Borohydride Ionic Liquids and Borane/Ionic‐Liquid Solutions as Hypergolic Fuels with Superior Low Ignition‐Delay Times

In propellant systems, fuels of choice continue to be hydrazine and its derivatives, even though they comprise a class of acutely carcinogenic and toxic substances which exhibit rather high vapor pressures and require expensive handling procedures and costly safety precautions. Hypergolic ionic liquids tend to have low volatility and high thermal and chemical stability, and often exhibit wide liquid ranges, which could allow the use of these substances as bipropellant fuels under a variety of conditions. A new family of borohydride ionic liquids and borane–ionic‐liquid solutions is described which meets nearly all of the desired important criteria for well‐performing fuels. They exhibit ignition‐delay times that are superior to that of any known hypergolic ionic liquid and may thus be legitimate replacements for hydrazine and its derivatives.     

Molecularly imprinted SPE coupled with HPLC for the selective separation and enrichment of alkyl imidazolium ionic liquids in environmental water samples

A novel 1‐butyl‐3‐methylimidazolium chloride ionic liquid surface imprinted solid‐phase sorbent was synthesized. The as‐prepared material was characterized by SEM, Brunauer–Emmett–Teller surface area analysis and Fourier Transform IR measurements. Then its adsorption properties for alkyl imidazolium ionic liquids, including adsorption capacities, adsorption kinetics, and properties of selective separation and enrichment were studied in detail. It was shown that the ionic liquid surface imprinted polymer exhibited high selective recognition characteristics for the imidazolium chloride ionic liquids with short alkyl chains (C_nmimCl, n = 2, 4, 6, 8) and the adsorption equilibrium was achieved within 25 min. Various parameters were optimized for the 1‐butyl‐3‐methylimidazolium chloride ionic liquid surface imprinted polymer SPE column, such as flow rate, eluent solvent, selectivity, and reusability of the column. Then, the SPE column coupled with HPLC was used for the determination of alkyl imidazolium ionic liquids. Experimental results showed that the existence of their structural analogs and common concomitants in environmental matrices did not affect the enrichment of 1‐butyl‐3‐methyl imidazolium chloride ionic liquid. The average recoveries of 1‐butyl‐3‐methylimidazolium chloride ionic liquid in spiked water samples were in the range of 92.0–102.0% with the RSD lower than 5.8%.     

Cyanoborohydride‐Based Ionic Liquids as Green Aerospace Bipropellant Fuels

In propellant systems, the most common bipropellants are composed of two chemicals, a fuel (or reducer) and an oxidizer. Currently, the choices for propellant fuels rely mainly on hydrazine and its methylated derivatives, even though they are extremely toxic, highly volatile, sensitive to adiabatic compression (risk of detonation), and, therefore, difficult to handle. With this background, the search for alternative green propellant fuels has been an urgent goal of space science. In this study, a new family of cyanoborohydride‐based ionic liquids (ILs) with properties and performances comparable to hydrazine derivatives were designed and synthesized. These new ILs as bipropellant fuels, have some unique advantages including negligible vapor pressure, ultra‐short ignition delay (ID) time, and reduced synthetic and storage costs, thereby showing great application potential as environmentally friendly fuels in bipropellant formulations.     

Geminal Ionic Liquids: A Combined Approach to Investigate Their Three‐Dimensional Organisation

Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3′‐di‐n‐butyl‐1,1′‐(1,3‐phenylenedimethylene)diimidazolium and 3,3′‐di‐n‐butyl‐1,1′‐(1,4‐phenylenedimethylene)diimidazolium bis[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different shapes of the two cations of the isomers, which could induce different properties and packing in the liquid state. Data collected here show that the two geminal ionic liquids are characterised by a different degree of structural order that induces, for example, a different sensitivity of the two solvent systems to temperature changes or to the presence of a co‐solvent such as methanol.     

Atom transfer radical polymerization of styrenic ionic liquid monomers and carbon dioxide absorption of the polymerized ionic liquids

Polymeric forms of ionic liquids have many potential applications because of their high thermal stability and ionic nature. Two ionic liquid monomers, 1‐(4‐vinylbenzyl)‐3‐butyl imidazolium tetrafluoroborate (VBIT) and 1‐(4‐vinylbenzyl)‐3‐ butyl imidazolium hexafluorophosphate (VBIH), were synthesized through the quaternization of N‐butylimidazole with 4‐vinylbenzylchloride and a subsequent anion‐ exchange reaction with sodium tetrafluoroborate or potassium hexafluorophosphate. Copper‐mediated atom transfer radical polymerization was used to polymerize VBIT and VBIH. The effects of various initiator/catalyst systems, monomer concentrations, solvent polarities, and reaction temperatures on the polymerization were examined. The polymerization was well controlled and exhibited living characteristics when CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine or CuBr/2,2′‐bipyridine was used as the catalyst and ethyl 2‐bromoisobutyrate was used as the initiator. Characterizations by thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction showed that the resulting VBIT polymer, poly[1‐(4‐vinylbenzyl)‐3‐butyl imidazolium tetrafluoroborate] (PVBIT), was amorphous and had excellent thermal stability, with a glass‐transition temperature of 84 °C. The polymerized ionic liquids could absorb CO₂ as ionic liquids: PVBIT absorbed 0.30% (w/w) CO₂ at room temperature and 0.78 atm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1432–1443, 2005     

Zur Hydrolyse von 2,3‐Dihydro‐1,3‐di‐tert‐butyl‐4,5‐dimethylimidazol‐2‐yliden. Die Kristallstruktur von 1,3‐Di‐tert‐butyl‐4,5‐dimethylimidazoliumhydrogencarbonat

On the Hydrolysis of 2,3‐Dihydro‐1,3‐di‐tert‐butyl‐4,5‐dimethylimidazol‐2‐ylidene. The Crystal Structure of 1,3‐Di‐tert‐butyl‐4,5‐dimethylimidazolium Bicarbonate 1,3‐Di‐tert‐butyl‐4,5‐dimethylimidazolium bicarbonate ( 7 ), formed on the exposure of 2,3‐dihydro‐1,3‐di‐tert‐butyl‐4,5‐dimethylimidazol‐2‐ylidene ( 6 ) towards air, is prepared on the reaction of 6 with ammonium bicarbonate; its crystal structure analysis reveals the presence of dimeric bicarbonate anions linked to each other and to the imidazolium ions with hydrogen bonds.     

Preparation and Characterization of New Phosphonyl‐Substituted Imidazolium Ionic Liquids

A new series of diethoxyphosphinyl‐substituted imidazolium ‘room‐temperature ionic liquids’ (RTILs) were synthesized and characterized. The new compounds 1 – 12 (Table 1) were shown to have similar densities, but higher viscosities, than common ionic liquids. The new materials remain liquid over a broad temperature range, possess extremely low vapor pressures, display relatively high thermal stabilities (up to 325°), and decompose in a two‐step process. Analysis of the solid/liquid phase transition showed that all of the new RTILs possess low glass‐transition temperatures (T_g) associated with an intense change in molar heat capacity (ΔC_pm).     

Microwave‐enhanced Efficient Synthesis of Some Polyfunctional Pyridazines

Microwave‐enhanced highly efficient protocol for the synthesis of polyfunctional pyridazines beginning from 3,6‐dichloropyridazine in environmentally benign ionic liquids have been developed. The products obtained were 3‐amino‐6‐chloropyridazine, 3,6‐diaminopyridazine, and 3‐chloro‐6‐methoxypyridazine. These derivatives were then be converted to a variety of polyfunctional pyridazine derivatives. The ionic liquids used were 1‐n‐butyl‐3‐methylimidazolium hydroxide/tetrafluoroborate/hexafluorophosphate and 1,3‐di‐n‐butylimidazolium hydroxide. This powerful strategy is less time‐consuming green methodology. The ionic liquid employed may be recovered and recycled.     

Adding magnetic ionic liquid monomers to the emulsion polymerization tool‐box: Towards polymer latexes and coatings with new properties

Magnetic ionic liquid monomers were synthesized and then polymerized to get magnetic polymer latexes and films. First, a series of 1‐vinyl‐3‐dodecyl‐imidazolium monomers having metal halides counter‐anions such as FeCl₃Br^?, CoCl₂Br^?, and MnCl₂Br^? were synthesized. These ionic liquid monomers were first homopolymerized to lead to magnetic poly(ionic liquids) and characterized. Secondly, magnetic latexes were synthesized by using the magnetic ionic liquids as surfmers (surfactant + monomer) in the emulsion polymerization of methyl methacrylate/n‐butyl acrylate. It was found that the powders obtained by freeze‐drying the latexes presented a paramagnetic behavior with weak antiferromagnetic interactions between the adjacent metal ions. Although the ratio of magnetic ionic liquid/monomer was only 2% these poly(methyl methacrylate‐co‐butyl acrylate) powders and latexes responded to a magnetic field due to the surfmer paramagnetic nature. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1145–1152     

An efficient and convenient approach for the synthesis of novel 2‐hydroxy‐12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthene‐11‐ones using p‐toluenesulfonic acid in ethanol and ionic liquid

A novel series of 2‐hydroxy‐12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthene‐11‐ones were synthesized by the one‐pot multicomponent condensation of 2,7‐dihydroxynaphthalene, aromatic aldehydes, and cyclic 1,3‐dicarbonyl compounds in the presence of a catalytic amount of p‐toluenesulfonic acid in ethanol and in ionic liquid butyl methyl imidazolium tetrafluroborate ([bmim]BF₄). The newly developed protocol is operationally convenient, widely applicable, and gives excellent yields of the diversely substituted title compounds in high purity by easy workup. J. Heterocyclic Chem., (2011).     

Microwave Synthesis of Fused Pyrans by Humic Acid Supported Ionic Liquid Catalyst and Their Antimicrobial,Antioxidant, Toxicity Assessment,and Molecular Docking Studies

A series of fused quinolinyl and quinolonyl pyrans were synthesized via a one‐pot reaction of quinolinyl and quinolonyl carbaldehydes, malononitrile, and a 1,3‐diketone. The reactions were catalyzed by a new humic acid supported 1‐butyl‐3‐methyl imidazolium thiocyanate ionic liquid under microwave irradiation conditions. Antimicrobial, antioxidant, and toxicity studies displayed various biological activities depending on structure of the pyrans.     

Dissolution capacity and rheology of cellulose in ionic liquids composed of imidazolium cation and phosphate anions

Cellulose is one of the most abundant natural polymer sources, but the applications of cellulose are limited due to difficulty in dissolving cellulose in water and common chemical solvents. In the past decades, ionic liquids have been studied to dissolve cellulose efficiently, sustainably, and in an eco‐friendly manner. In this study, a series of imidazolium‐based ionic liquids were synthesized to explore as solvents for cellulose, including 1,3‐dimethylimidazolium dimethylphosphate ([mmim]dmp), 1‐ethyl‐3‐methylimidazolium dimethylphosphate ([emim]dmp), 1‐butyl‐3‐methylimidazolium dimethylphosphate ([bmim]dmp), 1‐hexyl‐3‐methylimidazolium dimethylphosphate ([hmim]dmp), 1‐ethyl‐3‐methylimidazolium diethylphosphate ([emim]dep), 1,3‐diethylimidazolium diethylphosphate ([eeim]dep), and 1‐butyl‐3‐ethylimidazolium diethylphosphate ([beim]dep). Rheology experiments were conducted to study the flow behavior of cellulose in these ionic liquids and cosolvents. We found that the dissolution capacity of cellulose increases with decreasing viscosity of the solvent and that the rheological properties depend most strongly on the concentration of cellulose dissolved. Systems composed of cellulose in [mmim]dmp, [emim]dmp, and [emim]dep behave as viscoelastic gels, while formulations of cellulose in [bmim]dmp, [hmim]dmp, [eeim]dep, and [beim]dep show viscoelastic liquid behavior. These results will impact development of new solvents for processing of cellulose‐based polymeric materials.     

Exploring Sustainable Rocket Fuels: [Imidazolyl−Amine−BH2]+‐Cation‐Based Ionic Liquids as Replacements for Toxic Hydrazine Derivatives

The application of hypergolic ionic liquids as propellant fuels is a newly emerging area in the fields of chemistry and propulsion science. Herein, a new class of [imidazolyl?amine?BH₂]⁺‐cation‐based ionic liquids, which included fuel‐rich anions, such as dicyanamide (N(CN)₂^?) and cyanoborohydride (BH₃CN^?) anions, were synthesized and characterized. As expected, all of the ionic liquids exhibited spontaneous combustion upon contact with the oxidizer 100 % HNO₃. The densities of these ionic liquids varied from 0.99–1.12 g cm^?3, and the heats of formation, predicted based on Gaussian 09 calculations, were between ?707.7 and 241.8 kJ mol^?1. Among them, the salt of compound 5 , that is, (1‐allyl‐1H‐imidazole‐3‐yl)?(trimethylamine)?dihydroboronium dicyanamide, exhibited the lowest viscosity (168 MPa s), good thermal properties (T_gT_d>130 °C), and the shortest ignition‐delay time (18 ms) with 100 % HNO₃. These ionic fuels, as “green” replacements for toxic hydrazine‐derivatives, may have potential applications as bipropellant formulations.     

Comparative Investigation of the Ionicity of Aprotic and Protic Ionic Liquids in Molecular Solvents by using Conductometry and NMR Spectroscopy

Electrical conductivity (σ), viscosity (η), and self‐diffusion coefficient (D) measurements of binary mixtures of aprotic and protic imidazolium‐based ionic liquids with water, dimethyl sulfoxide, and ethylene glycol were measured from 293.15 to 323.15 K. The temperature dependence study reveals typical Arrhenius behavior. The ionicities of aprotic ionic liquids were observed to be higher than those of protic ionic liquids in these solvents. The aprotic ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, [bmIm][BF₄], displays 100 % ionicity in both water and ethylene glycol. The protic ionic liquids in both water and ethylene glycol are classed as good ionic candidates, whereas in DMSO they are classed as having a poor ionic nature. The solvation dynamics of the ionic species of the ionic liquids are illustrated on the basis of the ¹H NMR chemical shifts of the ionic liquids. The self‐diffusion coefficients D of the cation and anion of [HmIm][CH₃COO] in D₂O and in [D₆]DMSO are determined by using ¹H nuclei with pulsed field gradient spin‐echo NMR spectroscopy.     

Co‐electroosmotic capillary electrophoresis of basic proteins with 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids as non‐covalent coating agents of the fused‐silica capillary and additives of the electrolyte solution

The paper reports the results of a study carried out to evaluate the use of three 1‐alkyl‐3‐methylimidazolium‐based ionic liquids as non‐covalent coating agents for bare fused‐silica capillaries and additives of the electrolyte solutions (BGE) for CE of basic proteins in the co‐EOF separation mode. The three ionic liquids are differentiated from each other by the length of the alkyl group on the imidazolium cation, consisting of either an ethyl, butyl or octyl substituent, whereas tetrafluoroborate is the common anionic component of the ionic liquids. Coating the capillary with the ionic liquid resulted in improved peak shape and protein separation, while the EOF was maintained cathodic. This indicates that each ionic liquid is effective at masking the protein interaction sites on the inner surface of the capillary, also when its adsorption onto the capillary wall has not completely neutralized all the negative charges arising from the ionization of the silanol groups and the ionic liquid is not incorporated into the BGE employed for separation. Using the coated capillaries with BGE containing the ionic liquid employed for the coating, at concentration low enough to maintaining the EOF cathodic, both peak shape and protein separation varied to different extents, based on the particular ionic liquid used and its concentration. Fast and efficient separation of the model basic protein mixture in co‐electroosmotic CE is obtained with the 1‐butyl‐3‐methylimidazolium tetrafluoroborate coated capillary and 100 mM acetate buffer (pH 4.0) containing 4.4 mM 1‐butyl‐3‐methylimidazolium tetrafluoroborate as the BGE.     

Ionic liquids as hypergolic fuels

In propellant systems, fuels of choice continue to be hydrazine and its derivatives, even though they comprise a class of acutely carcinogenic and toxic substances which exhibit rather high vapor pressures and require expensive handling procedures and costly safety precautions. Only recently (2008), ionic liquids (salts with melting points less than 100 °C) with the dicyanamide anion were shown to exhibit hypergolic properties (instantaneous ignition when contacted with oxidizers (100 % nitric acid, WFNA)). Such liquids tend to have low volatilities, and high thermal and chemical stabilities, and often exhibit long liquid ranges which could allow utilization of these substances as bipropellant fuels over a variety of conditions. A new family of dicyanoborates is presented, which can be synthesized in water, with substituted N‐acyclic, N‐cyclic, and azolium cations has met nearly all of the desired important criteria needed for well‐performing fuels.     

Electroanalysis of Benazepril Hydrochloride Antihypertensive Drug Using an Ionic Liquid Crystal Modified Carbon Paste Electrode

Electroanalysis of benazepril HCl was successful using a carbon paste electrode modified with an ionic liquid crystal ( 1‐butyl‐1‐methylpiperidinium hexafluorophosphate) in presence of sodium dodecyl sulfate. The electrode performance was compared to ionic liquids (1‐n‐hexyl‐3‐methyl imidazolium tetrafluoroborate and 1‐butyl‐4‐methyl pyridinium tetrafluoroborate). Electrochemical determination of benazepril HCl was in the linear dynamic range of 8.89×10^?7 to 1.77×10^?5 mol L^?1 (correlation coefficient 0.999) and LOD 7.17×10^?9 mol L^?1. benazepril HCl was determined using this sensor in presence of urine metabolites such as uric acid, ascorbic acid. Binary mixtures of dopamine/benazepril and amlodipine/benazepril were also determined successfully.     

DFT Study of the Geometrical and Electronic Structures of Geminal Dicationic Ionic Liquids 1,3‐Bis[3‐methylimidazolium‐1‐yl]hexane Halides

In this work, the geometrical and electronic properties of the mono cationic ionic liquid 1‐hexyl‐3‐methylimidazolium halides ([C₆(mim)]⁺_X^?, X=Cl, Br and I) and dicationic ionic liquid 1,3‐bis[3‐methylimidazolium‐1‐yl]hexane halides ([C₆(mim)₂X₂], X=Cl, Br and I) were studied using the density functional theory (DFT). The most stable conformer of these two types ionic liquids (IL) are determined and compared with each other. Results show that in the most stable conformers, in both monocationic ILs and dicationic ILs, the Cl^? and Br^? anions prefer to locate almost in the plane of the imidazolium ring whereas the I^? anion prefers nearly vertical location respect to the imidazolium ring plan. Comparison of hydrogen bonding and ionic interactions in these two types of ionic liquids reveals that these ionic liquids can be formed hydrogen bond by Cl^? and Br^? anion. The calculated thermodynamic functions show that the interaction of cation — anion pair in the dicationic ionic liquids are more than monocationic ionic liquids and these interactions decrease with increasing the halide anion atomic weight.     

Ionothermal Synthesis of Germanosilicate Zeolites Constructed with Double‐Four‐Ring Structure‐Building Units in the Presence of Organic Base

The crystallization chemistry of silica‐based zeolites in ionic liquids remains highly puzzling and interesting in the field of zeolite science. Herein, we report the successful ionothermal synthesis of germanosilicate zeolites. The ionothermal templating effect with respect to the structure, alkalinity and concentration of organic additives was comparatively studied. The results showed that a small amount of organic base could effectively aid the dissolution of silica source and facilitate the crystallization of germanosilicate zeolites with ionic liquid as template. Remarkably, STW and IRR structures constructed with double‐four‐ring (D4R) structure‐building units were ionothermally prepared using 1‐ethyl/butyl‐3‐methyl imidazolium and 1‐benzyl‐3‐methyl imidazolium ionic liquids as template, respectively. Ionothermal synthesis tailored with organic base showed suitable chemistry for the formation of germanium‐containing siliceous D4R units. This finding will be helpful for the rational exploration of novel extra‐large‐pore zeolitic structures.     

Catalytic polymerization of phenylacetylene with dimeric [Rh(OMe)(cod)]2 complex in ionic liquids

Dimeric rhodium(I) complex [Rh(OMe)(cod)]₂ was found to be an active catalyst of phenylacetylene polymerization to poly(phenylacetylene) (PPA) in ionic liquids containing imidazolium or pyridinium cations. The highest yield of PPA (92%) was obtained in 1‐butyl‐4‐methylpyridinium tetrafluoroborate as reaction medium. The yield of PPA in imidazolium ionic liquids containing BF₄^? or PF₆^? anions increased to 83–99% when Et₃N or cycloocta‐1,5‐diene were added as co‐catalysts. In 1‐methyl‐3‐octylimidazolium chloride (MOI · Cl) polymerization rate was much lower than in other ionic liquids, although the highest M_w (72 400) was obtained. Spectroscopic studies confirmed that [Rh(OMe)(cod)]₂ reacted with MOI · Cl forming new carbene Rh(I) complex, which can participate in the polymerization process. Copyright © 2006 John Wiley & Sons, Ltd.