Structural characterization and DFT study of V(IV)O(acac)2 in imidazolium ionic liquids

We report the structural characterization of vanadyl acetylacetonate in imidazolium room temperature ionic liquids--bbimNTf(2), bmimNTf(2), C(3)OmimNTf(2), bm(2)imNTf(2), bmimPF(6), bmimOTf, bmimBF(4), bmimMeCO(2), bmimMeSO(4), bmimMe(2)PO(4) and bmimN(CN)(2)--and organic solvents. The complex was characterized by visible electronic (Vis) and EPR spectroscopies. VO(acac)(2) shows solvatochromism in the selected ionic liquids and behaves as in organic solvents, evidencing coordination of the ionic liquid anion in the solvents with higher coordinating ability. The Lewis basicity order obtained for the IL anions was: PF(6)(-) < NTf(2)(-) < OTf(-)≈ MeCO(2)(-) < MeSO(4)(-) < BF(4)(-)≈ N(CN)(2)(-) < Me(2)PO(4)(-). The solvent effect on the spectroscopic data was tentatively examined using linear solvation energy relationships based on the Kamlet-Taft solvent scale (α, β and π*), however no suitable correlation was found with all data. The EPR characterization showed the presence of two isomers in bmimOTf, bmimMeCO(2) and bmimMe(2)PO(4), suggesting coordination of the ionic liquid anions in both equatorial and axial positions. The full geometry optimization of cis-/trans-VO(acac)(2)(OTf)(-) and cis-/trans-VO(acac)(2)(OTf)(mmim) structures was done at the B3P86/6-31G* level of theory. The calculations confirm that the anion OTf(-) is able to coordinate to VO(acac)(2) with the trans isomer being more stable than the cis by 4.8 kcal mol(-1).     

Synthesis and characterization of ionic liquids incorporating the nitrile functionality

A series of imidazolium salts with the nitrile functional group attached to the alkyl side chain, viz. [CnCNmim][X] (where CnCNmim is the 1-alkylnitrile-3-methylimidazolium cation and Cn= (CH2)(n), n = 1-4; X = Cl, PF(6), and BF(4)) and [C3CNdmim][X] (where CnCNdmim is the 1-alkylnitrile-2,3-dimethylimidazolium cation and C(n) = (CH2)(n), n = 3; X = Cl, PF(6), and BF(4)), have been prepared and characterized using spectroscopic methods. The majority of the nitrile-functionalized imidazolium salts can be classed as ionic liquids since they melt below 100 degrees C. Four of the imidazolium salts have been characterized in the solid state using single-crystal X-ray diffraction analysis to reveal an extensive series of hydrogen bonds between H atoms on the cation and the anion. The relationship between the solid-state structure and the melting point is discussed. Key physical properties (density, viscosity, and solubility in common solvents) of the low melting ionic liquid have been determined and are compared with those of the related 1-alkyl-3-methylimidazolium and 1-alkyl-2,3-dimethylimidazolium ionic liquids. It was envisaged that these ionic liquids could act as both solvent and ligand for catalyzed reactions, and this application is demonstrated in hydrogenation reactions, which show that retention of the catalyst in the ionic liquid during product extraction is extremely high.     

A microextraction procedure based on a task‐specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task‐specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho‐positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0–24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination.     

Ionic liquids as a convenient recyclable medium for the generation of transient carbonyl ylides: syntheses of oxa and dioxa-bridged polycyclic systems

The tandem cyclization-cycloaddition reactions of α-diazo ketones in the presence of rhodium(II) acetate, rhodium(II) octanoate or copper(II) acetyl acetonate as catalyst were performed in different imidazole based ionic liquids as solvent. A successful generation of the transient five- or six-membered-ring carbonyl ylides, followed by the 1,3-dipolar cycloaddition with olefin or carbonyl functional groups in ionic liquid is described to furnish the oxa and dioxa-bridged polycyclic systems with high stereoselectivity. Significant advantages of this process are the recovery of rhodium catalyst, the re-use of ionic liquid, replacement of hazardous organic solvents and the resulting high stereoselectivity.     

Generation and detection of the cyclohexadienyl radical in phosphonium ionic liquids

The formation of the cyclohexadienyl radical, C(6)H(6)Mu, in ionic and molecular solvents has been compared. This is the first time that a muoniated free radical is reported in an ionic liquid. In marked contrast to molecular liquids, free radical generation in ionic liquids is significantly enhanced. Comparison of the hyperfine interactions in the ionic liquid and in molecular solvents and with theoretical calculations, suggests significant and unforeseen solvent interaction with the cyclohexadienyl radical.     

Efficient copper(II)-catalyzed addition of activated methylene compounds to alkenes

Efficient regioselective addition of beta-diketones to styrenes, norbornene, cyclic enol ether, and diene has been realized by means of copper(II) triflate as the catalyst. The solvent effect is prominent on the reactions, and the desired addition products were obtained in good to excellent yields only in dioxane or ionic liquid [bmim]PF6. The mechanism suggests that copper(II) triflate activates the enolic O-H bond of a beta-diketone substrate to initiate the addition reaction.     

Formation of higher chloride complexes of Np(IV) and Pu(IV) in water-stable room-temperature ionic liquid [BuMeIm][Tf2N

A UV/vis/near-IR spectroscopic study shows that in [BuMeIm][(CF3SO2)2N] hydrophobic room-temperature ionic liquid solutions, [BuMeIm]2[AnCl6] complexes, where BuMeIm+ is 1-n-butyl-3-methylimidazolium and An(IV) is Np(IV) or Pu(IV), have an octahedral An(IV) environment similar to that observed in solid complexes. Water has no influence on the absorption spectra of AnCl6(2-) complexes, indicating their stability to hydrolysis in ionic liquid. Adding [BuMeIm]Cl modifies the UV/vis/near-IR absorption spectra of An(IV) in the ionic liquid and causes solids to precipitate. The solid-state reflectance spectra of the precipitates reveal considerable differences from the corresponding An(IV) hexachloro complexes. A voltammetric study indicates that AnCl6(2-) complexes are electrochemically inert in [BuMeIm][(CF3SO2)2N] at the glassy carbon working electrode. By contrast, quasi-reversible electrochemical reduction An(IV)/An(III) and An(IV) oxidation are observed in ionic liquids in the presence of [BuMeIm]Cl. The oxidation wave of noncoordinated chloride ions interferes with the An(IV) oxidation waves. The spectroscopic and voltammetric data clearly indicate the formation of nonoctahedral actinide(IV) chloride complexes with a Cl-/An(IV) ratio exceeding 6/1 in [BuMeIm][(CF3SO2)2N] in excess chloride ions.     

Modelling catalytic turnover frequencies in ionic liquids: the determination of the bimolecular rate constant for solvent displacement from [(C6H6)Cr(CO)2Solv] in 1-n-butyl-3-methylimidazolium hexafluorophosphate

The bimolecular rate constant for solvent displacement, k(2), from [(C(6)H(6))Cr(CO)(2)Solv] by an incoming ligand has been determined in the room temperature ionic liquid, [bmim][PF(6)], and is compared to that for the same process in cyclohexane and dichloroethane.     

A novel one step synthesis of silver nanoparticles using room temperature ionic liquid and their biocidal activity

This article reports the synthesis of silver Nan particles (SNPs) using 1-(dodecyl) 2 amino-pyridinium bromide ionic liquid. This is a new one phase method for the synthesis of uniform monodispersed crystalline silver nanoparticles in a water-ionic liquid system. In this work, the functionalized room temperature IL acts as stabilizing agent and solvent. Hydrazine hydrate acts as reducing agent. To the best of our knowledge, there is no report of the synthesis of metal nanoparticles using this ionic liquid. The synthesis of silver nanoparticles is very primarily studied by UV-Visible spectroscopic analysis. The TEM and particle size distribution was used to study morphology and size of the particles. The charge on synthesized SNPs was determined by Zeta potential. The silver nanoparticles have been known to have inhibitory and bactericidal effect. The investigation of antibacterial activities of ionic liquid stabilized silver nanoparticles was performed by measurement of the minimum inhibitory concentration.     

Spectrophotometric determination of Hg(II) in water samples by dispersive liquid liquid microextraction with use ionic liquid after derivatization with a water soluble Fe(II) phthalocyanine

This study reports the synthesis of water soluble iron(II) phthalocyanine and a facile method for spectrophotometric determination of Hg(II) in environmental water samples by ionic liquid based dispersive liquid–liquid microextraction (IL-DLLME). In the method, 1-heptyl-3-methylimidazolium hexafluorophosphate (250 µL) as extraction solvent, acetonitrile (750 µL) as dispersive solvent and Triton X-100 (200 µL) as anti-sticking agent were used. After the extraction of the Hg(II) complex (Hg(II):q-Fe(II)-Pc) into thin droplets of ionic liquid, the sample was centrifuged for 4 min at 2000 rpm. The upper aqueous phase was removed and the residue diluted to 250 µL with methanol and transferred to a 250 µL cell for spectrophotometric detection at 280 nm. The linear range of the method is 0.05–1 µg/mL. The limits of detection and quantification is 0.01 and 0.03 µg/mL, respectively. The RSD for the developed method was calculated as 0.78% at 0.50 µg/mL Hg(II).     

Ionic liquid based dispersive liquid-liquid microextraction combined with ICP-OES for the determination of trace quantities of cobalt, copper, manganese, nickel and zinc in environmental water samples

We describe a method for ionic liquid based dispersive liquid-liquid microextraction of Co(II), Cu(II), Mn(II), Ni(II) and Zn(II), followed by their determination via flow injection inductively coupled plasma optical emission spectrometry. The method is making use of the complexing agent 1-(2-thenoyl)-3,3,3-trifluoracetone, the ionic liquid 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide, and of ethanol as the dispersing solvent. After extraction and preconcentration, the sedimented ionic liquid (containing the target analytes) is collected, diluted with 1-propanol, and introduced to the ICP-OES. Effects of pH, ionic strength, ligand to metal molar ratio, volumes of extraction and disperser solvents on the performance of the microextraction were optimized in a half-fractional factorial design. The significant parameters were optimized using a face-centered central composite design. The method has detection limits between 0.10 and 0.20?ng?mL^?1 of the metal ions, preconcentration factors between 79 and 102, linear responses in 0.25 to 200?ng?mL^?1 concentration ranges, and relative standard deviations of 3.4 to 6.0%. The method was successfully applied to the analysis of drinking water, a fish farming pond water, and waste water from an industrial complex.

原位聚合制备的离子液体/聚合物电解质的研究

采用原位聚合制备出新型的BMIPF6/PMMA聚合物电解质透明弹性膜. 研究结果表明, BMIPF6/PMMA聚合物电解质体系在305 ℃时仍具有较好的热稳定性, 其安全性能优于含有机溶剂的传统非水电解质体系. 随着离子液体含量的增加, 其玻璃化转变温度逐渐减小, 离子电导率升高; 且离子电导率与温度的关系服从VTF方程. 其中, 当BMIPF6的质量分数为50%时, 该聚合物电解质的室温离子电导率高达0.15 mS/cm.     

Speciation of copper(II) complexes in an ionic liquid based on choline chloride and in choline chloride/water mixtures

A deep-eutectic solvent with the properties of an ionic liquid is formed when choline chloride is mixed with copper(II) chloride dihydrate in a 1:2 molar ratio. EXAFS and UV-vis-near-IR optical absorption spectroscopy have been used to compare the coordination sphere of the cupric ion in this ionic liquid with that of the cupric ion in solutions of 0.1 M of CuCl(2)·2H(2)O in solvents with varying molar ratios of choline chloride and water. The EXAFS data show that species with three chloride ions and one water molecule coordinated to the cupric ion as well as species with two chloride molecules and two water molecules coordinated to the cupric ion are present in the ionic liquid. On the other hand, a fully hydrated copper(II) ion is formed in an aqueous solution free of choline chloride, and the tetrachlorocuprate(II) complex forms in aqueous choline chloride solutions with more than 50 wt % of choline chloride. In solutions with between 0 and 50 wt % of choline chloride, mixed chloro-aquo complexes occur. Upon standing at room temperature, crystals of CuCl(2)·2H(2)O and of Cu(choline)Cl(3) formed in the ionic liquid. Cu(choline)Cl(3) is the first example of a choline cation coordinating to a transition-metal ion. Crystals of [choline](3)[CuCl(4)][Cl] and of [choline](4)[Cu(4)Cl(10)O] were also synthesized from molecular or ionic liquid solvents, and their crystal structures were determined.     

Photochemistry of a chiral salen aluminum complex in nonconventional solvents: use of imidazolium ionic liquids and chiral alcohols

The photochemistry of a chiral (salen)aluminum(III) chloride complex has been studied in nonconventional solvents, namely, two imidazolium ionic liquids differing on the hydrophobicity (hydrophilic BF(4)(-) or hydrophobic PF(6)(-) counter anions) and in chiral 2-butanols (R and S). Upon 355 nm laser excitation, the same transient absorption spectrum (with some solvatochromic shift in lambda(max)) was recorded in all cases and assigned to the (salen)Al(II) complex with radicaloid character at the metal atom. This intermediate arises from the photoinduced homolytic cleavage of the apical Al-Cl bond. The half-life of this radicaloid Al(II) species varies depending on the solvent, indicating that its reactivity is governed by the nature of the ionic liquid and also on the R or S configuration of the chiral alcohol.     

Ionic liquid-based dispersive liquid–liquid microextraction for the separation and preconcentration of lead in water samples prior to FAAS determination without chelating agent

In the present study, an environment-friendly sample preparation method termed ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry has been developed for the determination of Pb(II) ion in water samples prior to flame atomic absorption spectrometry determination. In this method, ionic liquid was used as an extraction solvent instead of the organic solvent used in the conventional dispersive liquid–liquid microextraction (DLLME) assay, and there is no need for a chelating agent. Several variables that may affect extraction efficiencies, including pH, the volume of ionic liquid, the type and volume of disperser solvent, salt addition, and the time for centrifugation and extraction were studied and optimised. Under the optimised conditions, the calibration curve exhibited linearity over the range of 20.0–1000.0 μg L^?1. The enrichment factor and the limit of detection based on 3S_b/m were 35.0 and 5.9 μg L^?1, respectively. Seven replicate determination of a solution containing of 100.0 μg L^?1 Pb(II) ions gave a relative standard deviation of ±2.1%. Finally, the feasibility of the proposed method for Pb(II) determination was assessed by the analysis of certi?ed reference material and various water samples and the satisfactory results were obtained.     

Extraction and preconcentration of hemin from human blood serum and breast cancer supernatant

A green, facile, fast, and sensitive liquid‐phase microextraction method is presented for the extraction and preconcentration of hemin in the presence of free iron ions prior to flame atomic absorption spectroscopic determination. In this technique, an anion‐functionalized task‐specific ionic liquid is used as the extracting solvent. The interface between the extracting solvent and the bulk aqueous phase containing hemin is enormously enlarged by dispersing the ionic liquid to the aqueous phase with the help of ultrasound radiation. Hemin is selectively extracted into the ionic liquid after interaction with the functional group of the ionic liquid. Then, the concentration of the extracted hemin is determined through the absorbance of the iron ions contained in the hemin structure using flame atomic absorption spectroscopy. Different experimental parameters affecting the extraction efficiency have been optimized. Under the optimized conditions, the proposed method has a hemin concentration linear range of 0.020–0.80 mg/L with a detection limit of 0.0080 mg/L. This method has been successfully applied to the extraction and determination of hemin in human serum and supernatant samples.     

离子液体溶剂浮选-光度法测定水中痕量四环素类抗生素

将离子液体应用于气浮溶剂浮选分离/富集四环素类抗生素(TCs),建立了一种离子液体1-丁基-3-甲基咪唑六氟磷酸盐(\PF6)取代传统有机溶剂气浮溶剂浮选分离/富集四环素类抗生素的新方法.TCs与镧能形成疏水性络合物,易于浮选至离子液体相,考察了在离子液体中加入有机溶剂的种类和体积,试液的pH值、La的加入量、气体流速、浮选时间以及共存物质对浮选效率的影响,优化了浮选条件,与溶剂萃取方法相比,离子液体溶剂浮选四环素类抗生素富集倍数高,且无毒,无污染,试剂用量少,实测了鱼塘水和辽河水样,RSD分别为3.0%和4.3%(n=5),回收率为97%.本方法适合于环境水样中痕量四环素总量的分析检测.     

Polyaddition of bifunctional cyclic carbonate with diamine in ionic liquids: In situ ion composite formation and simple separation of ionic liquid

Polyaddition of bifunctional cyclic carbonates and diamines in ionic liquids proceeded smoothly to afford polyurethanes having hydroxyl groups in the side chain (i.e., poly(hydroxyurethane)). The reaction mixtures separated into ionic liquids and ionic composites consisting of poly(hydroxyurethane) and ionic liquids. The ionic composites originated from the interactions between hydroxyl groups in the side chains and the ionic liquids, confirmed by IR spectroscopic analysis. When the polyaddition was conducted in the mixed solvent consists of water and N‐n‐butylimidazolium hexafluorophosphate. After the reaction, the polymer and the ionic liquid could be separated easily. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4629–4635, 2009     

Determination of metal ions in tea samples using task‐specific ionic liquid‐based ultrasound‐assisted dispersive liquid–liquid microextraction coupled to liquid chromatography with ultraviolet detection

Task‐specific ionic liquid‐based ultrasound‐assisted dispersive liquid–liquid microextraction was used for the preconcentration of cadmium(II), cobalt(II), and lead(II) ions in tea samples, which were subsequently analyzed by liquid chromatography with UV detection. The proposed method of preconcentration is free of volatile organic compounds, which are often used as extractants and dispersing solvents in classic techniques of microextraction. A task‐specific ionic liquid trioctylmethylammonium thiosalicylate was used as an extractant and a chelating agent. Ultrasound was used to disperse the ionic liquid. After microextraction, the phases were separated by centrifugation, and the ionic liquid phase was solubilized in methanol and directly injected into the liquid chromatograph. Selected microextraction parameters, such as the volume of ionic liquid, the pH of the sample, the duration of ultrasound treatment, the speed and time of centrifugation, and the effect of ionic strength, were optimized. Under optimal conditions an enrichment factor of 200 was obtained for each analyte. The limits of detection were 0.002 mg/kg for Cd(II), 0.009 mg/kg for Co(II), and 0.013 mg/kg for Pb(II). The accuracy of the proposed method was evaluated by an analysis of the Certified Reference Materials (INCT‐TL‐1, INCT‐MPH‐2) with the recovery values in the range of 90–104%.