Hofmeister series and ionic effects of alkali metal ions on DNA conformation transition in normal and less polarised water solvent

Normal and less polarised water models are used as the solvent to investigate Hofmeister effects and alkali metal ionic effects on dodecamer d(CGCGAATTCGCG) B-DNA with atomic dynamics simulations. As normal water solvent is replaced by less polarised water, the Hofmeister series of alkali metal ions is changed from Li⁺ > Na⁺ ? K⁺ ? Cs⁺ ? Rb⁺ to Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺. In less polarised water, DNA experiences the B→A conformational transition for the lighter alkali metal counterions (Li⁺, Na⁺ and K⁺). However, it keeps B form for the heavier ions (Rb⁺ and Cs⁺). We find that the underlying cause of the conformation transition for these alkali metal ions except K⁺ is the competition between water molecules and counterions coupling to the free oxygen atoms of the phosphate groups. For K⁺ ions, the ‘economics’ of phosphate hydration and ‘spine of hydration’ are both concerned with the DNA helixes changing.     

Synthesis and Spectral Study of Several Solid M3[Eu(2,6-Pyridinedicarboxylate)3] Salts (M=Li+, Na+, K+, Rb+, Cs+, NH4 +, and Pyridinium+)

Abstract

Salts of the [Eu(2,6-pyridinedicarboxylate)₃]^3- complex anion and various monovalent inorganic and organic counterions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH₄ ⁺, and pyridinium⁺) have been synthesized and studied by emission spectroscopy. The Eu³⁺ ion emission spectra exhibited by these salts have been observed with high resolution (less than 1.0 cm^?1) and at low temperature (77 K). The emission spectra of these compounds indicate that changing the attached counterion does not affect the site symmetry observed by the europium ion beyond slight distortions indicated by small shifts in the energies of the Eu³⁺ electronic levels.     

Counter anion effect on structural,opto-electronic and charge transport properties of fused π-conjugated imidazolium compound

The structure–activity relationship of fused π-conjugated imidazolium cation with three counter anion molecules, BF₄^?, CF₃SO₃^? and (CF₃SO₂)₂N^?, was studied using electronic structure calculations. The structural, opto-electronic and charge transport properties of these complexes were studied. The charge transfer from π-conjugated imidazolium(I) to counter anion was confirmed in all the studied complexes. Interaction energy varies significantly depending on the counter anion and the stability was found higher for I-BF₄ complex than both I–CF₃SO₃ and I–(CF₃SO₂)₂N complexes. The strong (C–H)⁺···F^? hydrogen bond of length 1.95 Å between fused π-conjugated imidazolium and BF^?₄ anion is the driving force for the strongest interaction energy in I–BF₄ complex. The energy decomposition analysis confirms that the interaction between imidazolium and counter anion is mainly driven by electrostatic and orbital interaction. It has been observed that the absorption spectra of the complex are independent of anion nature but the influence of anion character is observed on frontier molecular orbital pattern. The charge transport property of I–BF₄ complex was studied by using tight-binding Hamiltonian approach and found that the hole mobility in I–BF₄ is 1.13 × 10^?4 cm² V^?1 s^?1.     

Electronic structure of zintl compounds (NaTl) and alkali pnictides

The presence of both like and unlike atom nearest neighbours in the NaTl lattice is used to test the dependence of tight-binding interactions on bond type. The atoms are found to be almost neutral, and little evidence of the classic Na⁺Tl^- bonding models is found. The bands of alkali pnictides such as Li₃Sb are calculated by scaling interactions from LiAl. The Li salts are found to have almost neutral sites whereas the Cs salts are strongly ionic. We classify the bonding generally as charge transfer, not covalent.     

Crystal structure analysis of novel complex hydrides formed by the combination of LiBH4 and LiNH2

Combination of LiBH₄ and LiNH₂ by ball milling forms the series of novel complex hydrides Li₂BNH₆, Li₃BN₂H₈ and Li₄BN₃H₁₀, depending on the combination ratios. The crystal structure of Li₄BN₃H₁₀ analyzed by synchrotron X-raydiffraction measurements is determined to be a cubic system (space group: I2₁3) with the lattice constant of a=10.673(2)Å. It should be emphasized that Li₄BN₃H₁₀ is an ionic crystal which is composed of a lithium cation Li⁺ and two different kinds of the complex anion [BH₄]^- and [NH₂]^-. These anions are located in the vertex and face-center of the cubic sub-lattice, and the lithium cation Li⁺ in the interstitial site between the anions, respectively. The other series of complex hydrides, Li₂BNH₆ and Li₃BN₂H₈, are also predicted to possess similar structures composed of a lithium cation Li⁺ and two different kinds of the complex anion [BH₄]^- and [NH₂]^-.     

Characterization of solid electrolytes prepared from ionic glass and ionic liquid for all-solid-state lithium batteries

Glassy solid electrolytes were prepared by combining the 50Li₂SO₄·50Li₃BO₃ (mol%) ionic glass and the 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([EMI]BF₄) ionic liquid. High-energy ball milling was carried out for the mixture of the inorganic ionic glass and the organic ionic liquid. The ambient temperature conductivity of the glass electrolyte with 10 mol% [EMI]BF₄ was 10⁻⁴ S cm⁻¹, which was three orders of magnitude higher than that of the 50Li₂SO₄·50Li₃BO₃ glass. The addition of [EMI]BF₄ to the ionic glass decreased glass transition temperature (T_g) of the glass and the decrease of T_g is closely related to the enhancement of conductivity of the glass. Morphology and local structure of the glass electrolyte was characterized. The dissolution of an ionic liquid in an ionic glass with Li⁺ ion conductivity is a novel way to developing glass electrolytes for all-solid-state lithium secondary batteries.     

Electronic polarisabilities of ions in alkali halide crystals

Tessman, Kahn and Shockley calculated the electronic polarisabilities of ions in alkali halide crystals using the long wavelength limiting values of the visible light dielectric constants. We have recalculated these widely used polarisabilities using the more accurate room-temperature dielectric constant data of Lowndes and Martin and a better minimisation procedure of Pirenne and Kartheuser. We have also calculated for the first time the low temperature values of these polarisabilities. The computed values of the polarisability in ų are Li⁺ 0·029, Na⁺ 0·285, K⁺ 1·149, Rb⁺ 1·707, Cs⁺ 2·789, F^? 0·876, Cl^? 3·005, Br^? 4·168, I^? 6·294 at 300°K and Li⁺ 0·029, Na⁺ 0·290, K⁺ 1·133, Rb⁺ 1·679, Cs⁺ 2·743, F^? 0·858, Cl^? 2·947, Br^? 4·091, I^? 6·116 at 4°K. The relative standard deviations for all the alkali halides are 1·20 and 1·43 per cent at 300°K and 4°K respectively justifying the additive nature of the individual ion polarisabilities.     

Rotating sulfate ion contribution to electrical conductivity in Li2SO4 and LiNaSO4?

The results of a.c. electrical conductivity measurements on Li₂SO₄ incorporating WO^2-₄ as guest ion in SO^2-₄ sublattice and on LiNaSO₄ incorporating SiO^4-₄ as guest ion in SO^2-₄ sublattice show convincingly that the anion-rotation “cogwheel” or “paddle-wheel” mechanism does not contribute to the high mobility of Li⁺ in Li₂SO₄-based compounds. The enhanced conductivity observed at the higher frequency in the anion-doped compounds suggests relaxation effect and rigid network effect in the anion sublattice.     

Raman study of cation effect on sulfate vibration modes in solid state and in aqueous solutions

Raman spectra of potassium, sodium, and ammonium sulfates (K₂SO₄, Na₂SO₄, and (NH₄)₂SO₄) are reported and analyzed. These sulfates have been investigated under two states: solid (anhydrous and hydrated) salts and aqueous solutions. The effects of monovalent ions (K⁺, Na⁺, and NH₄⁺) and hydration on the position of Raman lines assigned to internal vibrations of sulfate anion SO₄²⁻ are discussed. In solid salts, the line position of each Raman peak is shown to decrease with increasing radius of the cation. The main ν₁ mode of sulfate molecule is particularly affected. It is emphasized that this sensitivity in solid sulfates vanishes in aqueous solutions. As a consequence, this mode can be probed by Raman spectroscopy as the main signature of SO₄²⁻ to determine its concentration within a single calibration. Copyright © 2013 John Wiley & Sons, Ltd.     

Density functional theory study of the bis‐3‐benzo‐crown ethers and their complexes with alkali metal cations Na+, K+, Rb+ and Cs+

The binding interactions of bis‐3‐benzo‐15‐crown‐5 ethers and bis‐3‐benzo‐18‐crown‐6 ethers (neutral hosts) with a series of alkali metal cations Na⁺, K⁺, Rb⁺ and Cs⁺ (charged guests) were investigated using quantum chemical density functional theory. Different optimized structures, binding energies and various thermodynamic parameters of free crown ethers and their metal cation complexes were obtained based on the Becke, three‐parameter, Lee–Yang–Parr functional using mixed basis set (C, H, O, Na⁺ and K⁺ using 6‐31 g, and the heavier cation Rb⁺ and Cs⁺ using effective core potentials). Natural bond orbital analysis is conducted on the optimized geometric structures. The main types of driving force host–guest interactions are investigated. The electron donating O offers a lone pair of electrons to the contacting LP* (1‐center valence antibond lone pair) orbitals of metal cations. The bis‐3‐benzocrown ethers are assumed to have sandwich‐like conformations, considering the binding energies to gauge the exact interactions with alkali cations. It is found that there are two different types of complexes: one is a tight ion pair and the other is a separated ion pair. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrothermal reactions of simple molecules by real-time infrared spectroscopy

Abstract

The relative roles of the materials of construction of the reactor (stainless steel or titanium) and the effects of Group 1 cations are discussed in terms of their effect on the rate of decarboxylation of acetic acid derivatives, RCO₂H. Past work indicates that the reaction container composition has a very large effect when R is CH3—. A smaller but significant effect is seen when R is electron neutral (i.e., R=H). When R is electron Withdrawing the rate depends less on the reactor type than the nature of R. The effect of the counter ion M on the rate of decarboxylation of monovalent malonate salts, HC&CHzC02M, is discussed for M=Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. The rate generally increases with the ionic radius except that the Rb⁺ salt exhibits the fastest rate. Preliminary explanations are given.     

Colorimetric quantitative sensing of alkali metal ions based on reversible assembly and disassembly of gold nanoparticles

A novel and simple method for the colorimetric quantitative sensing of individual alkali metal ions (Li⁺, Na⁺, K⁺, and Rb⁺) based on the reversible properties of self-assembled aggregates and individual gold nanoparticles (Au NPs) is described. This paper demonstrates reversible self-assembly processes where the degree of assembly and disassembly is dependent on the individual alkali metal ion concentration, nanoparticle size, and alkali metal ionic radii. The color changes of the colloidal Au NPs with metal ion concentrations in colloidal NP solutions occur reversibly. Below a certain concentration of alkali metal ions, the aggregates of Au NPs are redispersed. As the Au NP diameters and the alkali metal ionic radii increase, the critical concentration decreases.     

Electrical conductivity of superionic solid solutions of Na2SO4 with Mx (XO4)y -[M=Na,K, Rb,Cd, GdandX=W,Mo, S,Si;x=1, 2, 4 andy=1, 3]

Electrical conductivity data are reported for solid solutions of Na₂SO₄, K₂WO₄, Na₂WO₄, Na₂MoO₄, Rb₂SO₄, Na₄SiO₄ and Gd₂ (SO₄)₃. In all cases, except K₂SO₄, we observed an increase in Na⁺ conductivity effected by lattice expansion and/or incorporation of ion vacancies in addition to a structural transformation. Boundary conditions were shown to exist for these factors to yield a limiting Na⁺ conductivity with a constant fraction of Na⁺ based on a percolation model of transport. The higher conductivity data observed for the larger radius isovalent WO^2-₄ and aliovalent SiO^4-₄ doped Na₂SO₄ show conclusively that the anion-rotation ”cogwheel” mechanism does not contribute to the cationic conductivity in Na₂SO₄.     

Etude par R.P.E. d'electrolytes vitreux appartenant au systeme B2O3-Li2O-LiCl

An EPR study of fast Li⁺ ion vitreous conductors belonging to the B₂O₃-Li₂O-LiCl system has been carried out. The samples have been subjected to X-ray irradiation at room temperature. Two types of paramagnetic centers have been observed. The first one is the Cl₂^- species (Vk center) present in the part of the vitreous domain which corresponds to low LiCl concentrations, it vanishes when Li⁺ and Cl^- begin to order. The second one is of the B.O.H.C. type often present in alkali borate glasses. Its presence shows the similarity between the boron-oxygen network of the alkali borate glasses and of our samples containing alkali chloride.     

Type I FA (Rb, Cs) and II FA (Li, Na) tunable laser activities and donor-acceptor properties of O and O at KCl (001) surface: first principle calculations

Type I F_A (Rb⁺, Cs⁺) and II F_A (Li⁺, Na⁺) tunable laser activities, adsorptivity and donor-acceptor properties of O and O⁻ adsorbates at the flat surface of KCl crystal were investigated using an embedded cluster model and ab initio methods of molecular electronic structure calculations. Ion clusters were embedded in a simulated Coulomb field that closely approximates the Madelung field of the host surface, and the nearest neighbor ions to the defect site were allowed to relax to equilibrium. Based on the calculated Stokes shifted optical transition bands, F_A tunable laser activities were found to be inversely proportional to the size of the dopant cation (Li⁺, Na⁺, Rb⁺, Cs⁺) relative to the host cation (K⁺). This relation was explained in terms of the axial perturbation of the impurity cation. The probability of orientational bleaching attributed to the RES saddle point ion configuration along the 〈110〉 axis was found to be inversely proportional to the size of the dopant cation, with activation energy barriers of ca. 0.44-3.34 eV. Surface relaxation energies of type II F_A centers were more important than those of type I F_A centers. In terms of defect formation energies, the products of type II F_A center imperfection were more stable than those of type I F_A. The difference between F or F_A band energies and exciton bands depended almost exclusively on the size of the positive ion species. As far as the adsorptivity of O and O⁻ is concerned, the results confirm that surface imperfection enhances the adsorption energies by ca. 4.38-16.37 eV. O and O⁻ penetrate through the defect-containing surface. The energy gap between the adsorbate and the defect containing surface and the donor-acceptor property of adsorbate play the dominant role in the course of adsorbate substrate interactions and the results were explained in terms of electrostatic potential curves and Mulliken population analysis.     

影响聚合物离子导体电导率的一些因素

本文研究了极性基团浓度、碱金属盐阳离子和阴离子尺寸对均聚物聚环氧氯丙烷(PECH)和共聚物聚环氧氯丙烷-聚环氧乙烷(PECH-PEO)电导率的影响。对锂盐络合物,极性基团浓度增高,电导率降低。钠盐络合物则正好相反,极性基团浓度越高,电导率越高。碱金属盐阳离子和阴离子尺寸对聚合物离子导体电导率都有明显影响。所研究的聚环氧氯丙烷与三种碱金属盐络合物PECH-MI(M=Li,Na,K)的电导率数据表明,钠盐络合物的电导率最高,锂盐和钾盐络合物的电导率较低。碱金属盐阴离子越大,PECH络合物的电导率越低。此外,还 关键词：     

Spectroscopic investigation of pressure-induced phase transitions in TCNQ complex salts

In most of the TCNQ complex salts, conduction electrons are localized on specific TCNQ sites, so that these salts show nonmetalic behavior. The caesium salt, Cs₂(TCNQ)₃, is one of the 2:3 complex salts. In the crystal, TCNQ molecules form trimeric units, which consist of two TCNQ radical anion sandwiching a neutral TCNQ along the column. The rubidium salt, Rb₂(TCNQ)₃, also has a similar crystal structure to Cs₂(TCNQ)₃. We measured infrared absorption (IR) and Raman spectra for these salts under high pressure by using a diamond anvil cell. In the case of IR spectra, Cs₂(TCNQ)₃ showed a spectral change probably due to a pressure-induced phase transition. Similar feature was not clearly observed in the Rb₂(TCNQ)₃. On the other hand, the Raman spectra, Cs₂(TCNQ)₃ showed two phase transition at 2.5 and 4.1 GPa in the compression stage. The change from localization phase to delocalization phase occurred at latter transition with large hysteresis. Similar phase transition occurred at 3.2 GPa in the Rb₂(TCNQ)₃. The reason for the difference in transition pressure is that the ion radius of Rb⁺ is smaller than that of Cs⁺, because a small ion radius of the counter ion probably favors the charge localization-delocalization transition of the TCNQ column.     

Effect of solvent on the cation-sensitive fluorescence of polyanions bearing 4′-acryloylbenzo-18-crown-6 Units

Changes in the fluorescence intensity of polyanions bearing 4-acryloylbenzo-18-crown-6 units on the addition of cations were studied in a mixed solvent of methanol and water at 30°C. The sensitivity of the change in fluorescence intensities of the polymers toward cations was strongly enhanced compared to that of the corresponding model compound. When alkali metal cations were added, the fluorescence intensity of the polymers decreased in the orders Li⁺>Na⁺>Cs⁺>Rb⁺>K⁺ in a methanol-water (19) mixture and Li⁺>Na⁺>Rb⁺>K⁺Cs⁺ in a methanol-water (91) mixture. Alkaline earth metal cations and alkylamine hydrochlorides decreased the fluorescence intensity of the polymers in a methanol-water (19) mixture. The cation-dependent decrease in the fluorescence intensity of the polymers was affected by the water fraction in a mixed solvent of methanol and water.     

The migration of alkali metal (Na+, Li+, and K+) ions in single crystalline vanadate nanowires: Rasch-Hinrichsen resistivity

We report the synthesis of single crystalline alkali metal vanadate nanowires, Li-vanadate (Li₄V₁₀O₂₇), Na-vanadate (NaV₆O₁₅), and K-vanadate (KV₄O₁₀) and their electrical properties in a single nanowire configuration. Alkali metal vanadate nanowires were obtained by a simple thermal annealing process with vanadium hydroxides(V(OH)₃) nanoparticles containing Li⁺, Na⁺, and K⁺ ions and further the analysis of the migration of charged particles (Li⁺, Na⁺, and K⁺) in vanadate by measuring the conductivity of them. We found that their ionic conductivities can be empirically explained by the Rasch-Hinrichsen resistivity and interpreted on the basis of transition state theory. Our results thus indicate that the Li ion shows the lowest potential barrier of ionic conduction due to its small ionic size. Additionally, Na-vanadate has the lowest ion number per unit V₂O₅, resulting in increased distance to move without collision, and ultimately in low resistivity at room temperature.     

Role of monovalent alkali ions in the Yb3+ centers of CaF2 laser crystals

Yb³⁺ and M⁺ monovalent alkali ions (M⁺ = Li⁺, Na⁺, K⁺)-co-doped CaF₂ cubic laser crystals were grown by the micro-pulling-down method (μ-PD) under CF₄ atmosphere. Structural and spectroscopic characterizations of Yb³⁺ in substitution of Ca²⁺ (absorption, emission and decay curves) were carried out to study the effect of M⁺ ions as charge compensators.