Number Of Solvents Research Articles

Solvent Stripping Dynamics of Lithium ion solvated by ethylene carbonates: A direct ab-initio molecular (AIMD) Study

Solvent dissociation dynamics from solvated lithium ion solvated by ethylene carbonates (EC) have been investigated by means of direct ab-initio molecular dynamics (AIMD) method. The lithium ion was solvated by four EC molecules as the first solvation shell. It was found that the solvation number of lithium ion is drastically changed from 4 to 1 when the solvated lithium ion accepts an excess electron. The binding energy of Li-EC decreased to a one-tenth. Finally, the contact ion pair composed of Li+ and EC− was formed as the product. The mechanism of solvent dissociation was discussed on the basis of theoretical results.

Molecular interactions in some synthesized pyrimidine derivatives in methanol and DMF solutions at 308.15 K

Some new pyrimidine derivatives have been synthesized and their characterization was done by IR, 1H NMR and mass spectral data. The measurement of density (ρ), ultrasonic velocity (U) and viscosity (η) of pure solvents and solutions of pyrimidine derivatives in methanol and dimethylformamide was done at 308.15K over a wide range of concentrations (0.01 to 0.1M). Using these experimental data, some acoustical parameters such as adiabatic compressibility (κs), intermolecular free length (Lf), solvation number (Sn), apparent molar compressibility (ϕk), apparent molar volume (ϕv) etc., have been evaluated for the understanding of the effect of solvents on molecular interactions in these solutions.

Solvation and Association of 3:1 Electrolytes in N,N-Dimethylformamide

A detailed study has been made of the solvation and ion association of the trifluoromethanesulfonate (Tf(-)) salts of aluminum(III), scandium(III), and lanthanum(III) in N,N-dimethylformamide (DMF) at 25 °C using dielectric relaxation spectroscopy over the frequency range of 0.1 ≲ ν/GHz ≤ 89. The spectra of all solutions exhibited either two (for ScTf3 and LaTf3) or three (for AlTf3) relaxation processes, a dominant mode centered at ∼15 GHz due to the solvent and one or (for AlTf3 solutions) two solute-related processes at lower frequencies (νmax ≲ 2 GHz). Effective solvation numbers, Zib, calculated from the solvent relaxation process indicated that all three cations were strongly solvated by DMF with Zib(0) values at infinite dilution in the order (Al(3+) ≈ Sc(3+) ≈ 10) < (La(3+) ≈ 13), consistent with at least partial formation of a second solvation shell around each cation. One solute-related mode for each set of salt solutions was assigned to the rotational diffusion of solvent-shared ion pairs (SIPs) of 1:1 stoicheometry; the additional slower process for AlTf3 solutions in DMF was attributed to the presence of double-solvent-separated IPs. The overall association constants at infinite dilution for the 1:1 IPs, KA°(MTf(2+)), were significant, but as expected from Debye-Hückel considerations, the KA values decreased rapidly with increasing solute concentration.

Study of molecular interactions in solutions of azomethines of sulfamethoxazole in N,N-dymethylformamide and tetrahydrofuran

Density, ultrasonic velocity and viscosity of azomethines containing sulfamethoxazole nucleus have been measured in N,N-dimethylformamide and tetrahydrofuran solutions over a wide concentration range at temperature 308.15 K. From these experimental data, acoustical parameters such as intermolecular free path length, isentropic compressibility and relaxation strength have been evaluated, that help understanding the molecular interactions occurring in these solutions. Furthermore, compressibility solvation number, the apparent molar compressibility and apparent molar volume of the solutions have been determined and discussed.

Effect of solvation with salting effect on solubilities of fluorocarbons in alcohols

In our previous work, we found that salting-out effect of a fluorocarbon in an alcohol–NaOH solution brought solubility decrease which could be expressed in terms of the Setchenov coefficient. In this work, a group contribution method for the Setchenov coefficients was made, for dichrodifluoromethane (CFC-12), penafluoroethane (HFC-125), difluoromethane (HFC-32), 1,1,1,2-tetarfluoroethane (HFC-134a) and 1,1-difluoroethane (HFC-152a) in methanol–NaOH and ethanol–NaOH solvents. Moreover, as a simple model, we derived the relationship between the Setchenov coefficients and solvation number of alcohols around a NaOH molecule. Therefore, once information of the Setchenov coefficients was obtained, the solvation numbers could be predicted based on the model. Prediction of the Setchenov coefficients for VOC solublities in water–salt system is possible with the new method.

Partial molar volumes and viscosity B-coefficients for N,N/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride in methanolic solutions of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate at T = (298.15, 308.15, and 318.15) K

Ion–ion and ion–solvent interactions for N,N/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H2O)2]Cl, dissolved in solutions of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, [bdmim]BF4 (0.005 to 0.020mol·dm−3) in methanol (MeOH) were investigated by a combination of physicochemical properties at 298.15, 308.15 and 318.15K under ambient pressure. From measured solution densities and viscosities apparent molar volume (φV), the slope (SV∗), standard partial molar volume (φV0), transfer volume (ΔtφV0), the viscosity B-coefficient, its temperature derivative (∂B/∂T), solvation number (Sn), etc. were calculated and discussed on the basis of ion–ion and ion–solvent interactions. In the investigated temperature range, the relation: φV0=a0+a1T, was used to determine the temperature dependence of the partial molar volumes φV0, i.e., partial molar expansibilities (φE0). Temperature dependence of the viscosity B-coefficient (∂B/∂T) values revealed the complex to be a long-range structure breaker. Thermodynamics of viscous flow were discussed on the basis of the transition state theory.

Unusual Li+Ion Solvation Structure in Bis(fluorosulfonyl)amide Based Ionic Liquid

Raman spectra of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide [C2mIm+][FSA–] ionic liquid solutions dissolving LiFSA salt of various concentrations were measured at 298 K. FSA– ((FSO2)2N–) is an analogue anion of bis(trifluoromethanesulfonyl)amide ((CF3SO2)2N–; TFSA–). We found that a solvation number of the Li+ ion in [C2mIm+][FSA–] is 3, though it has been well established that Li+ ion is solvated by two TFSA– anions in the corresponding ionic liquids below the Li+ ion mole fraction of xLi+ < 0.2. To yield further insight into larger solvation numbers, Raman spectra were measured at higher temperatures up to 364 K. The Li+ ion solvation number in [C2mIm+][FSA–] evidently decreased when the temperature was elevated. Temperature dependence of the Li+ ion solvation number was analyzed assuming an equilibrium between [Li(FSA)2]− and [Li(FSA)3]2–, and the enthalpy ΔH° and the temperature multiplied entropy TΔS° for one FSA– liberation toward a bulk ionic liquid were successfully evaluated to be 35(2)...

Preparation and characterization of polybenzimidzaole/diethylamine hydrogen sulphate for medium temperature proton exchange membrane fuel cells

Diethlyamine bisulphate/sulphate, an ionic liquid, was synthesised and characterised for high temperature fuel cell applications. Composite hybrid membranes of PBI and the ionic liquid diethlyamine bisulphate/sulfate were fabricated at different composition ratios PBI/xDESH. FTIR spectra showed that the IL did not change the PBI structure. The ionic liquid only weakly interacts with PBI and remains free inside the structure allowing for the observed ionic conduction.PBI/xDESH membranes could operate under a higher temperature values/low humidity conditions with conductivity >0.01 S cm−1.The measured proton conductivity, from symmetrical H2 cell, however, is ca. 4 times lower than that of the measured ionic conductivity. This could be estimated roughly by considering proton conduction where the proton is associated with two anions A− resulting in ionic agglomerate HA2− with more than double the ionic radius of A− and consequently less than half of its diffusivity. Additionally, considering the solvation number of that agglomerate to be 1.0 will result not only in a slower proton diffusion and lower conductivity but will also cause serious flooding and mass transport limitation at the cathode. This cumulative effect will limit the life of the cell due to the IL migration from anode and membrane to the cathode.

7-(Dimethylamino)coumarin-3-carbaldehyde and Its Phenylsemicarbazone: TICT Excited State Modulation, Fluorescent H-Aggregates, and Preferential Solvation

The photophysical properties of 7-(dimethylamino)coumarin-3-carbaldehyde 3 and its phenylsemicarbazone 4 were investigated in solvents of various polarity and in differing solvent mixtures. The different fluorescent quantum yield (ΦF) behavior of 3 and 4 in highly polar solvents is discussed in terms of Twisted Intramolecular Charge-Tranfer (TICT) state formation and the specific solute-solvent interactions. Because of the weak intermolecular hydrogen bonding ability of both the radiative ICT and nonradiative TICT excited state of 3 and the linear steep decrease in ΦF from a medium to high polarity region, coumarin 3 could be a useful polarity probe for microenvironments containing hydrogen bonding groups. Compared to 3, coumarin 4 exhibits the highest ΦF values in highly polar solvents with strong hydrogen bond acceptor ability. The high quantum yield of fluorescence in DMSO, DMF, and alcohols qualifies coumarin 4 as a laser dye in the given medium, with kF higher than k(nr). Contrary to previous reports that many H-aggregates are nonfluorescent in nature, coumarin 3 forms highly fluorescent H-aggregates in MeOH and EtOH. On the basis of the restrictions of the Kasha-exciton theory model, we assume that the formation of fluorescent H-dimer aggregates of 3 is driven by π(+)-π(-) interactions. To the best of our knowledge, this is the first report on aggregation of coumarin dye in alcoholic solutions. In addition, restrictions in the fitting procedure relating to determination of the solvation number, n, using the Covington-Newman model of preferential solvation and also the solvent nonideality parameter, h', are discussed in this article.

Effect of ionic liquid on the solvation behavior of nonaqueous N,N′-salicylidenephenylediamine Schiff base (Salophen) solutions at 298.15 K

Thermodynamic properties of N,N′-salicylidenephenylediamine Schiff base (Salophen) in the solutions of ionic liquid, 1-butyl-3-methylimidazolium bromide ([BMIm]Br)+organic solvents (N,N-dimethylacetamide DMA, and dimethylsulfoxide DMSO) have been measured at 298.15K. The measured density and viscosity values have been used to calculate apparent molar volumes, Vϕ, standard partial molar volumes, Vϕ0, standard partial molar volumes of transfer, ΔtrVϕ0, viscosity B-coefficients, and solvation numbers, B/Vϕ0, for the solutions being studied. All of these parameters were used to interpret the solute–solvent interactions and solvation process occurring between ionic liquid and Salophen.

Electrochemical Behavior and Solvation Analysis of Rare Earth Complexes in Ionic Liquids Media Investigated by SECM and Raman Spectroscopy

In this study, the electrochemical behavior of neodymium complexes; Nd(III) in the phosphonium ionic liquid; P2225TFSA triethyl-pentyl-phosphonium bis(trifluoromethylsulfonyl)amide was examined by the voltammetric method using a platinum tip electrode. The diffusional behavior of Nd(III) was certificated to be similar behavior of other rare earth complexes such as Sm. The ideal steady-state approach current of the positive feed back was obtained in Nd(III)/P2225TFSA and the fitted function of this approach curve was determined through mathematical treatment. Moreover, the concentration gradient and the related current distribution using ferrocene redox mediator for the electrodeposition process of Nd(III) were investigated by scanning electrochemical microscopy. This result revealed that the current distribution on the platinum substrate for Nd(III) in P2225TFSA was drastically altered after the electrodeposition of Nd(III). Furthermore, it was revealed the interaction between Nd trivalent ion and free TFSA anion would be relatively strong considering from the solvation number analyzed by Raman spectroscopy.

Electrochemical lithium ion intercalation into graphite electrode in propylene carbonate-based electrolytes with dimethyl carbonate and calcium salt

Electrochemical intercalation of Li+ ions into graphite electrodes in propylene carbonate (PC)-dimethyl carbonate (DMC)-based electrolytes containing Ca2+ ions was studied. The molar ratio of PC, Li+ ion, and Ca2+ ion was PC:Li+:Ca2+ = 12:1.0:0.5. Intercalation of Li+ ions became possible by adding DMC to the PC-based electrolytes containing Ca2+ ions: Li+ ion intercalation did not take place when the amount of DMC was DMC/PC = 6 (molar ratio) and below, and Li+ ions intercalated when the amount of DMC was above DMC/PC = 8. Intercalation of Li+ ions did not take place in PC-DMC-based electrolyte of no Ca2+ ions, and both Ca2+ ion and DMC were necessary for Li+ ion intercalation. Successful Li+ ion intercalation can be attributed to smaller solvation number of PC on Li+ ions by addition of DMC and Ca2+ ions to the PC-based electrolyte.

Modification of the Pasynski method for determining the hydration numbers of nonelectrolytes

This paper presents a way of modifying the well known Pasynski method of calculating the solvation numbers towards more realistic assumptions concerning compressibility of the solvation shell including the non-zero value of this parameter. Assuming the compressibility of hydrates of simple non-electrolytes (methanol, tert-butanol, etc.) equal to that of solid crystalline clathrate hydrates yields hydration numbers well comparable to the stoichiometries of these hydrates deduced from the Endo theory. Applying the value of compressibility of solid hydrates close to that of ice, however, leads to hydration numbers close to those obtained from original Pasynski equation.

Concentration dependence of NaCl in a wide range of temperatures and pressures

We use our own and literature data on density, ultrasound propagation velocity, and isobaric heat capacity to study the concentration, temperature, and pressure dependences of solvation numbers in aqueous NaCl solutions. We show that, in the parameter range: m = 0–6.0 mol·kg−1, p = 1–1000 bar, and T = 283.15–323.15 K, the solvation numbers decrease with increasing concentration, pressure, and temperature.

Effect of temperature and solvents on thermo-physical properties of 1,3,4-oxadiazole derivative at atmospheric pressure

The density (ρ), viscosity (η) and ultrasonic velocity (U) of pure solvents: chloroform (CF), N,N-dimethylformamide (DMF), solutions of 2-((4-acetyl-5-(4-bromophenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl)methylthio)-3-o-tolylquinazolin-4(3H)-one (PDI-D) in CF and DMF were investigated at 303, 308 and 313K and at atmospheric pressure. Using ρ, η and U data various acoustical and thermodynamic parameters such as acoustical impendence (Z), isentropic compressibility (κS), intermolecular free path length (Lf), Rao's molar sound function (Rm), Van der Waals constant (b), internal pressure (π), relaxation time (τ), free volume (Vf) and solvation number (Sn) were calculated and fairly good co-relationship between calculated parameters were obtained. A fairly good to excellent correlation between a given parameter and concentration is observed at all temperatures and solvent systems studied. Linear or non-linear increases or decreases of acoustical parameters with concentration and temperature indicated the existence of strong molecular interactions between studied systems. Moreover, the experimental results for the pure solvents and solutions of compound PDI-D studied has been carried out to analyze carefully how the structural modifications affect the values of Gibbs energy of activation (ΔG*), enthalpy of activation (ΔH*) and entropy of activation (ΔS*) in CF and DMF.

The hydration of the protein stabilizing agents: Trimethylamine-N-oxide, glycine and its N-methylderivatives – The volumetric and compressibility studies

The densities at T=(288.15, 293.15, 298.15, 303.15, and 308.15)K and sound velocities at T=298.15K have been measured for aqueous solutions of trimethylamine-N-oxide, glycine, N-methylglycine (sarcosine), N,N-dimethylglycine, N,N,N-trimethylglycine (betaine). From these data the apparent molar volumes, VΦ, the apparent molar isentropic compressions, KS,Φ, and the solvation numbers of solutes have been determined. The concentration dependencies of the calculated quantities and their limiting values are discussed in terms of solute–solvent and solute–solute interactions. The obtained quantities are compared with the analogous data for urea and its derivatives. These two groups of osmolyties (stabilizers and denaturants of the proteins) reveal clearly different volumetric and compression features.

Solvation of lithium chloride in aqueous and mixed solutions of an aprotic solvent

The dynamic hydration and solvation numbers of lithium chloride are estimated on the basis of experimental data on the limiting electrodialysis concentration of an electrolyte from aqueous and aqueousorganic solutions containing aprotic solvent N,N-dimethylacetamide. It is established that the dependence of the hydration numbers of the salt on the volume fraction of the aprotic solvent is of an extreme character, and its solvation number on N,N-dimethylacetamide does not depend on the composition of the mixed solution.

Hydrotropy: binding models vs. statistical thermodynamics

Hydrophobic drugs can often be solubilized by the addition of hydrotropes. We have previously shown that preferential drug-hydrotrope association is one of the major factors of increased solubility (but not "hydrotrope clustering" or changes in "water structure"). How, then, can we understand this drug-hydrotrope interaction at a molecular level? Thermodynamic models based upon stoichiometric solute-water and solute-hydrotrope binding have long been used to understand solubilization microscopically. Such binding models have shown that the solvation numbers or coordination numbers of the water and hydrotrope molecules around the drug solute is the key quantity for solute-water and solute-hydrotrope interaction. However, we show that a rigorous statistical thermodynamic theory (the fluctuation solution theory originated by Kirkwood and Buff) requires the total reconsideration of such a paradigm. Here we show that (i) the excess solvation number (the net increase or decrease, relative to the bulk, of the solvent molecules around the solute), not the coordination number, is the key quantity for describing the solute-hydrotrope interaction; (ii) solute-hydrotrope binding is beyond the reach of the stoichiometric models because long-range solvation structure plays an important role.

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

Binary mixtures of the protic ionic liquid ethylammonium nitrate (EAN) and acetonitrile (AN) were studied at 25 °C over the entire composition range by means of broadband dielectric spectroscopy covering 0.2 ≤ ν/GHz ≤ 89. The dielectric spectra could be decomposed into two relaxation processes, both of which proved to be composite modes. For dilute solutions the higher-frequency Debye relaxation centered at ∼60 GHz is associated with the rotational diffusion of AN molecules, whereas at higher salt concentrations ultra-fast intermolecular vibrations and librations of EAN dominate the process. For EAN-rich solutions the lower-frequency relaxation is mainly due to jump reorientation of the ethylammonium cation, whereas contact ion pairs (CIPs) dominate this mode for dilute solutions. From the relaxation amplitudes effective solvation numbers and ion-pair concentrations were determined. For vanishing EAN mole fraction, xEAN → 0, an effective cation solvation number of ∼7 was found which steeply drops until xEAN ≈ 0.2 but shows only moderate decrease later on. The obtained association constant for EAN, K0(A) = 970 L mol(-1), exceeds that of other 1 : 1 electrolytes in AN by a factor of ∼30-50. This observation, as well as the fact that CIPs are formed despite strong cation solvation, indicates that ion pairing is mainly driven by the formation of strong hydrogen bonds between anions and cations.

Analysis of the solvation structure of rubidium bromide under nanoconfinement

We report results from a molecular simulation study of aqueous rubidium bromide solutions confined in slit-shaped carbon pores 6.5–16 Å in width, which encompasses the range typically found in nanoporous carbon electrode materials. For each slit-pore model, the structure of the solvation shells surrounding the Rb+ and Br− ions in 0.1, 0.5 and 1.0 M solutions was examined using the ion–water radial distribution functions. The impact of pore geometry on solvation structure of ions was also investigated using a disordered carbon model that morphologically resembles real nanoporous carbon electrodes. Monte Carlo simulations were used to determine the propensity of ions to reside in pores of specific sizes in the model carbon, allowing the solvation structure of Rb+ and Br− ions to be analysed as a function of pore size. We find that a dramatic drop in the solvation number occurs in pore sizes below 10 Å for slit-shaped pores, while more complex geometries see a steady decrease in solvation number as pore size is decreased. Our results suggest that, when compared to the disordered carbon model, the slit-pore model may not provide qualitatively accurate predictions regarding the structural properties of electrolytes confined in complex electrode materials.