Occurring during the Thermal Decomposition of Alkalides and Electrides
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Alkalides and electrides thermally decompose by a reductive elimination process leading to the formation of ethylene and a ring opened complexant which has lost an ethylenic unit.Surprisingly, gas phase nmr also shows the formation of ethane and butane.We postulated that these compounds arise from a reduction of the first-formed ethylene by the alkalide or electride.
- Cauliez, P. M.,Jackson, J. E.,Dye, J. L.
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p. 5039 - 5042
(2007/10/02)
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- Process for the preparation of the parylene dimer
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An improved process is provided for the preparation of the dimer, 2,2-paracyclophane, which is useful as the starting material for parylene conformal coatings used in the electronics industry for the protection of various sensitive electronic components. The process comprises optimization of the normally low yield of dimer formed by the Hofmann elimination reaction of p-methylbenzyltrimethylammonium hydroxide by conducting the elimination reaction in the presence of a cosolvent and certain reaction promoters.
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- Excited-State Proton-Transfer Reactions of Naphthylammonium Ion-18-Crown-6 Complexes
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Proton-transfer reactions in the excited singlet state of naphthylammonium ion-18-crown-6 complexes in MeOH-H2O (9:1) mixtures have been studied by means of the single photon counting method with fluorimetry.It is found that the complex formation of naphthylammonium ions with 18-crown-6 decreases markedly the proton-transfer rate (k1) in the excited state, resulting in an increase of its lifetime.The back protonation rate in the excited state is negligibly small compared with those of the other decay processes; there is no excited-state prototropic equilibrium in the naphthylammonium ion-crown complexes (RN(1+)H3-crown).The one-way proton transfer reaction is elucidated by the presence of the excited neutral amine-crown complex (RNH2-crown)* produced by deprotonation of (RN(1+)H3-crown)*, where protonation to the amino group is structurally blocked by 18-crown-6 and the naphthyl group (R) of the complex.However, proton-induced quenching (k'q) occurs effectively especially in the 1-naphthylammonium ion-crown complex.The ground-state association constants (Kg) of the complexes can be determined easily by the fluorescence titration method.Temperature effects upon the excited-state proton-transfer reactions of the complexes have been also carried out in order to study their thermodynamic properties.A Corey-Pauling-Kolton model of the anilinium ion-18-crown-6 complex proposed by Izatt et al. is strongly supported by the present work.
- Shizuka, Haruo,Kameta, Kosei,Shinozaki, Tsutomu
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p. 3956 - 3963
(2007/10/02)
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- AFFINITIES OF CROWN ETHERS, GLYMES, AND POLYAMINES FOR ALKALI PICRATES IN TOLUENE. APPLICATION OF POLYMER-SUPPORTED LINEAR POLYETHERS.
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This work reports the measurements of K values for polyamines, glymes, a few glycols (including that of a long-chain polyethylene glycol, carbowax 6000), and some frequently used cation-binding ligands as complexers of lithium or sodium picrate in toluene as solvent. K values for different resins obtained with the same soluble ligand provide a comparison of the effectiveness of these resins in binding ionic solutes.
- Xu,Smid
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p. 3790 - 3796
(2007/10/02)
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- Chemistry of crown ethers (XVI). A safe and efficient procedure for the isolation and purification of crown ethers by complex formation with alkaline earth metal alkanedisulfonates
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A safe, efficient and selective method has been developed for the isolation and purification of crown ethers to replace the conventional procedure, which involves repeated vacuum distillations and has reportedly led to destructive explosions.The method is based on the formation of an insoluble 1 : 1 complex upon stirring a solution of a crown ether in an organic solvent with solid metal salts of 1,n-alkanedisulfonic acids, such as barium and strontium methanedisulfonate and barium 1,2-ethanedisulfonate.This extraction procedure can be applied to several crown ethers (including 18-crown-6) dissolved in a variety of solvents.Almost quantitative recovery of the crown ether is achieved by continuous extraction with nitromethane.The usefulness of the method was illustrated by isolating 18-crown-6 from the crude mixture obtained in the course of its preparation.Whereas conventional workup (including two distillation steps) gave a 25percent yield of pure 18-crown-6, the CH2(SO3)2Ba-based method gave a yield of 34percent.
- Jong, F. de,Reinhoudt, D. N.,Zon, A. van,Torny, G. J.,Vondervoort, E. M. van de
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p. 449 - 452
(2007/10/02)
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- USE OF ALKALI- AND ALKALINE-EARTH-METAL IONS IN THE TEMPLATE SYNTHESIS OF 12-CROWN-4, 15-CROWN-5, AND 18-CROWN-6
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The synthesis of 15-crown-5 and 18-crown-6 from bis(2-chloroethyl)ether and the appropriate polyethylene glycol has been investigated using alkali- and alkaline-earth-metal hydroxides as 'template' agents in comparison to tetra-n-butylammonium hydroxide.A classical template effect is observed for the alkali metals, giving optimum yields for Na and K in the synthesis of 15-crown-5 and 18-crown-6 respectively, but the action of the alkaline-earth metals is more complex, particularly for Mg and Ca where involvement with the counter ion prevents a good yield.The importance of base strenght in the synthesis of 15-crown-5 and 12-crown-4 is demonstrated, e.g. in the synthesis of 15-crown-5 the most effective base is found to be sodium methoxide.A novel synthesis of 12-crown-4, utilising lithium hydride as the base, gives a 24 percent yield, the highest yield so far reported.
- Bowsher, Brian R.,Rest, Antony J.
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p. 1157 - 1161
(2007/10/02)
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- Chemistry of crown ethers XVIII. Isolation and purification of 18-crown-6 by selective complexation with non-ionic compounds
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A number of non-ionic compounds have been found to form solid complexes with 18-crown-6.The highest efficiencies of isolation and the highest selectivities were obtained with nitromethane, dimethyl carbonate and dimethyl oxalate.The usefulness of these compounds was demonstrated in the isolation of >98percent pure 18-crown-6 from crude reaction mixtures.
- Zon, A. van,Jong, F. de,Reinhoudt, D. N.,Torny, G. J.,Onwezen, Y.
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p. 453 - 459
(2007/10/02)
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- Influence of Steric and Electronic Effects on the Binding of Arenediazonium Cations to 18-Crown-6 in Methanol at 25 deg C
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Log K, ΔH, and TΔS values for the interaction of several arenediazonium salts with 18-crown-6 were determined in methanol at 25 deg C by the calorimetric titration technique.The complex of benzenediazonium cation with 18-crown-6 is enthalpy stabilized with log K = 2.50.Substitution of a methyl group onto the ortho position(s) of benzenediazonium cation results in a total loss of complex stability.Substitution of various groups onto the para position results in changes in complex stability according to the electronic effect exerted in the diazonium moiety.A linear Hammett relationship (ρ = 0.65) was found between log K and ?+p values associated with the para substituent.
- Izatt, R. M.,Lamb, J. D.,Swain, C. S.,Christensen, J. J.,Haymore, Barry L.
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p. 3032 - 3034
(2007/10/02)
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- POTASSIUM FLUORIDE ON ALUMINA AS BASE FOR CROWN ETHER SYNTHESIS
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Alumina coated with potassium fluoride was found to be an effective and practical reagent for the synthesis of some simple crown ethers.
- Yamawaki, Junko,Ando, Takashi
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p. 533 - 536
(2007/10/02)
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- COMPLEXES OF LANTHANIDE IONS WITH THE CROWN ETHER 1,4,7,10,13,16-HEXAOXACYCLO-OCTADECANE
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The title crown ether forms three types of compound with lanthanide ions, (M=La-Nd), M4(NO3)12(crown)3 (M=La-Gd), and crown (M=Gd-Lu).Crystal structures of the first and third types have been determined by X-ray diffraction.The complex is orthorombic, space group Pbca, with a=12.249, b=15.618, c=21.852 Angstroem, and Z=8.Least-squares refinement using 3607 observed 1.5?(I)> intensity data has given R=0.0399.The lanthanum co-ordination comprises the six crown oxygens and two oxygens from each of the three bidentate nitrates molecule by O...HO bonds.The Gd-O bond lengths are 2.41-2.53(1) Angstroem for nitrato- and 2.30-2.46(1) Angstroem for water oxygens.
- Backer-Dirks, J. D. Julius,Cooke, James E.,Galas, Anita M. R.,Ghotra, Joginder S.,Gray, Colin J.,at all.
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p. 2191 - 2207
(2007/10/02)
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