Alkali Metal Ions In Solution Research Articles

Molecular Insights into the Influence of Ions on the Water Structure. I. Alkali Metal Ions in Solution.

In this study, we explore the impact of alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) on the hydration structure of water using molecular dynamics simulations carried out with MB-nrg potential energy functions (PEFs). Our analyses include radial distribution functions, coordination numbers, dipole moments, and infrared spectra of water molecules, calculated as a function of solvation shells. The results collectively indicate a highly local influence of all of the alkali metal ions on the hydrogen-bond network established by the surrounding water molecules, with the smallest and most densely charged Li+ ion exerting the most pronounced effect. Remarkably, the MB-nrg PEFs demonstrate excellent agreement with available experimental data for the position and size of the first solvation shells, underscoring their potential as predictive models for realistic simulations of ionic aqueous solutions across various thermodynamic conditions and environments.

Postsynthetic ion exchange and characterization of alkali metal ions ordered in the pores of anionic Zr metal–organic framework

AbstractBinding alkali metal ions in solutions is an important yet difficult task and it is especially true for a solid host in aqueous systems. This study shows that a water stable, anionic metal–organic framework (Zr‐dobdc) is capable of capturing M+ (M = Li, Na, K, Rb, and Cs) ions dissolved in water through ion exchange. The alkali metal ions captured at the unique cation‐binding pockets of Zr‐dobdc and their ordered alignments in the crystal lattice are unambiguously characterized by X‐ray single‐crystal and powder diffraction studies. The apparent selectivity for alkali metal ions over other metal ions is also explained.

Conformation of alkali metal ion-calix[4]arene complexes investigated by IR spectroscopy in the gas phase.

We measure the IR spectra of calix[4]arene (C4A) complexes with K+, Rb+, and Cs+ ions in the 3200-3700 cm-1 region by IR-UV double-resonance spectroscopy performed under cold (∼10 K) gas-phase conditions. All the complexes show two bands that can be assigned to the stretching vibrations of hydrogen-bonded OH groups in the C4A part. Quantum chemical calculations predict several isomers having different IR spectra, but the IR spectrum of the "cone" conformer reproduces the IR-UV spectrum very well, indicating that all the complexes adopt the cone conformation including the metal ions in the cone. The frequency of the OH stretching vibrations decreases with increasing the ion size from K+ (3357 and 3513 cm-1) to Rb+ (3323 and 3463 cm-1) and Cs+ (3279 and 3379 cm-1), but it is substantially higher than that of hydrogen-bonded OH groups in bare C4A (3158 cm-1). These results suggest that C4A encapsulates the metal ions by distorting the cone cavity, and that the distortion of the cone conformation is reduced more and the hydrogen bond between the OH groups becomes stronger with increasing the ion size from K+ to Cs+. The Cs+ complex has the smallest distortion of the C4A cavity among the alkali metal ion complexes. This can be one origin for the predominant encapsulation of Cs+ ions by C4A over smaller alkali metal ions in solution.

Silacrown Ethers-Clay Intercalation Materials: Application in Potentiometric Sensors for Detection of Alkali-Ions

Abstract Dimethylsila-14-crown-5 (DMS14C5) and dimethylsila-17-crown-6 (DMS17C6) macrocyclic polyethers have been intercalated into montmorillonite layered silicates containing Li+, Na+ or K+ cations as exchangeable cations. XRD and FTIR spectroscopy offer information on the disposition of the macrocycle in the interlayer and accommodation of cations within the cavity of the polyoxyethylene ligand. 13C and 23Na solid-state NMR spectroscopy provides information about the replacement of water molecules from the hydration shell of interlayer cations by the macrocyclic ligand and confirms differences in the interactions depending on the nature of the ligand. The resulting montmorillonite intercalation materials were tested as active phase of PVC electrodes for the development of potentiometric sensors, in a preliminary attempt to evaluate their electrochemical response towards alkali-metal ions in solution.

Reshaping Rubrene by Controlled Reduction with Alkali Metals

AbstractMono‐, di‐ and tetraanions of rubrene, (C42H28, Rub0), were generated by the controlled reduction of neutral polyarene with various alkali metals in the appropriate solvent. The X‐ray diffraction studies of the resulting adducts of Rub1–, Rub2– and Rub4– with alkali‐metal ions revealed the distortion of the rubrene core upon the stepwise acquisition of electrons. Coordination of the Cs+ ion and a noticeable deformation of Rub1– are observed at the first reduction step. Two types of rubrene dianions showing an essentially different conformation and coordination environment for the central tetracene core have been seen in the cesium adduct of Rub2–. Various types of supramolecular assembly between the tetrareduced rubrene anion, Rub4–, and lithium or rubidium cations have been found in the corresponding products in the solid state. The structures of rubrene anions and their aggregation with alkali‐metal ions in solution have been studied by ESR and multinuclear NMR (1H, 13C, 7Li and 133Cs) spectroscopy.

A Study of the Hydration of the Alkali Metal Ions in Aqueous Solution

The hydration of the alkali metal ions in aqueous solution has been studied by large angle X-ray scattering (LAXS) and double difference infrared spectroscopy (DDIR). The structures of the dimethyl sulfoxide solvated alkali metal ions in solution have been determined to support the studies in aqueous solution. The results of the LAXS and DDIR measurements show that the sodium, potassium, rubidium and cesium ions all are weakly hydrated with only a single shell of water molecules. The smaller lithium ion is more strongly hydrated, most probably with a second hydration shell present. The influence of the rubidium and cesium ions on the water structure was found to be very weak, and it was not possible to quantify this effect in a reliable way due to insufficient separation of the O–D stretching bands of partially deuterated water bound to these metal ions and the O–D stretching bands of the bulk water. Aqueous solutions of sodium, potassium and cesium iodide and cesium and lithium hydroxide have been studied by LAXS and M–O bond distances have been determined fairly accurately except for lithium. However, the number of water molecules binding to the alkali metal ions is very difficult to determine from the LAXS measurements as the number of distances and the temperature factor are strongly correlated. A thorough analysis of M–O bond distances in solid alkali metal compounds with ligands binding through oxygen has been made from available structure databases. There is relatively strong correlation between M–O bond distances and coordination numbers also for the alkali metal ions even though the M–O interactions are weak and the number of complexes of potassium, rubidium and cesium with well-defined coordination geometry is very small. The mean M–O bond distance in the hydrated sodium, potassium, rubidium and cesium ions in aqueous solution have been determined to be 2.43(2), 2.81(1), 2.98(1) and 3.07(1) Å, which corresponds to six-, seven-, eight- and eight-coordination. These coordination numbers are supported by the linear relationship of the hydration enthalpies and the M–O bond distances. This correlation indicates that the hydrated lithium ion is four-coordinate in aqueous solution. New ionic radii are proposed for four- and six-coordinate lithium(I), 0.60 and 0.79 Å, respectively, as well as for five- and six-coordinate sodium(I), 1.02 and 1.07 Å, respectively. The ionic radii for six- and seven-coordinate K+, 1.38 and 1.46 Å, respectively, and eight-coordinate Rb+ and Cs+, 1.64 and 1.73 Å, respectively, are confirmed from previous studies. The M–O bond distances in dimethyl sulfoxide solvated sodium, potassium, rubidium and cesium ions in solution are very similar to those observed in aqueous solution.

Synthesis of, and Structural Assignments to the Stereoisomers of Bis (2,2‘)- and Tris (2,2‘,2‘ ‘)-Tetrahydrofurans: Conformational Features and Ionic Binding Capacities of These Gateway Polycyclic Networks

Construction of the polytetrahydrofuranyl building blocks 6-10 from the common bissiloxyacetone precursor 11 is detailed. The approach is concise and, for the bis-(THF) pair, capitalizes on the full retention of configuration observed during the rhodium-promoted decarbonylation of aldehydes 18 and 19. The capability of the title compounds to associate with alkali metal ions in solution and the gas phase has demonstrated a preference for Li+ over Na+ and K+ in all cases, with 6 and 7 exhibiting somewhat higher binding selectivities than 8-10. The relative energy orderings of attainable conformations with the bis-THF and tris-THF series were explored computationally. The various envelope arrangements present in the individual THF units are shown to play a significant role alongside prevailing gauche interactions. The "gauche effect" is shown computationally not to be an accurate predictor of the lowest energy conformer.

Study of Spectral Character of Alkali Metals Using Microwave Plasma Torch Simultaneous Spectrometer

A microwave plasma torch (MPT) simultaneous spectrometer was used to study the spectral character and the matrix effect on alkali metal ions in solution. The main parameters were optimized. The microwave forward power was 100 W. The argon flow rate that was used to sustain the Ar-MPT included the flow rate of carrier gas and the flow rate of support gas, which were 0.8 and 1.0 L/min, respectively. The HC1 concentration in the solution was 0.02 mol/L. The observation height was 9.0 mm. The detection limits of Li, Na, K, Rb, and Cs were 0.0003, 0.0004, 0.009, 0.07 and 2.4 mg/L, respectively, and the results obtained by the Ar-MPT were compared with those obtained by argon inductively coupled plasma(Ar-ICP) and argon microwave induced plasma(Ar-MIP). The interference effects of several matrix elements were also studied.

Alkali metal-mediated proline aggregation in solution observed by coldspray ionization mass spectrometry.

L-Proline aggregates to form cyclic clusters in the presence of alkali metal ions in solution, whereas a large-scale-aggregated chain structure was observed for several other amino acids. The major cyclic clusters are suggested to be constructed from trimeric and tetrameric subunits on the basis of direct solution analysis by coldspray ionization mass spectrometry.

Solution cation-binding properties of segmented polyethylene oxide-A13C NMR spectroscopic study

Two segmented polyethylene oxides, SPEO-3 and SPEO-4, were prepared using a novel transetherification methodology. Their structures were confirmed by H-1 and C-13 NMR spectroscopy. The complexation of these SPEO's with alkali-metal ions in solution was investigated by C-13 NMR spectroscopy. The mole-fraction method was used to determine the complexation ratio of SPEO with LIClO4 at 25 degrees C, which showed that these formed 1:1 (polymer repeat unit/salt) complexes. The association constant, K, for the complex formation was calculated from the variation of the chemical shift values with salt concentration, using a standard nonlinear least-square fitting procedure. The maximum change in chemical shift (Delta delta) and the K values suggest that both SPEO-3 and SPEO-4 formed stronger complexes with lithium salts than with sodium salts. Unexpectedly, the K values were found to be different, when the variation of delta of different carbons was used in the fitting procedure. This suggests that several possible complexed species may be in equilibrium with the uncomplexed one. Structurally similar model compounds were also prepared and their complexation studies indicated that all of them also formed 1:1 complexes with Li salts. Interestingly, it was observed that the polymers gave higher K values suggesting the formation of more stable complexes in polymers when compared to the model analogues. (C) 2000 John Wiley & Sons, Inc.

Ein makrobicyclischer Großhohlraum zur selektiven Komplexierung von Alkalimetall‐Ionen

A Large Macrobicyclic cavity for the Selective Complexation of Alkali Metal Ions The preparation of the new ligand 3 was carried out starting with the podand 8 and the triamine 11. Ligand 3 forms complexes with alkali metal ions in solution (chloroform) as well as under the conditions of FAB mass spectrometry, whereby Cs⊕ selectivity is observed.

Preliminary studies in the determination of the alkali metals by microwave induced plasma (MIP) spectrometry

A microwave induced plasma (MIP) detector is discussed for the sensitive determination of the alkali metal ions in solution. The microwave power and argon flow utilized to sustain the Ar-MIP were optimized for the determination of Li, Na, K, Rb and Cs ions in solution. The utilization of moderate power levels ( ca. 150–500 W) facilitates the direct introduction of aqueous aerosols into the plasma. Spectral profiles, relative line intensities and sensitivities, and detection limits obtained with the Ar-MIP are compared with those acquired with a commercial argon inductively coupled plasma (Ar-ICP), utilizing the same spectrometer, optics and data collection system. The Ar-MIP detection limits and sensitivities are ten to several hundred times improved over those obtained with the Ar-ICP.

Core Electron Spectroscopy of Alkali Metal Ions in Solution

Core photoelectron and Auger electron energies of alkali metal ions in solution have been measured and related to the corresponding energies in the gas phase. The magnitude of the electronic polarization contribution to the solvation energies of hard ions is discussed on the basis of measured solvation shifts of photo- and Auger electron lines. Through a combined use of the two types of shift an assessment can be made of the numerical value of the electronic solvation energy with Na+ and ions of the same radius as an example. The electronic polarization is found to be of major importance in the solvation of hard ions.

SUGAR ABSORPTION BY CHAETOMIUM GLOBOSUM

SummaryThe absorption of the sugars, glucose and fructose, by Chaetomium globosum does not involve an accumulation against an internal concentration but is associated with immediate assimilation. The process is sensitive to the presence of inhibitors, anaerobiosis, and to the concentration supplied. The relationship to concentration is hyperbolic and the half maximum rates occur at about 6–8 × 10‐3 M for fructose and 9 × 10‐5 M for glucose. Glucose and fructose compete for the uptake mechanism so that in mixed solutions when the glucose concentration is at about 13% of that of fructose the uptake of the latter is abolished.The uptake of carbohydrate from sucrose solutions is mainly an uptake of the hexose moeities released from sucrose. The amount of sucrose absorbed intact is very small. Sucrose is split by an enzyme system which appears to be located at or near the hyphal surface. It is relatively resistant to temperature and metabolic inhibitors and appears to be stimulated by alkali metal ions in solution.

Studies on the binding of small ions in protein solutions with the use of membrane electrodes. VII. The binding of the alkali-metal ions in solutions of phosphoproteins

The binding of the alkali ions with phosvitin, casein, and a phosphopeptide of casein has been studied as a function of pH and cation concentration. The maximum binding of sodium at pH 7.5 is 175 moles/ 10 5 g., 18 moles/10 5 g., and 100 moles/10 5 g. for phosvitin, casein, and the phosphopeptide, respectively; lithium binding is slightly stronger, and potassium binding is slightly weaker. It is suggested that the localization of negatively charged groups within the casein molecule is responsible for its binding of the alkali ions.