Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents

Abstract  Solvatochromic parameters (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E _T ^N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π* and β are nearly ideal for all solutions except for solutions of methanol with the IL. The applicability of nearly ideal combined binary solvent/Redlich–Kister equation was proved for the correlation of various solvatochromic parameters with solvent composition. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute–solvent and solvent–solvent interactions were applied to interpret the results. Graphical Abstract  Predicted values of solvatochromic parameters (SP) (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) from the correlation equations versus its experimental values for binary mixtures of 2-hydroxyethylammonium formate with water, methanol, ethanol, propan-1-ol and propan-2-ol.      

Solvent Effects on Tautomeric and Microscopic Protonation Constants of Glycine in Different Aqueous Solutions of Methanol and Ethanol

The acid-base equilibria of glycine have been studied in different aqueous solutions of methanol and ethanol (0?C45?% v/v) using a potentiometric method. In this study, the macro and micro protonation constants of the amino acid and its tautomeric constant have been determined at 25?°C and constant ionic strength (0.1 mol?dm^?3 NaClO₄). The protonation and the tautomeric constants of glycine in different binary mixtures were analyzed in terms of the Kamlet, Abboud and Taft (KAT) parameters. Single-parameter correlations of the constants versus ?? (hydrogen-bond donor acidity), ?? (hydrogen-bond acceptor basicity) and ?? ^? (dipolarity/polarizability) are poor in all solutions. Multi-parameter correlations show better results, but dual-parameter correlations represent significant improvements with regard to the single- and multi-parameter models. Linear correlation is observed when the experimental protonation constant values are plotted versus the calculated ones when the KAT parameters are considered. Finally, the results are discussed in terms of the effect of the solvent on protonation and tautomeric constants.     

Determination of Henry’s constant using a photoacoustic sensor

We present a simple method for measuring Henry’s constant k_Hof ethanol using photoacoustic spectroscopy. At T =  298.1 K the measured value fork_H is (0.877  ±  0.039)kPa · kg · mol ^− 1. Our data show that Henry’s law is valid at ethanol molalities between 0.1mol · kg ^− 1 and 1.4 mol · kg ^− 1. The temperature dependence of Henry’s constant was carefully examined by measuring the ethanol vapour pressure of six different aqueous solutions between T =  273.1 K and T =  298.1 K. By analysing the gas phase concentration and applying Henry’s law, an ethanol molality of 0.864 mol · kg ^− 1in the liquid phase can be measured with an error of  ± 0.038mol · kg ^− 1. The detection limit of the photoacoustic sensor is a gaseous ethanol pressure of 10 ^− 3kPa. Ethanol molality changes as low as 1.10 ^− 3mol · kg ^− 1can be measured.     

Solubility of gallic acid in liquid mixtures of (ethanol + water) from (293.15 to 318.15) K

The solubility of gallic acid in (water + ethanol) binary solvents was determined from (293.15 to 318.15) K at atmospheric pressure using a thermostatted reactor and UV/vis spectrophotometer analysis. The effects of binary solvents composition and temperature on the solubility were discussed. It was found that gallic acid solubility in (water + ethanol) mixed solvents presents a maximum-solubility effect. Two empirical equations were proposed to correlate the solubility data. The calculated solubilities show good agreement with the experimental data within the studied temperature range. Using the experimentally measured solubilities, the thermodynamic properties of dissolution of the gallic acid such as Gibbs energy (Δ_solG°), molar enthalpy of dissolution (Δ_solH°), and molar entropy of dissolution (Δ_solS°) were calculated.     

Use of hydrophobins in formulation of water insoluble drugs for oral administration

The poor water solubility of many drugs requires a specific formulation to achieve a sufficient bioavailability after oral administration. Suspensions of small drug particles can be used to improve the bioavailability. We here show that the fungal hydrophobin SC3 can be used to make suspensions of water insoluble drugs. Bioavailability of two of these drugs, nifedipine and cyclosporine A (CyA), was tested when administered as a SC3-based suspension. SC3 (in a 1:2 (w/w) drug:SC3 ratio) or 100% PEG400 increased the bioavailability of nifedipine to a similar degree (6 ± 2- and 4 ± 3-fold, respectively) compared to nifedipine powder without additives. Moreover, SC3 (in a 7:1 (w/w) drug:hydrophobin ratio) was as effective as a 20-fold diluted Neoral^® formulation by increasing bioavailability of CyA 2.3 ± 0.3-fold compared to CyA in water. Interestingly, using SC3 in the CyA formulation resulted in a slower uptake (p < 0.001 in T_max) of the drug, with a lower peak concentration (C_max 1.8 mg ml^?1) at a later time point (T_max 9 ± 2 h) compared to Neoral^® (C_max 2.2 mg ml^?1; T_max 3.2 ± 0.2). Consequently, SC3 will result in a more constant, longer lasting drug level in the body. Taken together, hydrophobins are attractive candidates to formulate hydrophobic drugs.     

Excess molar volumes and partial molar volumes for (propionitrile + an alkanol) at T = 298.15 K and p = 0.1 MPa

The excess molar volumes and the partial molar volumes for (propionitrile + an alkanol) at T = 298.15 K and at atmospheric pressure are reported. The hydrogen bonding between the OH⋯NC groups are discussed in terms of the chain length of the alkanol. The alkanols studied are (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-pentanol).The excess molar volume data was fitted to the Redlich–Kister equation The partial molar volumes were calculated from the Redlich–Kister coefficients.     

A new calcium trimellitate coordination polymer with a chain-like structure

The calcium trimellitate, Ca(H₂O)[(O₂C)₂–C₆H₃–CO₂H], was hydrothermally synthesized from a mixture of calcium hydroxide, 1,2,4-benzenetricarboxylic (or trimellitic) acid and water at 180 °C for 24 h (under autogenous pressure). Its crystal structure has been determined by single-crystal X-ray diffraction analysis using synchrotron radiation (station 9.8, SRS Daresbury, UK). It consists of infinite chains of calcium bicapped trigonal prismatic polyhedra connected to each other through the 1,2,4-benzenetricarboxylate ligand. The eight-fold coordinated calcium cation is bonded to one terminal water molecule, two carboxylate groups with a chelating conformation and three carboxylate groups in a monodentating mode. One of the monodentate carboxylate is terminal with the occurrence of protonated C–OH bonding.Triclinic space group P-1 with a = 6.9073(4) Å, b = 6.9917(4) Å, c = 10.3561(6) Å, α = 87.178(1)°, β = 83.233(1)°, γ = 69.576(1)°, V = 465.41(5) Å³.     

Unusual solvatochromism within 1-butyl-3-methylimidazolium hexafluorophosphate + poly(ethylene glycol) mixtures

Hybrid "green" solvent systems composed of room-temperature ionic liquids (ILs) and poly(ethylene glycols) (PEGs) may have enormous future potential. Solvatochromic absorbance probe behavior is used to assess the physicochemical properties of the mixture composed of IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) and PEG (average molecular weights of 200, 400, 600, and 1500) at ambient conditions. Lowest energy intramolecular charge-transfer absorbance maxima of a betaine dye, i.e., E(T)(N), indicates the dipolarity/polarizability and/or hydrogen-bond donating (HBD) acidity of the [bmim][PF 6] + PEG mixtures to be even higher than that of neat [bmim][PF(6)], the solution component with higher dipolarity/polarizability and/or HBD acidity. Dipolarity/polarizability (pi*) obtained separately from the electronic absorbance response of probe N, N-diethyl-4-nitroaniline shows a trend similar to E(T)(N ) thus confirming the unusually high dipolarity/polarizability of the [bmim][PF(6)] + PEG mixtures. Similar to E(T)(N ) and pi*, the HBD acidity (alpha) of [bmim][PF(6)] + PEG mixtures is also observed to be anomalously high. Contrary to what is observed for E(T)(N ), pi*, and alpha, the hydrogen-bond accepting (HBA) basicity (beta) of the [bmim][PF(6)] + PEG mixtures is observed to be lower than that predicted from ideal additive behavior indicating diminished HBA basicity of the mixture as compared to its neat components. A four-parameter simplified combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) equation is shown to satisfactorily predict the solvatochromic parameters within [bmim][PF(6)] + PEG mixtures. It is demonstrated that [bmim][PF(6)] + PEG mixtures possess physicochemical properties that are superior to those of either the neat IL or the neat PEG.     

Study of immobilized candida rugosa lipase for biodiesel fuel production from palm oil by flow microcalorimetry

Enzymatic transesterification of palm oil with methanol and ethanol was studied. Of the four lipases that were tested in the initial screening, lipase Candida Rugosa (CR) resulted in the highest yield of mono alkyl esters. Lipase CR was further investigated in immobilized form within an activated carbon as support. The activated carbon was prepared by activation physical. Using the immobilized lipase CR, the effects of water and alcohol concentration, enzyme loading and enzyme thermal stability in the transesterification reaction were investigated. The optimal conditions for processing 50 g of palm oil were: 37 °C, 1:14.5 oil/methanol molar ratio, 1.0 g water and 500 mg lipase for the reactions with methanol, 35 °C, 1:15.0 oil/ethanol molar ratio, 1.0 g water, 500 mg lipase for the reactions with ethanol, and 35 °C, 1:10.0 oil/n-butanol molar ratio, 1.0 g water, 500 mg lipase for the reactions with ethanol. Subject to the optimal conditions, methyl and ethyl esters formation of 70 and 85 mol% in 1 h of reaction were obtained for the immobilized enzyme reactions. The flow microcalorimetry is an important and novel techniques is used in evaluation of biodiesel production.     

Bioelectrocatalytic formate oxidation and carbon dioxide reduction at high current density and low overpotential with tungsten-containing formate dehydrogenase and mediators

We show a great possibility of mediated enzymatic bioelectrocatalysis in the formate oxidation and the carbon dioxide (CO₂) reduction at high current densities and low overpotentials. Tungsten-containing formate dehydrogenase (FoDH1) from Methylobacterium extorquens AM1 was used as a catalyst and immobilized on a Ketjen Black-modified electrode. For the formate oxidation, a high limiting current density (j_lim) of ca. 24 mA cm^− 2 was realized with a half wave potential (E_1/2) of only 0.12 V more positive than the formal potential of the formate/CO₂ couple (E°′_CO2) at 30 °C in the presence of methyl viologen (MV^2 +) as a mediator, and j_lim reached ca. 145 mA cm^− 2 at 60 °C. Even when a viologen-functionalized polymer was co-immobilized with FoDH1 on the porous electrode, j_lim of ca. 30 mA cm^− 2 was attained at 60 °C with E_1/2 = E°′_CO2 + 0.13 V. On the other hand, the CO₂ reduction was also realized with j_lim ≈ 15 mA cm^− 2 and E_1/2 = E°′_CO2 − 0.04 V at pH 6.6 and 60 °C in the presence of MV^2 +.     

Preparation via microemulsion method and proton conduction at intermediate-temperature of BaCe1−xYxO3−α

The ceramic powders of BaCe_1?xY_xO_3?α (x = 0.05, 0.10, 0.15, 0.20) have been prepared via a microemulsion method. Green compacts of the powders were sintered to densities higher than 95% of theoretical at the lower temperature (1500 °C). The obtained ceramics showed a single-phase of orthorhombic perovskite. The proton conduction was investigated by employing the techniques of AC impedance and electrochemical hydrogen permeation (hydrogen pumping) at 300–600 °C. It was found that the ceramics were almost pure proton conductors in wet hydrogen, and the highest proton conductivity was observed for x = 0.15 at 600 °C. Ammonia was synthesized successfully from nitrogen and hydrogen at atmospheric pressure in the electrolytic cell using BaCe_0.85Y_0.15O_3?α. The maximum rate of NH₃ formation was found to be 2.1 × 10^?9 mol s^?1 cm^?2 at 500 °C with an applied current of 0.75 mA.     

Nonstoichiometry,point defects and magnetic properties in Sr2FeMoO6−δ double perovskites

The phase stability, nonstoichiometry and point defect chemistry of polycrystalline Sr₂FeMoO_6?δ (SFMO) was studied by thermogravimety at 1000, 1100, and 1200 °C. Single-phase SFMO exists between ?10.2≤log pO₂≤?13.7 at 1200 °C. At lower oxygen partial pressure a mass loss signals reductive decomposition. At higher pO₂ a mass gain indicates oxidative decomposition into SrMoO₄ and SrFeO_3?x. The nonstoichiometry δ at 1000, 1100, and 1200 °C was determined as function of pO₂. SFMO is almost stoichiometric at the upper phase boundary (e.g. δ=0.006 at 1200 °C and log pO₂=?10.2) and becomes more defective with decreasing oxygen partial pressure (e.g. δ=0.085 at 1200 °C and log pO₂=?13.5). Oxygen vacancies are shown to represent majority defects. From the temperature dependence of the oxygen vacancy concentration the defect formation enthalpy was estimated (ΔH_OV=253±8 kJ/mol). Samples of different nonstoichiometry δ were prepared by quenching from 1200 °C at various pO₂. An increase of the unit cell volume with increasing defect concentration δ was found. The saturation magnetization is reduced with increasing nonstoichiometry δ. This demonstrates that in addition to Fe/Mo site disorder, oxygen nonstoichiometry is another source of reduced magnetization values.     

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.     

PVT,viscosity, and surface tension of ethanol: New measurements and literature data evaluation

In this work, the results of density, viscosity, and surface tension measurements for ethanol are presented. Ethanol with stated mass fraction purity greater than 0.998 was further purified using molecular sieves. Density was measured within the temperature and pressure ranges, respectively, T = (278.15 to 353.15) K and p = (0.1 to 35) MPa by means of a vibrating tube densimeter, model DMA 512P from Anton Paar with an estimated uncertainty of ±0.5 kg · m^?3. The experimental (p, ρ, T) results have been correlated by Tait equation. From this equation the isobaric expansivity, the isothermal compressibility, and the thermal pressure coefficient have been calculated. Viscosity was measured over the range T = (273.15 to 346.15) K using an Ubbelohde viscometer with a Schott–Geräte automatic measuring unit (Model AVS-470) with the associated uncertainty of ±0.001 mPa · s. The measured values were combined with selected values from the literature covering the range T = (223 K to 503) K, and the VTF model has been fitted to all the data. The surface tension of the liquid was measured using a tensiometer KSV Sigma 70 with a Du-Noüy ring for the range of T = (274.77 to 318.99) K with an uncertainty of ±0.01 mN · m^?1. Using these data and critically assessed data of other authors compiled from the literature, a form of the IAPWS equation was used to correlate the surface tension within the temperature range 223 K up to the critical temperature.     

A calorimetric and thermodynamic investigation of A2[(UO2)2(MoO4)O2] compounds with A = K and Rb and calculated phase relations in the system (K2MoO4 + UO3 + H2O)

A calorimetric and thermodynamic investigation of two alkali-metal uranyl molybdates with general composition A₂[(UO₂)₂(MoO₄)O₂], where A = K and Rb, was performed. Both phases were synthesized by solid-state sintering of a mixture of potassium or rubidium nitrate, molybdenum (VI) oxide and gamma-uranium (VI) oxide at high temperatures. The synthetic products were characterised by X-ray powder diffraction and X-ray fluorescence methods. The enthalpy of formation of K₂[(UO₂)₂(MoO₄)O₂] was determined using HF-solution calorimetry giving Δ_fH° (T = 298 K, K₂[(UO₂)₂(MoO₄)O₂], cr) = −(4018 ± 8) kJ · mol⁻¹. The low-temperature heat capacity, С_р°, was measured using adiabatic calorimetry from T = (7 to 335) K for K₂[(UO₂)₂(MoO₄)O₂] and from T = (7 to 326) K for Rb₂[(UO₂)₂(MoO₄)O₂]. Using these С_р° values, the third law entropy at T = 298.15 K, S°, is calculated as (374 ± 1) J · K⁻¹ · mol⁻¹ for K₂[(UO₂)₂(MoO₄)O₂] and (390 ± 1) J · K⁻¹ · mol⁻¹ for Rb₂[(UO₂)₂(MoO₄)O₂]. These new experimental results, together with literature data, are used to calculate the Gibbs energy of formation, Δ_fG°, for both phases giving: Δ_fG° (T = 298 K, K₂[(UO₂)₂(MoO₄)O₂], cr) = (−3747 ± 8) kJ · mol⁻¹ and Δ_fG° (T = 298 K, Rb₂[(UO₂)₂(MoO₄)], cr) = −3736 ± 5 kJ · mol⁻¹. Smoothed С_р°(Т) values between 0 K and 320 K are presented, along with values for S° and the functions [H°(T) − H°(0)] and [G°(T) − H°(0)], for both phases. The stability behaviour of various solid phases and solution complexes in the (K₂MoO₄ + UO₃ + H₂O) system with and without CO₂ at T = 298 K was investigated by thermodynamic model calculations using the Gibbs energy minimisation approach.     

Temperature and sodium chloride effects on the solubility of anthracene in water

The solubility of anthracene was measured in pure water and in sodium chloride aqueous solution (salt concentration, m/mol · kg^?1 = 0.1006, 0.5056, and 0.6082) at temperatures between (278 and 333) K. Solubility of anthracene in pure water agrees fairly well with values reported in earlier similar studies. Solubility of anthracene in sodium chloride aqueous solutions ranged from (6 · 10^?8 to 143 · 10^?8) mol · kg^?1. Sodium chloride had a salting-out effect on the solubility of anthracene. The salting-out coefficients did not vary significantly with temperature over the range studied. The average salting-out coefficient for anthracene was 0.256 kg · mol^?1.The standard molar Gibbs free energies, Δ_trG°, enthalpies, Δ_trH°, and entropies, Δ_trS°, for the transfer of anthracene from pure water to sodium chloride aqueous solutions were also estimated. Most of the estimated Δ_trG° values were positive [(20 to 1230) J · mol^?1]. The analysis of the thermodynamic parameters shows that the transfer of anthracene from pure water to sodium chloride aqueous solution is thermodynamically unfavorable, and that this unfavorable condition is caused by a decrease in entropy.     

Preferential crystallization in an unusual case of conglomerate with partial solid solutions

Ethanolamine mandelate (E.M.) crystallizes as a stable conglomerate and has been found to form partial solid solutions. The crystal structure of the pure enantiomer has been solved from single-crystal X-ray diffraction. In order to determine the extreme compositions of the partial solid solutions in equilibrium (87% ee), the isothermal ternary section in the system [(+)-E.M.–(−)-E.M.–(ethanol–water azeotropic mixture)] was established at 25 °C. Several consecutive preferential crystallization attempts (AS3PC method) were undertaken between T_B = 41 °C (starting temperature) and T_F = 25 °C (final temperature) on a 2-L scale.We initially expected to obtain crude crops whose enantiomeric purities would be close to that defined by the isothermal ternary phase diagram (T_F). In fact, the filtered solid phases are of lower enantiomeric excesses: ca. 62% ee. The monitoring of the mother liquor composition over the course of the entrainment shows that the enantiomeric composition of the filtered solid is related to the metastable equilibria involved in the preferential crystallization.     

(Solid + liquid) equilibria,i.r., and semi-empirical studies of carbazole with selected tertiary amides

(Carbazole  + tert -amide) systems were investigated through measurement of (solid  +  liquid) equilibria (s.l.e.), i.r. study, and semi-empirical calculations. The s.l.e. studies included three systems, namely (carbazole  +  tetramethylurea, orN , N - diphenylacetamide, or N -acetylcarbazole). In spite of the identical tertiary N-atom, andC = O group occurring in each studied amide assumed to dominate molecular interactions, the liquidus curves have revealed the presence of a hydrogen-bond complex only in the first system. The remaining two are simple eutectic systems, probably owing to sterical hindrance exhibited by large substituents. Each system, as well as (carbazole  + N, N - dimethylformamide) were studied using i.r. spectroscopy in 1,1,2,2-tetrachloroethene solutions. In contrast to s.l.e. data, hydrogen-bond formation manifested itself in each system studied by the i.r. method. The enthalpy of complex formation was determined from the spectroscopic data for each system except for (carbazole  + N -acetylcarbazole). The i.r. studies were supported by semi-empirical calculations performed for the optimized hydrogen-bond geometries.     

Electrode properties of Sr doped La2CuO4 as new cathode material for intermediate-temperature SOFCs

High performance La_2−xSr_xCuO_4−δ (x = 0.1, 0.3, 0.5) cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFCs) were prepared and characterized. The investigation of electrical properties indicated that La_1.7Sr_0.3CuO₄ cathode has low area specific resistance (ASR) of 0.16 Ω cm² at 700 °C and 1.2 Ω cm² at 500 °C in air. The rate-limiting step for oxygen reduction reaction on La_1.7Sr_0.3CuO₄ electrode changed with oxygen partial pressure and measurement temperature. La_1.7Sr_0.3CuO₄ cathode exhibits the lowest overpotential of about 100 mV at a current density of 150 mA cm⁻² at 700 °C in air.     

Phage Langmuir monolayers and Langmuir–Blodgett films

Stable, insoluble Langmuir monolayer films composed of Staphylococcus aureus-specific lytic bacteriophage were formed at an air–water interface and characterized. The phage monolayer was very strong, withstanding a surface pressure of ～40 mN/m at 20 °C. The surface pressure–area (Π–A) isotherm possessed a shoulder at ～7 × 10⁴ nm²/phage particle, attributed to a change in phage orientation at the air–water interface from horizontal to vertical capsid-down/tail-up orientation as surface pressure was increased. The Π–A-dependence was accurately described using the Volmer equation of state, assuming horizontal orientation to an air–water interface at low surface pressures with an excluded area per phage particle of 4.6 × 10⁴ nm². At high pressures phage particles followed the space-filling densely packed disks model with a specific area of 8.5 × 10³ nm²/phage particle. Lytic phage monolayers were transferred onto gold-coated silica substrates from the air–water interface at a constant surface pressure of 18 mN/m by Langmuir–Blodgett method, then dried and analyzed by scanning electron microscopy (SEM) and ellipsometry. Phage specific adsorption (Γ) in Langmuir–Blodgett (LB) films measured by SEM was consistent with that calculated independently from Π–A isotherms at the transfer surface pressure of 18 mN/m (Γ = 23 phage particles/μm²). The 50 nm-thickness of phage monolayer measured by ellipsometer agreed well with the horizontal phage average size estimated by SEM. Surface properties of phage Langmuir monolayer compare well with other monolayers formed from nano- and micro-particles at the air–water interface and similar to that of classic amphiphiles 1,2-diphytanoyl-sn-glycero-3-phosphocholine (phospholipid) and stearic acid.