共查询到20条相似文献,搜索用时 31 毫秒
1.
Er Wei LI Kun GAO Zhong Jian JLA 《中国化学快报》2005,16(9):1230-1232
Two new eremophilenolides, 1β-hydroxy-2β-methylsenecioyloxyeremophil-7 (11)-en- 8β (12)-olide (1), 1β-hydroxy-2β-methylsenecioyloxy-8α-methoxyeremophil-7 (11)-en-8β (12)- olide (2), were isolated from the roots of Cacalia pilgeriana. Their structures were elucidated by spectroscopic methods and X-ray diffraction analysis. 相似文献
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β-二酮钛配合物/甲基铝氧烷催化体系用于苯乙烯的间规聚合 总被引:5,自引:3,他引:5
β 二酮钛配合物/甲基铝氧烷催化体系用于苯乙烯的间规聚合许学翔谢光华(中国科学院化学研究所北京100080)关键词β 二酮钛配合物,苯乙烯,甲基铝氧烷,间规聚合苯乙烯聚合物可分为无规聚苯乙烯(a PS),等规聚苯乙烯(i PS),间规聚苯乙烯(s?.. 相似文献
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以自组装方式在石英晶体谐振器的金电极表面修饰末端含巯基的β 环糊精衍生物(β CDd),用石英晶体微天平(QCM)在线监测α 、β 萘磺酸盐与之发生包结反应的过程,探讨了温度、浓度、取代基位置对包结反应稳定常数Kin和速率常数ka的影响.从理论上推导并通过实验验证了Kin和ka所遵从的关系式.结果表明:所形成的包结配合物中β CDd与萘磺酸盐的化学计量均为1:1;包结配位反应过程符合Langmuir吸附模型;取代基在萘环上的位置对Kin和ka有很大影响,说明不同取代位置的萘磺酸盐与β CDd的包结行为存在明显差异. 相似文献
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Yong Jiao Pin Yang 《中国化学快报》2007,18(3):357-360
The inhibitory mechanism of copper(Ⅱ) on the aggegation of amyloid β-peptide (Aβ) was investigated by molecular dynamics simulations. The binding mode ofcopper(Ⅱ) with Aβ is characterized by the imidazole nitrogen atom, Nπ, of the histidine residue H 13, acting as the anchoring site, and the backbone's deprotoned amide nitogen atoms as the main binding sites. Drove by the coordination bonds and their induced hydrogen bond net, the conformations of Aβ converted from β-sheet non-β-sheet conformations, which destabilized the aggregation of Aβ into fibrils. 相似文献
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The wavelength for the peak of fluorescence emission of thioflavin T(ThT) was changed from 445 nm to 481 nm when ThT was added in Aβ solution which indicating theβ-sheet structure of Aβ fibril.The significant decrease in the intensity of fluorescence at 481 nm was observed when the baicalein was added in mixed solution of Aβ and ThT,suggesting that the depolymerization of Aβ fibrils happened and there were Aβfibrils left to react with ThT to keep the initial fluorescence intensity.And the existing Aβfibrils are disaggregated by baicalein in a time- and dose-dependent manner.AFM images of the morphologies of the Aβ1-42 fibrils obviously changed smaller and more dispersive when baicalein added indicating also the depolymerization of Aβ.The results demonstrate a basis for development of a potential herb drug candidate for the treatment of Alzheimer’s disease(AD). 相似文献
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ZHAO Zhen-Qian CAI Li-Zhen CHEN Wen-Tong GUO Guo-Cong ② HUANG Jin-Shun 《结构化学》2008,27(6):753-756
Two new bimetallic cyano-bridged complexes [Ln(DMSO)2(H2O)(μ-CN)4Fe(CN)2] (Ln = Ce 1, Eu 2) have been prepared by the grinding reaction method and structurally characterized by X-ray single-crystal structure analysis. Crystallographic data for 1: C10H14CeFeN6O3S2, Mr = 526.36, monoclinic, P2/n, a = 7.852(4), b = 10.729(5), c = 11.181(5)A,β = 96.992(8)°, V = 935.0(7) A^3, Z = 2, Dc = 1.870 g/cm^3,/1 = 3.421 mm^-1, F(000) = 512, R = 0.0363 and wR = 0.0971; and those for 2: C10H14EuFeN6O3S2, Mr = 538.20, monoclinic, P21n, a = 7.739(5), b = 10.668(7), c = 11.008(7) A,β = 96.943(3)°, V = 902.1(11) A^3, Z = 2, Dc = 1.981 g/cm^3,/1 = 4.499 mm^-1, F(000) = 522, R = 0.0345 and wR = 0.0855. In each complex the lanthanide ion is seven-coordinated in a pentagonal bipyramidal arrangement, and the Fe(Ⅲ) ion is in a nearly regular octahedral environment. The title complexes can be described as two- dimensional (2-D) stair-like structures, which are further connected by hydrogen bonds to form three-dimensional (3-D) frameworks. 相似文献
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十一钨锌杂多配合物位置异构体的合成、表征及催化性能 总被引:6,自引:0,他引:6
Keggin结构阴离子 SiW12O404-主要有α和β两种异构体。 SiW12O404-由一个中心原子 Si和四个 W3O13集团构成。当四个 W3O13共角相连,并以四面体方式配位于 Si周围就构成了α 异构体( Td对称性),α异构体中的一组 W3O13基团绕 C3轴旋转 60°,则构成了β 异构体( C3V对称性)。在β SiW12O404-结构中存在 3种不同环境的钨原子,当失去一个 WO4+后,可衍生出 3种含有缺位的β i SiW11O398-异构体。若空位位于旋转组的对位,称为β 1 SiW11O398-型体,若空位位于旋转组的相邻的钨原子位置,称为β 2 SiW… 相似文献
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Ng Seik Weng 《结构化学》2009,28(12):1657-1660
The procedure for collecting diffraction data at –173 °C on a twinned specimen of methyl 2-aminopyrazine-3-carboxylate by using the APEX-II software followed by de-twinning the non-merohedrally-twinned reflection data with PLATON is described. De-twinning significantly lowers the R index from 0.141 to 0.038 owing to 49% twinning. Crystal data: C6H7N3O2,monoclinic,P21/c (a = 6.3149(1),b = 16.5274(2),c = 6.4544(1) A,β = 95.759(1)°,V = 670.24(2) A^3). 相似文献
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A new crystal of O,Oˊ-dipropyl-α-(2,4-dichlorolphenoxyacylamido)-α-(4-methoxyphenyl) methylphosphonates has been prepared at room temperature and characterized by elemental analysis and IR,MS,1H NMR spectra,13C NMR spectra and X-ray single-crystal determination.The complex crystallizes in triclinic,space group P1 with a = 7.858(2),b = 12.621(4),c = 12.621(4),α = 96.17(3),β = 90.960(3),γ = 90.960(3)°,V = 1243.9(7)3,Dc = 1.346 Mg/m3,Z = 2,μ = 0.362 mm-1and F(000) = 528. 相似文献
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Adsorption separation of carbon dioxide,methane, and nitrogen on Hβ and Na-exchanged β-zeolite 下载免费PDF全文
Xiaoliang Xu Xingxiang Zhao Linbing Sun Xiaoqin Liu 《天然气化学杂志》2008,17(4):391-396
Adsorption isotherms of carbon dioxide (CO2), methane (CH4), and nitrogen (N2) on Hβand sodium exchanged β-zeolite (Naβ) were volumetrically measured at 273 and 303 K. The results show that all isotherms were of Brunauer type I and well correlated with Langmuir-Freundlich model. After sodium ions exchange, the adsorption amounts of three adsorbates increased, while the increase magnitude of CO2 adsorption capacity was much higher than that of CH4 and N2. The selectivities of CO2 over CH4 and CO2 over N2 enhanced after sodium exchange. Also, the initial heat of adsorption data implied a stronger interaction of CO2 molecules with Na+ ions in Naβ . These results can be attributed to the larger electrostatic interaction of CO2 with extraframework cations in zeolites. However, Naβ showed a decrease in the selectivity of CH4 over N2, which can be ascribed to the moderate affinity of N2 with Naβ. The variation of isosteric heats of adsorption as a function of loading indicates that the adsorption of CO2 in Naβ presents an energetically heterogeneous profile. On the contrary, the adsorption of CH4 was found to be essentially homogeneous, which suggests the dispersion interaction between CH4 and lattice oxygen atoms, and such interaction does not depend on the exchangeable cations of zeolite. 相似文献
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ZHAO Xing-E ;SHANG Pei-Hua ;CHENG Chang-Mei ;CHEN Lang-Qiu ;WANG Ru-Ji ;ZHAO Yu-Fen 《结构化学》2008,27(10):1175-1180
In this paper, 5'-O-tosyl-2,3'-anhydrothymidine has been synthesized and its crystal structure was analyzed. The crystal belongs to the triclinic system, space group P1, with a = 5.397(2), b = 6.1886(18), c = 3.507(5)A, α = 87.74(2),β = 89.84(4),γ = 73.79(2)°, C17H18N2O6S, Mr = 378,39, Z = 1, V = 432.8(3)A^3, Dc = 1.452 g/cm^3, F(000) = 198 and Flack = -0.11(14). No intermolecular hydrogen bonds exist in the crystal, and the angle between benzene ring and pyrimidine planes is 32.23°. 相似文献
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α-蒎烯、β-蒎烯、苧烯阳离子聚合的研究 总被引:1,自引:0,他引:1
比较了萜烯单体α 蒎烯、β 蒎烯、烯的阳离子聚合性能,还考察了这三种单体的活性聚合可能性.在Lewis酸AlCl3作用下,聚合速率大小顺序为:β 蒎烯>烯>α 蒎烯.α 蒎烯、烯的聚合产物分子量较低;β 蒎烯的聚合产物分子量较高.AlCl3与SbCl3复合后,α 蒎烯、烯的聚合速率增加,β 蒎烯的聚合速率反而下降.α 蒎烯的聚合速率增加幅度大于烯,使得前者聚合速率高于后者.与使用AlCl3相比,添加SbCl3后产物的分子量变化是:α 蒎烯变大,烯不变,β 蒎烯则变小.添加SbCl3对β 蒎烯、烯的聚合物结构无影响,而α 蒎烯聚合产物的结构则发生显著变化.活性较高的β 蒎烯在适当的引发体系,如苯乙烯 HCl加成物/TiCl3(OiPr)作用下,可以实现活性聚合.α 蒎烯、烯则由于本身单体活性太小,难以实现活性聚合. 相似文献
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The new title compound 4-dibenzaldehydeamino-4H-1,2,4-triazole diacetate (C16H18N8O4,Mr = 386.38) has been prepared and its crystal structure was determined by single- crystal X-ray diffraction. The crystal is of monoclinic,space group P21/n with a = 8.1371(17),b = 7.1237(12),c = 16.325 (2)A,β = 100.366(2)°,V = 930.9(3) A^3,Z = 2,Dc = 1.378,F(000) = 404,μ = 0.104 mm^-1,MoKa radiation (λ = 0.71073 ),R = 0.0307 and wR = 0.1196 for 4632 observed reflections with I 〉 2σ(I). X-ray diffraction analysis reveals that the molecule is not flat and the crystal structure is stabilized mainly by van der Waals interactions. 相似文献
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A new macrocycle based on diethoxycarbonyl glycoluril 3,C26H30N6O10,has been synthesized and characterized by single-crystal X-ray diffraction. It crystallizes in monoclinic,space group P21/c with a = 12.7291(10),b = 25.157(2),c = 8.5489(7) A,β = 104.4760(10)°,V = 2650.7(4) A^3,Z = 4,C26H30N6O10,Mr = 586.56,F(000) = 1232,T = 292(2) K,Dc = 1.470 g/cm^3,μ = 0.115 mm^-1,the final R = 0.0590 and wR = 0.1299 for 4918 observed reflections with I 〉 2σ(I). In the structure of the title compound,a three-dimensional microporous architecture is formed via intermolecular hydrogen bonding interactions. 相似文献
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A new polyoxometalate comPOund formulated as Na2(C3H5N2)4[MnMo9O32]·2H2O 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum and single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic system, space group C2/c, with a = 16.076(2), b = 14.6488(19), c = 18.767(2)A ,β = 108.6030(10)°, V = 4188.6(9)A^3, C12H24MnMo9NsNa2O34, Mr = 1788.77, Dc = 2.837 g/cm^3,μ(MoKa) = 3.024 mm^-1, F(000) = 3396, Z = 4, the final R = 0.0270 and wR = 0.0605 for 3829 observed reflections (I 〉 2σ(I)). 相似文献
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A pair of E/Z-isomers of 2-phenyl-6,7-dihydrobenzofuran-4(5H)-one O-cyanomethyl oxime,C16H14N2O2,as potential drugs for treating peptic ulcer and other acid-related diseases have been synthesized and characterized by IR,MS and NMR spectra.Meanwhile,the crystal of IIIa was obtained and determined by X-ray single-crystal diffraction.Crystal data: monoclinic system,space group P21 /c,a = 8.423(8),b = 19.596(16),c = 8.770(8),β = 107.750(12)°,V = 1379(2)3,Z = 4,F(000) = 560,Dc = 1.283 g/cm3,μ = 0.086 mm 1,R = 0.0681 and wR = 0.2029 for 14472 independent reflections(Rint = 0.0782) and 2428 observed ones(I 2σ(I)). 相似文献
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CHEN Jun XU Xing-You GAO Jian LI Yan-Hui XU Guo-Xiang 《结构化学》2007,26(6):632-636
A new mononuclear [Zn(H-1L)2] (L = 1H-indole-3-ethylene-salicylaldimine) was synthesized through the reaction of Zn(Ac)2, salicylaldehyde and tryptamine in hot ethanol solution and characterized by X-ray crystal structure analysis. The crystal belongs to monoclinic, space group P21/n with a = 15.014(2), b = 10.857(1), c = 17.489(1)A,β = 95.49(1)°, V = 2837.8(5) A^3, Z = 4, Dc = 1.386 g/cm^3, μ = 0.904 mm-1, F(000) = 1232, the final R = 0.0463 and wR = 0.0890 for 4990 independent reflections. In the complex, the Zn2+ ion presents a distorted N2O2 tetrahedral coordination involving two H-1L ligands. 相似文献