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81.
Bernd GüNTHER 《中国科学B辑(英文版)》2007,50(6)
The interaction between stabilizers and nanoparticles is one of the important factors to prepare stable magnetic fluids. The magnetic nano-size Fe3O4 core with single domain and the average grain size around 8-12 nm were prepared by chemical precipitation method. The O/Fe molar ratio of the particle surface was measured by X-ray photoelectron spectroscopy (XPS). The heat effects of stabilizers ad- sorption on nanoparticles were measured by solution calorimetry. The excess amount of oxygen was possibly the result of the hydroxygen formed on the surface of the nanoparticles. The heat effects showed that compounds containing carboxyl groups can be adsorbed chemically on magnetite by forming chemical bonds. The other stabilizers involving NH-groups, such as polyethylene-imine, can be adsorbed physically. The exothermic value is about half of the former case. 相似文献
82.
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84.
Salama Tarek A. El-Ahl Abdel-Aziz S. Khalil Abdel-Galil M. Girges Margret M. Lackner Bernd Steindl Christian Elmorsy Saad S. 《Monatshefte für Chemie / Chemical Monthly》2003,134(9):1241-1252
Summary. Several new 1-aryl-, aralkyl-, and heteroaryl-5-(4-phenylbuta-1,3-dienyl)tetrazole derivatives and annulated tetrazole derivatives were efficiently and regiospecifically prepared in nearly quantitative yield via a facile one step reaction of dienones with a combination of tetrachlorosilane and sodium azide in acetonitrile under mild conditions. A complete structure assignment of three representative examples of the tetrazoles was achieved by advanced 2D NMR measurements including COSY, TOCSY, HSQC, HMBC, NOESY, and ROESY experiments.Received March 17, 2003; accepted March 18, 2003
Published online July 28, 2003 相似文献
85.
The density-matrix renormalization group algorithm has emerged as a promising new method in ab initio quantum chemistry. However, many problems still need to be solved before this method can be applied routinely. At the start of such a calculation, the orbitals originating from a preceding quantum chemical calculation must be placed in a specific order on a one-dimensional lattice. This ordering affects the convergence of the density-matrix renormalization group iterations significantly. In this paper, we present two approaches to obtain optimized orderings of the orbitals. First, we use a genetic algorithm to optimize the ordering with respect to a low total electronic energy obtained at a predefined stage of the density-matrix renormalization group algorithm with a given number of total states kept. In addition to that, we derive orderings from the one- and two-electron integrals of our test system. This test molecule is the chromium dimer, which is known to possess a complicated electronic structure. For this molecule, we have carried out calculations for the various orbital orderings obtained. The convergence behavior of the density-matrix renormalization group iterations is discussed in detail. 相似文献
86.
(CF3)4Te is formed from the reaction of (CF3)2TeCl2 with (CF3)2Cd·glyme in CH3CN at ?10°C via the intermediate (CF3)3TeCl as a yellow liquid and identified by n.m.r. and mass spectra. 相似文献
87.
Bernd?Lackner Yulita?Popova Christoph?Etzlstorfer Andrija A.?Smelcerovic Christian W.?Klampfl Heinz?FalkEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(5):777-793
Summary. The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1). 相似文献
88.
Marx T Mosel B Pantenburg I Hagen S Schulze H Wesemann L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(18):4472-4478
The tetrasubstituted polyanions of platinum, palladium, and gold [M(SnB(11)H(11))(4)](x-) (x=6, M=Pd, Pt; x=5, M=Au) have been prepared and characterized by single-crystal X-ray diffraction, elemental analysis, IR, Raman, (11)B, and (119)Sn heteronuclear NMR spectroscopy. In the case of the platinum derivative [Bu(3)MeN](6)[Pt(SnB(11)H(11))(4)] (2) (119)Sn M?ssbauer spectroscopy has been carried out. The isolated salts are stable towards moisture and air and the complexes 2 and 3 were treated with 1,3-bis(diphenylphosphino)propane (dppp) to give the respective substitution products [Bu(3)MeN](2)[(dppp)M(SnB(11)H(11))(2)] (M=Pd, Pt). 相似文献
89.
Tarek A. Salama Abdel-Aziz S. El-Ahl Abdel-Galil M. Khalil Margret M. Girges Bernd Lackner Christian Steindl Saad S. Elmorsy 《Monatshefte für Chemie / Chemical Monthly》2003,20(5):1241-1252
Several new 1-aryl-, aralkyl-, and heteroaryl-5-(4-phenylbuta-1,3-dienyl)tetrazole derivatives and annulated tetrazole derivatives were efficiently and regiospecifically prepared in nearly quantitative yield via a facile one step reaction of dienones with a combination of tetrachlorosilane and sodium azide in acetonitrile under mild conditions. A complete structure assignment of three representative examples of the tetrazoles was achieved by advanced 2D NMR measurements including COSY, TOCSY, HSQC, HMBC, NOESY, and ROESY experiments. 相似文献
90.
Bernd G. Müller 《无机化学与普通化学杂志》1982,491(1):245-252
New Fluoropalladates(II) Single crystal investigations on \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {[6][4]} \\ {{\rm CsPdPdF}_{\rm 5} } \\ \end{array} $\end{document} (orange brown) demonstrate the close structural relationship to the CsAgFeF6 – and CsNiNiF6-type, respectively. One half of the Pd2+ ions is surrounded octahedrally, whereas the other half, because of the “absence” of one F?, is coordinated planar quadratically. CsPd2F5 crystallizes orthorhombic (Imma – D, No. 74; Z = 4) with a = 6.533, b = 7.862, c = 10.79 Å (four circle diffractometer data). From Guinier data are isotypic CsMgPdF5 (yellow, a = 6.603(2), b = 7.415(2), c = 10.548(3) Å), CsZnPdF5 (beige, a = 6.576(1), b = 7,483(2), c = 10.645(2) Å), CsNiPdF5 (yellow, a = 6.499(1), b = 7.504(2), c = 10.575(3) Å) and CsCoPdF5 (brown, a = 6.527(1), b = 7.553(1), c = 10.659(2) Å). Besides of CsPd2F5 there exist compounds of the composition Me3PdF5 on the alkali-rich side of the system MeF/PdF2. Single crystal investigations for Rb3PdF3 (yellow, P4/mbm–D, No. 127; Z = 2) led to a = 7.467, c = 6.497 Å (four circle diffractometer data). Isotypic are (single crystal data) Cs3PdF5 (yellow, a = 7.848, c = 6.688 Å) and Rb2CsPdF5 (yellow, ordered distribution of the alkali ions, a = 7.575, c = 6.445 Å). 相似文献