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991.
I. G. Voigt-Martin Z. X. Zhang D. H. Yan A. Yakimanski R. Matschiner P. Krämer C. Glania R Wortmann N. Detzer D. Schollmeyer 《Colloid and polymer science》1997,275(1):18-37
4-Dimethylamino-3-cyanobiphenyl (4-DMA-3-CB) was characterized with respect to linear and nonlinear optical properties in
a crystal as well as in solution. The crystal structure was studied dependent on the crystallization conditions. It is shown
that the crystal structure exhibiting NLO-activity can completely be solved by a combination of electron diffraction and computer
modeling. There are four molecules per unit cell in the space group Pna21 with dimensions a=10.28 Å, b=22.64 Å, c=5.27 Å. From this model structure the values and orientation of the dipole μ and static second order polarizability β can
be calculated. Their relevance to the values obtained by a combination of polarization dependent measurements of Electric
Field Induced Second Harmonic Generation (EFISH) and Hyper-Rayleigh-Scattering (HRS) in solution are discussed. The molecular
second order polarizability tensor was found to be dominated by one single component. The orientations of the dipole and the
vectorial parts of the second order polarizability delivered by the semiempirical calculations are in good agreement with
the results of the EFISH and HRS-measurements and allow a deeper insight into the nonlinear optical properties of the crystal.
Received: 15 April 1996 Accepted: 21 June 1996 相似文献
992.
仲碳伯胺萃淋树脂吸萃金的性能及机理 总被引:3,自引:0,他引:3
研究了仲碳伯胺(N1923)萃淋树脂吸萃金的机理,溶液酸效应、吸附等温线、吸附速率、盐析剂效应及柱操作条件的影响等,将该树脂用于矿样中金含量的测定,结果与717^#离子交换树脂吸附法一致,取得了较好的结果。 相似文献
993.
A new reagent proflavine-N, N, N', N'-tetraacetic acid (PTA) synthesized in our laboratory has been found useful as a chemiluminescence reagent for the determination of ruthenium (Ru) in pH 2.5 sulfuric acid solution containing acetone, it can be oxidized catalytically by hydrogen peroxide. With Ru(III) as catalyst, it emits light selectively. The linear range is between 2.0 x 10(-8) and 2.0 x 10(-5) g/ml. The detection limit and the recovery rate of the method are 1.0 x 10(-9)g/ml and 96.0-102%, respectively. The method has been satisfactorily applied to determine trace Ru(III) in synthesized sample. 相似文献
994.
超声波作用下羰基化合物的还原偶联反应 总被引:5,自引:0,他引:5
超声波在一些有机反应中有明显的促进作用「“,Luche等认为超声波的作用有两种主要类型[’j.一类是涉及电子转移的自由基或离子一自由基型反应,由于超声波的空化作用所产生的局部高温高压可以促进电子转移,从而明显地加快反应速度;对大多数离子型反应,超声波只能起到机械的物理作用.我们曾报道偕二卤化合物在Li、Na、Mg等金属作用下产生卡宾的反应是单电子转移过程,该反应可由于超声辐射而大大加速[‘];而在芳基叔脚的断裂反应中,超声波可以促进三苯基俄与金属馊反应生成二苯基脚负离子,但对它进一步的亲核取代反应却没有明… 相似文献
995.
996.
A nickel catalyst was nodeled with ligand L^2,[NH=CH-CH=CH-0]^-,which should have potential use as a syndiotactic plyolefin catalyst,and the reaction mechanism was studied by theoretical calculations using the density functinal method at the B3LYP/LANL2MB level.The mechanism involves the formation of the intermediate [NiL^2Me]^ ,in which the metal occupies a T-shaped geometry.This intermediate has two possible structures with the methyl group trans either to the oxygen or to the nitrogen atom of L^2.The results show that both structures can lead to the desired product via similar reaction paths,A and B.Thus,the polymerization could be considered as taking place either with the alkyl group occupying the position trans to the Ni-0 or trans to the Ni-N bond in the catalyst.The polymerization process thus favors the catalysis of syndiotactic polyolefins.The syndiotactic synthesis effects could also be enhanced by varations in the ligand substituents.From energy considerations,we can conclude that it is more favorable for the methyl ttrans-O position to form a complex than to occupy the trans-N position.From bond length considerations,it is also more favoured for ethene to occupy the trans-O position than to occupy the trans-N position. 相似文献
997.
998.
The novel complex [K(18-C-6)]2[Cd(mnt)2][18-C-6-18-crown-6,nmt=1,2-dicyanoethene-1,2-dithiolate,C2S2-(CN)2^2-] was synthesized and characterized by elemental analysis,IR spectrum and X-ray diffraction analysis.The complex displays two-dimensional network structure of [K(18-C-6)] complex segments and [Cd(nmt)2] complex segment bridged by S-K-S,S-K-N and N-K-N interactions between adjacent[K(18-C-6)] and [Cd(mnt)2]units. 相似文献
999.
A Minor New Flavone from Scutellaria baicalensis Georgi 总被引:1,自引:0,他引:1
A new flavone,6,2′-dihydroxy-5,7,8,6′-tetramethoxyflavone,was isolated from the roots of Scutellaria baicalensis. Its structure was established on the basis of spectral evidences. 相似文献
1000.
钯的高选择性流动注射分析方法的研究 总被引:2,自引:0,他引:2
Pd(Ⅱ)与DBC-偶氮氯膦在硫酸介质中经加热发生络合显色反应,将此显色反应与流动注射分析技术结合,研究了影响该流动注射显色体系的各种因素,建立了钯的流动注射分析方法.用该方法可不经分离直接测定二次阳极泥和氯化渣中的钯. 相似文献