排序方式: 共有122条查询结果,搜索用时 250 毫秒
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Aleksandr G. Shipov Evgeniya P. Kramarova Elizaveta A. Mamaeva Oksana A. Zamyshlyaeva Vadim V. Negrebetsky Yuri E. Ovchinnikov Sergey A. Pogozhikh Alan R. Bassindale Peter G. Taylor Yuri I. Baukov 《Journal of organometallic chemistry》2001,620(1-2):139-149
Reactions of 2-sila-5-morpholinones, 4-acyl-2-silamorpholines and 4-acyl-2,6-disilamorpholines with electrophilic reagents generally lead to the opening of the sila- or disilacycle by cleavage of the Si–O bond with subsequent rearrangement to form five-membered chelate derivatives where the amide oxygen atoms coordinate with the silicon to form pentacoordinate silicon species. Multinuclear NMR spectroscopy and X-ray diffraction studies were used for structural investigation of the products. 4-Acyl-2,6-disilamorpholines initially form adducts with strong acids where the amide oxygen is protonated by the acid as demonstrated by X-ray crystallography. 相似文献
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Levy E Puzenko A Kaatze U Ben Ishai P Feldman Y 《The Journal of chemical physics》2012,136(11):114503
In this, the second part of our series on the dielectric spectrum symmetrical broadening of water, we consider ionic aqueous solutions. If in Part I, dipole-dipole interaction was the dominant feature, now ion-dipole interplay is shown to be the critical element in the dipole-matrix interaction. We present the results of high-frequency dielectric measurements of different concentrations of NaCl/KCl aqueous solutions. We observed Cole-Cole broadening of the main relaxation peak of the solvent in the both electrolytes. The 3D trajectory approach (described in detail in Part I) is applied in order to highlight the differences between the dynamics and structure of solutions of salts on one hand and dipolar solutes on the other hand. 相似文献
85.
Evgeniya V. Filatova Olga V. Turova Albert G. Nigmatov Sergei G. Zlotin 《Tetrahedron》2018,74(1):157-164
Novel pseudo-enantiomeric bifunctional tertiary amine-squaramides modified with long-chained alkoxy or polyfluoroalkoxy groups, have been synthesized. They catalyzed the asymmetric double-Michael cascade reactions of o-N-tosylaminophenyl α,β-unsaturated ketones with α-nitroolefins in carbon dioxide medium at significantly lower pressure (75 bar) and temperature (35 °C), than known less lipophilic catalysts. Both enantiomers of the pharmacologically valuable methoxy-substituted tetrahydroquinoline derivatives can be prepared in moderate to high yield with promising enantioselectivity (up to 98% ee) under the optimized conditions. 相似文献
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V. V. Chesnokov V. V. Kriventsov S. E. Malykhin A. S. Chichkan O. Yu. Podyacheva 《Journal of Structural Chemistry》2018,59(4):839-846
The paper considers the system of nitrogen-doped carbon nanofibers (N-CNFs) with palladium atoms deposited on their surfaces. The concentration of deposited palladium varied in the interval of 0.05-0.6 wt.%. The state of palladium was studied with the methods of quantum chemistry, electron microscopy, CO adsorption, and EXAFS. Carbon structures that contain porphyrin-like defects with four nitrogen atoms in the graphene layer interact strongly with palladium atoms and therefore can be stabilization centers of atomic palladium. 相似文献
88.
Galina L. Starova Anna S. Denisova Evgeniya M. Demyanchuk 《Journal of Molecular Structure》2007,830(1-3):139-142
The structures of 3,3′-dicarbometoxy-2,2′-bipyridine (dcmbpy) complexes with copper(II) and silver(I) cations have been determined using single crystal X-ray-diffraction. The crystals of Cu(dcmbpy)Cl2 are monoclinic, C2/c, a = 16.966(3), b = 18.373(3), c = 13.154(2) Å, β = 126.543(3)°. The crystals of Ag(dcmbpy)NO3 · H2O are also monoclinic, C2/c, a = 16.7547(13), b = 11.0922(9), c = 18.7789(18) Å, β = 100.228(7)°. The results have been compared with the literature data on the complexes of dcmbpy and its precursors: 2,2′-bipyridine (bpy) and 3,3′-dicarboxy-2,2′-bipyridine (dcbpy). Two types of complexes of 3,3′-carboxy derivatives of bpy are distinguished: (1) with metal atom bonded to two N atoms of the same molecule and (2) with metal atom bonded to two N atoms of two different molecules. The Cu(dcmbpy)Cl2 complex belongs to the first type, whereas Ag(dcmbpy)NO3 · H2O belongs to the second type. 相似文献
89.
Konarev DV Kovalevsky AY Lopatin DV Umrikhin AV Yudanova EI Coppens P Lyubovskaya RN Saito G 《Dalton transactions (Cambridge, England : 2003)》2005,(10):1821-1825
The first molecular complex of fullerene C60 with metal dithiocarbamate, namely, {CuII(dedtc)2}2.C60(dedtc: diethyldithiocarbamate) (1) was obtained as single crystals. Butterfly-shaped CuII(dedtc)2 molecules efficiently co-crystallized with spherical fullerene molecules to form a layered structure, in which closely packed hexagonal C60 layers alternate with the layers composed of CuII(dedtc)2 dimers. The formation of the complex with C60 changes geometry and the EPR spectrum of starting CuII(dedtc)2. Magnetic susceptibility of 1 follows the Curie-Weiss law in the 300-1.9 K range with the negative Weiss constant of -2.5 K showing a weak antiferromagnetic interaction between CuII centers in the dimers. The crystals of 1 have low dark conductivity of 10(-11) S cm-1, which is consistent with a neutral ground state of the complex. Illumination of the crystals by white light increases the photocurrent by 20-50 times. The photoconductivity spectrum of 1 has a maximum at 470 nm showing that both intermolecular charge transfer between neighboring C60 molecules and photoexcitation of CuII(dedtc)2 can contribute to photogeneration of free charge carriers. The effect of a weak magnetic field with Bo<0.5 T on the photoconductivity of 1 has been found. 相似文献
90.
We study the dynamics of multielement neuronal systems taking into account both the direct interaction between the cells via linear coupling and nondiffusive cell-to-cell communication via common environment. For the cells exhibiting individual bursting behavior, we have revealed the dependence of the network activity on its scale. Particularly, we show that small-scale networks demonstrate the inability to maintain complicated oscillations: for a small number of elements in an ensemble, the phenomenon of amplitude death is observed. The existence of threshold network scales and mechanisms causing firing in artificial and real multielement neural networks, as well as their significance for biological applications, are discussed. 相似文献