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991.
ShuJieHOU ChuanChunZOU PingShengLEI DeQuanYU 《中国化学快报》2005,16(5):593-596
Using thioglycosides as donors, trimethylsilyl trifluoromethanesulfonate (TMSOTf) and N-iodosuccinimide(NIS) as promoter, a modified procedure for the glycosylation of spirostanol was developed. A series of saponins were synthesized in mild condition with excellent yields. 相似文献
992.
Ten organotin derivatives with dithiocarbamates of the formulae (4‐NCC6H4CH2)2Sn(S2CNEt2)2 (1), (4‐NCC6H4CH2)2Sn(S2CNBz2)2 (2), (4‐NCC6H4CH2)2Sn[S2CN(CH2CH2)2NCH3]2 (3), (2‐ClC6H4CH2)2 Sn(S2CNEt2)2 (4), (2‐ClC6H4CH2)2Sn(S2CNBz2)2 (5), (4‐NCC6H4CH2)2Sn(Cl)S2CNEt2 (6), (4‐NCC6H4CH2)2Sn(Cl)S2CNBz2 (7), (4‐NCC6H4CH2)2Sn(Cl)S2CN(CH2CH2)2NCH3 (8), (2‐ClC6H4CH2)2 Sn(Cl)S2CNEt2 (9) and (2‐ClC6H4CH2)2Sn(Cl)S2CNBz2 (10) have been prepared. All complexes were characterized by elemental analyses, IR and NMR. The crystal structures of complexes 1 and 10 were determined by X‐ray single crystal diffraction. For complex 1, the central tin atom exists in a skew‐trapezoidal planar geometry defined by two asymmetrically coordinated dithiocarbamate ligands and two 4‐cyanobenzyl groups. In addition, because of the presence of close intermolecular non‐bonded contacts, complex 1 is a weakly‐bridged dimer. In complex 10, the central tin atom is rendered pentacoordinated in a distorted trigonal bipyramidal configuration by coordinating with S atoms derived from the dithiocarbamate ligand. In vitro assays for cytotoxicity against five human tumor cell lines (MCF‐7, EVSA‐T, WiDr, IGROV and M226) furnished the significant toxicities of the title complexes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
993.
Assembling Synthesis of ZnSe Orthohexagonal Slices through Emulsion Liquid Membrane System of Gas-liquid Transport 总被引:1,自引:0,他引:1
LuLIU QingShengWU YaPingDING HuaJieLIU 《中国化学快报》2005,16(3):375-378
Orthohexagonal slices assembled by ZnSe quantum dots were synthesized through emulsion liquid membrane system. These orthohexagonal slices were 1.5-3.5 μm in side length and were self-assembled by ZnSe quantum dots of 2-3 nm. It was proposed the surfactant molecules on ZnSe quantum dots played a key role in the self-assembly process. 相似文献
994.
Chun‐Hsiung Chien Yu‐Hsu Chang Chih‐Pin Tsai Chih‐Wei Peng Lung‐Shen Wang Pei‐Sun Sheng Chi‐Young Lee Hsin‐Tien Chiu 《中国化学会会志》2006,53(2):287-292
Black solid precursors obtained from reactions between MCl5 (M = Nb, Ta) and alkyllithiums, n‐butyllithium (nBuLi) and ethyllithium (EtLi), in tetrahydrofuran (THF) were heat treated under vacuum at 673–973 K to form nano‐sized particles (20–100 nm in diameter) of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). Stoichiometry of the reactants is critical and affects the phases of the products. Based on the volatile byproducts detected, a reaction pathway involving the activation of THF by alkyllithiums is proposed to be important for the formation of LiNbO3 and LiTaO3 precursors. 相似文献
995.
Electroluminescent porous Si (PS) diodes exhibit various useful functions under a high-electric field. The experimental PS diodes are composed of thin semitransparent metal films, PS layers (about 500 nm thick in minimum), p- or n-type Si substrates and ohmic back contacts. Definite nonlinear electrical behavior (negative resistance and nonvolatile bistable memory effects) and cold electron emission phenomena appear in these PS diodes associated with the EL emission. Both the negative resistance and memory effects are related to the charging of Si nanocrystallites by field-induced carrier injection. The electron emission observed in the PS diodes formed on n+–Si substrates is caused by hot electrons tunnelling through the top contact. By an appropriate structural control of PS, the effective drift length under a high-field conduction is significantly increased, and then electrons are emitted ballistically. These functions reflect the activity of PS as a nanocrystalline confined system. 相似文献
996.
997.
A new complex {[Na2(H2O)3(µ‐L)2Cu]4}∞ (L = N‐methyliminodiacetic acid) has been synthesized and structurally characterized. The complex crystallizes in the monoclinic, space group C2/c, with the unit cell parameters a = 16.556(3) Å, b = 8.0622(13) Å, c = 12.671(2) Å, α = 90°, β = 95.849(2)°, γ = 90°. The central metal Cu (II) ion is coordinated with two nitrogen atoms and four oxygen atoms belonging to two ligands. Simultaneously, the sodium is six‐coordinated with oxygen atoms coming from the ligand and water molecule; the sodium atoms related are bridged by oxygen atoms, forming a sodium chain. The structure consists of CuL2 moieties linked by sodium chain via the exo oxygen atoms of two ligands, forming a novel three‐dimensional structure. Moreover, elemental analysis, IR, UV‐vis, ESR spectroscopy and thermal stability were determined. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
998.
Chun Lei Sheng‐Xiong Huang Ji‐Jun Chen Jian‐Xin Pu Li‐Mei Li Wei‐Lie Xiao Jin‐Ping Liu Li‐Bin Yang Han‐Dong Sun 《Helvetica chimica acta》2007,90(7):1399-1405
Four new, highly oxygenated nortriterpenoids with the unique schisanartane skeleton, propindilactones A–D ( 1 – 4 ), were isolated from the aerial parts of Schisandra propinqua var. propinqua, together with four known schisanartane‐type compounds. The structures of the new plant constituents were established on the basis of extensive spectroscopic methods. 相似文献
999.
Bingzhi Chen Mingzhong Wang Saihong Sheng Runguang Sun 《European Polymer Journal》2004,40(6):1183-1191
The design, synthesis and characterization of three novel fluorene-alt-thienylenevinylene-based copolymers have been reported. All these polymers consist of similar repeating unit, while thiophene unit with different substitution position is incorporated to well tune the conjugation degree that realizes multi-color luminance. These polymers show emission maxima in the blue, orange and red region of the visible spectrum. Considering the compatibility of luminescent materials with similar structure units, our methodology provides a facile and effective way for designing multi-color luminescent polymeric blending to realize full color electroluminescent (EL) devices. All these polymers have been successfully tested in single-layer sandwiched EL devices. 相似文献
1000.
半平面上有限级Dirichlet级数的正规增长 总被引:23,自引:0,他引:23
本文在一般的指数条件下,研究了右半平面上有限级Dirichlet级数的增长性和正规增长性与它的系数的关系,得到了两个充要条件. 相似文献