A new synthetic procedure for the preparation of pyridinium tetrafluoroborate and hexafluorosilicate

Pyridinium tetrafluoroborate (C5H5NHBF4) and pyridinium hexafluorosilicate [(C5H5NH)2SiF6] have been prepared in good yields and high purity by the reaction of pyridinium poly(hydrogen fluoride) with oxides and acids of boron and silicon respectively. The salts have been characterised by melting points, IR, 1H and 19F NMR spectroscopy and chemical analysis.

A Novel Synthetic Route For The Preparation Of Ammonium And Alkali-Metal Tetrafluoroborates And Alkyl Substituted Ammonium Tetrafluoroborates Using Pyridinium Tetrafluoroborate As The Precursor

Ammonium and alkali metal tetrafluoroborates have been prepared by the cation exchange reaction of pyridinium tetrafluoroborate with the corresponding hydroxides/halides. The reaction of pyridinium tetrafluoroborate with primary, secondary and tertiary alkyl amines at room temperature gives rise to mono-, di- and tri-alkylammonium tetrafluoroborates, respectively. The yields are good and the samples are of high purity. The products have been characterised by elemental analysis, IR and PMR spectroscopy. The spectral data for most of the compounds are reported for the first time.

A Novel Synthetic Route for the Preparation of Silver Salts of Hexafluorophosphate, Tetrafluoroborate and Hexafluorosilicate

Silver salts of hexafluorophosphates, tetrafluoro-borates and hexafluorosilicates have been prepared by a metathetic reaction between the respective ammonium salts and silver nitrate in acetonitrile medium. This one step procedure at room temperature offers salts of high purity in good yields. The salts (AgpF6, AgBF4 and Ag2SiF6) have been characterised by IR spectral data analysis and chemical analysis.

Sensitive, Label-Free Protein Assay Using 1-ethyl-3-methylimidazolium Tetrafluoroborate Supported Microchip Electrophoresis with Laser-Induced Fluorescence Detection

Based on the dimer-monomer equilibrium movement of the fluorescent dye Pyronin Y (PY), a rapid, simple, highly sensitive, label-free method for protein detection was developed by microchip electrophoresis with LIF detection. PY formed a nonfluorescent dimer induced by the premicellar aggregation of an anionic surfactant, SDS, however, the fluorescence intensity of the system increased dramatically when proteins such as BSA, bovine hemoglobin, cytochrome c, and trypsin were added to the solution due to the transition of dimer to fluorescent monomer. Furthermore, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) instead of PBS was applied as running buffers in microchip electrophoresis.

Host-guest-like thiamine-anion complexation in thiaminium bis(tetrafluoroborate)

In the title compound, 3-[(4-amino-2-methyl-5-pyrimidin-1-io)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium(2+) bis(tetrafluoroborate), C12H18N4OS2+. 2BF(4)(-), the divalent thiamine cation (in the F conformation) is associated with BF4- anions via two characteristic bridging interactions between the thiazolium and pyrimidinium rings, i.e. C-H . . . BF4- . . . pyrimidinium and N-H . . . BF4- . . . thiazolium interactions. Thiamine molecules are linked by N-H . . .O hydrogen bonds to form a helical chain structure.

The electrochemical oxidation of catechol and dopamine on platinum in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF4]): Adsorption effects in ionic liquid voltammetry

The electrochemical oxidation of catechol and dopamine has been studied at a platinum micro-electrode (10 pm diameter) in two room temperature ionic liquids (RTILs): 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BE4]). For catechol in [C(2)mim][NTf2], an electrochemically quasi-reversible oxidation peak was observed at 1.1 V vs. Pt with a back peak at 0.4 V vs. Pt. This is assigned to the two-electron oxidation of catechol to doubly protonated o-benzoquinone. Double-step chronoamperometry gave a diffusion coefficient for the catechol and the oxidised species which is 3.8 x 10(-11) m(2) s(-1) for both. For catechol in [C(4)mim][BF4], a two-electron oxidation wave was observed at 1.0 V vs. Pt with no back peak. Another peak at less positive potential was also observed at 0.6 V vs. Pt in [C(4)mim][BF4] but not in [C(2)mim][NTf2] which is assigned to the adsorption of electrochemically formed neutral o-benzoquinone on the platinum electrode. The oxidised protonated o-benzoquinone is suggested to be deprotonated by the [BF4](-) anion, but not by the [NTf2](-) anion: hence adsorption of the neutral species at the platinum electrode, not the charged species. For dopamine in both RTILs, two chemically irreversible oxidation peaks were observed at 0.75 V and 1.1 V vs. Pt, and assigned to the oxidation of dopamine to the corresponding semi-quinone and the quinone. Potential-step chronoamperometry was carried out on the oxidation waves of dopamine in [C(2)mim][NTf2] and the diffusion coefficient of species in solution was calculated to be 6.85 x 10(-12) m(2) s(-1) and confirmed that the waves corresponded to one and two electron processes. A third wave was observed at 1.8 V vs. Pt which is attributed to the oxidation of the amine group to a radical cation with likely subsequent follow up chemistry. In [C(4)mim][BF4] a peak at less positive potential was observed for dopamine, similar to catechol which is assigned to the adsorption of the neutral quinone species on the platinum electrode formed by the reaction of the removal of protons from the oxidised dopamine with the [BF4](-) anion. (C) 2009 Elsevier B.V. All rights reserved.

Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in 1-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric

Experimental values for the solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon and carbon monoxide in 1-butyl-3- methylimidazolium tetrafluoroborate, [bmim][BF4] - a room temperature ionic liquid - are reported as a function of temperature between 283 K and 343 K and at pressures close to atmospheric. Carbon dioxide is the most soluble gas with mole fraction solubilities of the order of 10-2. Ethane and methane are one order of magnitude more soluble than the other five gases that have mole fraction solubilities of the order of 10-4. Hydrogen is the less soluble of the gaseous solutes studied. From the variation of solubility, expressed as Henry's law constants, with temperature, the partial molar thermodynamic functions of solvation such as the standard Gibbs energy, the enthalpy, and the entropy are calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry's law constants from appropriate smoothing equations is of 1%. © 2005 Elsevier Ltd. All rights reserved.

First study on the thermo-solvatochromism in aqueous 1-(1-butyl)-3-methylimidazolium tetrafluoroborate: A comparison between the solvation by an ionic liquid and by aqueous alcohols

The thermo-solvatochrornic behaviors of 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl) phenolate, RB; 2,6-dichloro-4-(2,4,6-triphenyloyridinium-1-yl) phenolate, WB; 2,6-dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr(2); 2,6-dibromo-4-[(E)-2-(1-n-octylpyridinium-4-yl)ethenyl] phenolate, OcPMBr(2), have been investigated in binary mixtures of the ionic liquid, IL, 1-(1-butyl)-3-methylimidazolium tetrafluorborate, [BuMeIm][BF(4)], and water (W), in the temperature range from 10 to 60 degrees C. Plots of the empirical solvent polarities, ET (probe) in kcal mol(-1), versus the mole fraction of water in the binary mixture, chi(w) showed nonlinear, i.e., nonideal behavior. Solvation by these IL-W mixtures shows the following similarities to that by aqueous aliphatic alcohols: The same solvation model can be conveniently employed to treat the data obtained; it is based on the presence in the system-bulk medium and probe solvation shell of IL, W, and the ""complex"" solvent 1:1 IL-W. The origin of the nonideal solvation behavior appears to be the same, preferential solvation of the probe, in particular by the complex solvent. The strength of association of the IL-W complex, and the polarity of the IL are situated between the corresponding values of aqueous methanol and aqueous ethanol. Temperature increase causes a gradual desolvation of all probes employed. A difference between solvation by IL-W and aqueous alcohols is that probe-solvent hydrophobic interactions appear to play a minor role in case of the former mixture, probably because solvation is dominated by hydrogen-bonding and Coulombic interactions between the ions of the IL and the zwitterionic probes.

Solid state ion transport and phase behaviour in composites of N,N-methyl propylpyrrolidinium tetrafluoroborate and amorphous polyethylene oxide

The binary and ternary addition of 2 wt.% LiBF₄ and 2 wt.% amorphous polyethylene oxide (aPEO) respectively to the plastic crystal forming salt P₁₃BF₄ (where P₁₃⁺=methylpropyl pyrrolidinium cation) was investigated with specific focus on the phase behaviour and evaluation of transport characteristics. Differential scanning calorimetry (DSC), optical thermomicroscopy, solid state nuclear magnetic resonance (NMR), and AC impedance spectroscopy were used to develop an understanding of the conduction process in the pure and mixed systems. The morphology of the ternary compound appeared as hexagonal spherulites upon solidification. Multinuclear NMR Pulsed Field Gradient measurements (¹H,¹⁹F,⁷Li) to probe both cation and anion diffusion coefficients are reported. The anion is shown to be the most diffusive (at 320 K:¹⁹F=2.5×10⁻¹¹ m² s⁻¹; 1H: 1.8×10⁻¹¹ m² s⁻¹; ⁷Li: 1.1×10⁻¹¹ m² s⁻¹) in the ternary compound, with enhanced conductivity (2.7×10⁻⁵ S cm⁻¹ at 310 K) just below the melt.

Transport and phase dynamics of poly(vinyl pyrrolidone) doped plastically crystalline N-methyl-N-propylpyrrolidinium tetrafluoroborate

The plastic crystal phase forming N-methyl-N-propylpyrrolidinium tetrafluoroborate organic salt (P₁₃BF₄) was combined with 2, 5 and 10 wt.% poly(vinyl pyrrolidone) (PVP). The ternary 2 wt.% PVP/2 wt.% LiBF₄/P₁₃BF₄ was also investigated. Thermal analysis, conductivity, optical thermomicroscopy, and Nuclear Magnetic Resonance (¹¹B, ¹⁹F, ¹H, ⁷Li) were used to probe the fundamental transport processes. Both the onset of phase I and the final melting temperature were reduced with increasing additions of PVP. Conductivity in phase I was 2.6 × 10^{− 4} S cm^{− 1} 5.2 × 10^{− 4} S cm^{− 1} 1.1 × 10^{− 4} S cm^{− 1} and 3.9 × 10− 5 S cm− 1 for 0, 2, 5 and 10 wt.%PVP/P₁₃BF₄, respectively. Doping with 2 wt.% LiBF₄ increased the conductivity by up to an order of magnitude in phase II. Further additions of 2 wt.% PVP slightly reduced the conductivity, although it remained higher than for pure P₁₃BF₄.

A surface characterisation and microstructural study by scanning electron microscopy of the N-methyl-n-alkylpyrrolidinium tetrafluoroborate organic salts

A microstructural characterisation of the family of N-methyl-N-alkylpyrrolidinium tetrafluoroborate organic salts was carried out by observation of powder surface morphologies with the aim of extending the microstructure-property correlation. Inherent difficulties limiting extensive studies of organic solids by SEM, including volatility under vacuum, charging due to electron beam irradiation, and air-sensitivity were overcome with the use of a Field Emission SEM and cryostage attachment. This technique, providing considerable improvements in image quality at low accelerating voltages, enabled direct observation of complex microstructural features in samples exhibiting high temperature plastic crystalline phases (N,N-dimethylpyrrolidinium tetrafluoroborate [P11BF4]; N-methyl-N-ethylpyrrolidinium tetrafluoroborate [P12BF4]; N-methyl-N-propylpyrrolidinium tetrafluoroborate [P13BF4]). Extensive lattice imperfections including grain boundaries, slip planes and dislocation pits were observed within particles of approximately 200 mgrm diameter. The N-methyl-N-butylpyrrolidinium tetrafluoroborate (P14BF4) sample in this series revealed columnar single crystals with high aspect ratios. The origin of plastic flow properties is discussed using single crystal and polycrystalline slip observations and a relationship proposed between defect characteristics and transport properties.

Structure and transport properties in an N,N-substituted pyrrolidinium tetrafluoroborate plastic crystal system

The structure and transport of N-propyl-N-methylpyrrolidinium tetrafluoroborate (P₁₃BF₄) has been investigated over a wide temperature range in consequence to exhibiting properties suitable for potential solid-state superionic electrolyte applications. Prior to melting, the organic salt, P₁₃BF₄, transforms into a plastic crystal phase. Intrinsic conductivity in this solid, phase I (45–65 °C), is comparable to that in the melt (_~10⁻³ S cm⁻¹). Ionic motion and transport properties were investigated by ¹H and ¹¹B nuclear magnetic resonance (NMR) spectroscopy. Pressure-induced plastic flow in this system may accommodate volume changes in device application and to this extent, X-ray diffraction (XRD) has been used. Scanning electron microscopy (SEM) revealed complex surface morphology and lattice imperfections associated with the strong orientational disorder of the plastic state.

N-methyl-N-alkylpyrrolidinium tetrafluoroborate salts : ionic solvents and solid electrolytes

A series of N-methyl-N-alkylpyrrolidinium tetrafluoroborate salts were synthesised. The spectroscopic, physical and electrochemical characteristics of this family of salts have been investigated with respect to potential usage as ionic solvents and electrolytes. The lowest melting point among the family is 64°C for the N-methyl-N-propylpyrrolidinium tetrafluoroborate (P₁₃BF₄). This is sufficiently low to enable this salt to be useful as an ionic liquid in chemical synthesis involving reactions above 70°C. Most of the compounds exhibit one or more solid–solid transitions below the melting point, this behaviour is thought to indicate the existence of plastic crystal phases.

Unusual phase behaviour of the organic ionic plastic crystal N,N-dimethylpyrrolidinium tetrafluoroborate

Analysis of N,N-dimethylpyrrolidinium tetrafluoroborate by ¹H and ¹¹B NMR, Raman spectroscopy and powder XRD shows that this organic ionic plastic crystal material exhibits unusual phase behaviour. ¹H NMR analysis indicates that the mobility of the pyrrolidinium cation decreases when the material is heated into phase I, while the X-ray diffraction pattern changes from a simple, one peak structure in phase II to a more complex pattern in phase I. The possible origins of these unusual transitions are discussed.