Highly effective binding and inverse fluorescent behavior of palmatine and l-tetrahydropalmatine alkaloids by p-sulfonatocalixarenes

The effects of pressure and solvent were examined for the inclusion complexation of phenothiazine dyes and trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium (St-4Me) with water-soluble p-sulfonatocalix[8]arene (Calix-S8). Depending on the bulkiness of the guest dyes, external pressures and solvent polarity increase the inclusion equilibrium constants of dyes with Calix-S8. From the pressure dependence of the inclusion equilibria, the reaction volumes for inclusion by Calix-S8 in the alcohol-water mixtures were estimated to be negative values (?19.8 to ?5.29 cm³ mol^?1 for the phenothiazine dyes and ?13.1 to ?9.85 cm³ mol^?1 for St-4Me). Analysis of the results of the high pressure indicated that the intrinsic volume change related to inclusion into the Calix-S8 cavity plays an important role in the inclusion of Calix-S8, depending on the bulkiness of the guest molecules. Based on ¹H NMR measurements, the structures of the inclusion complexes of Calix-S8 with phenothiazine dyes have been established and the differences in the inclusion behaviors of the phenothiazine dyes and St-4Me are discussed.     

Cyclopropanation of 5-(allyloxymethyl)- and 5-(methallyloxymethyl)-5-ethyl-1,3-dioxanes with methyl diazoacetate

Reactions of 5-(allyloxymethyl)- and 5-(methallyloxymethyl)-5-ethyl-1,3-dioxanes with methyl diazoacetate catalyzed by Rh₂(OAc)₄ or Cu(OTf)₂ in the presence of [bmim]⁺Cl⁻, [bmim]⁺BF₄ ⁻, and [bmim]⁺PF₆ ⁻ proceed regioselectively at the C=C bond and lead to the formation of the corresponding cyclopropane-containing 1,3-dioxanes in yields up to 62%.     

Polymerization of phenylacetylene catalysed by RhTp(cod) and RhBp(cod) in ionic liquids: effect of alcohols and of tetraammonium halides

RhTp(cod) ( 1 ) and RhBp(cod) ( 2 ), almost inactive in CH₂Cl₂, became good catalysts of phenylacetylene polymerization in ionic liquids ([bmim]Cl, [bmim]BF₄: bmim = 1‐butyl‐3‐methylimidazolium, [mokt]BF₄: mokt = 1‐methyl‐3‐oktylimidazolium, [bumepy]BF₄: 1‐butyl‐4‐methylpyridinium) and in CH₂Cl₂ in the presence of tetraammonium halides ([R₄N]X, R = Bu, Et; X = Cl, Br). The highest yields of polyphenylacetylene with catalyst 1 were obtained in [bmim]Cl at 65°C (64% after 2 h) and in [mokt]BF₄ at 20°C (56% after 24 h). In alcohols (CH₃OH, (CH₃)₂CHOH, (CH₃)₃COH) as solvents, up to 100% of the polymer was produced. When a mixture of an ionic liquid and CH₃OH was used as the reaction medium, the polymer yield was similar to the yield achieved in an ionic liquid only, but the molecular weight increased remarkably. Tetraammonium salts, [R₄N]X, are co‐catalysts for 1 , and the yield of the polymer increased in the order [Et₄N]Br < [Bu₄N]Br < [Et₄N]Cl < [Bu₄N]Cl. Polymers with molecular weights from 6900 to 38 800 Da were obtained with catalyst 2 in [R₄N]Br or [R₄N]Cl, whereas in ionic liquids ([bmim]Cl, [bmim]BF₄) the corresponding molecular weights were higher, from 51 300 to 60 300 Da. Copyright © 2004 John Wiley & Sons, Ltd.     

Effects of temperature and anion species on CO2 permeability and CO2/N2 separation coefficient through ionic liquid membranes

The permeability of carbon dioxide (CO₂) through imidazolium-based ionic liquid membranes was measured by a sweep gas method. Six species of ionic liquids were studied in this work as follows: [emim][BF₄], [bmim][BF₄], [bmim][PF₆], [bmim][Tf₂N], [bmim][OTf], and [bmim][dca]. The ionic liquids were supported with a polyvinylidene fluoride porous membrane. The measurements were performed at T = (303.15 to 343.15) K. The partial pressure difference between feed and permeate sides was 0.121 MPa. The permeability of the CO₂ increases with temperature for the all ionic liquid species. Base on solution diffusion theory, it can be explained that the diffusion coefficient of CO₂ in an ionic liquid affects the temperature dependence more strongly than the solubility coefficient. The greatest permeability was obtained with the [bmim][Tf₂N] membrane. The membrane of [bmim][PF₆] presents the lowest permeability.The separation coefficient between CO₂ and N₂ through the ionic liquid membranes was also investigated at the volume fraction of CO₂ at feed side 0.10. The separation coefficient decreases with the increase of temperature for the all ionic liquid species. The membrane of [emim][BF₄] and [bmim][BF₄] gives the highest separation coefficient at constant temperature. The lowest separation coefficient was obtained from [bmim][Tf₂N] membrane which presents the highest permeability of CO₂.     

Iridium-catalyzed regiospecific allylation of dimethyl malonate in ionic liquids

Allylation of dimethyl malonate with 1-(4-chlorophenyl)prop-2-enyl methyl carbonate in the presence of [Pd(All)Cl]₂, [Rh(COD)Cl]₂, [Ir(COD)Cl]₂ (COD is cycloocta-1,5-diene), and a chiral ferrocenyl-containing phosphite ligand based on (R)-BINOL (BINOL is 2,2′-dihydroxy-1,1′-binaphthyl) in CH₂Cl₂ gave a mixture of linear and branched cross-coupling products, the latter having a moderate optical purity (below 51%). The rhodium-and iridium-catalyzed reactions were very highly regioselective (regiospecific in the case of Ir), giving a branched product. In ionic liquids ([bmim][BF₄] and [bdmim][BF₄]) (bmim is 1-butyl-3-methylimidazolium and bdmim is 1-butyl-2,3-dimethylimidazolium), the Ir-catalyzed reaction regiospecifically afforded a branched product as a racemate. The same result was obtained with [Ir(COD)Cl]₂ as a catalyst; this reaction easily occurred in ionic liquids even without a base. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 519–521, March, 2007.     

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.     

Pressure-Induced Solidification of 1-Butyl-3-methylimidazolium Tetrafluoroborate

We have used Raman spectroscopy to investigate the high-pressure phase behavior of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), a representative ionic liquid, at pressures up to ~7.5 GPa. We have also studied how increasing pressure leads to conformational changes in the [bmim]⁺ cation. We have found that liquid [bmim][BF₄] undergoes pressure-induced solidification (freezing) into a superpressed (metastable) state at 2.5 GPa; another structural change probably occurs at ~6 GPa. Remarkably, conformational changes in the [bmim]⁺ cation between trans and gauche conformers are concordant with the metastable structural changes of [bmim][BF₄]. As the pressure is increased from ambient, the fraction of gauche conformers increases, but the gauche fraction decreases above the solidification pressure (2.5 GPa), and slope of the gauche/trans ratio changes again above 6 GPa. We interpret these results in terms of the fragility of the ionic liquid.     

Microwave‐assisted ring‐opening polymerization of trimethylene carbonate in the presence of ionic liquid

Microwave‐assisted ring‐opening polymerization (MROP) of trimethylene carbonate in the presence of 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄) ionic liquid was investigated. In the presence of 5 wt % [bmim]BF₄, poly (trimethylene carbonate) (PTMC) with a number‐average molar mass (M_n) of 36,400 g/mol was obtained at 5 W for only 60 min. The M_n of PTMC synthesized in the presence of [bmim]BF₄ was much higher than that produced in bulk at the same reaction time. In addition, compared with those produced by conventional heating, the M_n of PTMC and monomer conversion by MROP with or without [bmim]BF₄ were both higher. Thermal properties of the resulting PTMC were characterized by differential scanning calorimetry. Under microwave irradiation in the presence of ionic liquid, the polymerization could be carried out efficiently and effectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5857–5863, 2007     

Cationic ring-opening polymerization of 3,3-bis（chloromethyl）oxacyclobutane in ionic liquids

Cationic ring-opening polymerization of 3,3-bis(chloromethyl)oxacyclobutane catalyzed by BF_3·OEt_2 was carried out in ionic liquids [bmim]BF_4 and [bmim]PF_6.The influences of BCMO concentration and molar ratio of BCMO/BF_3·OEt_2 on the molecular weights and yield of PBCMO were investigated.The polymerization in ionic liquids proceed to high conversions,although molecular weights are limited,similar to polymerization in organic solvent such as CH_2Cl_2.Follow a viewpoint of green chemistry, we feel ionic liquid [bmim]BF_4 is superior to [bmim]PF_6.Extracting [bmim]PF_6 from the product using organic solvent as extractant limits its advantage as a green reaction media.     

Activity and stability of horseradish peroxidase in hydrophilic room temperature ionic liquid and its application in non-aqueous biosensing

The activity and stability of horseradish peroxidase (HRP) were investigated in a hydrophilic room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluroborate ([bmim][BF₄]) by electrochemical methods. Although no detectable activity exhibited in anhydrous [bmim][BF₄], HRP was active in the presence of a small amount of water (4.53%, v/v). And its activity can be improved by immobilization in agarose hydrogel. The immobilized HRP possesses excellent activity at 65 °C. It remained 80.2% of its initial activity after being immersed for 10.5 h in an aqueous mixture of [bmim][BF₄] with some hydrogen peroxide (H₂O₂) under room temperature, implying extremely high stability. Moreover, the immobilized HRP was found to be very sensitive and stable in H₂O-containing [bmim][BF₄] for the detection of H₂O₂, with a wide linear range of 6.10 × 10⁻⁷ to 1.32 × 10⁻⁴ mol l⁻¹ and low detection limit of 1.0 × 10⁻⁷ mol l⁻¹.     

Amine basicity: measurements of ion pair stability in ionic liquid media

The stability constants relevant to the formation of amine/p-nitrophenol ion pairs have been determined in [bmim][BF₄] solution, in the presence of butylamine, piperidine, and triethylamine, by using spectrophotometric measurements. In order to evaluate how the ion pair stability is affected by ionic liquid structure, piperidine has been chosen as model amine for studies in [bmim][PF₆], [bmim][NTf₂], [bm₂im][NTf₂] and in several [bmim][BF₄]/1,4-dioxane binary mixtures. Data obtained in ionic liquid solutions have been compared with those previously reported in conventional organic solvents.     

Microwave-Assisted Ionic Liquid-Catalyzed Selective Monoesterification of Alkylphosphonic Acids—An Experimental and a Theoretical Study

It is well-known that the P-acids including phosphonic acids resist undergoing direct esterification. However, it was found that a series of alkylphoshonic acids could be involved in monoesterification with C₂–C₄ alcohols under microwave (MW) irradiation in the presence of [bmim][BF₄] as an additive. The selectivity amounted to 80–98%, while the isolated yields fell in the range of 61–79%. The method developed is a green method for P-acid esterification. DFT calculations at the M062X/6–311+G (d,p) level of theory (performed considering the solvent effect of the corresponding alcohol) explored the three-step mechanism, and justified a higher enthalpy of activation (160.6–194.1 kJ·mol⁻¹) that may be overcome only by MW irradiation. The major role of the [bmim][BF₄] additive is to increase the absorption of MW energy. The specific chemical role of the [BF₄] anion of the ionic liquid in an alternative mechanism was also raised by the computations.     

Study on the alcoholysis of isoflavone catalyzed by ionic liquids

Alcoholysis of soybean isoflavone glucosides by butanol catalyzed by acidic ionic liquids was studied. The effects of the ionic liquid catalyst type, catalyst concentration, reaction time and reaction temperature on glycoside conversions, and aglycons yields were investigated. The optimum reaction conditions are found to be as follows: 0.036 g mL⁻¹ of ionic liquid [BIM]HSO₄ as catalyst, reaction temperature at 104±1°C, reaction time of 100 min. Under these optimum reaction conditions near complete conversions of the three kinds of glycosides (daidzin, glycitin and genistin) are obtained. Furthermore, the kinetics parameters for the alcoholysis were estimated. The activation energies of alcoholysis for the three kinds of isoflavone glucosides are 124 kJ mol⁻¹, 67 kJ mol⁻¹ and 115 kJ mol⁻¹, respectively.     

Layered structure of room-temperature ionic liquids in microemulsions by multinuclear NMR spectroscopic studies

Microemulsions form in mixtures of polar, nonpolar, and amphiphilic molecules. Typical microemulsions employ water as the polar phase. However, microemulsions can form with a polar phase other than water, which hold promise to diversify the range of properties, and hence utility, of microemulsions. Here microemulsions formed by using a room‐temperature ionic liquid (RTIL) as the polar phase were created and characterized by using multinuclear NMR spectroscopy. ¹H, ¹¹B, and ¹⁹F NMR spectroscopy was applied to explore differences between microemulsions formed by using 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) as the polar phase with a cationic surfactant, benzylhexadecyldimethylammonium chloride (BHDC), and a nonionic surfactant, Triton X‐100 (TX‐100). NMR spectroscopy showed distinct differences in the behavior of the RTIL as the charge of the surfactant head group varies in the different microemulsion environments. Minor changes in the chemical shifts were observed for [bmim]⁺ and [BF₄]^? in the presence of TX‐100 suggesting that the surfactant and the ionic liquid are separated in the microemulsion. The large changes in spectroscopic parameters observed are consistent with microstructure formation with layering of [bmim]⁺ and [BF₄]^? and migration of Cl^? within the BHDC microemulsions. Comparisons with NMR results for related ionic compounds in organic and aqueous environments as well as literature studies assisted the development of a simple organizational model for these microstructures.     

Complexation of [2.2]paracyclophane with β- and γ-cyclodextrins studied by HPLC and NMR

The NMR spectra of [2.2]paracyclophane with β- or γ-cyclodextrin in DMF-d₇ at room temperature do not show significant complexation, while HPLC of the complexes in mixed H₂O:alcohol solvents demonstrate complexation with different stoichiometries. At 243 K in DMF solution the H3 and H5 NMR signals of γ-cyclodextrin (but not β) exhibit complexation-induced chemical shifts denoting complex formation. According to HPLC, at room temperature the [2.2]paracyclophane complex with β-cyclodextrin in 20% H₂O:EtOH exhibits 1:2 stoichiometry with K ₁ = 1×10² ± 2, K ₂ = 9.0×10⁴ ± 2×10³ (K = 9×10⁶) while that with γ-cyclodextrin in 50% H₂O:MeOH exhibits 1:1 stoichiometry with K ₁ = 4×10³ ± 150 M⁻¹. Thermodynamic parameters for both complexes have been estimated from the retention time temperature dependence. For the β-cyclodextrin complexation at 25°C ΔG ⁰ _CD is −39.7 kJ mol⁻¹ while ΔH ⁰ _CD and ΔS ⁰ _CD are −88.2 kJ mol⁻¹ and −0.16 kJ mol⁻¹ K⁻¹. For γ-cyclodextrin, the corresponding values are ΔG ⁰ _CD = −20.5 kJ mol⁻¹, ΔH ⁰ _CD = −33.5 kJ mol⁻¹ and ΔS ⁰ _CD = −0.04 kJ mol⁻¹ K⁻¹.      

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF₄) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C _p,m [J K⁻¹ mol⁻¹]=181.43+51.297X −4.7816X ²−1.9734X ³+8.1048X ⁴+11.108X ⁵ [X=(T−135)/55] for the solid phase (80–190 K), C _p,m [J K⁻¹ mol⁻¹]= 349.96+25.106X+9.1320X ²+19.368X ³+2.23X ⁴−8.8201X ⁵ [X=(T−225)/27] for the glass state (198–252 K), and C _p,m[J K⁻¹ mol⁻¹]= 402.40+21.982X−3.0304X ²+3.6514X ³+3.4585X ⁴ [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BPBF₄ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BPBF₄ was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH _g=2.157 kJ mol⁻¹ and ΔS _g=11.12 J K⁻¹ mol⁻¹, respectively. The result showed that the melting point of the BPBF₄ is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH _m = 8.453 kJ mol⁻¹ and ΔS _m=30.21 J K⁻¹ mol⁻¹. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF₄ was determined to be Δ_c H _m⁰ = −5451±3 kJ mol⁻¹. The standard molar enthalpy of formation of BPBF₄ was evaluated to be Δ_f H _m⁰ = −1356.3±0.8 kJ mol⁻¹ at T=298.150±0.001 K.     

1-Butyl-3-methylimidazolium p-toluenesulfinate: a novel reagent for synthesis of sulfones and β-ketosulfones in ionic liquid

A novel task-specific ionic liquid, 1-butyl-3-methylimidazolium p-toluenesulfinate, [bmim][p-TolSO₂] has been synthesized and used as a nucleophile for the reaction with alkyl bromides and phenacyl bromides to prepare sulfones and β-ketosulfones in excellent yields (80-93%) in [bmim][BF₄] ionic liquid. The isolated yields of sulfones and β-ketosulfones were higher in [bmim][BF₄] than other organic solvents at room temperature.     

Solvent Effect on the Enthalpy of Solution and Partial Molar Volume of the Ionic Liquid 1-Butyl-3-methylimidazolium Tetrafluoroborate

Enthalpies of solution and partial molar volumes of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate were determined in 15 solvents of different polarity. Very large differences of the enthalpies of solution (????_sol H _IL=38.9?kJ?mol^?1) and partial molar volumes (??V _IL=43 cm³?mol^?1) are nearly the same as observed for lithium perchlorate solutions. These results clearly indicate that the low values of the macroscopic polarity parameters of [bmim]BF₄ do not correspond with the large differences of the intermolecular interactions in IL solutions. The values of the partial molar volume of the cation, $V_{[\mathrm{bmim}]^{+}}$ , were estimated for the first time. The changes of the partial molar volumes, V _IL, reflect mainly the changes of anion volume, $V_{\mathrm{BF}_{4}^{-}}$ . The rate of the Diels?CAlder reaction of 9,10-dimethylanthracene with maleic anhydride in the [bmim]BF₄ medium was nearly the same as in common molecular solvents.     

Extraction and determination of chloramphenicol in feed water,milk, and honey samples using an ionic liquid/sodium citrate aqueous two-phase system coupled with high-performance liquid chromatography

A green, simple, non-toxic, and sensitive sample pretreatment procedure coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of chloramphenicol (CAP) that exploits an aqueous two-phase system based on imidazolium ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim]BF₄) and organic salt (Na₃C₆H₅O₇) using a liquid–liquid extraction technique. The influence factors on partition behaviors of CAP were studied, including the type and amount of salts, the pH value, the volume of [Bmim]BF₄, and the extraction temperature. Extraction efficiency of the CAP was found to increase with increasing temperature and the volume of [Bmim]BF₄. Thermodynamic studies indicated that hydrophobic interactions were the main driving force, although electrostatic interactions and salting-out effects were also important for the transfer of the CAP. Under the optimal conditions, 90.1% of the CAP could be extracted into the ionic liquid-rich phase in a single-step extraction. This method was practical when applied to the analysis of CAP in feed water, milk, and honey samples with a linear range of 2~1,000 ng mL⁻¹. The method yielded a limit of detection of 0.3 ng mL⁻¹ and a limit of quantification of 1.0 ng mL⁻¹. The recovery of CAP was 90.4–102.7% from aqueous samples of real feed water, milk, and honey samples by the proposed method. This novel process is much simpler and more environmentally friendly and is suggested to have important applications for the separation of antibiotics.     

Enzymatic polyester synthesis in ionic liquids

The enzymatic synthesis of polyesters by ring-opening polymerization (ROP) and polycondensation in three ionic liquids, i.e., [bmim][Tf₂N], [bmim][PF₆] and [bmim][BF₄] was investigated. For the enzymatic ROP of ε-caprolactone it was found that [bmim][PF₆] and [bmim][BF₄] result in an inhomogeneous reaction mixture upon polymerization, causing polymerization characteristics similar to bulk polymerization. In contrast, for [bmim][Tf₂N] characteristics similar to toluene were observed. Molecular weights of 7000-9500 g/mol were obtained. In the polycondensation of dimethyl adipate and dimethyl sebacate, respectively, with 1,4-butanol the low volatility of ionic liquids was successfully utilized to perform the reactions in an open vessel at temperatures close to the boiling point of the condensation by-product. Molecular weights up to 5400 g/mol were obtained. This, in combination with the tunable solvent hydrophilicity of ionic liquids could offer an advantage in the polymerization of highly polar monomers with low solubility in organic solvents.