Rubidium Cations Research Articles

Synthesis and an X-ray diffraction study of Rb2[(UO2)2(C2O4)3

The synthesis and X-ray diffraction study of compound Rb2[(UO2)2(C2O4)3], which crystallizes in the monoclinic crystal system, are performed. The unit cell parameters are as follows: a = 7.9996(6) A, b = 8.8259(8) A, c = 11.3220(7) A, β = 105.394(2)°, and V = 770.7(1) A3; space group P21/n, Z = 2, and R 1 = 0.0271. [(UO2)2(C2O4)3]2− layers belonging to the AK 0.5 02 T 11 crystal chemical group of uranyl complexes (A = UO 2 2+ , K 02 = C2O 4 2− , and T 11 = C2O 4 2− ) are uranium-containing structural units of the crystals. The layers are connected with outer-sphere rubidium cations by electrostatic interactions.

X-ray diffraction study of Rb2[(UO2)2(CrO4)3(H2O)2] · 4H2O

The compound Rb2[(UO2)2(CrO4)3(H2O)2] · 4H2O was studied by X-ray diffraction. The crystals are monoclinic, a = 10.695(2) A, b = 14.684(3) A, c = 14.125(3) A, β = 108.396(4)°, sp. gr. P21/c, Z = 4, V = 2104.9(7) A3, and R = 0.0491. The main structural units are layers consisting of [(UO2)2(CrO4)3(H2O)2]2− anions belonging to the crystal-chemical group A2T23B2M21 (A = UL22+, T3 and B2 are CrO42−, and M1 is H2O) of uranyl complexes. The uranium-containing layered groups are held together by electrostatic interactions with rubidium cations, as well as by hydrogen bonds with the participation of inner- and outer-sphere water molecules.

Crucial effect of rubidium cation on catalytic activity of a polycrystalline gold electrode toward oxygen reduction reaction in alkaline media

Catalytic activity of a polycrystalline gold electrode toward oxygen reduction reaction (ORR) in aqueous alkaline media in the presence of various alkali-metal sulfates (M 2SO 4, M = Li, Na, K, Rb and Cs) was investigated by hydrodynamic voltammetry. The fraction of 4e − pathway in low overpotentials (− 0.1 to − 0.3 V) depended on the alkali-metal cations (Rb ≫ Na, K, Cs, Li). A complete 4e − reduction of O 2 was only attained in the presence of Rb + cation in the solution, which was comparable or even superior to that reported at the Au(100) single crystal electrode.

Metal Cation Dependence of Interactions with Amino Acids: Bond Energies of Rb+ to Gly, Ser, Thr, and Pro

The interactions of rubidium cations with the four amino acids (AA), glycine (Gly), serine (Ser), threonine (Thr), and proline (Pro), are examined in detail. Experimentally, the bond energies are determined using threshold collision-induced dissociation of the Rb(+)(AA) complexes with xenon in a guided ion beam tandem mass spectrometer. Analyses of the energy dependent cross sections include consideration of unimolecular decay rates, internal energy of reactant ions, and multiple ion-molecule collisions. 0 K bond energies of 108.9 +/- 7.0, 115.7 +/- 4.9, 122.1 +/- 4.6, and 125.2 +/- 4.5 kJ/mol are determined for complexes of Rb(+) with Gly, Ser, Thr, and Pro, respectively. Quantum chemical calculations are conducted at the B3LYP, B3P86, and MP2(full) levels of theory with geometries and zero point energies calculated at the B3LYP level using both HW*/6-311+G(2d,2p) and Def2TZVP basis sets. Results obtained using the former basis sets are systematically low compared to the experimental bond energies, whereas the latter basis sets show good agreement. For Rb(+)(Gly), the ground state conformer has the rubidium ion binding to the carbonyl group of the carboxylic acid, and a similar geometry is found for Rb(+)(Pro) except the secondary nitrogen accepts the carboxylic acid hydrogen to form the zwitterionic structure. Both Rb(+)(Ser) and Rb(+)(Thr) are found to have tridentate binding at the B3LYP and MP2(full) levels, whereas the B3P86 slightly prefers binding Rb(+) at the carboxylic acid. Comparison of these results to those for the lighter alkali ions provides insight into the trends in binding affinities and structures associated with metal cation variations.

Thiacalix[4]arene–rubidiumassembly: supramolecular architecture based on alkali metal coordination and cation–π interactions

Single-crystal X-ray diffraction study of a thiacalix[4]arene complex with a rubidium cation demonstrated in different coordination environments of two thiacalix[4]arene molecular units, η2 and η6 coordination between rubidium cations and thiacalix[4]arene aromatic rings outside of the cavities.

Rubidium uranyl phosphates and arsenates with polymeric tetrahedral anions: Syntheses and structures of Rb 4[(UO 2) 6(P 2O 7) 4(H 2O)], Rb 2[(UO 2) 3(P 2O 7)(P 4O 12)] and Rb[(UO 2) 2(As 3O 10)

The three new framework Rb uranyl phosphates and arsenates with anionic parts based on different type of polymeric anions have been prepared by high-temperature solid-state reactions: Rb 4[(UO 2) 6(P 2O 7) 4(H 2O)] ( 1), Rb 2[(UO 2) 3(P 2O 7)(P 4O 12)] ( 2), Rb[(UO 2) 2(As 3O 10)] ( 3). The crystal structures of the synthesized compounds have been solved by direct methods: 1—monoclinic P2 1/ c, a=9.672(1) Å, b=12.951(1) Å, c=32.231(3) Å, β=90.116(4)°, V=4037.3(6) Å 3, Z=4, R 1=0.0926 for 6351 unique reflections with | F 0 | ≥ 4 σ F ; 2—monoclinic, P2 1/ c, a=6.791(1) Å, b=16.155(3) Å, c=19.856(4) Å, β=97.48(5)°, V=2159.8(7) Å 3, Z=4, R 1=0.0286 for 3617 unique reflections with | F 0 | ≥ 4 σ F ; 3—orthorhombic, Pbcn, a=10.558(1) Å, b=11.037(1) Å, c=11.464(1) Å, V=1335.9(2) Å 3, Z=4, R 1=0.0489 for 1384 unique reflections with | F 0 | ≥ 4 σ F . The structures of title are compounds based on 3D negatively charged frameworks with chemical compositions [(UO 2) 6(P 2O 7) 4(H 2O)] 4− in 1, [(UO 2) 3(P 2O 7)(P 4O 12)] 2− in 2 and [(UO 2) 2(As 3O 10)] − in 3. These negative charges are compensated by rubidium cations which are in the channels of 1 and closed cages in structures of 2 and 3. The channels in 1 are directed along the a direction and have minimum dimensions ∼5 Å×6 Å. This is the first example of porosity generation through solid state synthesis in uranyl compounds. For the first time in uranium chemistry polymeric anionic groups P 4O 12 and As 3O 10 were observed in structure of 2 and 3.

Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation

This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb(+). Capillary affinity electrophoresis was employed for the experimental evaluation of the strength of the Val-Rb(+) complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb(+) cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb(+) cation concentration in the BGE (methanolic solution of 100 mM Tris, 50 mM acetic acid, 0-1 mM RbCl), the apparent binding (stability) constant (K(b)) of the Val-Rb(+) complex in methanol was evaluated as log K(b)=4.63+/-0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of Val-Rb(+) complex, Val is stabilized by strong non-covalent bond interactions of Rb(+) with six ester carbonyl oxygen atoms so that the position of the "central" Rb(+) cation in the Val cage is symmetric.

Catena-Poly[[diaquarubidium(I)](μ2-3-carboxypyrazine-2-carboxylato)(μ2-pyrazine-2,3-dicarboxylic acid)

The structural unit of the title compound, [Rb(C6H3N2O4)(C6H4N2O4)(H2O)2]n, consists of one rubidium cation, one hydrogen pyrazine-2,3-dicarboxyl­ate anion, one pyrazine-2,3-dicarboxylic acid mol­ecule and two water mol­ecules. This formulation is repeated twice in the asymmetric unit as the rubidium cation lies on an inversion centre. Each anion or acid mol­ecule is linked to two rubidium cations, while the rubidium cation has close contacts to four symmetry-equivalent organic ligands, with two different coordination modes towards this cation. In addition, each rubidium cation is coordinated by two water O atoms, raising the coordination number to eight. One of the carboxyl groups of the acid holds its H atom, which forms a hydrogen bond to a coordinated water mol­ecule. The other carboxyl group is deprotonated in half of the ligands and protonated in the other half, taking part in a strong O—H⋯O hydrogen bond disordered over an inversion centre. The stabil­ization of the crystal structure is further assisted by O—H⋯O and O—H⋯N hydrogen-bonding inter­actions involving the water mol­ecules and carboxyl­ate O atoms.

Synthesis and Structure of and Cation Distribution in the Zirconium Cluster Rb[(Zr6C)Cl15

Rb[(Zr6C)Cl15] was prepared by heating ZrCl4, Zr powder, RbCl and Al4C3 at 850 °C for 21 days. The crystal structure was determined by single crystal X-ray diffraction (space group Pmma, a = 18.484(3), b = 18.962(2), c = 9.708(1) Å, V = 2505.4(6) Å3, and Z = 4). Rb[(Zr6C)Cl15] crystallises in the Cs[Nb6Cl15]-type structure. It is built up from two interconnected types of cluster chains, one with linear Zr−Cla−a-Zr bridges, the other one with bent bridges. The rubidium cations are spread over three different sites within the cluster network which differs significantly from the cation distribution in the comparable potassium and caesium phases. The cation distribution can be rationalised considering the size of the cavities and the Coulombic interactions.

Poly[μ3-aqua-μ2-2,4-dinitrophenolato-rubidium(I)

The asymmetric unit of the title compound, [Rb(C6H3N2O5)(H2O)]n, comprises a rubidium cation, a 2,4-dinitro­phenoxide anion and a water mol­ecule. The Rb+ cation is 11-coordinated by O atoms from 2,4-dinitro­phenolate anions and water mol­ecules. The metal centre is firstly coordinated by two μ3-H2O to form a one-dimensional ladder-shaped unit, [Rb2(μ3-H2O)2], which is further linked by 2,4-dinitro­phenolate to give the three-dimensional framework of the title compound. The crystal structure involves O—H⋯O hydrogen bonds.

Synthesis and crystal structure of a new representative of the Rb2U2MoO10 uranomolybdate series

A new representative of the Rb2U2MoO10 uranomolybdate series, was synthesized; its single crystals were grown and studied by X-ray diffraction. The atomic crystal structure was solved: monoclinic system, space group P21/c, a = 8.542(1) A, b = 15.360(2) A, c = 8.436(1) A, b = 104.279(3)°, R1 = 0.064 for 1817 independent reflections with F > 4σ(F). The crystal structure is built of negatively charged infinite corrugated [U2MoO10]2∞δ− layers, which are linked through rubidium cations arranged between them. The compound was studied by IR spectroscopy; the absorption bands in the spectrum were assigned.

Synthesis, structure, ion mobility, phase transitions, and ion transport in rubidium ammonium hexafluorozirconates

Rubidium ammonium hexafluorozirconates Rb2−x (NH4)x ZrF6 (1.5 1.5 are isostructural with (NH4)2ZrF6. Rubidium cations are isomorphously substituted for the ammonium cations. The high-temperature modifications of the compounds, which form upon the phase transitions at 413–418 K, are characterized by translational diffusion of ions in the fluoride and ammonium sublattices. The 19F NMR spectra are characterized by uniaxial 19F magnetic shift anisotropy. The electrophysical properties of this series of compounds are studied in the temperature range 300–480 K.

Ionic mobility and structure of fluorozirconates Rb2−x (NH4) x ZrF6 (x > 1.5) by NMR, x-ray structure analysis, and impedance spectroscopy

The ionic mobility in the temperature interval 180 to 480 K, structure, and electrophysical properties of rubidium-ammonium hexafluorozirconates Rb2−x(NH4)xZrF6 (1.5 ≤ x ≤ 2.0) are studied by methods of the 19F, 1H NMR spectroscopy, x-ray structure analysis, differential thermal analysis, and impedance spectroscopy. Correlations between the composition of the cationic sublattice, the character of ionic motions, and the phase transition temperature (of the type order-disorder) are established in these compounds. The salient feature of the high-temperature modifications of these fluorozirconates with x ≥ 1.5 is the translation diffusion of ions inside the fluoride and ammonium sublattices and the 19F NMR spectra are characterized by monoaxial anisotropy of the magnetic shielding tensor of the fluorine nuclei. Fluorozirconates with x > 1.5 are shown to belong with the structural type (NH4)2ZrF6. The rubidium cations isomorphically replace the ammonium cations. The electrophysical characteristics of the compounds are examined in the temperature interval 300 to 480 K. It is established that the electroconductivity of these compounds increases with x.

Confined Water Clusters in a Synthetic Rubidium Gallosilicate with Zeolite LTL Topology

A rubidium gallosilicate with zeolite LTL framework topology has been synthesized under hydrothermal conditions, and the as-synthesized hydrated material was characterized via high-resolution synchrotron X-ray powder diffraction at room temperature. Rb-GaSi-LTL, Rb9.8Ga10.4Si25.6O72·17.5H2O, is hexagonal, space group P6/mmm, with a = 18.6260(1) Å and c = 7.6459(1) Å. The framework model shows complete disordering of Ga and Si in the tetrahedral sites, which is analogous to the framework chemistry of its potassium counterpart, K11Ga10.3Si25.7O72·15.1H2O with a = 18.5525(1) Å and c = 7.5619(1) Å, but contrasts to the proposed preferential aluminum partitioning for the 6-ring sites in the aluminosilicate analogues. Similar to the cation distribution in the potassium analogue, half of the rubidium cations in the unit cell fully occupy the sites associated with the narrow channels on the z = 1/2 plane (sites B and C), whereas the other half fill, on average, five out of the six 8-ring sites in the recessed walls of the main 12-ring channel on the z = 0 plane (site D). All of the water molecules are located along the main 12-ring channels at z = 0, 1/6, 1/3, and 1/2 planes. Water molecules on the latter three planes form clusters within the 12-ring windows confinement via hydrogen bonding to one another and to framework oxygen atoms, while those on the z = 0 plane separate the water clusters by coordinating to the site D cations in the main channel. This partitioning of water molecules in the main channel becomes modulated in the hydrated potassium analogue and seems to be dependent on the chemistry of non-framework cations.

Conformational Templation in a Singly Bridged Calix[7]arene Derivative Induced by Alkali Metal Cations

The first examples of alkali metal cation conformational templation of a calix[7]arene derivative were found in the alkali salts of 1,4-calix[7]crown-4, which were obtained by its treatment with the corresponding alkali metal carbonates. Competitive experiments showed that potassium and rubidium cations give the most effective templation, with a slight preference for the former. Experimental results and Monte Carlo conformational searches indicated that the cation interacts with all O-atoms including those of the crown-4 bridge.

Ein neuer Vertreter des A2B2CX4-Typs: Rb2Na2SiO4 / A New Member of the A2B2CX4-Type: Rb2Na2SiO4

Na2Rb2SiO4 crystallizes in a hitherto unknown A2B2CX4 type of structure. The ortho-silicate anions and sodium cations form a three-dimensional structure of connected tetrahedral and trigonalbipyramidal units. The larger rubidium cations complement the cationic part of the structure and display the motif of corrugated hexagonal layers with Rb-Rb distances of less than 400 pm. Single crystal structure data (space group Pbca, Z = 8, a = 983.20(7), b = 1092.26(6), c = 1113.04(8) pm) are given and a comparison to other A2B2CX4-type of structures is presented.

Crystal structure and vibrational spectra of rubidium salts of bis(dicyanomethylene)croconate (croconate violet)

The crystal structures and vibrational spectra of two alkaline salts of 3,5-bis-(dicyanomethylene)cyclopentane-1,2,4-trionate ( C 11 N 4 O 3 2 - ) , known as croconate violet, are described: 1-rubidium and potassium croconate violet (RbKCV), and 2-rubidium croconate violet (Rb 2CV). These compounds are isostructural and crystallize in triclinic P 1 ¯ space group. The stoichiometries of the salts show two water molecules to each M 2C 11N 4O 3 unit. The anions are displayed in layers linked to water molecules by hydrogen bonds, therefore forming an extended structure with two-dimensional arrangement (2D). Crystal structure shows two different metal sites (M1 and M2) that present different types of coordination: monodentate, quelate and bidentate in M1; and monodentate and bidentate in M2. In RbKCV the rubidium cation is predominant in M1 and M2 sites, presenting total occupation of 70% and the molecular formula of this salt is Rb 1.4K 0.6C 11N 4O 3 · 2H 2O. Vibrational spectra of RbKCV and Rb 2CV are similar to the spectra of potassium croconate violet (K 2CV). In the Raman spectrum of RbKCV some small wavenumber shifts are observed when compared K 2CV and Rb 2CV spectra. The structural difference in RbKCV salt is due to the interionic interactions between CV anion and potassium and rubidium cations; this effect could be responsible to spectral differences observed in RbKCV Raman spectra. However, the exchange between potassium and rubidium ions in the solid state structure does not alter croconate violet anion crystal packing, which can be observed in the vibrational spectra.

Substituent control of potassium and rubidium uptake by asymmetric calix[4]-thiacalix[4]tubes

Herein we report on the synthesis and ionophore properties of the first asymmetric p-tert-butylcalix[4]-p-R-thiacalix[4]tubes 7a-c (R = t-Bu, H, 1-adamantyl). The target compounds were obtained by the condensation of tosyloxyethoxy-p-tert-butylcalix[4]arene with the corresponding p-R-thiacalix[4]arenes in the presence of K2CO3 in acetonitrile. The complexation with sodium, potassium and rubidium iodides was studied in CDCl3-CD3OD (4:1) medium by means of 1H NMR measurements. It was found that the ionophore properties of calixtubes 7a-c are controlled by the character of the substituents at the upper rim of the thiacalix[4]arene fragment and it was shown that only the molecular tube 7c with an adamantane-containing thiacalixarene unit is capable of quantitatively binding potassium (swiftly) and rubidium (slowly) cations.

New phenotypes of functional expression of the mKir2.1 channel in potassium efflux‐deficient Saccharomyces cerevisiae strains

The functional expression of the mouse Kir2.1 potassium channel in yeast cells lacking transport systems for potassium and sodium efflux (ena1-4delta nha1delta) resulted in increased cell sensitivity to high external concentrations of potassium. The phenotype depended on the level of Kir2.1 expression and on the external pH. The activity of Kir2.1p in the yeast cells was almost negligible at pH 3.0 and the highest at pH 7.0. Kir2.1p was permeable for both potassium and rubidium cations, but neither sodium nor lithium were transported via the channel. Measurements of the cation contents in cells confirmed the higher concentration of potassium in cells with Kir2.1p. Specific inhibition of the mKir2.1 channel activity by Ba2+ cations was observed. The use of a mutant strain lacking both potassium efflux and uptake transporters (ena1-4delta nha1delta trk1delta trk2delta) enabled the monitoring of channel activity on two levels--the provision of the necessary amount of intracellular K+ in media with low potassium concentrations, and simultaneously, the channel's contribution to cell potassium sensitivity in the presence of high external K+. This combination of mutations proved to be a new, sensitive and practical tool for characterizing the properties of heterologously expressed transporters mediating both the efflux and influx of alkali-metal-cations.

Towards Operando Characterisation by Powder Diffraction Techniques of Molecular Sieves

Working molecular sieves imply numerous and various atoms and for their characterisation we need chemical selective probes. Thus they can be studied either by neutron powder diffraction or by anomalous X-ray powder diffraction techniques to extract structural information. We will illustrate the complementarities of these methods in the analysis of two different chemical processes on X-type zeolite. In the first case, a fully exchanged barium X-type zeolite was, firstly, characterised by neutron powder diffraction after an ex situ preparation step. During the preparation step, the sample was saturated with a mixture of heavy water and deuterated para-xylene. The selectivity of neutron diffraction for light elements allows the precise location of both water and xylene molecules. In the second example, an X-type zeolite exchanged by both strontium and rubidium cations was studied during the dehydration process. The in situ structural characterisation was performed by recording, for each state of the zeolite (hydrated, dehydrated), three X-ray powder patterns. Two of them were measured at an energy close to the absorption edge of each compensating cation (Sr2+ and Rb+) and one far from both absorption edges. The chemical selectivity of resonant diffraction allows an accurate determination of the distribution of compensating cations (location, distribution and mobility) during the dehydration process. Finally a comparison of some specificities and limitations of both methods are summarized.