Journal of Molecular Liquids (v.178, #C)

Effects of water and ethanol on the electrical conductivity of caprolactam tetrabutyl ammonium halide ionic liquids by ErHong Duan; YaNan Guan; Bin Guo; MiaoMiao Zhang; Di Yang; Kun Yang (1-4).
To determine the structure of caprolactam tetrabutyl ammonium halide (F, Cl and Br) ionic liquids and the interaction of ionic liquids and solvents (water and ethanol), the effects of solvents on the electrical conductivity of ionic liquids were investigated at atmospheric pressure and temperatures from 293.15 to 333.15 K. The electrical conductivity of ionic liquids increases with an increase in temperature, and the anion electronegativity decreases in the following order: F > Cl > Br. The electrical conductivity of the binary system of ionic liquid and solvents (water and ethanol) appears to decrease slightly with an increase in temperature. The electrical conductivity of the caprolactam tetrabutyl ammonium halide ionic liquid solutions is much larger than the electrical conductivity of the pure ionic liquids under the same conditions. The electrical conductivity of aqueous solutions of ionic liquids is very different from the electrical conductivity of ethanol solutions.► Electrical conductivity of caprolactam tetrabutyl ammonium halide (F, Cl and Br). ► Interaction of caprolactam tetrabutyl ammonium halide and water and ethanol. ► Effect of solvents, temperature, and anion electronegativity on the conductivity.
Keywords: Electrical conductivity; Caprolactam tetrabutyl ammonium halide; Water; Ethanol; Ionic liquid;

In this study, three-dimensional silk fibroin/chitosan (SF/CTS) composite sponges were successfully prepared with an interconnected porous structure and proper mechanical properties. Silk fibroin and chitosan have the potential to mimic a natural extra-cellular matrix (ECM). For the sponge preparation, silk fibroin from the Bombyx mori silkworm and chitosan were used, in different proportions, as composites. Sponges were prepared by means of freezing and lyophylization of corresponding composite solutions. The properties of composite sponges, such as the microstructure as well as the chemical and physical properties were studied. In the present investigation, silk fibroin, chitosan and their mixtures were characterized by attenuated total reflection Fourier transform infra-red spectroscopy (ATR-FTIR), swelling properties, thermogravimetric analysis and scanning electron microscopy (SEM). The ATR-FTIR analysis indicated a shift of band corresponding to C=O, C―N, C―O―C. Moreover, NH groups of SF and C=O and NH2 groups of chitosan might have participated in a specific intermolecular interaction among themselves. Thermogravimetric results suggested a higher temperature of decomposition for SF/CTS sponges than sponges made of pure silk fibroin or chitosan. Scanning electron microscopy observations showed the sponges of SF/CTS with pore size from 20 to 150 μm, which is appropriate for cell growth. Biocompatibility of sponges was confirmed by in vitro test. SF/CTS sponges have sufficient mechanical integrity to resist handling during implantation and in vivo loading. Both the compressive modulus and compressive strength for the sponge decrease with the increase of silk fibroin content in the sponge. Sponges made of silk fibroin/chitosan mixtures can be interesting materials for tissue engineering as scaffold for temporary supporting the formation of new tissue and organs.► We offer new material based on the blend of two natural polymers containing nanoparticles. ► We found the interaction between the components. ► We studied the structure and mechanical properties of 3D sponges as well as their biocompatibility.
Keywords: Silk fibroin; Chitosan; Scaffold; Biomaterial; Polymer blends;

In this work, thermodynamic properties measurement for KCl/RbCl/CsCl in N,N-dimethylacetamide (DMA) (w) + H2O (1 −  w) systems (where the w  = 0.10, 0.20, 0.30) was carried out by potentiometric method using ion-selective electrodes at 298.15 K. Modeling of the activity coefficients of these ternary systems was based on the Pitzer, the modified Pitzer and the extended Debye–Hückel equations. Meanwhile, the osmotic coefficients, the standard free energy of transference from the water to the mixture have also been reported.► Thermodynamic properties of KCl/RbCl/CsCl + DMA + H2O systems studied ► Experimental data fitted to the Pitzer, modified Pitzer and extended Debye–Hückel equations ► Activity coefficients, osmotic coefficients, and standard free energy of transfer reported
Keywords: KCl; RbCl; CsCl; Activity coefficients; N,N-dimethylacetamide; Potentiometric;

A liquid–liquid extraction (LLE)-flame atomic absorption spectrometry (FAAS) for the separation/analysis of copper has been developed. The method was based on the fact that the inclusion complex of copper(II) with 25, 27-di (5-phenanthrolinylaminocarbonylmethoxy)-26,28-dihydroxy-p-tert-butylcalix[4]arene (TBCP) could be extracted into room temperature ionic liquids (RTILs, 1-butyl-3-methylimidazolium hexafluoro-phosphate [C4mim] [PF6] as the green extractant, TBCP as the complexlant), and the copper(II) was subsequently determined by FAAS. The LLE was optimized in detail. The selectivity and mechanism of LLE were approached. Under optimized experimental conditions, the linear range of calibration curve for the determination of copper(II) was 0.020–10.0 μg/mL. The detection limit estimated (S/N = 3) was 3.59 ng/mL with 3.0% RSD. It has been applied for the determination of copper(II) in water samples with satisfactory results.► A novel method for the analysis of copper(II) ► The inclusion complex of Cu(II)-TBCP was extracted into the RTIL phase. ► The extraction mechanism was approached. ► It was applied for the analysis of Cu(II) in water samples with satisfactory results.
Keywords: Copper(II); Room temperature ionic liquid; p-tert-butyl-calix[4]arene; Liquid–liquid extraction; Flame atomic absorption spectrometry;

The behavior of aqueous acridine orange in presence of submicellar anionic surfactants has been studied through UV–vis, fluorescence spectroscopy and surface tension measurements. An observed increase in absorption in the 510–580 nm region of the UV–vis spectra of the dye in submicellar solutions has been attributed to protonation of the dye in the dye-surfactant ion pair (PDSIP). This PDSIP formation takes place in addition to the well known induced dimerization of the close packed dye-surfactant ion pairs (DSIP) or complexes. The surface tension measurements clearly show two critical micelle concentrations (CMCs) in the dye-surfactant system: the lower one (CMCIP) corresponds to micellization of the DSIP, which behaves like a nonionic surfactant and the higher one (CMC*) corresponds to the normal micellization of the anionic surfactant. The efficiencies of the DSIP and the anionic surfactant in the systems have been determined. The PDSIP is formed in the DSIP micelles and/or in the a/w interfacial monolayer. The observed changes in the fluorescence intensity indicate that the PDSIP gradually breaks down and the dye resides in a highly polar surface region of surfactant-rich surfactant-DSIP mixed micelles as the surfactant concentration approaches the CMC* before it moves towards the core of the normal micelles above the CMC*.Display Omitted► Acridine orange forms protonated dye-surfactant ion pair with anionic surfactants. ► Spectrophotometric and surface tension behavior evidence the formation. ► Two CMC's of the surfactants in presence of AO revealed from surface tension. ► Fluorescence behavior provides insight to the microenvironment of AO.
Keywords: Premicellar phenomenon; Acridine orange; Dye-surfactant ion pair; Ion pair micelle; Protonated dye-surfactant ion pair;

Single and binary adsorption of heavy metals on fly ash samples from aqueous solution by R. Shyam; J.K. Puri; H. Kaur; R. Amutha; A. Kapila (31-36).
Thousands of toxins are released every day into the environment through numerous industrial operations and this resulted in continuous search for newer adsorbents. Two types of adsorbents, 1:10 fly ash and 1:15 fly ash samples were prepared from coal fired thermal power plant fly ash by treating it with calculated amount of calcium carbonate and phosphoric acid. Adsorbents were characterized on the basis of FTIR, XRF, surface area, pH and particle size studies. Adsorption of Pb(II), Ni(II) and Cr(VI) from single metal solutions on 1:10 fly ash from aqueous solution was carried out as a function of initial metal ion concentration, adsorbent dose, contact time and pH of the solution. Adsorption data obtained was analyzed with Langmuir, Freundlich and Temkin adsorption isotherm equations. Binary adsorption of Pb(II) and Ni(II) was studied on 1:10 and 1:15 fly ash samples as a function of initial metal ion concentration to investigate their efficiencies in removing metal ions from aqueous solution. In the case of 1:10 and 1:15 fly ash samples, Pb(II) and Ni(II) removal was observed to be almost the same. The significant difference observed between single and binary metal adsorption is in the initial metal removal rate. Slightly lower initial metal removal rate observed in the case of binary adsorption is probably due to the presence of competing metal ions in the solution. Fly ash based adsorbents prepared in the laboratory exhibited comparatively more adsorption capacity than that of the parent material, fly ash. Further, used adsorbents can be disposed in the form of concrete blocks as leaching of toxic metals is almost nil both under mild acidic and basic conditions. As cost involved in developing adsorbents from fly ash is comparatively less than other commercial adsorbents, reactivation or regeneration of used adsorbents was not considered.► Use of fly ash based adsorbents for the removal of heavy metals is proposed. ► Prepared adsorbents exhibited significant adsorption capacities for heavy metals. ► The observed order of single and binary adsorption is Pb(II) > Ni(II) > Cr(VI). ► Lower solution pH favors maximum Cr(VI) adsorption on fly ash based adsorbents. ► About 90% of Pb(II) was removed in 30 minute contact time.
Keywords: Fly ash; Adsorption; Pb(II); Ni(II); Cr(VI);

Thermodynamic study of the non covalent interactions of phytate with xanthine derivatives and histamine in aqueous solution by Francesco Crea; Concetta De Stefano; Giuseppe Manfredi; Silvio Sammartano (37-43).
The interactions between some xanthine derivatives: caffeine (Cf), theophylline (Tp), theobromine (Tb), and histamine (Hm) with phytate (Phy) were studied at T  = 298.15 K and I  = 0.5 mol L− 1 in aqueous NaCl solution using ISE-[H+] potentiometry. For all of the investigated systems, [(Phy)(L)H q ](q  − 7) species (q  = 4 to 9, depending on the maximum protonation degree of the ligand) were formed in high yields (30–90%). The stability constants of the systems varied; higher stability was observed for the [(Phy)(Tb)H q ](q  − 7) (5 ≤  q  ≤ 8) species. For the [(Phy)(Tb)H8]+ and [(Phy)(Tb)H7] species, we obtained values of log K 8  = 8.1 and log K 7  = 5.58, respectively. The formation ΔH and TΔS parameters were determined for the PhyCf system at I  = 0.5 mol L− 1 in NaCl(aq) by calorimetric titrations. As an example, for the [(Phy)(Cf)H5]2 − species, we obtained the following values: ΔH  = − 4.0 ± 0.2 kJ mol− 1, − ΔG  = 14.6 ± 0.5 kJ mol− 1 and TΔS  = 10.5 ± 0.8 kJ mol− 1.Dependence of logK r on the number of protons in the complex; symbols: ⃞: PhyCaffeine; ⃝: PhyTheophylline; Δ: PhyTheobromine.Display Omitted► Non covalent interactions phytate-xanthine derivatives. ► Stability trend for the log K q: Phy-Tb  >  Phy-Tp  >  Phy-Hm  >  Phy-Cf. ► ΔH and TΔS parameters of the Phy-Cf complexes at I  = 0.5 mol L- 1 in NaCl(aq) by calorimetric titrations.
Keywords: Phytate; Xanthine derivatives; Histamine; Speciation; Weak phytate–xanthine interactions;

Application of Abraham solvation parameters for surface tension prediction of mono-solvents and solvent mixtures at various temperatures by Mehry Khoubnasabjafari; Vahid Jouyban; Anahita Fathi Azarbayjani; Abolghasem Jouyban (44-56).
A combined form of the Jouyban–Acree model and the Abraham solvation parameters was used to predict the surface tension of binary and ternary solvent mixtures at various temperatures. The new equations have been tested by comparisons with the experimental results for 364 binary and 79 ternary mixtures reported in the literature. After the training procedures, the models were used for the prediction of the surface tension of mixed solvent systems. The mean relative deviations (MRDs) between predicted and experimental surface tensions are used as an accuracy criterion. The overall MRD for binary mixtures was 6.5% and the corresponding value for ternary mixtures was 11.2%. These versions of the models require the experimental surface tension of the mono-solvents as input data. An attempt has been made here to correlate the surface tension of the mono-solvents at various temperatures using Abraham parameters. The model calculates the surface tension with the MRD of 11.0%. A combined version of the models was presented to predict the surface tension of binary and ternary mixtures without using any experimental input data in which the MRDs of 14.6 and 11.7% were obtained. Results show that the addition of solvation parameters may lead to an improvement in the calculated surface tension and show good agreement between theory and experiment.Display Omitted► Models for predicting the surface tension of solvent mixtures at various temperatures ► Ab initio models for surface tension of solvent mixtures at various temperatures ► Ab initio model for surface tension of mono-solvents at various temperatures
Keywords: Surface tension; Jouyban–Acree model; Solvent mixtures; Temperature; Abraham solvation parameters;

Conductivity and viscosity properties of associated ionic liquids phosphonium orthoborates by Alejandro García; Luis C. Torres-González; Karinjilottu P. Padmasree; Maria G. Benavides-Garcia; Eduardo M. Sánchez (57-62).
A new group of room temperature molten salts based on asymmetric isobutyl(trihexyl)phosphonium cation with different chelated orthoborate anions are presented in this report. The physicochemical properties of these compounds as glass transition temperature, thermal stability, viscosity and conductivity are determined and discussed on structural basis. The highest room temperature conductivity observed was for the isobutyl(trihexyl)phosphonium bis(malonate)borate. The results indicate that the prepared orthoborates have lower viscosities, better conductivities when compared to their precursor, isobutyl(trihexyl)phosphonium bromide. Our investigation has found that those new compounds have an intermediate-to-fragile behavior. We plotted the conductivity and viscosity data according to Walden's rule and found that they can be classified as an associated ionic liquid (AIL) an intermediate between a true ionic liquid and a molecular species.► Novel room temperature ionic liquids based on orthoborate phoshponiums. ► Those liquids displayed low glass transition temperatures. ► We observed associated ionic liquid behavior on Walden's diagram.
Keywords: Ionic liquids; Phosphoniums; Ionic conduction; Viscosity; Fragility;

Nanostructured polyaniline (PANI) doped with tungstophosphoric acid (TPA) was prepared; its structure was confirmed by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). An electrochemical sensor was fabricated in a simple way by modification of carbon paste electrode with this nanostructured material (CPE-PANI/TPA). Because of the catalytic activity of TPA and the unique properties of PANI, this sensor was used for catalytic determination of norepinephrine (NE), acetaminophen (AC) and folic acid (FA), individually and simultaneously. Cyclic voltammetry experiments showed that the oxidation potential of these substances shifted to negative values and their oxidation current increased sharply by use of this sensor rather than by use of bare carbon paste electrode. Linear dynamic ranges and detection limits were obtained respectively as 8.0 × 10− 8–2.0 × 10− 3  M and 5.0 × 10- 8  M for NE, 9.0 × 10− 7–1.9 × 10− 3  M and 2.0 × 10− 7  M for AC and 2.0 × 10− 6–2.1 × 10− 3  M and 3.0 × 10− 7  M for FA by differential pulse voltammetry. The proposed electrochemical sensor was used for the determination of these substances in pharmaceutical and blood serum samples.An electrochemical sensor was fabricated by incorporating nanostructured polyaniline doped with tungstophosphoric acid in carbon paste electrode and was used for simultaneous determination of norepinephrine (NE), paracetamol (AC) and folic acid (FA).Display Omitted► Synthesizing of nanostructured polyaniline doped with tungstophosphoric acid ► Confirming its special structure by FT-IR and SEM studies ► Fabrication of a sensor by carbon paste electrode modified with this nanostructure ► Electrochemical study of norepinephrine, acetaminophen and folic acid at the sensor ► Obtaining interesting linear ranges and detection limits by the sensor
Keywords: Electrochemical sensor; Polyaniline; Nanostructure; Norepinephrine; Acetaminophen; Folic acid;

Multi-wavelength spectrophotometric determination of acidity constants of some salicylaldimine derivatives by Maryam Bordbar; Ali Yeganeh Faal; Mohammad Mahdi Ahari-Mostafavi; Mehrnaz Gharagozlou; Razieh Fazaeli (70-77).
The acidity constants of 9 synthesized derivatives of Schiff base in dimethylformamide/water and ethanol/water (25:75 v/v) at 25 °C and an ionic strength of 0.1 M have been determined spectrophotometrically. All of the spectrophotometric data as pure spectra and distribution diagrams calculated with the SQUAD and MCR-ALS as hard modeling and soft modeling methods, respectively. Also the influence of substituents in the molecular structure on the ionization constants is discussed.► Schiff bases have very important applications. ► Their acidity constants determined spectrophotometrically. ► SQUAD and MCR-ALS methods used to this purpose.
Keywords: Schiff base; Salicylaldimine; Acidity constant; SQUAD;

The constrained molecular dynamics technique has been used to simulate solutions of sodium chloride ion pair in pure methanol (MeOH), pure dimethyl sulfoxide (DMSO) and DMSO–MeOH mixtures with MeOH mole fractions (xMeOH) of 0.25, 0.50 and 0.75. The potentials of mean force (PMFs) of the sodium chloride ion pair have been computed for all the above compositions. The PMFs for the pure solvents indicate that contact ion pairs (CIPs) are more stable than the solvent separated ion pairs (SSIPs). In the mixtures, contact ion pairs (CIPs) dominate the PMF and solvent assisted ion pairs (SAIPs) persist in all the compositions. As the mole fraction of DMSO increases, the stability of CIP increases. In all three solvent mixtures, the Na+ ―Cl ion pair is preferentially solvated by MeOH molecules. These results have been confirmed by dynamical ion pair trajectories for long times. A study of the running coordination numbers in the CIP and SAIP/SSIP configurations shows that the number of DMSO and methanol molecules around the ion pair does not change significantly with composition beyond xMeOH  = 0.50.The potentials of mean force (PMFs) for the sodium chloride ion pair in DMSO (dimethyl sulfoxide)–methanol mixtures show the presence of a strong contact ion pair in all compositions. Compositions other than pure DMSO support solvent assisted ion pairs whereas pure DMSO supports a solvent separated ion pair.Display Omitted► The potentials of mean force (PMFs) of the Na+ Cl are computed in DMSO-MeOH mixtures. ► Contact ion pairs (CIPs) are more stable than the solvent separated ion pairs (SSIPs). ► CIPs dominate over the solvent assisted ion pairs (SAIPs). ► As the mole fraction of DMSO increases, the stabilies of CIPs increase. ► In mixtures, the Na+ ―Cl ion pair is preferentially solvated by MeOH molecules.
Keywords: Potential of mean force; Contact ion pair; Solvent assisted ion pair; Solvent separated ion pair; Solvation structure of ion pair;

Electrical conductivities of KI, LiBr, LiNO3, AgNO3 and Et4NI have been studied in mixtures of propan-1-ol with water in a whole range of composition of mixtures at 298.15 K. The experimental data of conductance have been analyzed on the basis of low concentration Chemical Model (lcCM). The individual limiting ionic conductivities of K+, Li+, Ag+, Et4N+ and I ions were determined using the Fuoss–Hirsch assumption. The dependencies of the limiting molar conductances Λo and Walden products Λo η as a function of mixture composition were analyzed in the aspects of ion–solvent interactions.► Λo of KI, LiBr, LiNO3, AgNO3 and Et4NI in water + propan-1-ol mixtures at 298.15 K. ► Chemical Model (lcCM) has been used for calculation. ► The ionic limiting molar conductances λo ± and Walden products λo ±  ·  η were analyzed.
Keywords: Conductance; Binary mixtures; Water + propan-1-ol; Walden product;

The nanorods of Hg doped ZnO samples were prepared by a facile thermal decomposition method and the samples were characterized using various techniques. The transmission electron microscopy and X-ray diffraction results indicate the formation of hexagonal rod shaped Hg doped ZnO with the absence of impurities. The UV–Vis absorption measurements demonstrated that Hg doped ZnO shows a band edge shift towards visible region. The surface morphology was studied using FE-SEM techniques. In addition, the doped samples were used to degrade model organic dyes under visible condition and the results are discussed in detail.Display Omitted► Novel catalyst ► Visible light photocatalytic activity ► Preparation is a simple, fast and cost effective method ► Nanorods
Keywords: Photocatalytic activity; Novel catalyst; Thermal decomposition method; Visible light;

The apparent molar volumes, V ϕ , of monosodium salts of aliphatic dicarboxylic acids of the HOOC(CH2)n(COOH)2 [n = 0–5] types in dilute aqueous solution have been determined by precise density measurements, at T = 298.15 K. Densities were measured using a vibrating-tube densimeter (DMA 5000, Anton Paar, Austria) at T = 298.15 K. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.0050 ≤  m/(mol·kg− 1) ≤ 0.3000. A new method for determining the values of partial molar volume of the electrolyte of NaHA type has been proposed. This method takes into account all equilibrium occurring in the solution. The variations of V ϕ 0 values with aliphatic chain length of analyzed salts were determined.► The densities of aqueous solutions of monosodium salts of the dicarboxylic acids have been measured. ► A new method for determining the values of partial molar volume of the electrolyte has been proposed. ► The values of partial molar volumes of electrolytes have been determined. ► The variations of V ϕ 0 values with aliphatic chain length of analyzed salts were determined.
Keywords: Carboxylic acids; Monosodium salts of dicarboxylic acid; Apparent molar volume;

The experimental density, viscosity, and ultrasonic speeds of anisaldehyde (AA) and alkoxyethanols namely 2-methoxy ethanol (MOE), 2-ethoxy ethanol (EOE) and 2-butoxy ethanol (BOE) have been measured over the full range of compositions at atmospheric pressure and at different temperatures (303.15, 308.15, 313.15 and 318.15 K). From these experimental values the molar volume (Vm), adiabatic compressibility (βad) and intermolecular free length (Lf), are computed and their excess properties along with deviation in viscosity (Δη) are fitted to Redlich–Kister type equation, a multi parametric nonlinear regression analysis technique to derive the binary coefficients and to estimate the standard deviation between experimental and calculated data. The experimental data of viscosity is also used to test the applicability of empirical relations of Grunberg–Nissan, Katti–Chaudhri, Heric–Brewer and Hind et al. for the systems studied. Further, FT IR analysis of these binary mixtures at different concentrations, confirms the presence of hydrogen bonding, and supported the results as observed in thermodynamic analysis with respect to forces of association/dispersion between unlike molecules. The interaction of AA with alkoxyethanol is found to decrease with increase in alkyl chain length of the alkoxy group.Display Omitted► Binary mixtures of Anisaldehyde with some alkoxyethanols have been studied at different temperatures. ► Weak hydrogen bonding interactions between the components were confirmed. ► Experimental viscosity values are tested for applicability of empirical relations of viscosity. ► Interactions decrease with increasing chain length of oxyalcohols. ► IR studies gave a plausible evidence for the experimental and computational analysis results.
Keywords: Alkoxyethanol; Anisaldehyde; Ultrasonic speed; Excess molar volume; Redlich–Kister polynomial; FT-IR;

Synthesis, characterization and application of ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient catalyst for the preparation of hexahydroquinolines by Abdolkarim Zare; Fereshteh Abi; Ahmad Reza Moosavi-Zare; Mohammad Hassan Beyzavi; Mohammad Ali Zolfigol (113-121).
In this work, novel Brønsted acidic ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate {[Dsim]HSO4} is synthesized, and characterized by studying its FT-IR, 1H NMR, 13C NMR, mass, TG, DTG and XRD spectra. This ionic liquid, with three acidic functional groups, is utilized as a highly efficient, homogeneous and reusable catalyst for the preparation of hexahydroquinolines via one-pot multi-component condensation of arylaldehydes, dimedone (5,5-dimethylcyclohexane-1,3-dione), β-ketoesters and ammonium acetate under solvent-free conditions. The catalyst can form dual hydrogen-bond using its SO3H groups which this subject can direct to its assembly and efficiency.Display Omitted► Introducing a novel ionic liquid (IL) as catalyst for organic transformations ► Characterization of the IL using FT-IR, 1H and 13C NMR, mass, TG, DTG and XRD spectra ► Studying the efficiency of the IL to catalyze hexahydroquinoline synthesis ► Generality of the catalyst, high yields and short reaction times
Keywords: Brønsted acidic ionic liquid; 1,3-Disulfonic acid imidazolium hydrogen sulfate {[Dsim]HSO4}; Hexahydroquinoline; Self-assembly;

An efficient method for the multi-component synthesis of 2-amino-4H-chromenes by reaction of malononitrile with various aldehydes and phenols in the presence of gel entrapped DABCO as catalyst is reported.Display Omitted► A novel gel entrapped base catalyst (GEBC) has been synthesized by entrapping DABCO in the matrix of agar-agar. ► The catalyst showed excellent activity in the multi-component synthesis of 2-amino-4H-chromenes. ► The reaction condition is mild and eco-friendly.
Keywords: Multi-component reaction; Gel entrapped base catalyst; Recyclability;

A study on solvatochromism of some monoazo dye derivatives by İsa Sıdır; Yadigar Gülseven Sıdır; Halil Berber; Erol Taşal (127-136).
The UV–vis and fluorescence spectra of four monoazo dye derivatives were investigated in the solvents with different polarities. Characterization of UV–vis electronic bands is specified by calculating charge transfer energy (E CT) and ionization potential (I p). The solvent effects on the absorption and fluorescence band maxima (ν max) were discussed using the solvent parameters. The magnitude and characteristics of the solute–solvent interactions were determined with multiple linear regression analysis. The π–π* transitions of monoazo derivatives are mainly controlled by global interaction, which is induction-dispersive and orientation interactions.Display Omitted► Charge transfer band is specified by charge transfer energy and ionization potential. ► Positive solvatochromism of these compounds was observed upon increasing the solvent polarity. ► The solute–solvent interactions were determined on the basis of multiple linear regression analysis. ► The absorption and fluorescence band shifts are found to be dominantly affected by non-specific interactions.
Keywords: Azo dye; Electronic absorption spectra; Fluorescence spectra; Solvent effect; Push–pull molecule; Charge transfer band;

Glucose-based deep eutectic solvents: Physical properties by Adeeb Hayyan; Farouq S. Mjalli; Inas M. AlNashef; Yahya M. Al-Wahaibi; Talal Al-Wahaibi; Mohd Ali Hashim (137-141).
Deep eutectic solvents (DESs) are considered nowadays as green ionic liquid (IL) analogues. Despite their relatively short period of introduction as a special class of ILs, they have been under an increasing emphasis by the scientific community due to their favorable properties. In the present study, a glucose based DES of choline chloride (2-hydroxyethyl-trimethylammonium chloride) with the monosaccharide sugar d-glucose anhydrous was synthesized at different molar ratios. The physical properties of density, viscosity, surface tension, refractive index, and pH were measured and analyzed as function of temperature in the practical temperature range of 298.15–358.15 K. The analysis of these physical properties revealed that these novel DESs have the potential to be utilized for several possible industrial applications involving processing and separation of food constituents, pharmaceutical applications, as well as mediums for chemical reactions.► The main physical properties of d-glucose based DESs were measured with temperature. ► Certain physical properties depend on the eutectic composition of the mixture. ► Measurements indicated that this type of fluids have practical industrial potential.
Keywords: Glucose; Monosaccharides; Deep eutectic solvents; Ionic liquids;

The slow molecular mobility in three ionic liquids, 1-alkyl-3-methylimidazolium chlorides with alkyl tails C4, C6 and C8, has been investigated by thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC), in a temperature interval including the amorphous solid and the supercooled liquid state. A specific feature of these ionic liquids, compared with typical molecular liquids, is the existence of a slow relaxation close to the main relaxation but above T g, which is cooperative and shows a high dielectric strength.Display Omitted► Slow molecular mobility in 1-n-alkyl-3-methylimidazolium chlorides studied by TSDC ► Broad secondary relaxations arising from small amplitude oscillations of the cation's dipole ► Glass transformation with the features of a weakly fragile glass-former ► Slow relaxation close to the main relaxation but above T g, with high polarization and moderate degree of cooperativity
Keywords: RTIL; Ionic liquid; TSDC; Thermally stimulated current; Secondary-relaxation; α-Relaxation; Liquid–liquid transition;

Thermodynamic properties of aqueous solutions of two ammonium-based protic ionic liquids at 298.15 K by Mengyin Hou; Yingjie Xu; Yajuan Han; Bin Chen; Wenxia Zhang; Qinghua Ye; Jinzhi Sun (149-155).
Densities (ρ), refractive indices (nD ) and electrical conductivities (κ) of ethylammonium acetate (N2Ac) protic ionic liquid + water and propylammonium acetate (N3Ac) protic ionic liquid + water binary mixtures over the entire composition range were measured at 298.15 K under atmospheric pressure. The excess molar volumes (V E), apparent molar volumes (V ϕi ), partial molar volumes ( V ¯ m , i ) and excess partial molar volumes ( V ¯ m , i E ) of the binary mixtures were calculated from the density data. The refractive index deviations (ΔnD ) of the binary mixtures were determined using the refractive index data. The excess molar volumes and refractive index deviations were correlated with the Redlich–Kister equation. The excess molar volumes of the above-mentioned systems are negative over the whole composition range, while the refractive index deviations are positive. The concentration dependence of electrical conductivity was fitted according to the empirical Casteel–Amis equation. The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties.► Thermodynamic properties of ethylammonium acetate + water and propylammonium acetate + water systems were reported at 298.15 K. ► The interactions and structural effects were analyzed based on the volumetric, refractive index and conductivity properties. ► Redlich–Kister equation was used to correlate the excess molar volumes and refractive index deviations. ► The concentration dependence of electrical conductivity was fitted according to the empirical Casteel–Amis equation.
Keywords: Protic ionic liquid; Ethylammonium acetate; Propylammonium acetate; Thermodynamic properties;

Microscopic and transition investigation on the effect of cholesterol in AOT solution by Chun Yuan Tan; Kok Siong Khoo; Shahidan Radiman; Irman Abdul Rahman; Nur Farhana bt Amari (156-159).
The effects of cholesterol on vesicle were studied in this paper. Anionic bis-(2-ethylhexyl)sulfosuccinate (AOT) surfactant and brine water were used to prepare the vesicle. Effects on vesicle size were observed using polarized light microscopy (PLM) and dynamic light scattering (DLS), whereas thermal properties were measured using differential scanning calorimeter (DSC). The results were compared among AOT solutions before and after the addition of various amounts of cholesterol, showing difference in vesicle size, microscopy scale, hydrodynamic diameter, and main transition temperature (Tm). These changes were attributed to the entrapment of cholesterol molecules in the hydrophobic part of vesicles.► More vesicle observation with increasing cholesterol content ► Increase in main transition temperature from 35 °C to 85 °C ► Entrapment of cholesterol molecule in hydrophobic part ► Vesicle size increase due to net repulsion force
Keywords: Sodium bis-(2-ethylhexyl)sulfosuccinate (AOT); Cholesterol; Polarized light microscopy; Dynamic light scattering; Size distribution; Main transition temperature;

Absorption, steady state and time resolved fluorescence spectra of fast blue RR (FBRR) and fast violet B (FVB) were studied in hydroxypropyl-α-cyclodextrin (HP-α-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD). Dual emission observed in both CDs suggested that twisted intramolecular charge transfer (TICT) is present in both molecules. The normal Stokes shifted bands originated from the locally excited state and the large Stokes shifted bands were due to the emission from a TICT state. The ratio of the TICT to the normal emission increased with HP-β-CD concentration, while it was constant upon addition of HP-α-CD. This behavior was in accordance with CD dependent decay times of the TICT and normal emissions, indicating the formation of different 1:1 FVB/CD and FBRR/CD inclusion complexes. The benzoyl moiety of FVB/FBRR was deeply encapsulated in the HP-β-CD cavity, whereas in HP-α-CD, it was exposed to the water phase. Semiempirical quantum optimization was also carried out to assign the encapsulation of the FBRR and FVB.The energy minimized structures of (a) FBRR:HP-α-CD and (b) FVB:HP-α-CD inclusion complexes at PM3 level of theory.Display Omitted► TICT is observed in FBRR and FVB with water and CD solutions. ► FBRR and FVB form 1:1 complex with HP-α-CD and HP-β-CD. ► Aniline ring present in the hydrophilic part and benzoyl ring present in the hydrophobic part of the CD nano-cavity ► Triexponential decay was observed in the nanosecond time-resolved fluorescence.
Keywords: Fast violet B; Fast blue RR; Cyclodextrin; TICT; Inclusion complex; PM3 method;

The voltammetric behavior of 3, 5-Dinitrobenzoic acid (3, 5-DNBA) has been studied at a Glassy carbon electrode (GCE). 3, 5-DNBA was found to produce two reduction peaks in the forward scan i.e. 0.0 V to − 0.1 V. In acidic medium there were no peaks in the reverse scan, indicating irreversible system and diffusion controlled process. The effect of different parameters such as pH, scan rate, concentration, surfactants, repeatability and reproducibility was studied. Based on the results obtained a reduction mechanism was proposed for 3, 5-DNBA. The limits of detection (LOD) and limit of quantification (LOQ) values were found to be 0.68 × 10− 6  M and 2.26 × 10− 6  M respectively. The total number of electrons (n), diffusion coefficient (D), charge transfer coefficient (α), the number of electrons involved in rate determining step (n α) and area of the working electrode (A) were calculated as 12, 3.897 × 10− 3  cm2/s, 0.46, 2, 0.3743 × 10− 3  cm2 respectively. The electrochemical impedance spectroscopic (EIS) studies of 3, 5-DNBA at GCE and Pt electrode were also studied.► This work describes the determination of 3, 5- Dinitrobenzoic acid at GCE. ► Number of electrons, rate constant, diffusion and transfer coefficients, LOD and LOQ values were evaluated. ► The repeatability and reproducibility studies show that GCE was the good electrode for the determination of 3, 5-DNBA. ► The surfactant CTAB was found to exhibit a better response towards 3, 5-DNBA in compare SDS and TX-100. ► By using EIS studies the electron transfer rate at GCE was better in comparison with Pt electrode.
Keywords: 3, 5-Dinitrobenzoic acid; Glassy carbon electrode; Cyclic voltammetry; Differential pulse voltammetry; Electrochemical impedance spectroscopy; Surfactants;

Density and refractive index at (298.15, 303.15 and 308.15) K for the binary liquid mixtures of acetylacetone with n-Nonane, n-Decane and n-Dodecane have been measured over the entire mole fraction range of binary liquid mixtures. Using these data, excess molar volume and deviation in molar refraction were calculated. The computed quantities were fitted to Redlich–Kister polynomial equation to derive the coefficients and estimate the standard deviation values. These quantities have been discussed in terms of intermolecular interactions.► Density and refractive index of binary mixtures are measured. ► Using these data, excess molar volume and molar refractivity are calculated. ► The interactions of alkanes with acetylacetone have been investigated. ► The experimental results are analyzed by the Redlich and Kister polynomial equation. ► Based on these data molecular interactions are studied.
Keywords: Excess molar volume; Acetyl-acetone; Alkanes; Refractive index; Binary mixture;

The densities, ρ and refractive indices, n D of binary mixtures of dimethylsulphoxide (DMSO) with poly(ethylene glycol) 200 (PEG200), poly(ethylene glycol) 300 (PEG300) and poly(ethylene glycol) 400 (PEG400) over the entire composition range were measured at temperatures (298.15, 303.15, 308.15, and 313.15 K) and at atmospheric pressure. From the experimental data, the excess molar volumes, V m E and excess refractive indices, n D E were calculated. The partial molar volumes, V ¯ m, 1 ° ∞ and V ¯ m, 2 ° ∞ of the components at infinite dilution and excess partial molar volumes, V ¯ m, 1 ° E, ∞ and V ¯ m, 2 ° E , ∞ of the components at infinite dilution have been calculated. The V m E values were negative and n D E were positive for all the three systems at each investigated temperatures. The results indicate the presence of specific interactions between DMSO and PEG molecules. The negative deviations in V m E values follow the order: PEG200 < PEG300 < PEG400. It is observed that V m E and n D E values depend upon the chain length of PEG molecules. Further, the refractive indices of these binary mixtures were calculated theoretically from the refractive index data of pure components and densities of the mixtures by using various empirical and semi-empirical relations and the results were compared with the experimental findings.► This study reports densities and refractive indices of dimethylsulphoxide with poly(ethylene glycol) mixtures. ► Provides estimation of excess properties of dimethylsulphoxide with poly(ethylene glycol) mixtures ► The study elucidates interactions of dimethylsulphoxide with poly(ethylene glycol)s. ► Correlates physicochemical properties with interactions in these mixtures
Keywords: Density; Refractive index; Dimethylsulphoxide; Poly(ethylene glycol);

Osmotic vapor pressure and density measurements have been carried-out for binary aqueous solutions of glucose and ternary aqueous solutions containing glucose and a fixed concentration of β-cyclodextrin (β-CD) [0.01262 mol kg− 1] using techniques of vapor pressure osmometer and digital densitometer at 298.15 K. The measured water activities were used to estimate the activity coefficients and free energy changes in the binary system. The activity data of binary aqueous glucose solutions are further used to obtain the hydration number of glucose. The free energy change shows that at low concentration glucose forms almost an ideal solution in water. In ternary solutions the activity coefficient and transfer free energies of β-CD and glucose are studied as a function of concentration of glucose. Using earlier reported data for binary aqueous β-CD system and these newly studied systems, transfer free energies of β-CD from aqueous to aqueous glucose solutions are determined. These results are further subjected to McMillan–Mayer theory of solutions which yield the value of thermodynamic equilibrium constant (K) for β-CD:glucose complex in aqueous solutions after evaluation of salting constant and pair and triplet interaction parameters. It has been found that log K values are positive and high. These results are discussed in terms of hydrogen bonding, replacement of water molecules from β-CD cavity and solute–solute association equilibria involving pair and triplet interactions.Display Omitted► Volumetric and activity measurements for glucose + H2O solutions and glucose +  β-CD + H2O solutions at 298.15 K are reported. ► The hydration number of ~ 10 is estimated from the activity data of glucose. ► The value obtained for thermodynamic equilibrium constant indicates formation of β-CD:glucose complex in solution phase. ► Results are discussed in terms of H-bonding, replacement of H2O from β-CD cavity and solute-solute association equilibria.
Keywords: β-CD; Glucose; Activity and activity coefficients; Gibbs free energy of transfer; Hydrophobic interactions; Thermodynamic equilibrium constant;