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Alkali Metal Ions (alkali + metal_ion)
Selected AbstractsFacilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid,Liquid InterfaceELECTROANALYSIS, Issue 12 2008Akgemci, Emine Guler Abstract 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 ,1°), and 8.36 (log ,2°), respectively. [source] A Cyclic Fc,Histidine Conjugate: Synthesis and Properties , Interactions with Alkali Metal IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2006Somenath Chowdhury Abstract The synthesis of the novel N,N, -(ferrocenophane-1,1,-diyldicarbonyl)-bridged histidine methyl ester 1 and of the acyclicbis(histidine methyl ester) derivative 3 are reported. The structure of 1 was studied in the solid state and in solution. The single-crystal structure of 1 shows that both proximal ferrocenyl (Fc) carbonyl groups are syn with respect to each other, which is a new structural motif for Fc,amino acid conjugates. This new syn conformation allows effective binding to alkali metal cations. Binding is evaluated by cyclic voltammetry monitoring the halfwave potential of the Fc group. Cation binding causes a shift to lower potential (Na+ > Li+ > K+, Cs+). Upon binding, compound 1 shows selectivity towards Na+ ions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Structure of a d(TGGGGT) quadruplex crystallized in the presence of Li+ ionsACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2007Christophe Creze A parallel 5,-d(TGGGGT)-3, quadruplex was formed in Na+ solution and crystallized using lithium sulfate as the main precipitating agent. The X-ray structure was determined to 1.5,Å resolution in space group P21 by molecular replacement. The asymmetric unit consists of a characteristic motif of two quadruplexes stacked at their 5, ends. All nucleotides are clearly defined in the density and could be positioned. A single bound Li+ ion is observed at the surface of the column formed by the two joined molecules. Thus, this small alkali metal ion appears to be unsuitable as a replacement for the Na+ ion in the central channel of G-quartets, unlike K+ or Tl+ ions. A well conserved constellation of water molecules is observed in the grooves of the dimeric structure. [source] Facilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid,Liquid InterfaceELECTROANALYSIS, Issue 12 2008Akgemci, Emine Guler Abstract 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 ,1°), and 8.36 (log ,2°), respectively. [source] Mechanistic Studies of Metal Aqua Ions: A Semi-Historical PerspectiveHELVETICA CHIMICA ACTA, Issue 3 2005Stephen A semi-historical review of the establishment of the nature of metal aqua ions ranging from the alkali metal ions to the lanthanides and the mechanism of water exchange and ligand substitution on them is presented. [source] Research on Advanced Materials for Li-ion BatteriesADVANCED MATERIALS, Issue 45 2009Hong Li Abstract In order to address power and energy demands of mobile electronics and electric cars, Li-ion technology is urgently being optimized by using alternative materials. This article presents a review of our recent progress dedicated to the anode and cathode materials that have the potential to fulfil the crucial factors of cost, safety, lifetime, durability, power density, and energy density. Nanostructured inorganic compounds have been extensively investigated. Size effects revealed in the storage of lithium through micropores (hard carbon spheres), alloys (Si, SnSb), and conversion reactions (Cr2O3, MnO) are studied. The formation of nano/micro core,shell, dispersed composite, and surface pinning structures can improve their cycling performance. Surface coating on LiCoO2 and LiMn2O4 was found to be an effective way to enhance their thermal and chemical stability and the mechanisms are discussed. Theoretical simulations and experiments on LiFePO4 reveal that alkali metal ions and nitrogen doping into the LiFePO4 lattice are possible approaches to increase its electronic conductivity and does not block transport of lithium ion along the 1D channel. [source] Synthesis, properties and solid state structure of 5-diphenylphosphino-2-hydroxy-1,3-xylyl-18-crown-5JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2006Rex A. Corbin 5-Diphenylphosphino-2-hydroxy-1,3-xylyl-18-crown-5 has been synthesized from 5-bromo-2-hydroxy-18-crown-5 by reacting it in sequence at low temperature with n -butyl lithium and methyl diphenylphosphonite. The phosphorous donor properties of this phenol phosphine (OH derivative) and the corresponding phenoxide (O, derivative) have been studied in the presence and absence of alkali metal ions by determining the frequencies of the A1 ,(CO) bands of Ni(CO)3L complexes. For the OH and O, derivatives, the latter generated by addition of CsOH to the former, the ,(CO) bands are observed at 2067.6 and 2063.4 cm,1, respectively, providing the trend predicted by Hammett parameters for OH and O, substituents. Addition of Na+ or K+ to the OH derivative has little effect on this stretching frequency, but the former ion shifts the O, derivative band to 2067.7 cm,1 A solid state structure has been obtained of the OH derivative, and two independent molecules were found in the unit cell. Both have a single water molecule hydrogen bonded to two across-ring oxygen atoms and the phenol hydrogen. The crown ether ring has the usual gauche and anti arrangements for the C-C and CO bonds. [source] Pseudomerohedrally twinned monoclinic structure of unfolded `free' nonactin: comparative analysis of its large conformational change upon encapsulation of alkali metal ionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Ilia A. Guzei The title compound, C40H64O12, crystallizes in a pseudomerohedrally twinned primitive monoclinic cell with similar contributions of the two twin components. There are two symmetry-independent half-molecules of nonactin in the asymmetric unit. Each molecule has a pseudo- S4 symmetry and resides on a crystallographic twofold axis; the axes pass through the molecular center of mass and are perpendicular to the plane of the macrocycle. The literature description of the room-temperature structure of nonactin as an order,disorder structure in an orthorhombic unit cell is corrected. We report a low-temperature high-precision ordered structure of `free' nonactin that allowed for the first time precise determination of its bond distances and angles. It possesses an unfolded and more planar geometry than its complexes with encapsulated Na+, K+, Cs+, Ca2+ or NH4+ cations that exhibit more isometric overall conformations. [source] | ||||||||||