Strong Lewis acids of air-stable metallocene bis(perfluorooctanesulfonate)s as high-efficiency catalysts for carbonyl-group transformation reactions

Strong Lewis acids of air-stable metallocene bis(perfluorooctanesulfonate)s [M(Cp)(2)][OSO(2)C(8)F(17)](2)?nH(2)O?THF (M = Zr (2?a?3?H(2)O?THF), M = Ti (2?b?2?H(2)O?THF)) were synthesized by the reaction of [M(Cp)(2)]Cl(2) (M = Zr (1?a), M = Ti (1?b)) with nBuLi and C(8)F(17)SO(3)H (2?equiv) or with C(8)F(17)SO(3)Ag (2?equiv). The hydrate numbers (n) of these complexes were variable, changing from 0 to 4 depending on conditions. In contrast to well-known metallocene triflates, these complexes suffered no change in open air for a year. thermogravimetry-differential scanning calorimetry (TG-DSC) analysis showed that 2?a and 2?b were thermally stable at 300 and 180?°C, respectively. These complexes exhibited unusually high solubility in polar organic solvents. Conductivity measurement showed that the complexes (2?a and 2?b) were ionic dissociation in CH(3)CN solution. X-ray analysis result confirmed 2?a?3?H(2)O?THF was a cationic organometallic Lewis acid. UV/Vis spectra showed a significant red shift due to the strong complex formation between 10-methylacridone and 2?a. Fluorescence spectra showed that the Lewis acidity of 2?a fell between those of Sc(3+) (λ(em)=474?nm) and Fe(3+) (λ(em)=478?nm). ESR spectra showed the Lewis acidity of 2?a (0.91?eV) was at the same level as that of Sc(3+) (1.00?eV) and Y(3+) (0.85?eV), while the Lewis acidity of 2?b (1.06?eV) was larger than that of Sc(3+) (1.00?eV) and Y(3+) (0.85?eV). They showed high catalytic ability in carbonyl-compound transformation reactions, such as the Mannich reaction, the Mukaiyama aldol reaction, allylation of aldehydes, the Friedel-Crafts acylation of alkyl aromatic ethers, and cyclotrimerization of ketones. Moreover, the complexes possessed good reusability. On account of their excellent catalytic efficiency, stability, and reusability, the complexes will find broad catalytic applications in organic synthesis.     

Enantiomeric determination of azole antifungals in wastewater and sludge by liquid chromatography–tandem mass spectrometry

A sensitive and reliable liquid chromatographic-tandem mass spectrometric method for enantiomeric determination of five chiral azole antifungals (econazole, ketoconazole, miconazole, tebuconazole, and propiconazole) in wastewater and sludge has been established and validated. An isotope-labeled internal standard was used for quantification. Recovery of the individual enantiomers was usually in the range of 77-102 % for wastewater and 71-95 % for sludge, with relative standard deviations within 20 %. No significant difference (p>0.05) was observed between recovery of pairs of enantiomers of the chiral azole antifungals except for those of tebuconazole. Method quantification limits for individual enantiomers were 0.3-10 ng L(-1) and 3-29 ng g(-1) dry weight for wastewater and sludge, respectively. The method was used to investigate the enantiomeric composition of the azole pharmaceuticals in wastewater and sludge samples from a sewage treatment plant in China. Enantiomers of miconazole, ketoconazole, and econazole were widely detected. The results showed that the azole antifungals in wastewater and sludge were generally racemic or marginally non-racemic. The method is a useful tool for investigation of the enantiomeric occurrence, behavior, and fate of the chiral azole antifungals in the environment.     

Rational design of core–shell molecularly imprinted polymer based on computational simulation and Doehlert experimental optimization: application to the separation of tanshinone IIA from Salvia miltiorrhiza Bunge

Computational simulation and Doehlert experimental optimization were done for the rational design of a core-shell molecularly imprinted polymer (CS-MIP) for use in the highly selective separation of Tanshinone IIA (TSIIA) from the crude extracts of Salvia miltiorrhiza Bunge (SMB). The functional monomer layer of the polymer shells directed the selective occurrence of imprinting polymerization at the surface of silica through the copolymerization of vinyl end groups with functional monomers and also drove TSIIA templates into the formed polymer shells through the charge-transfer complex interactions between TSIIA and the functional monomer layer. As a result, the maximum rebinding capacity was achieved with the use of optimal grafting ratio by the Doehlert design. The CS-MIP exhibited high recognition selectivity and binding affinity to TSIIA. When the imprinted particles were used as dispersive solid phase extraction sorbents, the recovery yield of TSIIA reached 93% by a one-step extraction from the crude extracts of SMB, and the purity of TSIIA was larger than 98% by HPLC analysis. These results show the possibility of a highly selective separation and enrichment of TSIIA from the SMB using the TSIIA-imprinted core-shell molecularly imprinted polymers.     

Transport of topical anesthetics in vitamin E loaded silicone hydrogel contact lenses

Transport of surface active anesthetic drugs through silicone hydrogel contact lenses containing nanosized vitamin E aggregates is explored for achieving extended anesthetics delivery. Commercial silicone hydrogel contact lenses release most ophthalmic drugs including local anesthetics for only a few hours, which is not adequate. Here we focus on creating dispersion of highly hydrophobic vitamin E aggregates in the lenses as barriers for drug diffusion for increasing the release durations. This approach has been shown previously to be successful in extending the release durations for some common hydrophilic ophthalmic drugs. The topical anesthetic drugs considered here (lidocaine, bupivacaine, and tetracaine) are hydrophilic at physiologic pH due to the charge, and so these cannot partition into the vitamin E barriers. However, these surface active drug molecules adsorb on the surface of the vitamin E barriers and diffuse along the surface, leading to only a small decrease in the effective diffusivity compared to non-surface-active hydrophilic drugs. The drug adsorption can be described by the Langmuir isotherm, and measurements of surface coverage of the drugs on the vitamin E provide an estimate of the available surface area of vitamin E, which can then be utilized to estimate the size of the aggregates. A diffusion controlled transport model that includes surface diffusion along the vitamin E aggregates and diffusion in the gel fit the transport data well. In conclusion, the vitamin E loaded silicone contact lens can provide continuous anesthetics release for about 1-7 days, depending on the method of drug loading in the lenses, and thus could be very useful for postoperative pain control after corneal surgery such as the photorefractive keratectomy (PRK) procedure for vision correction.     

Thermodynamic and conformational investigation of the influence of CdTe QDs size on the toxic interaction with BSA

Water-soluble fluorescent colloidal quantum dots (QDs) have been widely used in some biological and biomedical fields, so the interaction of QDs with biomolecules recently attracts increasing attention. In this study, the fluorescence (FL) quenching method, circular dichroism (CD) technique, attenuated total reflection-Fourier transform infrared (ATR-FTIR) and UV-vis absorption spectra were used to investigate systematically the influence of CdTe QDs size on the toxic interaction with bovine serum albumin (BSA). Three size CdTe QDs with maximum emission of 543 nm (green-emitting QDs, GQDs), 579 nm (yellow-emitting QDs, YQDs) and 647 nm (red-emitting QDs, RQDs) were tested. The Stern-Volmer quenching constant (K_sv) at different temperatures, corresponding thermodynamic parameters (ΔH, ΔG and ΔS), and information of the structural features of BSA were gained. The FL results indicated that QDs can effectively quench the FL of BSA in a size-dependent manner, electrostatic interactions play a major role in the binding reaction, and the nature of quenching is static, resulting in forming QDs-BSA complexes. The CD and ATR-FTIR spectra showed that the secondary structure of BSA was changed by QDs, indicating the toxic on protein.     

Application of 1H-NMR-based metabolomics for detecting injury induced by long-term microwave exposure in Wistar rats’ urine

There has been growing public concern regarding exposure to microwave fields as a potential human health hazard. This study aimed to identify sensitive biochemical indexes for the detection of injury induced by microwave exposure. Male Wistar rats were exposed to microwaves for 6 min per day, 5 days per week over a period of 1 month at an average power density of 5 mW/cm(2) (specific absorption rate of 2.1 W/kg). Urine specimens were collected over 24 h in metabolic cages at 7 days, 21 days, 2 months, and 6 months after exposure. (1)H NMR spectroscopy data were analyzed using multivariate statistical techniques. Urine metabolic profiles of rats after long-term microwave exposure were significantly differentiated from those of sham-treated controls using principal component analysis or partial least squares discriminant analysis. Significant differences in low molecular weight metabolites (acetate, succinate, citrate, ketoglutarate, glucose, taurine, phenylalanine, tyrosine, and hippurate) were identified in the 5 mW/cm(2) microwave exposure group compared with the sham-treated controls at 7 days, 21 days, and 2 months. Metabolites returned to normal levels by 6 months after exposure. These data indicated that these metabolites were related to the perturbations of energy metabolism particularly in the tricarboxylic acid cycle, and the metabolism of amino acids, monoamines, and choline in urine represent potential indexes for the detection of injury induced by long-term microwave exposure.     

不同比例的MEH-PPV与PCBM共混体系光电池性能研究

以MEH-PPV(poly(2-methoxy-5-(2^/-ethylhexoxy)-1,4-phenylene vinylene)为电子给体材料(donor,D), PCBM(1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C₆₁)为电子受体材料(acceptor,A),制成了不同比例的共混体系太阳电池.从不同比例的D/A材料共混体系的原子力图、光荧光谱、器件的单电荷传输的暗导J-V图、太阳电池的光敏图及器件双电荷传输的光、暗导J-V图方面,详细分析了不同比例的D/A材料对器件性能影响.得出了当D/A材料比例为1∶4时,器件中活性层能形成良好的互穿网络,光生激子能有效地分离,被分离的电荷能有效地传输,太阳电池的性能最好.其光电池在100mW/cm²强度光照下,其开路电压V_oc为0.8V,短路电流密度J_sc为3.47mA/cm²,填充因子FF为55.9%,能量转换效率η为1.55%. 关键词： 太阳能电池 聚合物 性能     

铁酸镁超微粒子的制备及结构特征

采用两种方法制得了尖晶石结构纯相MgFe2O4样品．Moessbauer分析发现，一种样品表现出了完全的超顺磁性，另一种表现出了部分超顺磁性．这揭示出了样品具有很小的粒子尺度．首次在实验上发现了MgFe2O4IR-V2谱带的劈裂现象，报导了拉曼光谱，通过ESR分析，进一步揭示了两样品的结构特征，并讨论了性质之间的相关性。     

Fe／ZrO_2气凝胶超细粒子催化剂的制备、表征及F－T反应性能的研究

用超临界流体干燥法制备出大孔高比表面高分散态Ｆｅ／ＺｒＯ_２气凝胶超细粒子催化剂，研究了在其制备过程中织构性质、颗粒大小、体相和表面结构的变化，并与普通浸渍法制备的Ｆｅ／ＺｒＯ_２催化剂作了对比。对几种Ｆｅ／ＺｒＯ_２催化剂的Ｆ－Ｔ反应性能考察表明，Ｆｅ／ＺｅＯ_２气凝胶超细催化剂显示出高的反应活性；随载体ＺｒＯ_２颗粒尺寸减小，活性组分铁的分散度变大，其颗粒尺寸变小，催化剂比表面积增大，反应活性增大，甲烷和低碳烃生成量增加，重质组分减少，认为产物烃分布主要受催化剂活性相颗粒尺寸效应制约。     

氢化物发生石墨炉原位富集直接测定高温镍基合金中碲

通过选择碲的氢化物发生条件，克服了高含量镍对碲的干扰，把氢化物富集在涂钯石墨管里，然后再原子化，成功地测定了高温镍基合金中碲。