Solubility of CO2 in 1-(2-hydroxyethyl)-3-methylimidazolium ionic liquids with different anions

The solubility of carbon dioxide in a series of 1-(2-hydroxyethyl)-3-methylimidazolium ([hemim]⁺) based ionic liquids (ILs) with different anions, viz. hexafluorophosphate ([PF₆]^?), trifluoromethanesulfonate ([OTf]^?), and bis-(trifluoromethyl)sulfonylimide ([Tf₂N]^?) at temperatures ranging from 303.15 K to 353.15 K and pressures up to 1.3 MPa were determined. The solubility data were correlated using the Krichevsky–Kasarnovsky equation and Henry’s law constants were obtained at different temperatures. Using the solubility data, the partial molar thermodynamic functions of solution such as Gibbs free energy, enthalpy, and entropy were calculated. Comparison showed that the solubility of CO₂ in the ILs studied follows the same behaviour as the corresponding conventional 1-ethyl-3-methylimidazolium ([emim]⁺) based ILs with the same anions, i.e. [hemim][NTf₂] > [hemim][OTf] > [hemim][PF₆] > [hemim][BF₄].     

Thermophysical properties of 1-methyl-3-methylimidazolium dimethylphosphate and 1-ethyl-3-methylimidazolium diethylphosphate

The density and surface tension of 1-methyl-3-methylimidazolium dimethylphosphate, [C₁mim](CH₃O)₂PO₂ and 1-ethyl-3-methylimidazolium diethylphosphate, [C₂mim](CH₃CH₂O)₂PO₂ ionic liquids have been measured over the temperature range from (283.15 to 338.15) K. The coefficients of thermal expansion were calculated from the experimental density results using an empirical correlation for T = (283.15 to 338.15) K. Molecular volume and standard entropies of these ILs were calculated from the experimental density values. The surface properties of ILs were investigated. The critical temperature and enthalpy of vapourization were also discussed.     

Approaches to (R)- and (S)-1′-(1-aminoethyl)ferrocene-1-carboxylic acid derivatives

Lipase-catalyzed esterification of (±)-methyl 1′-(1-hydroxyethyl)ferrocene-1-carboxylate 4 afforded its (R)-acetate (−)-5 (ee = 99%) and (S)-(+)-4 (ee = 90%). Stereoretentive azidation/amination/acetylation of (R)-(−)-5 gave (R)-(+)-methyl 1′-(1-acetamidoethyl)ferrocene-1-carboxylate (R)-3 (ee = 98%). In a similar manner (S)-(+)-4 was converted into (S)-(−)-3 (ee = 84%). Both enantiomers of 3 were obtained in high chemical yields without a loss of enantiomeric purity. The title compounds can be coupled with natural amino acids and peptides on both C- and N-termini.     

Thermophysical properties of 1-alkylpyridinum bis(trifluoromethylsulfonyl)imide ionic liquids

The thermophysical properties of 1-alkylpyridinium bis(trifluoromethylsulfonyl)imide, [C_npy][Tf₂N] ionic liquids where n = 4, 8, 10, or 12 have been determined. Density ρ, and dynamic viscosity η, were determined at T = (293.15 to 353.15) K and refractive index n_D, was measured at T = (293.15 to 333.15) K. Empirical correlations are proposed to represent the present experimental results. The values of the coefficient of thermal expansion were calculated from the experimental density values. The thermal decomposition temperature, T_d was also determined using thermogravimetric analyzer (TGA) at a heating rate of (10 and 20) K · min^?1.     

Synthesis,growth, and characterization of a new NLO material 3-(2,3-dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one

3-(2,3-Dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one (DMPP) a potential second harmonic generating (SHG) has been synthesized and grown as a single crystal by the slow evaporation technique at ambient temperature. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. DMPP crystallizes with orthorhombic system with cell parameters a = 20.3106(8) Å, b = 4.9574(2) Å, c = 13.4863(5) Å, α = 90°, β = 90°, γ = 90° and space group Pca2₁. The crystals were characterized by FT-IR, thermal analysis, UV–vis–NIR spectroscopy and SHG measurements. Various functional groups present in DMPP were ascertained by FTIR analysis. DMPP is thermally stable up to 80 °C and optically transparent in the visible region. The crystal exhibits SHG efficiency comparable to that of KDP.     

Measurements of (p, ρ, T) properties for isobutane in the temperature range from 280 K to 440 K at pressures up to 200 MPa

Measurements of (p, ρ, T) properties for isobutane in the compressed liquid phase have been obtained by means of a metal-bellows variable volumometer in the temperature range from 280 K to 440 K at pressures up to 200 MPa. The volume-fraction purity of isobutane used was 0.9999. The expanded uncertainties (k = 2) of temperature, pressure, and density measurements have been estimated to be less than 3 mK, 1.5 kPa (p ⩽ 7 MPa), 0.06% (7 MPa < p ⩽ 50 MPa), 0.1% (50 MPa < p ⩽ 150 MPa), and 0.2% (p > 150 MPa), and 0.11%, respectively. In region more than 100 MPa at 280 K and 440 K, the uncertainty in density measurements rise up to 0.15% and 0.23%, respectively. The differences of the present density values at the same temperature between two series of measurements, in which the sample fillings are different, are within the maximum deviation of 0.09% in density, which is enough lower than the expanded uncertainty in density. Eight (p, ρ, T) measurements at the same temperatures and pressures as the literature values have been conducted for comparison. In addition, vapour pressures were measured at T = (280, 300) K. Moreover, the comparisons of the available equations of state with the present measurements are reported.     

Solvation of ionic liquids based on N-methyl-N-alkyl morpholinium cations in dimethylsulfoxide – volumetric and compressibility studies

The density and sound velocity of the solutions of ionic liquids based on N-alkyl-N-methyl-morpholinium cations, N-ethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide, N-methyl-N-octyl-morpholinium bis(trifluoromethanesulfonyl)imide and N-decyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide in dimethylsulfoxide were measured at T = (298.15 to 318.15) K and at atmospheric pressure. The apparent molar volume and apparent molar compressibility values were evaluated from density and sound velocity values and fitted to the Masson equation from which the partial molar volume and partial molar isentropic compressibility of the ILs at infinite dilution were also calculated at working temperatures. By using the density values, the limiting apparent molar expansibilities were estimated. The effect of the alkyl chain length of the ILs and experimental temperature on these thermodynamic properties is discussed. In addition, molecular dynamics simulations were used to interpret the measured properties in terms of interactions of ILs with solvent molecules. Both, volumetric measurements results and molecular dynamics simulations for ionic liquids in dimethylsulfoxide were compared and discussed with results obtained for the same IL in acetonitrile.     

Third-order nonlinear optical properties and structures of (E)-N-(4-nitrobenzylidene)-2,6-dimethylaniline and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline

(E)-N-(4-Nitrobenzylidene)-2,6-dimethylaniline (1) and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline (2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450 nm, showing good optical transparency to the visible light. To provide an insight into the microscopic third-order nonlinear optical (NLO) properties of the investigated molecules, both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825–1125 nm and 1050–1600 nm wavelength areas have been computed using time-dependent Hartree–Fock (TDHF) method. According to the ab initio calculation results, the title molecules exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior.     

Estimation of VLE of binary systems (tert-butanol + 2-ethyl-1-hexanol) and (n-butanol + 2-ethyl-1-hexanol) using GMDH-type neural network

The group method of data handling (GMDH) method was used to estimate (vapour + liquid) equilibrium (VLE) for the binary systems of (tert-butanol + 2-ethy1-1-hexanol) and (n-butanol + 2-ethy1-1-hexanol). Using this method, a new model was proposed, which is suitable for predicting the VLE data. In this publication, the proposed model was ‘trained’ before requested predictions. The data set was divided into two parts: 70% were used as data for ‘training’ (either 10 or 12), and 30% were used as a test set, which were randomly extracted from the database (either 14 or 16). After the training on the input–output process, the predicted values were compared with those of experimental values in order to evaluate the performance of the GMDH neural network method. The model values showed a very good regression with the experimental results.     

Amberlite XAD-7 resin impregnated with 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2yl)-4-nitrophenol for enrichment of metal ions

The Amberlite XAD-7 resin modification was carried out by loading 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2yl)-4-nitrophenol (CPDPINP). Subsequently, this new sorbent was applied for the enrichment of metal ions such as Cu²⁺, Ni²⁺, Co²⁺ Zn²⁺ and Pb²⁺ ions. The effect of various parameters on their sorption and following recoveries was studied in column procedure. The preconcentrated ions were eluted by appropriate eluent and their contents were quantified by FAAS. This method has preconcentration factor of 150 and enrichment factor in the range of 20.8–29.1. At optimum values of all variables, the proposed method has linear calibration graphs in the range of 0.01 up to 0.29 μg mL⁻¹ with detection limit (3SDb/m, n = 15) between 1.6 and 2.6 ng mL⁻¹. This protocol is usable for successful analysis of Cu²⁺, Ni²⁺, Co²⁺ Zn²⁺ and Pb²⁺ ions in different matrices with reasonable recoveries (>93%) and acceptable relative standard deviation (<4.7%).     

The infrared spectrum of bis(fluorosulfonyl)imide revisited: Attractive performances of the PBE0/6-31G** model

We report a systematic investigation of the far- and mid-infrared spectra of ionic liquids (ILs) containing the bis(fluorosulfonyl)imide (FSI) anion, both in the liquid state at room temperature and in solid phases at low temperatures. We extended to lower frequencies a previous study, and we observed four additional vibration bands below 500 cm⁻¹, attributable to FSI. Moreover, DFT calculations of vibration frequencies were performed using three combinations of theory and basis set: (1) B3LYP/6-31G**, (2) B3LYP/6-311 + G(3df) and (3) PBE0/6-31G**. Model 1, largely used in the previous literature concerning ILs, shows the poorest performances; model 2, which generally gives a good agreement with the experiments, misses the vibration frequencies by ∼40 cm⁻¹ in the range 650–900 cm⁻¹ where one finds the largest spectral differences between cis- and trans-FSI; model 3 gives the best agreement with the experiments and, moreover, is much less time consuming than model 2. The comparison with calculations suggests that the band centered around 1217 cm⁻¹ is a good marker of the occurrence of the cis-FSI conformer. Finally, the bands located around 730 and 750 cm⁻¹ are attributable to cis- and trans- conformer of FSI, respectively.     

Experimental and computational thermochemistry of 1-phenylpyrrole and 1-(4-methylphenyl)pyrrole

The standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of 1-phenylpyrrole and 1-(4-methylphenyl)pyrrole, at T = 298.15 K, were derived from the standard molar energies of combustion in oxygen, measured by static-bomb combustion calorimetry. For these compounds, the standard molar enthalpies of sublimation, at T = 298.15 K, were determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. Using estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds, the standard (p° = 0.1 MPa) molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived. From the experimental values, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, were calculated.Additionally, the enthalpies of formation of both compounds were estimated using the composite G3(MP2)//B3LYP approach together with adequate gas-phase working reactions. There is a very good agreement between computational and experimental results.     

Prediction of thermophysical properties of novel ionic liquids based on serine [Cnmim][Ser] (n = 3, 4) using semiempirical methods

Two novel ionic liquids based on serine [C_nmim][Ser] (n = 3, 4) were prepared by the neutralization method and their structures were confirmed by ¹H NMR spectroscopy and differential scanning calorimetry (DSC). The density, surface tension, and refractive index of the two ILs were measured from T = (298.15 to 338.15) K. Since these ILs [C_nmim][Ser] (n = 3, 4) could form strong hydrogen bonds with water, small amount of water in the ILs is difficult to removed by common methods. In order to eliminate the effect of trace of water, the standard addition method (SAM) was applied to these measurements. On the basis of the experimental data, the speed of sound (μ), thermal expansion coefficient (α), molecular volume (V_m), standard entropy (S⁰298), entropy of surface (S_a), energy of surface (E_a), parachor (P), molar polarization (R_m), and polarization coefficient (α_p) were calculated, and the relationship between each of these properties of [C_nmim][Ser] (n = 3, 4) and temperatures was discussed. According to the additivity, the average value of anionic parachor, P_−(ave), was 180.81 for [Ser]⁻. At the same time, the surface tension of these serine ionic liquids could be estimated from their parachor and refractive index. The estimated values of the surface tension and the corresponding experimental data were almost identical.     

Slab calculations and Green’s function recursive methods combined to study the electronic structure of surfaces: application to Cu(1 1 1)–(4 × 4)-Na

We have recently developed an ab initio scheme for the calculation of the electronic structure of surfaces. The method is based on the combination of density functional calculations using finite slabs and the use of recursive methods to obtain the Green’s function of the surface. The slab calculations are performed using a linear combination of atomic orbitals as a basis set. From such calculation we directly obtain the surface Hamiltonian in a tight-binding form. Combining this information with that from a bulk calculation of the substrate, we gather all the pieces to construct the Hamiltonian of the semi-infinite system. The surface Green’s function is then computed using the transfer-matrix method and projected onto a wavepacket localized in the surface region. The width and energy of the surface electronic features are obtained from the analysis of such projection. With this approach we get rid of the finite size effects associated with the slab calculations. We have applied this method to the calculation of resonant charge transfer times from adsorbates to metallic substrates. We have focused in the case of core-excited Ar and S on Ru(0 0 0 1) to compare with core-hole clock spectroscopy experiments. We have also used our method to reveal the role of the elastic width in the scanning tunneling spectroscopy measurements of the quasi two-dimensional quantum well state appearing in p(2 × 2) ordered overlayers of Na and Cs on Cu(1 1 1). Here we present a new application of the method to study a more diluted alkali overlayer, the Cu(1 1 1)–(4 × 4)-Na surface. We present results for the relaxed geometries, binding energies, work function change and the position and width of the 3s Na resonance.     

Thermophysical properties for (diethyl carbonate + p-xylene + octane) ternary system

The density and speed of sound of the ternary mixture (diethyl carbonate + p-xylene + octane) have been measured at atmospheric pressure and in the temperature range T = (288.15 to 308.15) K. Besides, surface tension has been also determined for the same mixture at T = 298.15 K. The experimental measurements have allowed the calculation of the corresponding derived properties: excess molar volumes, excess isentropic compressibilities, and surface tension deviations. Excess properties have been correlated using Nagata and Tamura equation and correlation for the surface tension deviation has been done with the Cibulka equation. Good accuracy has been obtained. Based on the variations of the derived properties values with composition, a qualitative discussion about the intermolecular interactions was drawn.     

Spin-crossover in dimeric hydrogen-bonded iron(II) 2-(pyrazolyl)-pyridine and 2-(imidazolyl)-pyridine complexes

Five new hydrogen-bonded solvated iron(II) complexes of pyrazolyl- and imidazolyl-based N,N-chelating ligands have been synthesised. Water to ligand-NH hydrogen-bonded bridges occur in the pseudo-dimeric complexes {cis-[Fe(pypzH)₂(NCX)₂]₂(μ-OH₂)(H₂O)₂} · H₂O · MeOH (where X = S or Se), and in the chain complex {cis-[Fe(pypzH)₂(NCS)₂](μ-OH₂)}_n. A “half” spin-crossover (T_c = 125 K) was observed in the dimeric X = Se complex by means of magnetic measurements and no thermal hysteresis occurred between 4 and 300 K. The crystal structure at 123 K showed Fe–N distances consistent with the magnetism. Each Fe in the dimeric unit was structurally equivalent in the HS–LS state. Removal of the solvate molecules led to HS–HS behaviour over the temperature range 4–300 K. The pseudo-dimer with X = S also showed HS–HS behaviour as did the monomeric analogue cis-[Fe(pypzH)₂(NCS)₂]H₂O and a structurally different methanol-bridged dimer {cis-[Fe(pyimH)₂(NCS)₂]₂(μ-MeOH)₂} · 2MeOH (pypzH = 2-(1H-pyrazol-3-yl)-pyridine; pyimH = 2-(1H-imidazol-2-yl)-pyridine).     

Excess molar volumes and viscosities of (1,1,2,2-tetrabromoethane + 1-alkanols) at T = (293.15 and 303.15) K

Density and viscosity measurements for binary mixtures of (1,1,2,2-tetrabromoethane + 1-pentanol, or + 1-hexanol, or + 1-heptanol, or + 1-octanol, or + 1-decanol) at T = (293.15 and 303.15) K, have been conducted at atmospheric pressure. The excess molar volumes V^E, have been calculated from the experimental measurements, and the results were fitted to Redlich–Kister equation. The viscosity data were correlated with the model of Grunberg and Nissan, and McAllister four-body model. The excess molar volumes of (1,1,2,2-tetrabromoethane + 1-pentanol, or + 1-haxanol, or + 1-heptanol, or + 1-octanol) had a sigmoidal shape and the values varied from negative to positive with the increase in the molar fraction of 1,1,2,2-tetrabromoethane. The remaining binary mixture of (1,1,2,2-tetrabromoethane + 1-decanol) was positive over the entire composition range. The effects of the 1-alkanol chain length as well as the temperature on the excess molar volume have been studied. The results have been qualitatively used to explain the molecular interaction between the components of these mixtures.     

Thermodynamic properties of mixing for (1-alkanol + an-alkane + a cyclic alkane) atT = 298.15 K. I. (n-Hexane + cyclohexane + 1-butanol)

Experimental values of density, refractive index and speed of sound of (hexane  +  cyclohexane  +  1-butanol) were measured at T =  298.15 K and atmospheric pressure. From the experimental data, the corresponding derived properties (excess molar volumes, changes of refractive index on mixing and changes of isentropic compressibility) were computed. Such derived values were correlated using several polynomial equations. Several empirical methods were used in the calculation of the properties of ternary systems from binary data. The Nitta–Chao group contribution model was applied to predict excess molar volume for this mixture.     

Saturated liquid densities of propane at T = (280 to 365) K

Saturated liquid densities for propane were obtained by means of a metal-bellows variable volumometer at T = (280, 300, 320, 340, 360, and 365) K. The mol-fraction purity of the propane used in the measurements was 0.99997. The expanded uncertainties (k = 2) in temperature, pressure, and density measurements were estimated to be less than ±3 mK, 1.4 kPa (p ≦ 7 MPa), and ±0.09%, respectively. For the determination of the saturation boundary at each temperature for propane, we measured the density data at intervals of about 20 kPa very close to the saturation boundary. After such measurements had been completed, the saturated liquid density data at each temperature were determined as the intersection between the isotherm and our previously determined vapour pressure value. The discrepancies between the three series in the present measurements, in which different sample fillings were used, were also confirmed to be sufficiently lower than the experimental uncertainty. The saturated liquid density correlation was also provided for the systematic comparisons between the present measurements and the literature data.     

Thermodynamics of the ternary systems: (water + glycine,l-alanine and l-serine + di-ammonium hydrogen citrate) from volumetric,compressibility, and (vapour + liquid) equilibria measurements

The apparent molar volumes and isentropic compressibility of glycine, l-alanine and l-serine in water and in aqueous solutions of (0.500 and 1.00) mol · kg^?1 di-ammonium hydrogen citrate {(NH₄)₂HCit} and those of (NH₄)₂HCit in water have been obtained over the (288.15 to 313.15) K temperature range at 5 K intervals at atmospheric pressure from measurements of density and ultrasonic velocity. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated amino acids have been obtained and their variations with temperature and their transfer properties from water to aqueous solutions of (NH₄)₂HCit have also been obtained. The results have been interpreted in terms of the hydration of the amino acids. In the second part of this work, water activity measurements by the isopiestic method have been carried out on the aqueous solutions of {glycine + (NH₄)₂HCit}, {alanine + (NH₄)₂HCit}, and {serine + (NH₄)₂HCit} at T = 298.15 K at atmospheric pressure. From these measurements, values of vapour pressure, osmotic coefficient, activity coefficient and Gibbs free energy were obtained. The effect of the type of amino acids on the (vapour + liquid) equilibrium of the systems investigated has been studied. The experimental water activities have been correlated successfully with the segment-based local composition Wilson model. Furthermore, the thermodynamic behaviour of the ternary solutions investigated has been studied by using the semi-ideal hydration model and the linear concentration relations have been tested by comparing with the isopiestic measurements for the studied systems at T = 298.15 K.