IR and NMR Properties of Ionic Liquids: Do They Tell Us the Same Thing?

We used a combination of theoretical and experimental methods to derive the spectroscopic properties of imidazolium-based ionic liquids. Vibrational frequencies, NMR chemical shifts, and quadrupole coupling constants react in comparable manner to changes in the chemical environment. This suggests that both the IR and the NMR spectroscopic properties reflect a similar type of electronic perturbation caused by hydrogen bonding. These relationships of the spectroscopic properties provide detailed information about structural complexes and may thus serve as good indicators of ion-pair formation. They also help to decide which spectroscopic tool is the most sensitive for investigating molecular interactions. The measurement of only one spectroscopic property allows the prediction of other properties that cannot be so easily measured. In some cases, this is the only way to obtain reliable coupling constants for deriving molecular correlation times from macroscopic NMR relaxation times, thus opening a new path for studying structure-dynamics relations in ionic liquids.     

离子液体中电沉积制备钴纳米线阵列

Porous anodic alumina (PAA) was used as a template to prepare Co nanowires array from 1-ethyl-3-methylimidazolium chloride ionic liquid by direct current method. The surface morphology of porous anodic alumina template was observed by field emission-scanning tunneling microscopy (FE-SEM) before and after the electrodeposition of Co nanowires. The electrodeposition of Co nanowires was characterized by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). TEM results indicate that the Co nanowire surface is coarse and porous when aqueous solution was used as electrolyte， and the Co nanowire deposited from the ionic liquid is uniform and smooth. XRD results show that the electrodeposition of Co is a mixture of crystal and microcrystal phase.     

Adsorption of ionic surfactants on polar surfaces with a low content of chemically adsorbed alkyl chains

Colloidal silica and titanium dioxide were surface-modified by chemisorption of octadecyl dimethylmethoxy silane. The surface density of these alkyl silane groups was adjusted to less than 7% of the available surface hydroxyls, leaving the adsorbents hydrophilic and electrically charged in aqueous solution.Ionic surfactants (tetradecylpyridinium chloride and sodium lauryl sulfate) are adsorbed onto the surface-modified silica and titanium dioxide from aqueous solution, even in the case where the surface of the adsorbents exhibits the same sign of electrical charge as the surfactant ionic head groups. According to the adsorption model of Gu the chemiadsorbed alkyl chains are supposed to serve as anchors for small surface aggregates of the ionic surfactants.     

新型无毒离子液体催化“一锅煮”合成3,4-二氢嘧啶-2(1H)-酮

利用新型无毒离子液体(BMImSac)作催化剂, 芳香醛、1, 3-二羰基化合物和尿素或硫脲三组分“一锅煮”合成了3,4-二氢嘧啶-2(1H)-酮. 与传统方法相比, 该法是一种操作简单、产率高、用时少的环境友好方法.     

Buffers for the Physiological pH Range: Thermodynamics of the Second Dissociation of N-(2-Hydroxyethyl)piperazine-N′-2-hydroxypropanesulfonic Acid From 5 to 55°C

The second acidic dissociation constants pK ₂ of the ampholyte N-(2-hydroxyethyl) piperazine-N-2-hydroxypropanesulfonic acid (HEPPSO) have been determined at seven temperatures from 5 to 55°C from emf measurements utilizing hydrogen and silver–silver chloride cells without liquid junction. The thermodynamic quantities, G°, H°,S°, and C _p ^o have been calculated from the temperature coefficient of pK ₂. At 25°C, the pK ₂ = 8.042 and at 37°C, pK ₂ = 7.876; hence, buffer solutions of HEPPSO and NaHEPPSOate are important for pH control in the region close to that of clinical fluids (blood serum). Conventional pH values from 5 to 55°C as well as those obtained from liquid junction correction at 25 and 37°C have been reported for three buffer solutions with the compositions (molality scale): (1) equimolal mixture of HEPPSO (0.04 m) + NaHEPPSOate (0.04 m) + NaCl (0.12 m); (2) HEPPSO (0.08 m) + NaHEPPSOate (0.08 m); and (3) HEPPSO (0.08 m) + NaHEPPSOate (0.08 m) + NaCl (0.08 m).     

Ionic liquid analogues formed from hydrated metal salts

A dark green, viscous liquid can be formed by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties are characteristic of an ionic liquid. The eutectic composition is found to be 1:2 choline chloride/chromium chloride. The viscosity and conductivity are measured as a function of temperature and composition and explained in terms of the ion size and liquid void volume. The electrochemical response of the ionic liquid is also characterised and it is shown that chromium can be electrodeposited efficiently to yield a crack-free deposit. This approach could circumvent the use of chromic acid for chromium electroplating, which would be a major environmental benefit. This method of using hydrated metal salts to form ionic liquids is shown to be valid for a variety of other salt mixtures with choline chloride.     

Multivariate analysis of non-homogeneous peaks in liquid chromatography

Summary The effects of concentration, separation and spectral similarity as factors influencing the accuracy of iterative target testing factor analysis (ITT-FA) are investigated for three component systems by the application of analysis of variance (ANOVAR). ANOVAR is applied over a range of peak separations to map the changing effects of the three factors with increasing overlap. Two error responses were measured and analysed, (a) Relative cluster error (RCE) a measure of the error over all peaks in a cluster and (b) Relative peak error (RPE) the error of an individual peak. Multicomponent analysis (MCA) a method requiringa priori spectral information, is used as a referee method for ITT-FA.     

Electroconduction of Potassium Orthophosphate Modified with Triple-Charged Cations

Solid electrolytes in the systems K_{3 – 3x} Me _x PO₄ (Me = Sc, Y, In, La, Nd, Gd, Tb) are synthesized. Their phase composition and the temperature and concentration dependences of their electroconductivity are studied. In all the systems there form solid solutions based on K₃PO₄, which have a high potassium cation conductance. The latter is due to the formation of potassium vacancies at substitutions 3K⁺ Me³⁺ and, at lower temperatures, to stabilization of a high-temperature -modification of potassium orthophosphate. The electroconductivity of synthesized solid solutions, which equals (4–7) × 10^–3 and 10^–1 S cm^–1 at 300 and 700°C, is similar to that of solid electrolytes K_{3 – x} P_{1 – x} E _x ^VIO₄ and K_{3 – 4x} E _x ^IVPO₄.     

Optical and Bioelectrochemical Characterization of Water‐Miscible Ionic Liquids Based Composites of Multiwalled Carbon Nanotubes

Acidic treated multiwalled carbon nanotubes (AMWNTs) were ground with water‐miscible room temperature ionic liquids, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄), and resulted in AMWNTs‐[bmim]BF₄ composite. Its electrical‐ionic conductivity and optical properties were compared with the other two types of carbon materials‐[bmim]BF₄ composites: pyrolytic graphite powder (PGP), pristine multiwalled carbon nanotubes (PMWNTs), through the ac impedance technology and Raman spectroscopy. The impedance data show that AMWNTs‐[bmim]BF₄ composite exhibits the highest conductivity. Raman spectra study exhibits that the [bmim]BF₄ can form gel with PMWNTs and AMWNTs but only form a viscous liquid with PGP. AMWNTs‐[bmim]BF₄ gel modified GC electrode was applied in direct electrochemistry of heme proteins (Hb and HRP) and it catalysis to the reduction of H₂O₂ was investigated.