Family Of Ionic Liquids Research Articles

Solvent-free aza-Markovnikov and aza-Michael additions promoted by a catalytic amount of imidazolide basic ionic liquids

A family of imidazolide ionic liquids were synthesized and characterized. These ionic liquids combined the virtues of strong basicity and relatively good thermal stability. Catalytic properties of these imidazolide ionic liquids were investigated and satisfactory yield was achieved when 2.0mol% of [Bmim]Im was used as catalyst for aza-Markovnikov addition under solvent-free condition at room temperature in one hour. Experimental results show that a hydrogen bond is not formed between [Bmim]Im/imidazole and vinyl ester, and its existence is not necessary for the [Bmim]Im catalyzed aza-Markovnikov addition either. A possible mechanism for [Bmim]Im-catalyzed aza-Markovnikov addition was proposed. The use of imidazolide ionic liquids in aza-Michael addition was investigated as well.

C6(MIm)2]2W10O32. 2H2O: A novel and powerful catalyst for the synthesis of 4-arylidene-2-phenyl-5(4)-oxazolones under ultrasonic condition

Abstract Di[1,6-bis(3-methylimidazolium-1-yl)hexane] decatungstate dihydrate ([C6(MIm)2]2W10O32. 2H2O) as a new family of polyoxometalate-based dicationic ionic liquids (POM-DIL) is synthesized and employed as a novel and powerful heterogeneous catalyst in the synthesis of 4-arylidene-2-phenyl-5(4)-oxazolones (azlactones) under ultrasound-assisted solvent-free condition. On the basis of the results, the products were obtained in excellent yields under mild condition. Utilization of easy work-up and purification make it very interesting from an economic perspective. Moreover, a recycling study confirmed that the catalyst can be reused multiple times without significant loss of its activity.

Synthesis and characterization of ionic liquids containing copper, manganese, or zinc coordination cations

Copper-, manganese-, and zinc-based ionic liquids (Cu{NH(2)CH(2)CH(2)OH}(6)[CH(3)(CH(2))(3)CH(C(2)H(5))CO(2)](2) (2), Cu{NH(CH(2)CH(2)OH)(2)}(6)[CH(3)(CH(2))(3)CH(C(2)H(5))CO(2)](2) (3A), Cu{NH(CH(2)CH(2)OH)(2)}(6)[CF(3)SO(3)](2) (3B), Cu{NH(CH(2)CH(2)OH)(2)}(6)[(CF(3)SO(2))(2)N](2) (3C), Mn{NH(CH(2)CH(2)OH)(2)}(6)[CF(3)SO(3)](2) (4), and Zn{NH(2)CH(2)CH(2)OH}(6)[CF(3)SO(3)](2) (5)) are synthesized in a single-step reaction. Infrared data suggest that ethanolamine preferentially coordinates to the metal center through the amine group in 2 and the hydroxyl group in 5. In addition, diethanolamine coordinates through the amine group in 3A, 3C, and 4 and the hydroxyl group in 3B. The compounds are viscous (>1000 cP) at room temperature, but two (3C and 4) display specific conductivities that are reasonably high for ionic liquids (>20 mS cm(-1)). All of the compounds display a glass transition (T(g)) below -50 °C. The cyclic voltammograms (CVs) of 2, 3A, 3B, and 3C display a single quasi-reversible wave associated with Cu(II)/Cu(I) reduction and re-oxidation while 5 shows a wave attributed to Zn(II)/Zn(0) reduction and stripping (re-oxidation). Compound 4 is the first in this new family of transition metal-based ionic liquids (MetILs) to display reversible Mn(II)/Mn(III) oxidation and re-reduction at 50 mV s(-1) using a glassy carbon working electrode.

Azepanium ionic liquids

The seven-member alicyclic secondary amine, azepane, has been used as starting material to synthesise a new family of room temperature ionic liquids. Such useful transformations of this coproduct of diamine production processes, generated in large amounts in the polyamide industry, would mitigate its disposal, which usually involves combustion. Reaction of azepane with 1-bromoalkanes or 1-bromoalkoxyalkanes produced the corresponding tertiary amines with good selectivity; further quaternisation reactions with the appropriate methylating agents yielded quaternary azepanium salts, [Rmazp]X (R = alkyl or alkoxyalkyl; X− = I−, [CF3CO2]− or [OTf]−; Tf = (trifluoromethyl)sulfonyl). Analogous [NTf2]− salts have also been produced by metathetic reactions. Liquid temperature ranges are significantly affected by the nature of the anion and the substituents on the azepanium cation core; for example, [CF3CO2]− or [OTf]− salts based on cations with alkyl substitution are solids, whereas those with alkoxyalkyl substitution are liquids at ambient temperature. The crystal structures of [C4mazp][CF3CO2], [C4mazp]I and [C6mazp][NTf2] (C4 = butyl, C6 = hexyl) are reported. The effects of the structural features of cations and anions on density, viscosity and conductivity data are discussed. The presence of ether linkages in the cationic side chains causes a marked decrease in viscosities and an increase in conductivities. Cyclic voltammetry showed that azepanium ionic liquids exhibit extremely wide electrochemical windows, thus becoming promising and safe alternatives to electrolytes based on volatile organic compounds.

Molecular dynamics simulations of the structure and transport properties of tetra-butylphosphonium amino acid ionic liquids

Systematic molecular dynamics simulations are used to study the structure, dynamics and transport properties of the ionic liquids composed of the tetra-butylphosphonium ([TBP](+), or [P(C(4)H(9))(4)](+)) cation with six amino acid ([AA](-)) anions. The structural features of these ionic liquids were characterized by calculating the partial site-site radial distribution functions, g(r), and computing the dihedral angle distribution of n-butyl side chains in the [TBP](+) cations. The dynamics of the ionic liquids are described by studying the velocity autocorrelation function (VACF) and the mean-square displacement (MSD) for the centers of mass of the ions at different temperatures. The ionic diffusion coefficients and the electrical conductivities were evaluated from both the Einstein and Green-Kubo methods. The cross-correlation terms in the electric-current autocorrelation functions, which are an indication of the ion pair correlations, are investigated. The cationic transference numbers were also estimated to study the contributions of the anions and cations to the transport of charge in these ionic liquids. We determined the role of the amino acid anion structures on the dynamical behavior and the transport coefficients of this family of ionic liquids. In general, the MSD and self-diffusion coefficients of the relatively heavier non-planar [TBP](+) cations are smaller than those of the lighter amino acid anions. Introducing polar functional groups (acid or amide) in the side chain of [AA](-) decreases the diffusion coefficient and electrical conductivity of AAILs. The major factors for determining the magnitude of the transport coefficients are the chemical functionality and the length of the alkyl side chain of the [AA](-) anion of these [TBP][AA] ionic liquids.

Hypergolic Reaction of Dicyanamide-Based Fuels with Nitric Acid

Understanding the ignition reactions for hypergolic propellants is an important step in developing a complete reaction model that can be used in engine design and optimizing the composition of the fuel−oxidizer pair. To that end, an experimental study of the hypergolic reaction of sodium dicyanamide with nitric acid was conducted to investigate a recently proposed reaction mechanism for ignition of this family of ionic liquids. Sodium dicyanamide was used to simplify contributions to products from the cation of the fuel. Gas-phase reaction products were studied using microprobe sampling and mass spectrometric analysis. In addition, a chemical assay was used to test for the presence of dinitrobiuret, the key intermediate in the proposed mechanism. Most of the results from the study support the proposed mechanism, with the only exception being the lack of direct evidence for dinitrobiuret. Additional reactions for the ignition reaction scheme are proposed.

Reactive Scattering as a Chemically Specific Analytical Probe of Liquid Surfaces.

In this Perspective, we highlight some recent progress in the reactive scattering of "chemical probe" species such as atoms or small radicals from liquid surfaces. We emphasize in particular the evolution of this area from purely dynamical studies of the scattering mechanism. The mechanistic understanding that has now been gained is sufficiently mature to allow the same methods to be used as an effective analytical tool. The use of this approach to measure liquid-surface composition and structure is illustrated through the scattering of O((3)P) atoms from a common, imidazolium-based family of ionic liquids.

Glass Dynamics and Anomalous Aging in a Family of Ionic Liquids above the Glass Transition Temperature

The present paper reports the results of a systematic rheological study of the dynamic moduli of 1-butyl 3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]), 1-butyl 3-methylimidazolium hexafluorophosphate ([Bmim][PF(6)]), and 1-ethyl 3-methylimidazolium ethylsulfate ([Emim][EtSO(4)]) in the vicinity of their respective glass transition temperatures. The results show an anomalous aging in that the dynamic and the low shear rate viscosities decrease with time at temperatures near to, but above, the glass transition temperature, and this is described. The samples that are aged into equilibrium obey the time-temperature superposition principle, and the shift factors and the viscosities follow classic super-Arrhenius behaviors with intermediate fragility values as the glass transition is approached. Similar experiments using a high-purity [Bmim][BF(4)] show that using a higher purity of the ionic liquid, while changing absolute values of the properties, does not eliminate the anomalous aging response. The data are also analyzed in a fashion similar to that used for polymer melts, and we find that these ionic liquids do not follow, for example, the Cox-Merz relationship between the steady shear viscosity and the dynamic viscosity.

Viscosity of (C2–C14) 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids in an extended temperature range

Dynamic viscosities of several members of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [Cnmim][NTf2], ionic liquids family, with the cation alkyl side-chain length varying from 2 to 14 carbon atoms, have been measured in the 278.15K to 393.15K temperature range using two different apparatuses. To the best of our knowledge, it is the first time that such an extensive assessment of viscosity – in terms of the number of compounds of a single ionic liquid homologous series, of the broad range of temperature covered, and the use of two different experimental techniques – is reported. The use of two different instruments, using different methodologies, provides information about the uncertainties in the measurement of viscosity of ionic liquids, including its dependence on the presence of traces of water and other impurities. An extensive critical analysis of the deviations between the data measured in this work and those reported in literature has been carried out.

Characterization of the Influence of the Ionic Liquid 1-Butyl-3-methylimidazolium Chloride on the Structure and Thermal Stability of Green Fluorescent Protein

Ionic liquids (ILs) are finding a vast array of applications as novel solvents for a wide variety of processes that include enzymatic chemistry, particularly as more biocompatible ILs are designed and discovered. While it is assumed that a native or near-native structure is required for enzymatic activity, there is some evidence that ILs alter protein structure and oligomerization states in a manner than can negatively impact function. The IL 1-butyl-3-methylimidazolium chloride, [bmim]Cl, is a well-studied, water-miscible member of the popular 1-alkyl-3-methylimidazolium IL family. To improve our understanding of the impact of water-miscible ILs on proteins, we have characterized the structure and oligomerization state of green fluorescent protein (GFP) in aqueous solutions containing 25 and 50 vol % [bmim]Cl using a combination of optical spectroscopy and small-angle neutron scattering (SANS). Measurements were also performed as a function of temperature to provide insight into the effect of the IL on the thermal stability of GFP. While GFP exists as a dimer in water, the presence of 25 vol % [bmim]Cl causes GFP to transition to a monomeric state. The SANS data indicate that GFP is a great deal less compact in 50 vol % [bmim]Cl than in neat water, indicative of unfolding from the native structure. The oligomerization state of the protein in IL-containing aqueous solution changes from a dimer to a monomer in response to the IL, but does not change as a function of temperature in the IL-containing solution. The SANS and spectroscopic results also demonstrate that the addition of [bmim]Cl to the solution decreases the thermal stability of GFP, allowing the protein to unfold at lower temperatures than in aqueous solution.

Tuning the Properties of Functional Pyrrolidinium Polymers by (Co)polymerization of Diallyldimethylammonium Ionic Liquids

The synthesis and polymerization of novel diallyldimethylammonium ionic liquid monomers is described. A free-radical polymerization follows a ring-closing cyclopolymerization mechanism similar to the one observed previously for diallyldimethylammonium halides that leads to pyrrolidinium functional polymers. As previously observed in other families of polymeric ionic liquids, their physico-chemical properties are seriously affected by the nature of the counter-anion. As an example, the thermal stability increases following the trend SCN(-) < ${\rm BF}_{4}^{ - }$ < ${\rm PF}_{6}^{ - }$ < bis(trifluoromethane)sulfonamide. Interestingly, this polymerization route may lead to the synthesis of a new family of random copolymers that have a similar poly(diallyldimethylammonium) backbone and a mixture of counter-anions determined by the comonomer selection.

Structure and dynamics of acetate anion-based ionic liquids from molecular dynamics study

Acetate anion-based ionic liquids (ILs) have found wide range of applications. The microstructure and dynamics of this IL family have not been clearly understood yet. We report molecular dynamics simulation results of three acetate anion-based ionic liquids that encompass the most common IL cations. Simulations are performed based on a set of proposed force field parameters for IL acetate anion which can be combined with existing parameters for IL cations to simulate large variety of ILs. The computed liquid density and IR spectral data for [BMIM][Ac] are found to match very well with available experimental results. The strong amino-group-associated interactions in [TMG][Ac] are seen to bring about higher cohesive energy density, stronger ion packing, and more restricted translational and rotational mobilities of the constituent ions. The IL anions are found to track the cation movements in all systems, implying that ions in ILs travel in pairs or clusters.

Physicochemical Properties of Glyme–Li Salt Complexes as a New Family of Room-temperature Ionic Liquids

Abstract Certain glyme–Li salt complexes, which are composed of equimolar mixtures of a glyme and a Li salt, are liquid under ambient conditions with physicochemical properties such as high thermal stability, wide potential window, high ionic conductivity, and high Li+ transference number and can be regarded as a new family of room-temperature ionic liquids.

Application of a Group Contribution Equation of State for the Thermodynamic Modeling of Gas + Ionic Liquid Mixtures

The group contribution equation of state (GC-EoS) is used to describe the phase behavior of gas + ionic liquid mixtures. With this equation, by application of the group contribution concept, if the parameters of the characteristic functional group of a family of ionic liquids are calculated using experimental data of a reduced number of ionic liquids of the family, then the phase behavior of all ionic liquids of the same family can be predicted. With this work, the parameter table of the GC-EoS is extended to systems that are comprised of an ionic liquid of the methylimidazolium bis[(trifluoromethyl)sulfonyl]imide family [−mim][Tf2N] and a gas (H2, CO, C2H4, O2, SO2, CH3OH, N2O, or Xe). Furthermore, a compilation of all GC-EoS parameters for gas + ionic liquid systems currently available in the literature is presented.

Measurements and Molecular Interactions for N,N-Dimethylformamide with Ionic Liquid Mixed Solvents

To understand the molecular interactions between N,N-dimethylformamide (DMF) with two families of ionic liquids (ILs), we have measured thermophysical properties such as densities (rho) and ultrasonic sound velocities (u) over the whole composition range at 25 degrees C under atmospheric pressure. The excess molar volume (V(E)) and the deviation in isentropic compressibilities (DeltaK(s)) were predicted using these properties as a function of the concentration of IL. These results are fitted to the Redlich-Kister polynomials. The materials investigated in the present study included two families of ILs such as ammonium salts and imidazolium salts. Diethylammonium acetate ([Et(2)NH][CH(3)COO], DEAA), triethylammonium actetate ([Et(3)NH][CH(3)COO], TEAA), triethylammonium dihydrogen phosphate ([Et(3)NH][H(2)PO(4)], TEAP), and triethylammonium sulfate ([Et(3)NH][HSO(4)], TEAS) are ammonium salts and 1-benzyl-3-methylimidazolium chloride ([Bmim][Cl]) belongs to the imidazolium family. The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors.

Assessing the Dispersive and Electrostatic Components of the Cohesive Energy of Ionic Liquids Using Molecular Dynamics Simulations and Molar Refraction Data

Molecular dynamics simulations were used to calculate the density and the cohesive molar internal energy of seventeen different ionic liquids in the liquid phase. The results were correlated with previously reported experimental density and molar refraction data. The link between the dispersive component of the total cohesive energy of the fluid and the corresponding molar refraction was established in an unequivocal way. The results have shown that the two components of the total cohesive energy (dispersive and electrostatic) exhibit strikingly different trends and ratios along different families of ionic liquids, a notion that may help explain their diverse behavior toward different molecular solutes and solvents.

Densities and derived thermodynamic properties of ternary mixtures 1-butyl-3-methyl-imidazolium tetrafluoroborate + ethanol + water at seven pressures and two temperatures

This work is a continuation of our studies on experimental measurements of physical properties on binary mixtures of the ionic liquid (IL) family 1-alkyl-3-methyl imidazolium tetrafluoroborate (CnMIM-BF 4) with water and ethanol. Here, we present density for the ternary system Butyl-MIM-BF 4 + ethanol + water at two temperatures (298.15 K and 323.15 K) and seven pressures (from 0.1 to 30 MPa). It should be noted that BMIM-BF 4 is the only IL of the family CnMIM-BF 4 that can be mixed with water and ethanol in all range of concentrations at room conditions. From the density data measured in function of pressure and temperature other important derived thermodynamic properties can be calculated, such us excess molar volumes, isothermal compressibility, isobaric expansion and the thermal pressure coefficients. These properties for selected ternary mixtures will be discussed and compared with data from the scarce number of published results for similar ternary mixtures with this same IL.

Cyto-toxicity and biocompatibility of a family of choline phosphate ionic liquids designed for pharmaceutical applications

Recently, the ionic liquid (IL) choline dihydrogen phosphate was demonstrated to improve the thermostability and shelf life of several model proteins, thus exhibiting potential as a stabilizing excipient or solvent for protein therapeutics. Before novel ILs can be used for biomedical applications, comprehensive data is required to establish biocompatibility, including cytotoxicity effects and solution behavior. In this study five phosphate-based anion moieties were analyzed: H2PO4− (DHP), dibutyl phosphate (DBP), bis(2-ethylhexyl) phosphate (BEH), bis(2,4,4-trimethylpentyl) phosphinate (TMP), and O,O′-diethyl dithiophosphate (DEP), all paired with the cation choline (C). Toxicity levels for these ILs, and a common sugar and salts, were established using a J774 murine macrophage cell line. The sugar trehalose, and the simple salts sodium chloride and choline chloride yielded EC50 values of >100, 63 and 34 mM, respectively. The EC50 values (mM) of CDHP (20), CDBP (9.1), and CDEP (8.2) were lower than, but within the range of simple salts NaCl (62.8) and choline Cl (33.7). The EC50 values of CTMP and CBEH were considerably lower, 0.25 and 0.30 mM, respectively. CDHP and CBEH displayed a hormetic response. Osmolality measurements indicated that CDHP, CDBP, and CDEP exhibit nearly complete dissociation in aqueous solution, with osmotic coefficients of 1.0, 0.9, and 0.8, whereas CTMP and CBEH have coefficients of 0.5 and 0.3, and are more molecular in character. A high correlation between the EC50 value and the anion mass fraction indicated that anion size and the presence of moderately long and/or branched alkyl chains may affect viability.

Three commentaries on the nano-segregated structure of ionic liquids

The concept that ionic liquids are nano-segregated fluids has allowed the rationalization at a molecular level of many of their complex and unusual properties, either as pure substances or as solvents. In this work we will use molecular dynamics simulation results to discuss in a semi-quantitative manner different aspects of such segregation: how it varies within a homologous ionic liquid family; the influence of the nature of the ions in the morphology of the segregated domains; and the interactions of those domains with molecular solutes or solvents.

Application of a group contribution equation of state for the thermodynamic modeling of binary systems (gas + ionic liquids) with bis[(trifluoromethyl)sulfonyl]imide anion

The properties of ionic liquids (ILs) can be modified by appropriate selection of cations and anions. Even if an infinite number of ionic liquids can be generated, only a limited number of families of anions and cations are used. The group contribution equation of state (GC-EoS) is a promising method for calculating the phase behavior of systems with ILs. If the parameters of the characteristic functional group of a IL family are fitted by using data of a reduced number of ILs of the family, then the phase behavior of all the ILs of the same family can be predicted using exclusively the data of the pure components. Previously, the parameters of the IL families with an imidazolium-based cation and the anions PF 6, BF 4NO 3, and Tf 2N were fitted to experimental data [19], and some ternary systems (CO 2 + organics + ionic liquid [bmim][BF 4]) were also modeled [22]. In this work, the GC-EoS was used to calculate phase behavior of gases {(CO 2, O 2, or SO 2) + ionic liquids} with Tf 2N anion and cations of the families 2,3-dimethyl-imidazolium, 1-alkyl-1-methyl-pyrrolidinium, and 1-alkyl-3-methyl-pyridinium. The GC-EoS was able to reproduce experimental data with deviations of the same order of experimental uncertainty. With the correlated parameters it will be possible to predict the phase behavior of systems with ILs of the families considered in this work.