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1.
It is shown by means of IR. spectroscopic methods that nigericin and monensin have a cyclic conformation similar to that of their silver salts. Complex formation constants with sodium and potassium ions follow the selectivity order determined by EMF. measurements on liquid membranes: nigericin: K+ > Rb+ > Na+ > Cs+ > Li+; monensin: Na+ > K+ > Li+ > Rb+ > Cs+. Transport experiments show that nigericin and monensin facilitate the diffusion of potassiumions across model membranes, although in electrolytic transport experiments the permeability is not affected. 相似文献
2.
Alireza Najafi Chermahini Mehdi Rezapour Abbas Teimouri 《Journal of inclusion phenomena and macrocyclic chemistry》2014,79(1-2):205-214
A density functional theory based on interaction of alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) with cyclic peptides constructed from 3 or 4 alanine molecule (CyAla3 and CyAla4), has been investigated using mixed basis set (C, H, O, Li+, Na+ and K+ using 6-31+G(d), and the heavier cations: Rb+ and Cs+ using LANL2DZ). The minimum energy structures, binding energies, and various thermodynamic parameters of free ligands and their metal cations complexes have been determined with B3LYP and CAM-B3LYP functionals. The order of interaction energies were found to be Li+ > K+ > Na+ > Rb+ > Cs+ and Li+ > Na+ > K+ ? Rb+ > Cs+, calculated at CAM-B3LYP level for the M/CyAla3 and M/CyAla4 complexes, respectively. Their selectivity trend shows that the highest cation selectivity for Li+ over other alkali metal ions has been achieved on the basis of thermodynamic analysis. The main types of driving force host–guest interactions are investigated, the electron-donating O offers lone pair electrons to the contacting LP* of alkali metal cations. 相似文献
3.
Selectivity of Crystalline CeIV Phosphate Sulphate Hydrates for Li+, Na+, K+, Rb+, Cs+, and NH in Absolute Methanol and Absolute Dimethylsulphoxide The sequence of exchange capacities of Cerium(IV) phosphate sulphate hydrate (CePO4)2(HPO4)0.74(SO4)0.26 · 4,74 H2O for alkalimetal ions and ammoniumions in absolute methanol at 25°C for the case of a small excess of the exchanger (in relation to the equivalent amount) is given by K+ > Rb+ ≥ NH4+ > Cs+ > Na+ > Li+. Between the exchange capacity A of these cations and their ionic radii r (given by Ladd) exists the simple relation A = const./r. For Na+ the radius of the inner hydration shell must be considered. In absolute dimethyl-sulphoxide under the same conditions the sequence is K+ ≥ NH4 > Rb+ > Na+ > Cs+ > Li+. For K+, NH4, Rb+ and Cs+ the exchange capacity is given by A = const./r + const. · r4. The sequences of the alkali ions in both solvents are among the group of 13 sequences which are physicaly significant according to EISENMANNS 's theory. The results are compared with the observations made with water as solvent. 相似文献
4.
《液相色谱法及相关技术杂志》2012,35(11):2115-2125
Abstract Stationary phases which have great affinity for Na+ were synthesized by incorporating 12-crown-4 polymer on silica gel for liquid chromatography of alkali and alkaline-earth metal ions. The stationary phases interact with Na+ most strongly of all alkali metal ions as expected, and the retention times on liquid chromatography of alkali metal ions were in the sequence Li+ < Cs+ < Rb+ < K+ < Na+. On the stationary phase, a mixture of Li+, Na+, and K+ can be separated completely by the elution with water/methanol mixture. By the use of spherical type silica gel instead of irregular type one and by effective end-capping of the residual silanol groups, the peak symmetry was improved significantly. 相似文献
5.
Pengyang Xin Huiyuan Kong Yonghui Sun Lingyu Zhao Haodong Fang Haofeng Zhu Tao Jiang Jingjing Guo Qian Zhang Wenpei Dong Chang‐Po Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2805-2810
A class of artificial K+ channels formed by pillararene‐cyclodextrin hybrid molecules have been designed and synthesized. These channels efficiently inserted into lipid bilayers and displayed high selectivity for K+ over Na+ in fluorescence and electrophysiological experiments. The cation transport selectivity of the artificial channels is tunable by varying the length of the linkers between pillararene and cyclodexrin. The shortest channel showed specific transmembrane transport preference for K+ over all alkali metal ions (selective sequence: K+ > Cs+ > Rb+ > Na+ > Li+), and is rarely observed for artificial K+ channels. The high selectivity of this artificial channel for K+ over Na+ ensures specific transmembrane translocation of K+, and generated stable membrane potential across lipid bilayers. 相似文献
6.
V. I. Volkov E. V. Volkov S. V. Timofeev E. A. Sanginov A. A. Pavlov E. Yu. Safronova I. A. Stenina A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2010,55(3):318-324
Water self-diffusion and ion mobilities in various ionic forms (H+, Li+, Na+, Rb+, Cs+, and Ba2+) of perfluorinated sulfocationic membranes MF-4SK were studied by NMR and impedance spectroscopy. When degrees of hydration
are low, the self-diffusion coefficients of water and ionic conductivities are considerably affected by the water content
of the membrane. The self-diffusion coefficients decrease in the order H+ > Ba2+ > Cs+ > Rb+ > Na+ > Li+, whereas the ion mobility decreases in the order H+ > Li+ > Na+ > Cs+ > Ba2+. 相似文献
7.
Measurements by fluoride ion-selective electrode potentiometry on the very weak monofluoride complexes of the alkali metal ions in aqueous solution at 25°C and an ionic strength of 1M indicate their stability constants lie in the order Li+ > Na+ > K+ > Rb+ ? Cs+. Data at varying ionic strengths and temperatures were used to calculate infinite dilution stability constants and enthalpies and entropies of complexation for LiF and NaF. 相似文献
8.
Farrokh Gharib Noushin Osouleddini Karim Zare Saeed Taghvaei-Ganjali 《Russian Journal of Inorganic Chemistry》2010,55(3):434-437
The synthesis and complexive abilities of 5,11,17-tris(tert-butyl)-23 amino-25,26,27,28-tetra-propoxycalix[4]arene towards
alkali cations Li+, Na+, K+, Rb+, Cs+ and alkali earth cations Mg2+, Ca2+, Sr2+ and Ba2+ in methanol-chloroform mixture have been evaluated at 25°C, using UV-Vis spectrophotometric techniques. The results showed
that the ligand is capable to complex with all the cations by 1: 1 metal to ligand ratios. The selectivity presented considering
the calculated formation constants are in the order Li+ > Na+ > K+ > Rb+ > Cs+ and Mg2+ > Ca2+ > Sr2+ > Ba2+ with the ligand. 相似文献
9.
Abhijit Chatterjee 《Journal of Chemical Sciences》2005,117(5):533-539
Clays are layered alumino-silicates. Clays swell and expand in aqueous solution. This property governs the usage of these
materials in synthesis of nano-composites and is a source of many of its catalytic applications. We used both localized and
periodic calculations within the realm of density functional theory (DFT) on a series of monovalent (Li+, Na+, K+, Rb+, Cs+), and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations, to monitor their effect on the swelling of clays. The activity order obtained for the exchangeable cations among
all the monovalent and divalent series studied is: Mg2+ > Ca2+ > Sr2+ > Ba2+ > Cs+ > Rb+ > Na+ > Li+ > K+. We have studied two types of clays, montmorillonite and beidellite, with different surface structures and with/without water
using periodic calculations. We have calculated the layer spacing at the first, second and third hydration shells of exchangeable
cation, to compare with the experimentald-spacing values to correlate with humidity. A novel quantitative scale is proposed in terms of the intermolecular relative
nucleophilicity of the active cation sites in their hydrated state through Fukui functions using hard-soft acid base (HSAB)
principle. Finally, a swelling mechanism is proposed. This is a unique study where a combination of periodic and localized
calculations has been performed to validate the capability of reactivity index calculations in material designing. 相似文献
10.
V. I. Volkov E. V. Volkov S. V. Timofeev E. A. Sanginov A. A. Pavlov E. Yu. Safronova I. A. Stenina A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2010,55(3):315-317
Water self-diffusion and ion mobilities in various ionic forms (H+, Li+, Na+, Rb+, Cs+, and Ba2+) of perfluorinated sulfocationic membranes MF-4SK were studied by NMR and impedance spectroscopy. When degrees of hydration are low, the self-diffusion coefficients of water and ionic conductivities are considerably affected by the water content of the membrane. The self-diffusion coefficients decrease in the order H+ > Ba2+ > Cs+ > Rb+ > Na+ > Li+, whereas the ion mobility decreases in the order H+ > Li+ > Na+ > Cs+ > Ba2+. 相似文献
11.
《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1994,33(1):83-90
The transporting ability of a new monensin derivative 26-(1,2-diphenyl-1-ethoxy) monensin, highly active against Gram-positive bacteria, was explored with the human erythrocyte model using three technical approaches: 23Na nuclear magnetic resonance (internal Na+), K+ atomic absorption (external K+) and H+ potentiometry (external H+) and compared with monensin 1 and 26-(4-chlorophenylurethane) monensin 3 of known transport selectivities for sodium and potassium respectively. Compound 2 proved to be a good carrier for both Na+ and K+ under our experimental conditions, thus constituting a new type of monensin derivative. The introduction of Li+, Rb+ or Cs+ in the external buffer as a replacement for Na+ led us to propose the transport sequence K+, Na+ ⪢ Rb+ > Li+ > Cs+ for 2. 相似文献
12.
The behaviour of Na+, K+, Rb+ and Cs+ ions on hydrated antimony pentoxide (HAP) has been studied, in various acid media and in ammonium hydroxide. The retention capacity of HAP for the alkali metal ions, as well as their retention rate, has been determined in all the media studied. Curves showing the variation of distribution coefficient values with acid or base concentration are presented. 相似文献
13.
F. Koike 《Chemical physics letters》1979,60(2):271-274
Core—core interaction potentials of alkali diatomic molecular ions are calculated for all the heteronuclear combinations of H+, Li+, Na+, K+, Rb+ and Cs+. The Thomas—Fermi—Dirac statistical model is employed to calculate the short-range repulsive interaction potential. The interaction due to core polarization is estimated. 相似文献
14.
Yan Li Xiaojun Wang Juanfang Wang 《Journal of Thermal Analysis and Calorimetry》2012,110(3):1199-1206
Na-montmorillonites were exchanged with Li+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, and Ba2+, while Ca-montmorillonites were treated with alkaline and alkaline earth ions except for Ra2+ and Ca2+. Montmorillonites with interlayer cations Li+ or Na+ have remarkable swelling capacity and keep excellent stability. It is shown that metal ions represent different exchange ability as follows: Cs+?>?Rb+?>?K+?>?Na+?>?Li+ and Ba2+?>?Sr2+?>?Ca2+?>?Mg2+. The cation exchange capacity with single ion exchange capacity illustrates that Mg2+ and Ca2+ do not only take part in cation exchange but also produce physical adsorption on the montmorillonite. Although interlayer spacing d 001 depends on both radius and hydration radius of interlayer cations, the latter one plays a decisive role in changing d 001 value. Three stages of temperature intervals of dehydration are observed from the TG/DSC curves: the release of surface water adsorbed (36?C84?°C), the dehydration of interlayer water and the chemical-adsorption water (47?C189?°C) and dehydration of bound water of interlayer metal cation (108?C268?°C). Data show that the quantity and hydration energy of ions adsorbed on montmorillonite influence the water content in montmorillonite. Mg2+-modified Na-montmorillonite which absorbs the most quantity of ions with the highest hydration energy has the maximum water content up to 8.84%. 相似文献
15.
The facilitated transfer of alkali metal ions (Na+, K+, Rb+, and Cs+) by 25,26,27,28‐tetraethoxycarbonylmethoxy‐thiacalix[4]arene across the water/1,2‐dichloroethane interface was investigated by cyclic voltammetry. The dependence of the half‐wave transfer potential on the metal and ligand concentrations was used to formulate the stoichiometric ratio and to evaluate the association constants of the complexes formed between ionophore and metal ions. While the facilitated transfer of Li+ ion was not observed across the water/1,2‐dichloroethane interface, the facilitated transfers were observed by formation of 1 : 1 (metal:ionophore) complex for Na+, K+, and Rb+ ions except for Cs+ ion. In the case of Cs+ a 1 : 2 (metal:ionophore) complex was obtained from its special electrochemical response to the variation of ligand concentrations in the organic phase. The logarithms of the complex association constants, for facilitated transfer of Na+, K+, Rb+, and Cs+, were estimated as 6.52, 7.75, 7.91 (log β1°), and 8.36 (log β2°), respectively. 相似文献
16.
E. Makrlík P. Vaňura M. Daňková 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):579-583
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium
M+(aq)+NaL+(nb)⇄ML+(nb)+Na+(aq) taking place in the two-phase water-nitrobenzene system (M+=Li+, K+, Rb+, Cs+; L=18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. The stability constants of the ML+ complexes in nitrobenzene saturated with water were calculated; they are found to increase in the cation order Cs+Li+Na+Rb+K+. Further, the individual extraction constants for the NaL+, KL+, RbL+ and CsL+ complex species in the wate-nitrobenzene system were determined; their values increase in the series Na+Rb+Cs+K+. 相似文献
17.
K. H. Lieser J. Bastian und A. B. H. Hecker 《Fresenius' Journal of Analytical Chemistry》1967,228(2):98-106
Zusammenfassung Die Trennung der Ionenpaare Rb+/Cs+, K+/Rb+, K+/Cs+, Na+/K+, Li+/Na+ mit Salzsäure oder Ammoniumchloridlösung als Elutionsmittel gelingt quantitativ oder nahezu quantitativ mit Hilfe von Titanhexacyanoferrat(II)-säulen. Die Cäsiumionen können nicht eluiert werden. Ebenso gelingt die Trennung der lonenpaare Sr2+/Ba2+, Ca2+/Ba2+, Ba2+/Cs+ und Sr2+/Cs+ quantitativ oder nahezu quantitativ. Auch eine partielle Trennung der Seltenen Erden ist möglich; Yttrium ist leichter eluierbar als die Lanthanide.
Summary The quantitative or nearly quantitative separation of the ion pairs Rb+/Cs+, K+/Rb+, k+/Cs+, Na+/K+ and Li+/Na+ can be achieved with hydrochloric acid or ammonium chloride solutions as eluents by means of columns of titanium hexacyanoferrate(II). The elution of the Cs+ ions is not possible. In the same way the quantitative or nearly quantitative separation of the ion pairs Sr2+/Ba2+, Ca2+/Ba2+, Ba2+/Cs+ and Sr2+/Cs+ can be achieved. Also a partial separation of the rare-earth elements is possible; yttrium is more easily eluted than the lanthanides.相似文献
18.
Todor Dudev Diana Cheshmedzhieva Peter Dorkov Ivayla Pantcheva 《Molecules (Basel, Switzerland)》2022,27(2)
The affinity of the polyether ionophore salinomycin to bind IA/IB metal ions was accessed using the Gibbs free energy of the competition reaction between SalNa (taken as a reference) and its rival ions: [M+-solution] + [SalNa] → [SalM] + [Na+-solution] (M = Li, K, Rb, Cs, Cu, Ag, Au). The DFT/PCM computations revealed that the ionic radius, charge density and accepting ability of the competing metal cations, as well as the dielectric properties of the solvent, have an influence upon the selectivity of salinomycin. The optimized structures of the monovalent metal complexes demonstrate the flexibility of the ionophore, allowing the coordination of one or two water ligands in SalM-W1 and SalM-W2, respectively. The metal cations are responsible for the inner coordination sphere geometry, with coordination numbers spread between 2 (Au+), 4 (Li+ and Cu+), 5/6 (Na+, K+, Ag+), 6/7 (Rb+) and 7/8 (Cs+). The metals’ affinity to salinomycin in low-polarity media follows the order of Li+ > Cu+ > Na+ > K+ > Au+ > Ag+ > Rb+ > Cs+, whereas some derangement takes place in high-dielectric environment: Li+ ≥ Na+ > K+ > Cu+ > Au+ > Ag+ > Rb+ > Cs+. 相似文献
19.
The predominant participation of anions of sorbed electrolytes in electrical charge transfer in polymers was demonstrated based on measurement of the transport numbers of Li+, Na+, K+, Rb+, Cs+, Tl+, and NO3
–ions through homogeneous polymer membranes containing dibenzo-18-crown-6 or dibenzo-24-crown-8. The coordination reaction of the cations with the crown ethers in the polymer phase is the cause of the decrease in the proportion of cations in electrical charge transfer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 310–314, February, 1990. 相似文献
20.
Y. Toh M. Oshima M. Koizumi A. Kimura Y. Hatsukawa 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):217-220
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq)+NaL+(nb)⇔ML+(nb)+Na+(aq) taking place in the two-phase water-nitrobenzene system [M+=Li+, K+, Rb+, Cs+; L = p-tert-butylcalix[4]arene-tetrakis (N, N-dimethylthioacetamide); aq = aqueous phase, nb = nitrobenzene phase] were evaluated. Furthermore,
the stability constants of the ML+ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Cs+<Rb+<K+<Li+<Na+. 相似文献