Rh(PPh3)3Cl/有机融盐催化烯烃硅氢加成反应

研究了Rh(PPh₃)₃Cl/二烷基咪唑六氟磷酸盐或烷基吡啶六氟磷酸盐催化三乙基氢硅烷与烯烃的硅氢加成反应. 实验结果表明, 二烷基咪唑六氟磷酸盐或烷基吡啶六氟磷酸盐的存在既有利于提高加成反应的转化率和β加成物的选择性, 又有利于反应结束后产物与催化剂的分离. C₁₆PyPF₆作为催化剂的载体, Rh(PPh₃)₃Cl催化苯乙烯与三乙基氢硅烷加成反应的转化率为95.7%, β加成物的选择性为87.8%, α加成物的选择性为0.001%, 脱氢加成产物的选择性为9.2%. 同时, 此催化剂重复使用7次以后仍具有较高的活性.     

Temperature‐controlled ionic liquid dispersive liquid‐phase microextraction combined with HPLC with ultraviolet detector for the determination of fungicides

Present study described a simple, environmental benign, easy to operate, and determination method for fungicides including thiram, metalaxyl, diethofencarb, myclobutanil, and tebuconazole. The method is based on temperature‐controlled ionic liquid dispersive liquid phase microextraction coupled to HPLC with ultraviolet detector. In the enrichment procedure, ionic liquid 1‐octyl‐3‐methylimidazolium hexafluorophosphate [C₈MIM][PF₆] was used as the extraction solvent. Variable affecting parameters such as the volume of [C₈MIM][PF₆], temperature, extraction time, centrifuging time, and salting‐out effect have been optimized in detail. Under the optimal conditions, this method has been found to have good linear relationship in the concentration range of 1.0–100 μg/L and excellent detection sensitivity with LODs (S/N = 3) in the range of 0.32–0.79 μg/L. Precisions of proposed method were in the range of 3.7–5.9% for intraday and 7.8–11.0% for interday (RSDs, n = 6). The proposed method was used for the analysis of real water samples and good spiked recoveries at two different spiked levels were achieved in the range of 84.6–102%.     

Efficient solid-phase synthesis of cyclic RGD peptides under controlled microwave heating

Cyclic RGD peptides are potent antagonists for the α_vβ₃ integrin receptor. In this Letter, microwave-assisted solid-phase synthesis of cyclic RGD peptides is described. In a coupling reaction between Fmoc-Arg(Pbf)-OH and high-loading H-Gly-Trt(2-Cl) resin, multiple coupling reactions were required for completion under the conventional HBTU activation. We found that the use of COMU, a new coupling reagent, under microwave heating to 50 °C accelerated the reaction even inside the resin. This method was applicable to the synthesis of linear pentapeptides, H-Asp(OtBu)-Xxx-Yyy-Arg(Pbf)-Gly-OH (Xxx = d-Phe(p-Br) or d-Tyr, Yyy = Lys(Boc) or MeVal). Cyclization of these peptides followed by deprotection gave the desired cyclic RGD peptides with high purity.     

Direct electrocatalvtic reduction of p-nitrophenol at room temperature ionic 1iquid modified electrode

Direct electrochemical reduction of p-nitrophenol(PNP)was investigated on a room temperature ionic liquid N-butylpyridinium hexafluorophosphate(BPPF6)modified carbon paste electrode(CILE).The cathodic peak potential was positively shifted and the peak currents were increased compared to that obtained on traditional carbon paste electrode(CPE).The results indicated that the presence of ionic liquid BPPF6 on the electrode surface showed excellent catalytic ability to the electrochemical reduction of PNP.The electrochemical behaviors of PNP on the CILE were investigated by cyclic voltammetry and the conditions such as the scan rate,the buffer pH,the substrate concentration were optimized.The electrochemical parameters were further calculated with the results of the electron transfer number(n),the charge-transfer coefficient(α)and the surface concentration(ΓΥ)as 1.76,0.37 and 2.47×10-9 mol/cm2,respectively,for the selected reducfive peak.The results indicated that PNP showed all irreversible adsorption-controlled electrode process on the CILE.     

Viscosity of ionic liquid mixtures of 1-alkyl-3-methylimidazolium hexafluorophosphate + CO2

The viscosities of the mixtures 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF₆]) + CO₂ and 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM][PF₆]) + CO₂ were measured with a rolling ball viscometer. The CO₂ mole fraction for one mixture ranged up to 0.434 and the other up to 0.447. The viscosities were measured at 293.15-353.15 K and 10-20.0 MPa. The experimental uncertainty in viscosity was estimated to be within ±3.0%. The experimental data were compared with McAllister's three-body model, which correlated with the experimental data within average absolute deviations of 5.9%.     

Direct Electrochemistry of Hemoglobin on Single‐Walled Carbon Nanotubes Modified Carbon Ionic Liquid Electrode and Its Electrocatalysis

In this article we report on the fabrication of a carbon ionic liquid electrode (CILE) by using a room temperature ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆) as binder. It was further modified by single‐walled carbon nanotubes (SWCNTs) to get a SWCNTs modified CILE denoted as SWCNTs/CILE. The redox protein of hemoglobin (Hb) was further immobilized on the surface of SWCNTs/CILE with the help of Nafion film. UV‐vis and FT‐IR spectra indicated that the immobilized Hb retained its native conformation in the composite film. The direct electrochemistry of Hb on the SWCNTs/CILE was carefully studied in pH 7.0 phosphate buffer solution (PBS). Cyclic voltammetric results indicated that a pair of well‐defined and quasireversible voltammetric peaks of Hb heme Fe(III)/Fe(II) was obtained with the formal potential (E°') at ?0.306 V (vs. SCE). The electrochemical parameters such as the electron transfer coefficient (α), the electron transfer number (n) and the apparent heterogeneous electron transfer rate constant (k_s) were calculated as 0.34, 0.989 and 0.538 s^?1, respectively. The fabricated Hb modified electrode showed good electrocatalytic ability to the reduction of trichloroacetic acid (TCA) in the concentration range from 20.0 to 150.0 mmol/L with the detection limit of 10.0 mmol/L (3σ).     

Fabrication and Electrochemical Behavior of Hemoglobin Modified Carbon Ionic Liquid Electrode

A new hemoglobin (Hb) and room temperature ionic liquid modified carbon paste electrode was constructed by mixing Hb with 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆) and graphite powder together. The Hb modified carbon ionic liquid electrode (Hb‐CILE) was further characterized by FT‐IR spectra, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Hb in the carbon ionic liquid electrode remained its natural structure and showed good direct electrochemical behaviors. A pair of well‐defined quasireversible redox peaks appeared with the apparent standard potential (E′) as ?0.334 (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The electrochemical parameters such as the electron transfer number (n), the electron transfer coefficient (α) and the heterogeneous electron transfer kinetic constant (k_s) of the electrode reaction were calculated with the results as 1.2, 0.465 and 0.434 s^?1, respectively. The fabricated Hb‐CILE exhibited excellent electrocatalytic activity to the reduction of H₂O₂. The calibration range for H₂O₂ quantitation was between 8.0×10^?6 mol/L and 2.8×10^?4 mol/L with the linear regression equation as I_ss (μA)=0.12 C (μmol/L)+0.73 (n=18, γ=0.997) and the detection limit as 1.0×10^?6 mol/L (3σ). The apparent Michaelis–Menten constant (K_M^app) of Hb in the modified electrode was estimated to be 1.103 mmol/L. The surface of this electrochemical sensor can be renewed by a simple polishing step and showed good reproducibility.     

Direct Electron Transfer of Hemoglobin on a Carbon Ionic Liquid Electrode with TiO2 Nanopatricle as Enhancer

Room temperature ionic liquids (RTILs) N‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) was fabricated and applied to adsorb the hemoglobin (Hb) and TiO₂ nanoparticles on the electrode surface step by step to form a Hb modified electrode noted as TiO₂/Hb/CILE. UV‐Vis and FT‐IR spectra showed that Hb in the film retained its native conformations. Cyclic voltammetric experiments indicated that a pair of well‐defined quasi‐reversible redox peaks appeared with the formal potential (E^0′) located at ?0.251 V (vs. SCE) at pH 7.0 phosphate buffer solution (PBS), which was the characteristic of heme Fe(III)/Fe(II) redox couples. Electrochemical parameters of the Hb in the film such as the electron transfer coefficient (α), the electron transfer number (n) and the standard electron transfer rate constant (k_s) were estimated as 0.469, 0.87 and 0.635 s^?1, respectively.     

Direct Electrochemistry of Myoglobin in a Nafion‐Ionic Liquid Composite Film Modified Carbon Ionic Liquid Electrode

In this paper two kinds of ionic liquids (ILs) were used for the construction of a myoglobin (Mb) electrochemical biosensor. Firstly a hydrophilic ionic liquid of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) was used as binder to prepare a carbon ionic liquid electrode (CILE), then a Nafion and hydrophobic ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆) composite film was applied on the surface of the CILE. The direct electrochemistry of Mb in the Nafion‐BMIMPF₆/CILE was achieved with the cathodic and anodic peak potentials located at ?0.345 V and ?0.213 V (vs. SCE). The formal potential (E°′) was located at ?0.279 V, which was the characteristic of Mb Fe^III/Fe^II redox couples. The electrochemical behaviors of Mb in the Nafion‐ionic liquid composite film modified CILE were carefully investigated. The Mb modified electrode showed good electrocatalytic behaviors to the reduction of trichloroacetic acid (TCA) and NaNO₂. Based on the Nafion‐BMIMPF₆/Mb/CILE, a new third generation reagentless biosensor was constructed.     

Sensitive determination of verticine and verticinone in Bulbus Fritillariae by ionic liquid assisted capillary electrophoresis-electrochemiluminescence system

CE/Ru(bpy)₃²⁺ electrochemiluminescence (ECL) system with the assistance of ionic liquids (ILs) was successfully established for sensitive determination of verticine and verticinone in Bulbus Fritillariae for the first time. Migration behavior of alkaloid largely relies on the hydrogen bonding interactions between alkyl imidazolium cations in ILs and the alkaloids. Running buffer containing 40 mmol/L 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF₄) IL-8 mmol/L phosphate resulted in significant changes in separation selectivity for alkaloids with similar structures. The highest sensitivity of the detection was obtained by maintaining the detection potential at 1.2 V. Under the optimized conditions, relative standard derivations of the ECL intensity and the migration time were 3.27 and 2.84% for verticine and 4.42 and 1.69% for verticinone, respectively. The standard curves were linear between 1 × 10⁻⁸ and 1 × 10⁻⁶ mol/L for verticine and between 5 × 10⁻⁸ and 1 × 10⁻⁶ mol/L for verticinone, respectively. Detection limits of 1.25 × 10⁻¹⁰ mol/L for verticine and 1 × 10⁻¹⁰ mol/L for verticinone were obtained (S/N = 3). Developed method was successfully applied to determine the amounts of alkaloids in Bulbus Fritillariae.