磁性高分子链的磁性质和构象性质的Monte Carlo模拟

采用退火 (Annealing)MonteCarlo方法 ,从高温到低温顺序模拟了简立方格点上考虑最近邻Ising相互作用的磁性高分子链在不同温度的磁性质和构象性质 .磁性高分子链在低温下存在自发磁矩 ,无限长链的临界温度Tc=1 77± 0 0 5J kB.在临界温度附近 ,高分子链经历了从伸展的无规线团到紧缩球体的塌缩相变 .对链的尺寸、形状、近邻数及能量的分析表明 ,高分子链的构象性质从温度Tc=1 77开始发生较明显的变化 ,这表明高分子Ising链的相变是Ising相互作用和链节运动协同作用的结果 .     

Two New Diterpenoids from Callicarpa pedunculata

Two new diterpenoids, pedunculatic acid A (= (4R,5α,7α)‐7‐ethoxy‐9β,13β‐dioxyabiet‐8(14)‐en‐18‐oic acid; 1 ) and pedunculatic acid B (= (4S,5α,12β)‐8β,14β‐epoxy‐12‐hydroxy‐11‐oxototaran‐19‐oic acid; 2 ), together with three known sesquiterpenoids, were isolated from the Chinese medicinal herb Callicarpa pedunculata R. Brown . Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR, and by high‐resolution mass spectrometry.     

C2-symmetric bis(oxazolinato)lanthanide catalysts for enantioselective intramolecular hydroamination/cyclization

C(2)-symmetric bis(oxazolinato)lanthanide complexes of the type [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), [(4S,5R)-Ar(2)Box]La[N(TMS)(2)](2), and [(4S)-Ph-5,5-Me(2)Box]La[N(TMS)(2)](2) (Box = 2,2'-bis(2-oxazoline)methylenyl; Ar = 4-tert-butylphenyl, 1-naphthyl; TMS = SiMe(3)) serve as precatalysts for the efficient enantioselective intramolecular hydroamination/cyclization of aminoalkenes and aminodienes. These new catalyst systems are conveniently generated in situ from the known metal precursors Ln[N(TMS)(2)](3) or Ln[CH(TMS)(2)](3) (Ln = La, Nd, Sm, Y, Lu) and 1.2 equiv of commercially available or readily prepared bis(oxazoline) ligands such as (4R,5S)-Ph(2)BoxH, (4S,5R)-Ar(2)BoxH, and (4S)-Ph-5,5-Me(2)BoxH. The X-ray crystal structure of [(4S)-(t)BuBox]Lu[CH(TMS)(2)](2) provides insight into the structure of the in situ generated precatalyst species. Lanthanides having the largest ionic radii exhibit the highest turnover frequencies as well as enantioselectivities. Reaction rates maximize near 1:1 BoxH:Ln ratio (ligand acceleration); however, increasing the ratio to 2:1 BoxH:Ln decreases the reaction rate, while affording enantiomeric excesses similar to the 1:1 BoxH:Ln case. A screening study of bis(oxazoline) ligands reveals that aryl stereodirecting groups at the oxazoline ring 4 position and additional substitution (geminal dimethyl or aryl) at the 5 position are crucial for high turnover frequencies and good enantioselectivities. The optimized precatalyst, in situ generated [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), exhibits good rates and enantioselectivities, comparable to or greater than those achieved with chiral C(1)-symmetric organolanthanocene catalysts, even for poorly responsive substrates (up to 67% ee at 23 degrees C). Kinetic studies reveal that hydroamination rates are zero order in [amine substrate] and first order in [catalyst], implicating the same general mechanism for organolanthanide-catalyzed hydroamination/cyclizations (intramolecular turnover-limiting olefin insertion followed by the rapid protonolysis of an Ln-C bond by amine substrate) and implying that the active catalytic species is monomeric.     

单分散磁性P(St/BA/MAA)微球的制备

在共沉淀法合成超细磁流体的基础上 ,以苯乙烯 (St)、丙烯酸丁酯 (BA)和甲基丙烯酸 (MAA)为共聚单体 ,在不同的介质体系中采用无皂乳液聚合法制备了单分散 ,粒径范围为 80～ 2 30nm的磁性P(St BA MAA)微球 .详细探讨了介质极性、磁流体中表面活性剂含量对磁性高分子微球粒径和单分散性的影响 .实验结果表明 ,在一定范围内随介质极性降低 ,磁性高分子微球的单分散性提高 ,随表面活性剂用量增加 ,单分散性变差 .总体来看 ,磁性高分子微球的单分散性与其表面静电斥力密切相关 ,过大或过小的静电斥力均会导致磁性高分子微球单分散性的降低 .     

Resonance Rayleigh scattering, frequency doubling scattering and second-order scattering spectra of the heparin-crystal violet system and their analytical application

In pH 6.0-11.2 Britton-Robinson buffer solution, binding of heparin with crystal violet (CV) can result in a significant enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering, such as frequency doubling scattering (FDS) and second-order scattering (SOS). Their maximum scattering wavelengths, λ_ex/λ_em, appear at 492 nm/492 nm for RRS, 984 nm/492 nm for FDS and 492 nm/984 nm for SOS, respectively. The optimum conditions of the reaction, the influencing factors and the relationship between the three scattering intensities and the concentration of heparin have been investigated. New methods for the determination of trace amounts of heparin based on the RRS, FDS and SOS methods have been developed. The methods exhibit high sensitivities, the detection limit for heparin is 2.9 ng ml⁻¹ for the RRS method, 3.5 ng ml⁻¹ for the FDS method and 3.3 ng ml⁻¹ for the SOS method. The methods have good selectivity and were applied to the determination of heparin in heparin sodium injection samples with satisfactory results.     

合成甲醇的催化剂Rh-ZnO/MWNTs的研究

研究新型的由多壁碳纳米管(MWNTs)负载的， ZnO助催的铑基甲醇合成催化剂. 当铑含量达到4％(w)时，催化剂具有较高的比表面积(99.6 m2•g－1), 催化剂的反应活化能为68.8 kJ•mol－1.在563 K, 1 MPa下，催化剂的最高催化活性和甲醇选择性分别为411.4 mg/gcat.•h和96.7％. TEM、TPR和TPD等表征结果显示，碳纳米管能增加Rh在催化剂表面的分散度，提高催化剂的还原温度并能增加氢物种的吸附量，这些结果将有助于更好地了解催化剂中各组分间的协同作用和催化活性中心本质.     

Synthesis of Derivatives of Pyrido[4,3‐d]pyrimidin‐4(3H)‐one via an Iminophosphorane

A series of new, 2‐substituted 3‐aryl‐8,9,10,11‐tetrahydro‐5‐methyl[1]benzothieno[3′,2′ : 5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐ones, compounds 5a – q , were designed and synthesized via the aza‐Wittig reaction as the key step. The iminophosphorane 1 reacted with phenyl isocyanate (or 4‐chlorophenyl isocyanate) to the carbodiimide 4 , which was cyclized to 5 upon addition of different amines, EtOH, or phenols in the presence of a catalytic amount of EtONa or K₂CO₃ (Schemes 1 and 2). The structures of compounds 5 were confirmed by IR, ¹H‐ and ¹³C‐NMR, EI‐MS, elemental analyses, and, in the case of 5l , by single‐crystal X‐ray diffraction (Figure).     

A new rubidium beryllium borate,RbBe4(BO3)3

Single crystals of a new rubdidium beryllium borate, RbBe₄(BO₃)₃, have been obtained by spontaneous nucleation from a high‐temperature melt. This new ortho­rhom­bic (Pnma) structure type contains [Be₂BO₄]⁻ rings, made of two BeO₄ tetra­hedra and one BO₃ triangle, which constitute the basic structural units. The m plane runs through the B and one of the O atoms and intersects the ring. These rings form chains in the a direction, which are connected in the b and c directions to form zeolite‐type cages in which the Rb⁺ cations are located, at sites of m symmetry.     

稳态荧光探针法测定三聚季铵盐表面活性剂的胶束聚集数

以芘为荧光探针, 十六烷基氯化吡啶(CPC)为猝灭剂, 以芘的饱和水溶液为溶剂配制表面活性剂溶液, 根据芘的荧光强度之比I1/I3随表面活性剂水溶液浓度的变化, 测定了三聚季铵盐表面活性剂CTTTA的cmc值, 测定值与表面张力法测定的cmc值一致；当猝灭剂CPC的浓度取0.1~0.3 mmol·L-1范围时, 用稳态荧光探针法测定了CTTTA的胶束聚集数. 实验数据表明, 表面活性剂溶液浓度为6~10倍cmc时, 胶束聚集数N随表面活性剂浓度增大而线性增大, 并用外推法得到CTTTA的临界胶束聚集数.     

平行光栅对在刻线不平行时的色散研究

 利用三维空间光线追迹法，分析了啁啾脉冲放大系统中的压缩光栅对，在刻线不平行而光栅面平行时光的衍射特性。导出了此时光通过光栅对的群延时，数值计算了系统2阶和3阶色散量，以及这些色散量在光栅对严格平行时的相对误差。得出了中心波长光的接收位置相对于光栅对严格平行时的偏移量，并且分析了它与入射角的变化关系。