Chiral pool based synthesis of pyrrolidinium ionic liquids

Chiral ionic liquids show promising applications in various different fields. A series of pyrrolidinium-based chiral ionic liquids bearing a chiral cation, a chiral anion or both was prepared in good yields using an efficient, economic and simple pathway. The chirality was introduced using (l)-lactate and (l)-menthol derivatives. The resultant chiral compounds were characterized by both spectroscopy and polarimetry. We envision that these new chiral compounds can serve as effective reaction media and chiral catalysts for asymmetric reactions, which are presently being investigated in our lab.     

Synthesis and characterization on a novel series of protic pyrrolidinium surfactants

<正>A novel series of protic tertiary pyrrolidinium surfactants were prepared and characterized by different techniques.These compounds show good conductivity and efficient ability to reduce surface tension.Thermogravimetric analysis proves their high thermal stability at decomposition temperatures over 250℃.Their lyotropic and thermotropic liquid crystalline properties are also discussed.     

Synthesis and characterization of protic ionic liquids containing cyclic amine cations and tetrafluoroborate anion

Several ionic liquids containing pyrrolidinium-, oxopyrrolidinium-, piperidinium-, morpholinium- and trialkylammonium-based cation are synthesized and their thermal property, refractive index, polarity, electrochemical property, and temperature dependency of dynamic viscosity, density and ionic conductivity are characterized. All tetrafluoroborate-based room temperature ionic liquids studied here have a high ionic conductivity (up to 31.4 mS cm^?1). These ILs were successfully used as suitable electrolytes for the diffusion coefficient measurement of ferrocene. Absorbance solvatochromic probes Nile red is used to investigate the relative polarity of these ionic liquids and compared them with several organic solvents. The relation of fluidity to conductance is considered in terms of a Walden plot that is shown to provide a useful basis for organizing the applications of solvent media for ??green?? synthetic reactions.     

Alkylammonium-based protic ionic liquids. Part I: Preparation and physicochemical characterization

Novel alkylammonium-cation-based protic acid ionic liquids (PILs) were prepared through a simple and atom-economic neutralization reaction between an amine, such as diisopropylmethylamine, and diisopropylethylamine, and a Br?nsted acid, HX, where X is HCOO-, CH 3COO-, or HF2-. The density, viscosity, acidic scale, electrochemical window, temperature dependency of ionic conductivity, and thermal properties of these PILs were measured and investigated in detail. Results show that protonated alkylammonium such as N-ethyldiisopropyl formate and N-methyldiisopropyl formate are liquid at room temperature and possess very low viscosities, that is, 18 and 24 cP, respectively, at 25 degrees C. An investigation of their thermal properties shows that they present a wide liquid range up to -100 degrees C and a heat thermal stability up to 350 degrees C. Alkylammonium-based PILs have a relatively low cost and low toxicity and show a high ionic conductivity (up a 8 mS cm(-1)) at room temperature. They have wide applicable perspectives for fuel cell devices, thermal transfer fluids, and acid-catalyzed reaction media and catalysts as replacements of conventional inorganic acids.     

Ultrafast dynamics of pyrrolidinium cation ionic liquids

We have investigated the ultrafast molecular dynamics of five pyrrolidinium cation room temperature ionic liquids using femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The ionic liquids studied are N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P14+/NTf2-), N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P1EOE+/NTf2-), N-ethoxyethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P1EOE+/NTf2-), N-ethoxyethyl-N-methylpyrrolidinium bromide P1EOE+, and N-ethoxyethyl-N-methylpyrrolidinium dicyanoamide P1EOE+/DCA-). For comparing dynamics among the five ionic liquids, we categorize the ionic liquids into two groups. One group of liquids comprises the three pyrrolidinium cations P14+, P1EOM+, and P1EOE+ paired with the NTf2- anion. The other group of liquids consists of the P1EOE+ cation paired with each of the three anions NTf2-, Br-, and DCA-. The overdamped relaxation for time scales longer than 2 ps has been fit by a triexponential function for each of the five pyrrolidinium ionic liquids. The fast ( approximately 2 ps) and intermediate (approximately 20 ps) relaxation time constants vary little among these five ionic liquids. However, the slow relaxation time constant correlates with the viscosity. Thus, the Kerr spectra in the range from 0 to 750 cm(-1) are quite similar for the group of three pyrrolidinium ionic liquids paired with the NTf2- anion. The intermolecular vibrational line shapes between 0 and 150 cm(-1) are fit to a multimode Brownian oscillator model; adequate fits required at least three modes to be included in the line shape.     

Synthesis and thermophysical properties of two new protic long-chain ionic liquids with the oleate anion

This work reports the synthesis of 2-hydroxy ethylammonium oleate and bis(2-hydroxy ethyl)ammonium oleate ionic liquids, which have a long aliphatic chain as well as the study of some of their physical properties, in particular the effect of temperature on their density, speed of sound, viscosity, and refractive index. ¹H and ¹³C NMR spectra were used to characterize the chemical structure of the species in concordance with FT-IR spectra. DOSY NMR spectra were used to determine the self-diffusion coefficients of 2-hydroxy ethylammonium oleate ionic liquid, which were consistent with the formation of a lamellar or micellar liquid crystal phase; due the similar structure, a similar aggregation in the bis(2-hydroxy ethyl)ammonium oleate ionic liquid it is expected.     

Diels-Alder reaction in protic ionic liquids

Protic imidazolium ionic liquids have been tested as reaction media in the Diels-Alder reaction between cyclopentadiene and two dienophiles (dimethyl maleate and methyl acrylate). Good conversions and endo/exo selectivities were achieved. The activation of the dienophile by hydrogen bonding with protic imidazolium ILs was demonstrated.     

A new class of cationic surfactants inspired by N-alkyl-N-methyl pyrrolidinium ionic liquids

A series of N-alkyl-N-methylpyrrolidinium halide salts have been synthesized and investigated as potentially useful and tunable detergents for a variety of applications.     

Electrochemistry of room temperature protic ionic liquids

Eighteen protic ionic liquids containing different combinations of cations and anions, hydrophobicity, viscosity, and conductivity have been synthesized and their physicochemical properties determined. In one series, the diethanolammonium cations were combined with acetate, formate, hydrogen sulfate, chloride, sulfamate, and mesylate anions. In the second series, acetate and formate anions were combined with amine bases, triethylamine, diethylamine, triethanolamine, di-n-propylamine, and di-n-butylamine. The electrochemical characteristics of the eight protic ionic liquids that are liquid at room temperature (RTPILs) have been determined using cyclic, microelectrode, and rotating disk electrode voltammetries. Potential windows of the RTPILs have been compared at glassy carbon, platinum, gold, and boron-doped diamond electrodes and generally found to be the largest in the case of glassy carbon. The voltammetry of IUPAC recommended potential scale reference systems, ferrocene/ferrocenium and cobaltocenium/cobaltocene, have been evaluated and found to be ideal in the case of the less viscous RTPILs but involve adsorption in the highly viscous ones. Other properties such as diffusion coefficients, ionic conductivity, and double layer capacitance also have been measured. The influence of water on the potential windows, viscosity, and diffusion has been studied systematically by deliberate addition of water to the dried ionic liquids. The survey highlights the problems with voltammetric studies in highly viscous room temperature protic ionic liquids and also suggests the way forward with respect to their possible industrial use.     

Amphiphilicity determines nanostructure in protic ionic liquids

The bulk structure of the two oldest ionic liquids (ILs), ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), is elucidated using neutron diffraction. The spectra were modelled using empirical potential structure refinement (EPSR). The results demonstrate that EAN exhibits a long-range structure of solvophobic origin, similar to a bicontinuous microemulsion or disordered L(3)-sponge phase, but with a domain size of only 1 nm. The alcohol (-OH) moiety in EtAN interferes with solvophobic association between cation alkyl chains resulting in small clusters of ions, rather than an extended network.     

Superbase-derived protic ionic liquids with chelating fluorinated anions

Eighteen new protic ionic liquids were synthesized in one step from five organic superbases and five commercially available fluorinated β-diketones. Physical properties of the ionic liquids, including thermal decomposition temperature were determined. Nine of the ionic liquids were examined as extraction media for La³⁺, with some very large distribution coefficients obtained.     

Formation of amphiphile self-assembly phases in protic ionic liquids

A range of protic ionic liquids (PILs) have been identified as being capable of supporting the self-assembly of the nonionic surfactants myverol 18-99 K (predominantly monoolein) and phytantriol. PIL-surfactant penetration scans have provided a high throughput technique to determine which lyotropic liquid crystalline phases were formed in the 40 PIL-surfactant systems investigated. Lamellar, inverse hexagonal, and bicontinuous cubic phases that are stable in excess PIL have been observed in surfactant-PIL systems. The studied PILs possess a wide range of solvent properties, including surface tension and viscosity. The nature of the formed amphiphile self-assembly phases is discussed in terms of the PIL structure and solvent properties.     

Communication: X-ray scattering from ionic liquids with pyrrolidinium cations

We report the structure functions obtained from x-ray scattering experiments on a series of four homologous ionic liquids. The ionic liquids are 1-alkyl-1-methylpyrrolidinium cations paired with the bis(trifluoromethylsulfonyl)amide anion, with alkyl chain lengths of n = 4, 6, 8, and 10. The structure functions display two intense diffraction peaks for values of the scattering vector q in the range from 0.6 to 1.5 ?(-1) for all samples. Both diffraction peaks shift to lower values of q for increasing temperature. First sharp diffraction peaks are observed in the structure functions for q < 0.5 ?(-1) for liquids with n = 6, 8, and 10.     

Enhanced membrane transport of pharmaceutically active protic ionic liquids

We show that pharmaceutically active protic ionic liquids can be designed to rapidly transport through model membranes as neutral hydrogen bonded clusters.     

Amphiphilic protic anionic oligomeric ionic liquids of hyperbranched structure

The method of synthesizing anionic amphiphilic protic hyperbranched ionic liquids with the controlled ratio between hydrophilic ionic-liquid groups and hydrophobic alkyl urethane fragments in the oligoester nucleus shell is developed. These compounds are synthesized by the interaction of excess hyperbranched polyesterpolyol containing 32 terminal hydroxyl groups with n-octadecyl isocynate followed by the acylation of hydroxyl groups by phthalic anhydride or 2-sulfobenzoic anhydride and the neutralization of the formed carboxyl or sulfonic groups by N-methylimidazole or 1,2,4-1H-triazole. With a rise in the content of alkyl urethane fragments, the synthesized compounds form the crystalline phase. Structuring of the system leads to different effects of the degree of ionicity of ionic-liquid groups on proton conductivity, which is within 10^–7–10^–4 S/cm at 100–120°C under anhydrous conditions. The thermal stability of the hyperbranched ionic liquids is determined by the nature of ionic-liquid groups and the amount of the introduced alkyl urethane fragments; it is in the range of 170–270°C.     

Pseudo-capacitance of nanoporous carbons in pyrrolidinium-based protic ionic liquids

Protic ionic liquids (PILs) were used as novel electrolyte for carbon-based supercapacitors. The cyclic voltammograms in three-electrode cells show reversible redox humps, revealing pseudo-faradaïc charge transfer. Oxidative treatment of activated carbon enriches the surface functionality and leads to a higher capacitance owing to a stronger pseudo-faradaïc contribution. The capacitors using PILs demonstrate a higher voltage window than with aqueous H₂SO₄, while keeping the same values of capacitance, and being able to operate at lower temperature. A combination of activated carbons and PILs holds promise for improving the energy characteristics of supercapacitors.     

Synthesis, characterization, and catalytic activity of ionic liquids based on biosources

New room-temperature ionic liquids were synthesized from natural and easily available feedstocks (choline hydroxide and amino acids) following an economical and green route in which the only by-product was water. They were successfully applied as catalysts for the Knoevenagel test reaction between benzaldehyde and different active methylene compounds, at room temperature and under solvent-free conditions, to produce α,β-unsaturated carbonyl compounds, exhibiting good conversions and high selectivities. The catalytic role of cholinium and aminoacetate ions in the Knoevenagel condensation is discussed.     

Preparation and characterization of new room temperature ionic liquids

A new series [C(n)O(m )mim][X] of imidazolium cation-based room temperature ionic liquids (RTILs), with ether and alcohol functional groups on the alkyl side-chain has been prepared. Some physical properties of these RTILs were measured, namely solubility in common solvents, viscosity and density. The solubility of LiCl, HgCl(2) and LaCl(3) in room temperature ionic liquids was also determined. The features of the solid-liquid phase transition were analysed, namely the glass transition temperature and the heat capacity jump associated with the transition from the non-equilibrium glass to the metastable supercooled liquid. These properties were compared with those reported for the 1-n-alkyl-3-methylimidazolium [C(n )mim][X] series. While the density and solid-liquid phase transition properties are similar for both series, the new RTILs present a considerably lower viscosity and an increased ability to dissolve HgCl(2) and LaCl(3) (up to 16 times higher).