四价锗与3, 4－二羟墓苯甲醛配合物的极谱研究

本文采用极谱法研究了Ge(Ⅳ)-3,4-二羟基苯甲醛(DHB)配合物的组成,条件稳定常数.并对该配合物的极谱波性质进行了研究.     

Application of symplectic algorithms to QCT calculation:H+H_2 system

The basic theory of symplectic algorithm was introduced. A comparison between Runge-Kutta method and symplectic integration method was preformed in the simulation of the long time behavior of H + H2 system on BKMP potential energy surface. Our results reveal a dis-sipative behavior in the integral of ordinary differential equation by the fourth order Runge-Kutta method, which causes incorrect simulation results in QCT calculations. However, when the symplectic integration method is applied, the dissipative behavior is not found in the same system. When the initial state is the same, the energy deviation of fourth order symplectic integral method is almost one percent of that of fourth order Runge-Kutta method in a 60000-step simulation, and that of sixth order symplectic integral method is much less. These results show that the symplectic integral methods are always the better choice in the integral calculation of the long time behavior in maintaining energy conservation.     

蒿甲醚在模拟体内酸碱环境中的代谢动力学研究

 利用高效液相法对蒿甲醚进行了模拟体内酸碱环境的代谢动力学研究 ,测定了蒿甲醚及其代谢产物双氢青蒿素、蒿甲醚呋喃酯的代谢曲线。结果表明 ,蒿甲醚在模拟体内肠道和血液的弱碱性环境条件下半衰期为2 87 2min(计算值 ) ;在模拟体内胃液的酸性环境条件下半衰期为 74 6min ;在两种条件下的主要代谢产物均为双氢青蒿素和蒿甲醚呋喃酯。该方法克服了以往文献所报道方法的一些缺点 ,不仅简化了样品制备方法 ,也提高了检测结果的准确性。     

Microstructure and Ion Exchange in Stearic Acid Langmuir-Blodgett Films Studied by Fourier Transform Infrared-Attenuated Total Reflection Spectroscopy

Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectra have been recorded of 11-layer Langmuir-Blodgett (LB) films of stearic acid deposited at various surface pressures (0.1, 15, and 35 mN/m), and the molecular orientation angles were evaluated quantitatively, which supplied insight into the molecular order with the alkyl chains tightly packed like crystal in the LB films deposited at the zero and higher surface pressures. These experimental results indicate that, in the Langmuir film as the precursor of LB films, stearic acid molecules self-aggregate to form two-dimensional crystalline domains already even at the zero surface pressure, which results in the inhomogeneity of monolayer. The analysis of dependence of nu(C=O) intensity on the surface pressure, surface density, and subphase temperature leads to the conclusion that the defects in LB films originate from the Langmuir film and be conserved upon deposition. Annealing below 50 degrees C and cooling could improve the monolayer homogeneity, and thus a defect-free or low-defect LB films can be deposited. Furthermore, ion exchange conducted in the LB films, on the other hand, confirms the existence of structure defects in LB films of stearic acid. The polar plane microstructure, lateral transport along the polar planes and the coordination types of stearic acid/cation system may be the rate-limiting process. The results have implication on the possible uses of stearic acid LB films as ion-exchange materials or sensors. Copyright 2001 Academic Press.     

Constructing chiral diazoacetoacetates by enantioselective catalytic Mukaiyama aldol reactions

Asymmetric catalysis of Mukaiyama aldol addition reactions of methyl 3-TMSO-2-diazo-3-butenoate 4 with aromatic aldehydes using AgF/(R)-BINAP at −20 °C produces chiral diazoacetoacetates in high chemical yields and with high enantiocontrol.     

无机分子纳米材料的研究进展

无机分子纳米材料是至少在一个维度上为纳米尺寸的分子及以其为单元组成的材料。由于其特殊的结构和性质，这种材料可以作为未来纳米分子电子器件、小分子吸附及储存材料。本文将从合成、结构、性质、应用等方面, 结合最新进展对这一充满活力并有着应用前景的领域作一简要概述。     

Ab initio study of the electronic spectrum of dichlorocarbene CCl2

The equilibrium geometries, excitation energies, force constants and vibrational frequencies for seven low-lying electronic states X ¹A₁, ¹B₁, ³B₁, ¹A₂, ³A₂, ¹B₂ and ³B₂ of dichlorocarbene CCl₂ have been calculated at the MRSDCI level with a double-zeta plus polarization basis set. Our calculated equilibrium geometry for the X ¹A₁ state, excitation energy for X ¹A₁ → ¹B₁ and vibrational frequencies for the X ¹A₁ and ¹B₁ states are in good agreement with experimental data. The electronic transition dipole moments, oscillator strengths for the ¹B₁ → X ¹A₁ and ¹B₂ → X ¹A₁ transitions, radiative lifetimes for the ¹B₁ and ¹B₁ states are calculated using MRSDCI wavefunctions, predicting results in reasonable agreement with experiment.     

Quality evaluation of Flos lonicerae through a simultaneous determination of seven saponins by HPLC with ELSD

A new HPLC coupled with evaporative light scattering detection (ELSD) method has been developed for the simultaneous quantitative determination of seven major saponins, namely macranthoidin B (1), macranthoidin A (2), dipsacoside B (3), hederagenin-28-O-beta-D-glucopyranosyl(6-->1)-O-beta-D-glucopyranosyl ester (4), macranthoside B (5), macranthoside A (6), and hederagenin-3-O-alpha-L-arabinopyranosyl(2-->1)-O-alpha-L-rhamnopyranoside (7) in Flos Lonicerae, a commonly used traditional Chinese medicine (TCM) herb. Simultaneous separation of these seven saponins was achieved on a C18 analytical column. The mobile phase consisted of (A) acetonitrile-acetic acid (95:0.5) and (B) 0.5% aqueous acetic acid using a gradient elution of 29%A at 0-10 min, 29-46%A at 10-25 min and 46%A at 25-30 min. The drift tube temperature of ELSD was set at 106 degrees C, and with the nitrogen flow-rate of 2.6 l/min. All calibration curves showed good linear regression (r2>0.9922) within test ranges. This method showed good reproducibility for the quantification of these seven saponins in Flos Lonicerae with intra- and inter-day variations of less than 3.0% and 6.0%, respectively. The validated method was successfully applied to quantify seven saponins in five sources of Flos Lonicerae, which provides a new basis of overall assessment on quality of Flos Lonicerae.     

12-钼磷酸与γ-Al2O3载体的相互作用

应用酸碱滴定、X射线衍射(XRD)、激光拉曼(LRS)和顺磁共振(EPR)等方法研究了磷钼酸(PMo_(12))与γ-Al_2O_3载体间的相互作用．结果表明，PMo_(12)在γ-Al_2O_3上随负载量增加出现三种不同的分散状态，据此提出了PMo_(12)在γ-Al_2O_3上的铺展模型．     

Preparation and electrochemistry of azobenzene self-assembled monolayers on gold--long range tunneling and end-group hydrogen bonding effect

A series of thiol-functionalied azobenzene derivatives (RAzoCnSH: R=H for n=3-6, abbreviated as AzoCnSH; R=CH(3)CONH for n=4, abbreviated as aaAzoC4SH) on gold electrodes were prepared and their self-assembly and electrochemical properties were studied by cyclic voltammetry. They all formed uniform and reproducible self-assembled monolayers (SAMs) on gold and showed well-behaved voltammetric responses in aqueous solution. Both the length of the alkyl chain spacer and the H-bonding of the end acetamino group had effects on the stability and the electrochemical kinetics of the SAMs, and the effect of the H-bonding was dominant. The surface coverage of the SAMs (AzoCnSH) is gradually increased with an increase of the alkyl chain spacer length, whereas the presence of the terminal acetamino group leads to a greater increase of the surface coverage. At a low scan rate, voltammetric responses corresponding to an irreversible two-electron, two-proton reduction/oxidation of the trans-azobenzene redox center were obtained in the range of +300 mV and -800 mV, which exhibited very large peak-to-peak splitting. At a high scan rate of 500 mV/s, two steps of reversible one-electron, one-proton reduction/oxidation corresponding to the cis-isomer in azobenzene-thiol SAMs (n is odd) was clearly observed between +300 and -200 mV. The apparent electron-transfer rate is decreased with increasing distance between the azobenzene redox center and the gold electrode. The existence of the end acetamino group which restricted the conformational change during the redox process also led to a decrease of the standard rate constant, and this restriction effect is more predominant than the distance effect.