Pressure-induced crystallization of 1-butyl-3-methylimidazolium hexafluorophosphate

We have investigated the pressure-induced crystallization of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) associated with the conformational changes of [bmim]⁺ by Raman spectroscopy. [bmim]⁺ has trans-trans and gauche-trans (GT) conformers of the butyl side chain at ambient pressure. Our result revealed that liquid to solid-phase transition occurs at 0.2–0.4 GPa region, where the GT conformer becomes dominant. We found that the GT dominant state continues up to 4 GPa.     

Green synthesis of ZnO nanoparticles in a room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Nanoparticles of ZnO with the wurtzite structure have been successfully synthesized via a microwave through the decomposition of zinc acetate dihydrate in an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as a solvent. Fundamental characterizations including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were conducted for the ZnO nanostructures.To explore the growth mechanism, the samples have been prepared in different irradiation time and also cetyltrimethylammonium bromide (CTAB) has been used as the capping reagent.     

Development of a united-atom force field for 1-ethyl-3-methylimidazolium tetracyanoborate ionic liquid

Three united-atom (UA) force fields are presented for the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate, abbreviated as [EMIM]⁺[B(CN)₄]^?. The atomistic charges were calculated based on the restrained electrostatic potential (RESP) of the isolated ions (abbreviated as force field 1, FF-1) and the ensemble averaged RESP (EA-RESP) method from the most stable ion pair configurations obtained by MP2/6-31G*+ calculations (abbreviated as FF-2 and FF-3). Non-electrostatic parameters for both ions were taken from the literature and Lennard–Jones parameters for the [B(CN)₄]^? anion were fitted in two different ways to reproduce the experimental liquid density. Molecular dynamics (MD) simulations were performed over a wide temperature range to identify the effect of the electrostatic and non-electrostatic potential on the liquid density and on transport properties such as self-diffusion coefficient and viscosity. Predicted liquid densities for the three parameter sets deviate less than 0.5% from experimental data. The molecular mobility with FF-2 and FF-3 using reduced charge sets is appreciably faster than that obtained with FF-1. FF-3 presents a refined non-electrostatic potential that leads to a notable improvement in both transport properties when compared to experimental data.     

Solvation of AgTFSI in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid investigated by vibrational spectroscopy and DFT calculations

In this paper we investigate the solvation of silver bis(trifluoromethylsulfonyl)imide salt (AgTFSI) in 1‐ethyl‐3‐methylimidazolium TFSI [EMI][TFSI] ionic liquid by combining Raman and infrared (IR) spectroscopies with density functional theory (DFT) calculations. The IR and Raman spectra were measured in the 200–4000 cm⁻¹ spectral region for AgTFSI/[EMI][TFSI] solutions with different concentrations ([AgTFSI] <0.2 mole fraction). The analysis of the spectra shows that the spectral features observed by dissolution of AgTFSI in [EMI][TFSI] solution originate from interactions between the Ag⁺ cation and the first neighboring TFSI anions to form relatively stable Ag complexes. The ‘gas phase’ interaction energy of a type [Ag(TFSI)₃]²⁻ complex was evaluated by DFT calculations and compared with other interionic interaction energy contributions. The predicted spectral signatures because of the [Ag(TFSI)₃]²⁻ complex were assessed in order to interpret the main IR and Raman spectral features observed. The formation of such complexes leads to the appearance of new interaction‐induced bands situated at 753 cm⁻¹ in Raman and at 1015 and 1371 cm⁻¹ in IR, respectively. These specific spectral signatures are associated with the ‘breathing’ mode and the S–N–S and S–O stretching modes of the TFSI anions engaged in the complex. Finally, all these findings are discussed in terms of interaction mechanisms enabling the electrodeposition characteristics of silver from AgTFSI/[EMI][TFSI] IL‐based electrolytic solutions. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrochemical behavior of cobalt from 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

The electrodeposition of metallic cobalt from a 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid was investigated. The electrochemical behavior of Co(II) in the ionic liquid on a platinum working electrode at 60 °C was studied by cyclic voltammetry and chronoamperometry. The results from the cyclic voltammetry showed that the electrodeposition of metallic Co in the ionic liquid was an irreversible process and controlled by the diffusion of Co(II) on a platinum working electrode. The average value of αn_α was calculated to be 0.35 and the diffusion coefficient (D₀) of Co(II) was calculated to be 1.76 × 10⁻⁸ cm²/s at 60 °C. Chronoamperometric results indicated that the electrodeposition of Co on a platinum working electrode followed the mechanism of instantaneous nucleation and three-dimensional growth with diffusion-controlled. The cobalt plating was uniform, dense, shining in appearance with good adhesion to the platinum substrate at 60 °C. The scanning electron microscope (SEM) micrographs were used to confirm that the cobalt plating was denser and finer at 60 °C. Energy dispersive X-ray analysis (EDAX) profile showed that the obtained plating was pure cobalt. X-ray diffraction (XRD) pattern indicated that there was a preferred orientation direction and the average size of cobalt grains was 40 nm.     

Structure,thermodynamic and transport properties of imidazolium-based bis(trifluoromethylsulfonyl)imide ionic liquids from molecular dynamics simulations

Molecular dynamics (MD) simulations have been performed in order to investigate the properties of [C _n mim⁺][Tf₂N^?] (n?=?4,?8,?12) ionic liquids (ILs) in a wide temperature range (298.15?498.15?K) and at atmospheric pressure (1 bar). A previously developed methodology for the calculation of the charge distribution that incorporates ab initio quantum mechanical calculations based on density functional theory (DFT) was used to calculate the partial charges for the classical molecular simulations. The wide range of time scales that characterize the segmental dynamics of these ILs, especially at low temperatures, required very long MD simulations, on the order of several tens of nanoseconds, to calculate the thermodynamic (density, thermal expansion, isothermal compressibility), structural (radial distribution functions between the centers of mass of ions and between individual sites, radial-angular distribution functions) and dynamic (relaxation times of the reorientation of the bonds and the torsion angles, self-diffusion coefficients, shear viscosity) properties. The influence of the temperature and the cation's alkyl chain length on the above-mentioned properties was thoroughly investigated. The calculated thermodynamic (primary and derivative) and structural properties are in good agreement with the experimental data, while the extremely sluggish dynamics of the ILs under study renders the calculation of their transport properties a very complicated and challenging task, especially at low temperatures.     

Lithium solvation and diffusion in the 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid

The Raman spectra of (1 − x)(BMITFSI), xLiTFSI ionic liquids, where 1‐butyl‐3‐methylimidazolium cation (BMI⁺) and bis(trifluoromethane‐sulfonyl)imide anion (TFSI⁻) are analyzed for LiTFSI mole fractions x < 0.4. As expected from previous studies on similar TFSI‐based systems, most lithium ions are shown to be coordinated within [Li(TFSI)₂]⁻ anionic clusters. The variation of the self‐diffusion coefficients of the ¹H, ¹⁹F, and ⁷Li nuclei, measured by pulsed‐gradient spin‐echo NMR (PGSE‐NMR) as a function of x, can be rationalized in terms of the weighted contribution of BMI⁺ cations, TFSI⁻ ‘free’ anions, and [Li(TFSI)₂]⁻ anionic clusters. This implies a negative transference number for lithium. Copyright © 2008 John Wiley & Sons, Ltd.     

Electrical and electromechanical properties of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-blended cellulose

The effect of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI) blending on the electromechanical and electrical properties of cellulose was premeditated by taking bending actuator test and electrical impedance analysis. Dispersion of BMITFSI in cellulose matrix was carried out by solution blending technique. Upon blending BMITFSI, bending displacement of the actuator was enhanced by eight times as compared to that of the pristine cellulose. Similar improvement in the AC conductivity of cellulose was observed. The effect of BMITFSI content and humidity on electromechanical and electrical properties of BMITFSI-loaded cellulose was discussed.     

Ionic transport properties of PVdF-HFP-MMT intercalated nanocomposite electrolytes based on ionic liquid, 1-butyl-3-methylimidazolium bromide

Ionic conductivity and transport properties of polyvinylidenefluoride–co-hexafluoropropylene– montmorillonite intercalated nanocomposite electrolytes based on ionic liquid 1-butyl-3-methylimidazolium bromide have been studied for various concentrations of montmorillonite clay. Ionic conductivity of the order of 10^?3?S?cm^?1 at room temperature with thermal stability up to about 235 °C has been obtained for the electrolyte system. The electrolyte system has superior properties at 5 wt% of clay loading with highly amorphous morphology as seen from selected area electron diffraction micrograph. Scanning electron microscope studies show that the electrolyte system has highly porous morphology and the ionic liquid is trapped in the pores. Dielectric properties of the electrolyte system have been studied to investigate the relaxation processes occurring in the system. Variation of real part of dielectric permittivity with frequency shows two relaxation processes occurring in the system, slow at low frequency and fast at high frequency. Kohlrausch exponential parameter has been calculated from modulus formalism, and the values show that the distribution of conductivity relaxation times becomes narrower with increasing clay loading.     

Lithium solvation in a PMMA membrane plasticized by a lithium‐conducting ionic liquid based on 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide

The Raman and Infrared (IR) spectra of poly(methyl methacrylate) (PMMA) membranes plasticized by ionic liquids of the (1 − x)[1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI)],xLiTFSI type, where BMI⁺ is the 1‐butyl‐3‐methylimidazolium cation and TFSI⁻ the bis(trifluoromethanesulfonyl)imide anion, are analyzed for a lithium bis(trifluoromethane sulfone)imide (LiTFSI) mole fraction x = 0.23 and PMMA contents from 0 to 50 wt%. The lithium is found to have an average coordination of about three CO groups and less than one TFSI⁻ anion. It plays the role of a cross‐linker between the ester groups of PMMA and the nonvolatile ionic liquid. Addition of PMMA to the (1 − x)(BMITFSI),xLiTFSI ionic liquid lowers the conductivity but might improve the lithium transference number by transforming the [Li(TFSI)₂]⁻ anionic clusters present in the pure ionic liquid into a mixed coordination by ester groups and TFSI⁻ anions. Copyright © 2008 John Wiley & Sons, Ltd.     

Dissolution and Regeneration in Films of Natural Luffa in 1-butyl-3-methylimidazolium Chloride

Regenerated cellulose film was successfully prepared from natural luffa, a new cellulose raw material. A pretreatment of natural luffa was carried out by an alkali and hydrogen peroxide mixed solution. The dissolution process of the pretreated luffa in 1-butyl-3-methylimidazolium chloride ([BMIM]C1) was observed by polarized optical microscope. The structures and properties of the luffa films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TGA), and porosity measurements. The results showed that the luffa fibers were transformed to fibrils after the pretreatment. [BMIM]Cl was a good non-derivatizing solvent for the luffa cellulose. The solution conditions were 80°C and 10 h for a 15% solution. After being regenerated, as films, from the luffa/[BMIM]Cl solution, the crystalline structure of the luffa film was transformed completely from cellulose I to cellulose II. The film showed the strong characteristic functional groups of cellulose in FTIR results. The surface of the film was smooth with a compact structure. The porosity of the film was 66.2% and the average pore size was 17.8 nm. It was thermally stabile up to 280°C.     

Ultrasound-promoted catalyst-free one-pot four component synthesis of 2H-indazolo[2,1-b]phthalazine-triones in neutral ionic liquid 1-butyl-3-methylimidazolium bromide

A catalyst-free one-pot four component methodology for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones under ultrasonic irradiation at room temperature using 1-butyl-3-methylimidazolium bromide, [Bmim]Br, as a neutral reaction medium is described. A broad range of structurally diverse aldehydes (aromatic aldehydes bearing electron withdrawing and/or electron releasing groups as well as heteroaromatic aldehydes) were applied successfully, and corresponding products were obtained in good to excellent yields without any byproduct.     

Raman and ab initio study of the conformational isomerism in the 1‐ethyl‐3‐methyl‐imidazolium bis(trifluoromethanesulfonyl)imide ionic liquid

The calculated and experimental Raman spectra of the (EMI⁺)TFSI⁻ ionic liquid, where EMI⁺ is the 1‐ethyl‐3‐methylimidazolium cation and TFSI⁻ the bis(trifluoromethanesulfonyl)imide anion, have been investigated for a better understanding of the EMI⁺ and TFSI⁻ conformational isomerism as a function of temperature. Characteristic Raman lines of the planar (p) and non‐planar (np) EMI⁺ conformers are identified using the reference (EMI⁺)Br⁻ salt. The anion conformer of C₂ symmetry is confirmed to be more stable than the cis (C₁) one by 4.5 ± 0.2 kJ mol⁻¹. At room temperature, the population of trans (C₂) anions and np cations is 75 ± 2% and 87 ± 4%, respectively. Fast cooling quenches a metastable glassy phase composed of mainly C₂ anion conformers and p cation conformers, whereas slow cooling gives a crystalline phase composed of C₁ anion conformers and of np cation conformers. Copyright © 2006 John Wiley & Sons, Ltd.     

Relevance of sonochemistry or ultrasound (US) as a proficient means for the synthesis of fused heterocycles

Medicinal chemistry has been benefited by combinatorial chemistry and high throughput parallel synthesis. The use of sonochemistry under controlled conditions has been proved beneficial for medicinal chemistry and drug discovery process since it dramatically reduces reaction times, from days or hours to minutes. In addition, sonochemistry synthesis provides higher yields, lower cost, easy workups and greater purity as compared to lower yields, tedious workups, longer reaction times, lesser purity and termination of many by-products in the conventional thermal methods.     

Mechanism and dynamics of hydrodynamic-acoustic cavitation (HAC)

Bubble clusters in hydrodynamic cavitation, acoustic cavitation and hydrodynamic-acoustic cavitation (HAC) are investigated via high-speed photography. By introducing a cavitation state variable, a method for cavitation characterization is proposed. The periodic characteristics and intensity distributions of hydrodynamic cavitation, acoustic cavitation and HAC are quantitatively analyzed using this method. It is found that the range of HAC is evidently widened and the strength of HAC is significantly enhanced compared with hydrodynamic cavitation or acoustic cavitation. Furthermore, we developed a preliminary physical model describing the dynamics of a cavitation bubble in HAC and proposed a mechanism to explain the enhancement of the intensity in HAC.     

Ionic liquids based on the bis(trifluoromethylsulfonyl)imide anion for high‐pressure Raman spectroscopy measurements

Assembling a diamond anvil cell for high‐pressure measurements involves placing in a gasket hole the sample of interest, a pressure transmitting fluid, and a material for pressure calibration. In this communication, we propose the use of ionic liquids containing the bis(trifluoromethylsulfonyl)imide anion ([Tf₂N]^‐), [(CF₃SO₂)₂ N]^‐, as a simultaneous pressure transmitting and calibrant material for high‐pressure Raman spectroscopy measurements of solid samples that are not soluble in ionic liquids. The position of the characteristic Raman band of the [Tf₂N]^‐ anion at 740 cm⁻¹ exhibits linear frequency shift for pressures up to 2.5 GPa. High‐pressure Raman spectra of different ionic liquids containing the same anion indicate that the actual magnitude of the pressure‐induced frequency shift of the [Tf₂N]^‐ normal mode depends on the counterion, the typical shift being 4.2 cm⁻¹/GPa. Ionic liquids based on the [Tf₂N]^‐ anion are also good pressure transmitting mediums because hydrostatic condition is kept at high pressure, and no crystallization is observed up to 4.0 GPa. Copyright © 2012 John Wiley & Sons, Ltd.     

Volumetric, acoustic and spectroscopic studies for binary mixtures of ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) with alkoxyalkanols at T = (288.15 to 318.15) K

Densities and speeds of sound have been measured for the binary mixtures of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF₆] with ethylene glycol monoethyl ether (EGMEE), diethylene glycol monoethyl ether (Di-EGMEE), triethylene glycol monoethyl ether (Tri-EGMEE) over the whole composition range at atmospheric pressure. Experimental densities have been used to estimate excess molar volumes, V^E. Changes in isentropic compressibility, Δκ_s have been estimated by using experimental speed of sound and density values. Excess properties were fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard errors. The molecular scale interactions between ionic liquid and alkoxyalkanols have been investigated through ¹H NMR spectroscopy. NMR chemical shifts for hydroxyl group of alkoxyalkanols and their deviations show hydrogen bonding interactions of varying strengths between ionic liquid and alkoxyalkanol in their binary mixtures.     

Chemical sensing based on the plasmonic response of nanoparticle aggregation: Anion sensing in nanoparticles stabilized by amino-functional ionic liquid

We report the synthesis, characterization and modellization of optical anion sensors based on gold nanoparticles (Au NPs) stabilized by amino-functional imidazolium ionic liquids (AFIL). The addition of different salts results in anion exchange of the imidazolium ionic liquid stabilizer leading to a change in the optical response of the original nanoparticle aqueous solution. In all cases except with dodecylbenzenesulfonic acid sodium salt, a sufficient amount of salt concentration (5 times larger than equimolar) leads to the appearance of an absorption band between 600 and 700 nm in the ultravioletvisible (UV-vis) spectrum. The presence of the salt produces aggregation of the particles that localise the optical response and produce a large spectral red shift. Transmission electron microscopy images demonstrated that this optical change was due to the aggregation of the nanoparticles. We simulate the optical response of both situations, before and after salt addition, and interpret the experimental observations in terms of the different response of metallic single nanoparticles and nanoparticle aggregates. Theoretical calculations for single nanoparticle and single nanoparticle dimers demonstrate that the colour change is not due to the enlargement or structural changes of the Au NPs, but due to the formation of NP aggregation. These results show the potential of nanoparticle plasmonics to perform effective chemical sensing.