Synthesis and Characterization of 5‐Cyanotetrazolide‐Based Ionic Liquids

New salts based on imidazolium, pyrrolidinium, phosphonium, guanidinium, and ammonium cations together with the 5‐cyanotetrazolide anion [C₂N₅]^? are reported. Depending on the nature of cation–anion interactions, characterized by XRD, the ionic liquids (ILs) have a low viscosity and are liquid at room temperature or have higher melting temperatures. Thermogravimetric analysis, cyclic voltammetry, viscosimetry, and impedance spectroscopy display a thermal stability up to 230 °C, an electrochemical window of 4.5 V, a viscosity of 25 mPa s at 20 °C, and an ionic conductivity of 5.4 mS cm^?1 at 20 °C for the IL 1‐butyl‐1‐methylpyrrolidinium 5‐cyanotetrazolide [BMPyr][C₂N₅]. On the basis of these results, the synthesized compounds are promising electrolytes for lithium‐ion batteries.     

Synthesis and Improved Properties of Hypergolic Boronium‐Based Ionic Liquids

A series of asymmetric monoimidazolium dihydroboronium‐based ionic liquids (ILs) were synthesized from amine‐boranes. All the resulting ILs were fully characterized by ¹H and ¹³C NMR, IR spectroscopy, elemental analysis or high resolution mass spectrum. Compared with the symmetric bisimidazolium dihydroboronium‐based ILs, these new ILs exhibited improved properties with shorter ignition delay times (IDs), higher densities, and lower phase transition temperature showing the promising application potential as green propellants.     

Boronium‐Cation‐Based Ionic Liquids as Hypergolic Fluids

Two series of boronium‐cation‐based ionic liquids were prepared and fully characterized by ¹H, ¹³C, and ¹¹B NMR and infrared spectroscopy, differential scanning calorimetry (DSC), and elemental analysis. The structure of bis(1‐methyl‐1H‐imidazole‐3‐yl)dihydroboronium dicyanoborohydride ( 5 a ) was determined by single‐crystal X‐ray diffraction. The densities of these ionic liquids range from 1.05 to 1.28 g cm^?3, and the heats of formation, predicted on the basis of Gaussian 03 calculations, fall between ?164.6 and 430.5 kJ mol^?1. Compound 5 b , bis(1‐allyl‐1H‐imidazole‐3‐yl)dihydroboronium dicyanoborohydride, exhibits the lowest viscosity (35 mPa s) and shortest ignition‐delay time (14 ms) in combination with 100 % HNO₃.     

Task‐Specific Ionic Liquids

In recent years, ionic liquids have attracted the attention of many chemists as a result of their unique properties as solvents for chemical transformations. The focus of this Minireview is on applications of so‐called “task‐specific” ionic liquids, whereby the role of the ionic liquid goes beyond that of a solvent. Such ionic liquids find application in a wide range of areas, including catalysis, synthesis, gas absorption, and analysis.     

How a Transition‐Metal(II) Chloride Interacts with a Eutectic AlCl3‐Based Ionic Liquid: Insights into the Speciation of the Electrolyte and Electrodeposition of Magnetic Materials

Electrostatic interactions are characteristic of ionic liquids (ILs) and play a pivotal role in determining the formation of species when solutes are dissolved in them. The formation of new species/complexes has been investigated for certain ILs. However, such investigations have not yet focused on eutectic liquids, which are a promising class of ILs. These liquids (or liquid coordination complexes, LCCs) are rather new and are composed of cationic and anionic chloro complexes of metals. To date, these liquids have been employed as electrolytes to deposit metals and as solvents for catalysis. The present study deals with a liquid that is prepared by mixing a 1.2:1 mol ratio of AlCl₃ and 1‐butylpyrrolidine. An attempt has been made to understand the interactions of FeCl₂ with the organic molecule using spectroscopy. It was found that dissolved Fe(II) species interact mainly with the IL anion and such interactions can lead to changes in the cation of the electrolyte. Furthermore, the viability of depositing thick magnetic films of Fe and Fe–Al has been explored.     

Novel Cyclic Sulfonium‐Based Ionic Liquids: Synthesis,Characterization, and Physicochemical Properties

A new series of ionic liquids composed of three cyclic sulfonium cations and four anions has been synthesized and characterized. Their physicochemical properties, including their spectroscopic characteristics, ion cluster behavior, surface properties, phase transitions, thermal stability, density, viscosity, refractive index, tribological properties, ion conductivity, and electrochemical window have been comprehensively studied. Eight of these salts are liquids at room temperature, at which some salts based on [NO₃]^? and [NTf₂]^? ions exhibit organic plastic crystal behaviors, and all the saccharin‐based salts display relatively high refractive indices (1.442–1.594). In addition, some ionic liquids with the [NTf₂]^? ion exhibit peculiar spectroscopic characteristics in FTIR and UV/Vis regions, whilst those salts based on the [DCA]^? ion show lower viscosities (34.2–62.6 mPa s at 20 °C) and much higher conductivities (7.6–17.6 mS cm^?1 at 20 °C) than most traditional 1,3‐dialkylimidazolium salts.     

Tunable Aryl Alkyl Ionic Liquids with Weakly Coordinating Tetrakis((1,1,1,3,3,3‐hexafluoropropan‐2‐yl)oxy)borate [B(hfip)4] Anions

Weakly coordinating borate or aluminate anions have recently been shown to yield interesting properties of the resulting ionic liquids (ILs). The same is true for large phenyl‐substituted imidazolium cations, which can be tuned by the choice, position, or number of substituents on the aromatic ring. We were therefore interested to combine these aryl alkyl imidazolium cations with the weakly coordinating tetrakis((1,1,1,3,3,3‐hexafluoropropan‐2‐yl)oxy)borate [B(hfip)₄]^? anions to study the physical properties and viscosities of these ionic liquids. Despite the large size and high molecular weight of these readily available ILs, they are liquid at room temperature and show remarkably low glass transition points and relatively high decomposition temperatures.     

Cobalt(II) Complexes of Nitrile‐Functionalized Ionic Liquids

A series of nitrile‐functionalized ionic liquids were found to exhibit temperature‐dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trifluoromethylsulfonyl)imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C₁C_1CNPyr)₂(Tf₂N)₄] and [Co(C₁C_2CNPyr)₆][Tf₂N]₈, which were isolated from ionic‐liquid solutions, gave an insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt‐containing ionic liquids.     

Tailored Palladate Tunable Aryl Alkyl Ionic Liquids (TAAILs)

We present a new class of tunable aryl alkyl ionic liquids (TAAILs) containing different palladate counter ions. Solid-state structures for representative compounds have been obtained. Their properties are presented in comparison to those of newly synthesized and reported palladate ionic liquids with conventional counter ions. It was found that the aryl substitution pattern and the type of anion have a profound influence on the melting point. The speciation of the different anions in solution has been rationalized by DFT calculations.     

Microwave Irradiation for the Facile Synthesis of Transition‐Metal Nanoparticles (NPs) in Ionic Liquids (ILs) from Metal–Carbonyl Precursors and Ru‐, Rh‐, and Ir‐NP/IL Dispersions as Biphasic Liquid–Liquid Hydrogenation Nanocatalysts for Cyclohexene

Stable chromium, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium metal nanoparticles (M‐NPs) have been reproducibly obtained by facile, rapid (3 min), and energy‐saving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal–carbonyl precursors [M_x(CO)_y] in the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF₄]). This MWI synthesis is compared to UV‐photolytic (1000 W, 15 min) or conventional thermal decomposition (180–250 °C, 6–12 h) of [M_x(CO)_y] in ILs. The MWI‐obtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long‐term stable M‐NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED), and dynamic light scattering (DLS)). The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active and easily recyclable catalysts for the biphasic liquid–liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product) (mol Ru)^?1 h^?1 and 884 (mol product) (mol Rh)^?1 h^?1 and give almost quantitative conversion within 2 h at 10 bar H₂ and 90 °C. Catalyst poisoning experiments with CS₂ (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of Ru‐NPs.     

Temperature Dependence of the Dielectric Properties and Dynamics of Ionic Liquids

No solo dancers: The temperature dependence of dielectric spectra suggests that the lower‐frequency relaxation dominating the dynamics of imidazolium‐based room temperature ionic liquids cannot be solely due to independent rotational diffusion of the cations (see picture), but must also include cooperative motions of the surrounding particles.

     

Synthesizing 2D and 3D Selenidostannates in Ionic Liquids: The Synergistic Structure‐Directing Effects of Ionic Liquids and Metal–Amine Complexes

Presented are the ionothermal syntheses, characterizations, and properties of a series of two‐ and three‐dimensional selenidostannate compounds synergistically directed by metal–amine complex (MAC) cations and ionic liquids (ILs) of [Bmmim]Cl (Bmmim=1‐butyl‐2,3‐dimethylimidazolium). Four selenidostannates, namely, 2D‐(Bmmim)₃[Ni(en)₃]₂[Sn₉Se₂₁]Cl ( 1 , en=ethylenediamine), 2D‐(Bmmim)₈[Ni₂(teta)₂(μ‐teta)]Sn₁₈Se₄₂ ( 2 , teta=triethylenetetramine), 2D‐(Bmmim)₄[Ni(tepa)Cl]₂[Ni(tepa)Sn₁₂Se₂₈] ( 3 , tepa=tetraethylenepentamine), and 3D‐(Bmmim)₂[Ni(1,2‐pda)₃]Sn₈Se₁₈ ( 4 , 1,2‐pda=1,2‐diaminopropane), were obtained. Single‐crystal X‐ray diffraction analyses revealed that compounds 1 and 2 possess a lamellar anionic [Sn₃Se₇]_n^2n? structure comprising distinct eight‐membered ring units, whereas 3 features a MAC‐decorated anionic [Ni(tepa)Sn₁₂Se₂₈]_n^6n? layered structure. In contrast to 1 – 3 , compound 4 exhibits a 3D open framework of anionic [Sn₄Se₉]_n^2n?. The structural variation from 1 to 4 clearly indicates that on the basis of the synergistic structure‐directing ability of the MACs and ILs, variation of the organic polyamine ligand has a significant impact on the formation of selenidostannates.     

Electrodeposition of Metals and Semiconductors in Air‐ and Water‐Stable Ionic Liquids

In addition to their stability, the advantages of air‐ and water‐stable ionic liquids over chloroaluminate ionic liquids, which were intensively investigated in the past, are that they are easy to dry, purify, and handle. Moreover, some of these ionic liquids have an extremely large electrochemical window of more than 5 V, and hence they give access to the electrodeposition of many metals and semiconductors, such as Ta, Ti, Si, and Ge. The results to date for the electrodeposition of metals and semiconductors in the most popular air‐ and water‐stable ionic liquids are presented.     

Copper(II)‐Specific Fluorogenic Task‐Specific Ionic Liquids as Selective Fluorescence Probes and Recyclable Extractants

The designed synthesis of a series of copper(II) specific fluorogenic hydrophobic task‐specific ionic liquids (TSILs) from a new naphthalene‐based tetradentate ligand is reported. Absorption and fluorescence spectral studies reveal both the ligand and its derivative TSILs show exclusive selectivity towards copper(II) ions. The Stern–Volmer method for calculation of the detection limit for ligand and TSIL_1–3 shows values of 0.12, 20, 17, and 15 μM , respectively. Extraction and striping studies by doping these TSILs in [bmim][NTf₂] demonstrated that these TSILs are recyclable extractants for the selective recovery of Cu^II ions from a mixture of 14 relevant metal chloride aqueous solutions in biphasic liquid–liquid extraction with approximately 95 % recovery.     

Synthesis and Properties of Azide‐Functionalized Ionic Liquids as Attractive Hypergolic Fuels

Hypergolic ionic liquids (ILs) have shown a great promise as viable replacements for toxic and volatile hydrazine derivatives used as propellant fuels, and hence, have attracted increasing interest over the last decade. To take advantage of the reactivity and high energy density of the azido group, a family of low‐cost and easily prepared azide‐functionalized cation‐based ILs, including fuel‐rich anions, such as nitrate, dicyanamide, and nitrocyanamide anions, were synthesized and characterized. All the dicyanamide‐ and nitrocyanamide‐based ILs exhibited spontaneous combustion upon contact with 100 % HNO₃. The densities of these hypergolic ILs varied in the range 1.11–1.29 g cm^?3, and the density‐specific impulse, predicted based on Gaussian 09 calculations, was between 289.9 and 344.9 s g cm^?3. The values of these two key physical properties are much higher than those of unsymmetrical dimethylhydrazine (UDMH). Among the studied compounds, compound IL‐3b, that is, 1‐(2‐azidoethyl)‐1‐methylpyrrolidin‐1‐ium dicyanamide, shows excellent integrated properties including the lowest viscosity (30.9 M Pa s), wide liquid operating range (?70 to 205 °C), shortest ignition‐delay time (7 ms) with 100 % HNO₃, and superior density specific impulse (302.5 s g cm^?3), suggesting promising applications with potential as bipropellant formulations.     

功能化苯并咪唑类离子液体的合成及性质

合成了一系列由磺酸基、 羧基修饰的新型功能化苯并咪唑类离子液体, 采用IR, ¹H NMR, ¹³C NMR和ESI-MS对其结构进行了表征, 研究了化合物的热稳定性、 电导率以及室温下在各种溶剂中的溶解性等性质. 结果表明, 该类离子液体在 280 ℃以下基本没有失重, 热稳定性较好; 在水溶液浓度为1×10^-3 mol/L时, 随着温度的升高, 电导率几乎与温度呈正比增大; 能与大多数有机溶剂互溶, 溶解性随着溶剂极性的增加而增大.     

Synthesis and Physical Properties of Tunable Aryl Alkyl Ionic Liquids (TAAILs)

Tunable aryl alkyl ionic liquids (TAAILs) based on the imidazolium cation were first reported in 2009. Since then, a series of TAAILs with different properties due to the electron-donating or -withdrawing effect of the substituents at the aryl ring has been developed. Herein, a wide variety of those ionic liquids (ILs) is presented in terms of their cation structure. The authors synthesized ILs containing the bromide or bis(trifluoromethane)sulfonimide anion and 1-aryl-3-alkyl imidazolium cations with various substituents in the ortho and/ or para position of the phenyl ring and alkyl chains of different lengths varying from butyl to dodecyl. The differences of their physical properties (melting point, thermal decomposition, viscosity, electro-chemical window) of these ILs are reported according to their structure.     

Antimicrobial and Cytotoxic Activity of Novel Imidazolium-Based Ionic Liquids

In this study, a series of 10 novel 1-methyl-3-octyloxymethylimidazolium derivatives carrying various anionic moieties (4-hydroxybenzenesulfonate, benzenesulfonate, carvacroloxyacetate, chloride, formate, propionate, thymoloxyacetate, vanillinoxyacetate, eugenoloxyacetate and trimethylacetate) were synthesized. Compounds were tested for their antimicrobial activity against six microbe strains (Staph-ylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Enterococcus faecalis, and Candida albicans), cytotoxic activity against the mouse melanoma cell line (B16 F10), and surface active properties. All synthesized compounds exhibited antimicrobial activity (expressed as minimum inhibitory concentration; in range of 0.10–27.82 mM/L), especially against Gram-positive bacteria and fungi. In addition, all compounds demonstrated cytotoxicity on B16 F10 cells (IC50 values 0.0101–0.0197 mM/L). Surface properties defined as CMC values, ranged from 0.72 to 32.35 mmol L-1. The obtained results provide an insight into the promising activity of a novel group of quaternary imidazolium derivatives having ionic liquid properties. The most potent compounds, containing a thymoloxyacetate and eugenoloxyacetate moiety, could be candidates for new antimicrobial agents or surfactants.