Enhanced Li+ binding energies of some azines: a molecular orbital study

Summary Hartree-Fock calculations with the 6–31G* basis have been performed to investigate the structure and Li⁺ binding energies of the complexes between Li⁺ and pyridine, diazines, triazines and tetrazines. Structures have been fully optimized at the 3–21G level. As for azole-Li⁺ and methyldiazole-Li⁺ complexes, a topological analysis of the Laplacian of the electronic charge density reveals that the azine-Li⁺ is a typical closed-shell interaction and that the stabilization of the complex is mainly electrostatic. BSSE is quite significant, specially for Li⁺-bridging complexes. The correlation between calculated Li⁺ binding energies and proton affinities follows two different linear relationships, one for those cases where Li⁺ is singly coordinated and a different one for those cases in which an additional three-membered ring is formed. The enhanced stability of these particular conformations explains why while polyazines are less basic than pyridine when the reference acid is a proton; pyridazine and 1,2,4 triazine are more basic than pyridine when the reference acid is Li⁺. The effect on Li⁺ binding energies of systematic nitrogen substitution roughly follows an additive model.     

Visualized investigation of yeast transformation induced with Li+ and polyethylene glycol

The effects of Li⁺ and polyethylene glycol (PEG) on the genetic transformation of Saccharomyces cerevisiae were investigated by using fluorescence microscopy (FM) to visualize the binding of plasmid DNA labeled with YOYO-1 to the surface of yeast cells, scanning electron microscopy (SEM) and atomic force microscopy (AFM) to image the change in surface topography of yeast cells, coupled with transformation frequency experiments. The results showed that under the same conditions, the transformation frequencies of yeast protoplasts were much higher than those of intact yeast cells. PEG was absolutely required for the binding of DNA to the surface of intact yeast cells or yeast protoplasts, and had no effect on the surface topography of intact yeast cells or yeast protoplasts. In the presence of PEG, Li⁺ could greatly enhance the binding of plasmid DNA to the surface of intact yeast cells, increase their transformation frequency, and affect their surface topography. On the other hand, no effect on the DNA binding to the surface of protoplasts and no increase in the number of transformants and no surface topography changes were found upon the treatment with Li⁺ to protoplasts. In the present work, the effects of Li⁺ and PEG on yeast genetic transformation were directly visualized, rather than those deduced from the results of transformation frequencies. These results indicate that cell wall might be a barrier for the uptake of plasmid DNA. Li⁺ could increase the permeability of yeast cell wall, then increase the exposed sites of DNA binding on intact yeast cells. The main role of PEG was to induce DNA binding to cell surface.     

Lithium-7 NMR Study of Several Li+-Crown Ether Complexes in Binary Acetone-Nitrobenzene Mixtures

⁷Li NMR measurements were employed to monitor the stoichiometry andstability of Li⁺ ion complexes with 12-crown-4 (12C4), 15-crown-5 (15C5), benzo-15-crown-5 (B15C5) l8-crown-6 (18C6), dicyclohexano-18-crown-6 (DC18C6) and dibenzo-18-crown-6 (DB18C6) in binary acetone-nitrobenzene mixtures of varying composition. In all cases studied, the variation of ⁷Li chemical shift with the crown/Li⁺ mole ratio indicated the formation of 1:1 complexes. The formation constants of the resulting complexes were evaluated from computer fitting of the mole ratio data to an equation that relates the observed chemical shifts to the formation constant. In all solvent mixtures used, the stabilities of the resulting 1:1 complexes varied in the order15C5 > B15C5 > DC18C6 > 18C6 > 12C4 >DB18C6. It was found that,in the case of all complexes, an increase in the percentage of acetone in thesolvent mixtures significantly decreased the stability of the complexes.     

Performance of a highly lipophilic Li+ lonophore in solvent polymeric membranes

Ionophores based on non-cyclic triamides exhibiting Li⁺ selectivity in solvent polymeric membranes are described. Their lipophilicity (water/1-n-octanol partition coefficient) is up to 10^13.8 so that they can be used in ion-selective electrodes with a lifetime of up to 40 000 h even in permanent contact with whole blood or undiluted blood serum.On leave from the Department of General Chemistry, Technical University of Gdansk, PL-80-952 Gdansk, Poland     

Influence of the crystallinity on the Li+ intercalation process in Nb2O5 films

Nb₂O₅ thin films were prepared by the Pechini method. The effect of the film crystallinity on the electrochemical and electrochromic properties was investigated. A relationship between the crystalline structure and the Li⁺ intercalation/extraction process, stability and kinetics was observed. A significant decrease in the electrochemical response was observed as a function of the number of cycles for films treated at 400 and 450 °C. However, as the calcination temperature increases this effect disappears. XRD studies shown that at 400 °C, the material is amorphous, evolving to orthorhombic phase. The transmittance variation as well as the coloration efficiency increases as the temperature is increased. In the initial cycles the intercalation charge is higher for the amorphous oxide than for the orthorhombic phase. However, the variation in the optical density is small. On the other hand, the charge of the orthorhombic phase oxide does not change. These results suggest that there are two different processes associated with Li⁺ intercalation, but only one of them leads to the coloration process.     

Infrared spectra (700–200 cm−1) and6Li/7Li and H2O/D2O isotope effects for four isotopically substituted lithium formate monohydrates

The infrared spectra, in the 700–200 cm^–1 region, have been reported for⁶LiHCO₂ · H₂O,⁶LiHCO₂ · D₂O,⁷LiHCO₂ · H₂O and⁷LiHCO₂ · D₂O and the observed fundamental bands have been discussed taking into account the⁶Li/⁷Li and H₂O/D₂O isotope wavenumber shifts on the fundamental vibrations.

---

Infrarotspektren (700–200 cm^–1) und⁶Li/⁷Li- und H₂O/D₂O-Isotopeneffekte für vier isotopensubstituierte Lithiumformat-monohydrate

Zusammenfassung Die Infrarotspektren in der Region von 700–200 cm^–1 werden für⁶LiHCO₂ · H₂O,⁶LiHCO₂ · D₂O,⁷LiHCO₂ · H₂O und⁷LiHCO₂ · D₂O angegeben und die beobachteten Grundschwingungen zusammen mit den isotopischen Verschiebungen der Wellenzahlen diskutiert.

     

Diffusion of Li+ ions in concentrated solutions of LiNO3 in 1,3-diaminopropane

The temperature and composition dependences of the self-diffusion coefficient of Li⁺ ions were investigated for concentrated solutions of LiNO₃ in 1,3-diaminopropane by means of the NMR spin-echo technique from 20 to 50°C. The composition dependence of the activation energy shows a bend around 30 mol % LiNO₃. This is consistent with the previous results obtained from the electrical conductivity and the correlation time of the rotational motion of the solvating ions, and suggests that solvent molecules may act as bridges between Li⁺ ions at higher concentrations of LiNO₃.     

The crystal and molecular structures of bridged spherands: The host C52H52O8, its complex C52H52O8·Li+, and the complexes C50H48O6·Li+ and C52H52O6·Li+

The structures of the title novel hosts and host-guest complexes, synthesized by D. J. Cram and his colleagues, were determined by direct methods from diffractometer data and refined by least-squares. The hosts C₅₂H₅₂O₈,I, C₅₀H₄₈O₆,II, and C₅₂H₅₂O₆,III, are di-bridged derivatives of the prototype spherand C₄₈H₄₈O₆,IV. InIV, six 4-methylanisole units are joined in the 2,6 positions. InI two -CH₂CH₂OCH₂CH₂- bridges replace four of the methoxy methyl groups, joining pseudo-meta oxygen atoms; these two bridges are on the same face of the macrocycle (syn). InII andIII, trimethylene and tetramethylene bridges, respectively, are similarly situated, again replacing four methoxy methyls ofIV. CompoundsIa,IIa andIIIa are Li⁺ complexes of these hosts. The lithium ion is essentially hepta-coordinated inIa, penta-coordinated inIIa and hexa-coordinated inIIIa. These structures are extremely rigid, and the aromatic rings in them are greatly deformed. There are intramolecular oxygen contacts in each complex only slightly greater than 2.5 Å, about 10 percent shorter than the sum of the usual van der Waals radii for oxygen atoms. Thus the structures provide useful data for parameterizing potential functions for molecular mechanics calculations.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Li+3 ion beam irradiation induced changes in the thermodynamic and electrical parameters of 4-n-(nonyloxy) benzoic acid

Li⁺³ ion beam irradiation studies on 4-n-(nonyloxy) benzoic acid (NOBA) have been carried out. Thermodynamic measurements demonstrate that all the phase transition temperatures are depressed for low value of irradiation fluence as compared to those for the pure NOBA and thereafter increase linearly with increase in irradiation fluence. It has also been observed that the temperature range of N and SmC phases in the heating and cooling cycles is improved due to irradiation. Dielectric investigations show that both the transverse as well as the longitudinal components of the dielectric permittivity are increased as compared with those of the pure sample due to irradiation. The observed change in the thermodynamic and dielectric parameters is attributed to the increased concentration of NOBA monomers over the NOBA dimers due to fragmentation of the hydrogen bonding in some of the NOBA dimers.     

An NMR study of the stoichiometry and stability of lithium ion complexes with 12-crown-4, 15-crown-5 an 18-crown-6 in binary Acetonitrile-Nitrobenzene mixtures

Proton NMR spectroscopy was used to study the complexation reaction between lithium ion and 12-crown-4, 15-crown-5 and 18-crown-6 in a number of binary acetonitrile-nitrobenzene mixtures. In all cases the exchange between free and complexed crowns was fast on the NMR time scale and only a single population average¹H signal was observed. Formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability and the amount of acetonitrile in the mixed solvent. It was found that, in all solvent mixtures used, 15-crown-5 forms the most stable complex with Li⁺ ion in the series.     

Thermodynamics and selectivity of complexation of lithium and sodium thiocyanates with phosphorus-containing podands and compounds modeling the terminal groups of these podands

A series of model compounds and heptadentate neutral phosphorus-containing podands that differ in the conformational rigidity of the terminal groups and in the coordination properties of the phosphoryl groups were synthesized. The thermodynamic parameters of complexation and the cationic selectivity of organophosphorus compounds and podands with respect to LiNCS and NaNCS were studied by calorimetric titration in acetonitrile at 298 K. The reasons for the high selectivity of certain phosphorus-containing podands to the Li⁺ cation are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1581–1587, September, 1994.This work was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08848) and the International Science Foundation (Grant No. MTH000).     

Study of the intensity of M+, M2+ and MO+ signals in ICP-MS as a function of instrumental parameters

In addition to peaks from singly charged ions (M⁺), signals from oxide (MO⁺), hydroxide (MOH⁺) and doubly charged (M²⁺) ions, which may lead to spectral overlap interferences, are observed in ICP-MS spectra. Using a VG PlasmaQuad ratios of MO⁺/M⁺, MOH⁺/M⁺ and M²⁺/M⁺ were determined for a number of elements, covering a wide range of atomic masses, first and second ionisation energies and chemical properties. The temporal stability of the MO⁺/M⁺ and M²⁺/M⁺ ratios was investigated. The correlation between the ratios of MO⁺/M⁺ and M²⁺/M⁺ with the M-O bond strength and the difference between the second and the first ionisation energy respectively is discussed. The influence of several instrumental parameters, associated with sample introduction and plasma operation, on the M⁺, M²⁺ and MO⁺ signals and on the MO⁺/M⁺ and M²⁺/M⁺ ratios is studied. Simple qualitative explanations are given in order to explain some of the observed results. No quantitative results are given for the MO⁺/M⁺ and M²⁺/M⁺ ratios as the experiments pointed out that they are influenced to a large extent by several instrumental parameters.     

Li+掺杂对TeO2:Tm3+/Er3+/Yb3+纳米材料上转换发光的增强作用

采用水热法制备了发白光的Li+掺杂α-TeO2∶Tm3+/Er3+/Yb3+和β-TeO2∶Tm3+/Er3+/Yb3+纳米上转换发光材料。采用X射线衍射、透射电镜和上转换发光光谱对制备的TeO2∶Tm3+/Er3+/Yb3+/Li+纳米材料进行表征,结果显示:Li+的掺入基本不改变纳米材料的晶型和结构;在980 nm近红外光的激发下,纳米材料发射出中心波长476 nm的蓝光,525 nm及545 nm的绿光和659 nm及675nm的红光,分别对应于Tm3+的1G4→3H6能级跃迁,Er3+的2H11/2→4I15/2和4S3/2→4I15/2能级跃迁,Er3+的4F9/2→4I15/2能级跃迁和Tm3+的3F2→3H6能级跃迁;Li+的掺入能够增大白光体系的发光强度,基本不改变纳米材料的白光颜色。此外,探讨了纳米材料的上转换发光机理。     

Raman spectroscopic study of four isotopically substituted lithium hydroxide monohydrates

Raman spectral data of polycrystals of four isotopically substituted lithium hydroxide monohydrates,⁶LiOH·H₂O,⁷LiOH·H₂O,⁶LiOD·D₂O and⁷LiOD·D₂O, have been investigated in the 4,000–50 cm^–1 region. The observed spectra have been analyzed and discussed taking into account the results of the factor group analysis and the H/D and⁶Li/⁷Li isotope effects on the fundamental wavenumbers.

---

Raman-spektroskopische Untersuchung von vier isotopisch substituierten Lithiumhydroxid-Monohydraten

Zusammenfassung Raman-spektroskopische Daten von⁶LiOH·H₂O,⁷LiOH·H₂O,⁶LiOD·D₂O und⁷LiOD·D₂O werden im Bereich von 4000 bis 50 cm^–1 angegeben. Die beobachteten Spektren werden analysiert und im Hinblick auf Faktorgruppenanalyse und auf die Isotopeneffekte H/D und⁶Li/⁷Li diskutiert.

     

Resonant Ionic,Covalent Bond,and Steric Characteristics Present in 1Σu+ States of Li2

The molecular bonding in the excited states of the alkali dimers involves the resonant ionic, covalent bond and steric interactions. We show here the case of the ¹Σ_u⁺ states of Li₂ by ab initio calculation. These interactions as functions of the internuclear distance lead to complex potential energy curves, providing an important application for high resolution laser spectroscopy. The spectroscopic constants for the 4 and 5 ¹Σ_u⁺ states are obtained for the first time.     

Raman and infrared spectra of6Li2C2O4 and7Li2C2O4

Raman and infrared spectra of polycrystalline⁶Li₂C₂O₄ and⁷Li₂C₂O₄ have been investigated in the wavenumber region from 1,800 to 40 cm^–1. The internal C₂O₄ ^–2 vibrations have been studied on the basis of a D_2h molecular structure and the correlation field splittings have been found to be about 40 cm^–1 for the stretching modes and about 15 cm^–1 for the bending modes. The external vibrations of the Li⁺ and C₂O₄ ^–2 sites have been discussed by considering the results of the factor group analysis and the⁶Li/⁷Li isotope effect on the normal vibrations.

---

Raman- und Infrarot-Spektren von⁶Li₂C₂O₄ und⁷Li₂C₂O₄

Zusammenfassung Es wurdenRaman- und IR-Spektren von polykristallinem⁶Li₂C₂O₄ und⁷Li₂C₂O₄ im Bereich der Wellenzahlen von 1800 bis 40 cm^–1 untersucht. Die internen Schwingungen wurden auf der Basis einer D_2h Molekülstruktur analysiert. Für die Streckschwingungen wurde eine Korrelationsaufspaltung von etwa 40 cm^–1 gefunden, für die Deformationsschwingungen etwa 15 cm^–1. Die Diskussion der externen Schwingungen von Li⁺ und C₂O₄ ^–2 erfolgte unter Berücksichtigung der Resultate der Faktorgruppenanalyse und des⁶Li/⁷Li Isotopeneffekts auf die Normalschwingungen.

     

Proton NMR probing of stoichiometry and thermodynamic data for the complexation of Na and Li ions with 15-Crown-5 in acetonitrile-nitrobenzene mixtures

Proton NMR was used to study the complexation reaction of Li⁺ and Na⁺ ions with 15-Crown-5 (15C5) in a number of binary acetonitrile (AN)-nitrobenzene (NB) mixtures at different temperatures. In all cases, the exchange between free and complexed 15C5 was fast on the NMR timescale and only a single population average ¹H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift mole ratio data. There is an inverse relationship between the complex stability and the amount of AN in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated from the temperature dependence of the formation constants. In all the solvent mixtures studied, the resulting complex is enthalpy stabilized but entropy destabilized. Finally, the experimental results were compared with theoretical ones that were obtained from molecular modeling methods. Based on our results, it is most probable that Li⁺-15C5 in solvent stays in a rather nesting complex form with greater LogK_f values, but Na⁺-15C5 forms a complete perching complex form with lower LogK_f values.     

Conductance Study of the Thermodynamics of Complexation of K+, Rb+, Cs+ and Tl+ Ions with Dibenzo-24-crown-8 in Binary Acetonitrile–Nitromethane Mixtures

The complexation reactions between dibenzo-24-crown-8 (DB24C8) and K⁺, Rb⁺, Cs⁺ and Tl⁺ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in the order Tl⁺ > K⁺ > Rb⁺ > Cs⁺. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent mixture. The TΔS° vs. ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy compensation in the complexation reactions.     

Inhibition of Na+, K+-ATPase in the presence of crown ethers: modulation of ionic composition or pharmacological effects

It is believed that the biological effects of chelating agents such as crown ethers are largely related to their ability to form complexes with ions and/or to facilitate ion transport across membranes. Specific influences are rarely related. Here we present the evidence that even one of the simplest representatives of the crown ether super-family, 1,4,7,10,13,16-hexaoxacyclooctane (18-crown-6), is able to affect the activity of Na⁺, K⁺-ATPase directly. Using nonlinear regression fitting to kinetic data we have found that the crown ether diminishes the apparent Michaelis constant, K _m , and the maximal rate of ATP hydrolysis, V _m , acting as noncompetitive inhibitors. The apparent dissociation constants, K _i , for the crown interaction with the free ATPase and with the enzyme-substrate complex were established to be of 77 ± 3 mM and 21 ± 2 mM, respectively. So 18-crown-6 possesses weak but “direct” pharmacological activity on Na⁺, K⁺-ATPase hinders the formation of enzyme–substrate complex and detains the enzyme in this state.     

过饱和度、钙/草酸化学计量比对草酸钙晶体形成的影响及降解茯苓多糖的调控作用

为研究草酸钙(CaC₂O₄)晶体成核、生长和聚集,探讨降解茯苓多糖(PCP)的抑制作用,采用X射线衍射、FT-IR、扫描电镜、拉曼光谱、ζ电位仪和紫外分光光度计等方法对不同条件下形成的 CaC₂O₄晶体进行表征。结果表明,在低过饱和度(RS≤26.6)时,主要生成一水草酸钙(COM)晶体;至RS为37.6和46.0时分别生成了11.6%和38.3%的二水草酸钙(COD)晶体,且高RS时晶体的聚集程度增加。在RS相同时,随着Ca²⁺/Ox^2-(Ox^2-=C₂O₄^2-)化学计量比(n_Ca²⁺/n_Ox^2-)增大,晶体中COD比例增加。降解PCP的加入可增加体系中可溶性Ca²⁺浓度,减少生成的CaC₂O₄晶体质量,增加晶体表面ζ电位绝对值,这些均有利于抑制CaC₂O₄结石的形成。因此,高Ox^2-浓度对肾结石形成的风险远大于高Ca²⁺浓度,提示草酸的摄入对CaC₂O₄结石的风险远远大于钙的摄入,降解PCP能同时抑制CaC₂O₄晶体的成核、生长和聚集。