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Karlheinz Schüffler 《Archiv der Mathematik》1986,47(4):359-366
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An alternative model of the hexagonal boron nitride (h-BN) on nanomesh on the Rh(111) surface is presented. It explains the observed ultraviolet photoelectron spectroscopy spectra and reproduces experimental STM images introducing, instead of two, only one strongly corrugated layer of h-BN covering the whole Rh surface. In order to optimize the geometry of the BN layer we calculate the forces by density functional theory and analyze the interactions in the system. The final geometry is a result of a competition between BN-metal attraction or repulsion and elastic properties of the isolated h-BN layer. The calculated bonding energy is around 0.33 eV per BN molecule with a corrugation close to 0.55 A. 相似文献
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Synthesis of 2‐Unsubstituted 1,3‐Selenazoles by Cyclization of Selenoformamide with α‐Bromocarbonyl Compounds
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Harald Below Wolf‐Diethard Pfeiffer Karlheinz Geisler Ashot S. Saghyan Christine Fischer Peter Langer 《Journal of heterocyclic chemistry》2015,52(2):592-596
2‐Unsubstituted 1,3‐selenazoles were prepared by cyclization of selenoformamide with α‐bromoacetophenones. Parent 1,3‐selenazole was prepared by cyclization of selenoformamide with α‐bromoacetaldehyde. 相似文献
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Cyclometalated Iridium(III) Complexes Containing Semicarbazone Ligands: Synthesis,Characterization, Photophysical and Biological Studies
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Marion Graf Yvonne Gothe Nils Metzler‐Nolte Rafał Czerwieniec Karlheinz Sünkel 《无机化学与普通化学杂志》2015,641(10):1798-1802
The synthesis, crystal structure, photophysical properties, and biological activity of the novel bis‐cyclometalated complexes [Ir(ptpy)2(vnsc)] ( 2 ) and [Ir(ptpy)2(acsc)] ( 3 ) [ptpy = 2‐(p‐tolyl)pyridinato, vnsc = vanillin semicarbazone, acsc = acetone semicarbazone] are described. The new compounds were prepared by the reaction of [{Ir(μ‐Cl)(ptpy)2}2] ( 1 ) with the corresponding semicarbazone ligands under basic conditions. The molecular structure of compound 3 was confirmed by a single‐crystal X‐ray diffraction study. The complex crystallized from chloroform as a mono‐ solvate in the orthorhombic space group Pcab with eight molecules in the unit cell. 相似文献
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We propose a new notion of variable bandwidth that is based on the spectral subspaces of an elliptic operator where p > 0 is a strictly positive function. Denote by the orthogonal projection of Ap corresponding to the spectrum of Ap in ; the range of this projection is the space of functions of variable bandwidth with spectral set in Λ. We will develop the basic theory of these function spaces. First, we derive (nonuniform) sampling theorems; second, we prove necessary density conditions in the style of Landau. Roughly, for a spectrum the main results say that, in a neighborhood of , a function of variable bandwidth behaves like a band‐limited function with local bandwidth . Although the formulation of the results is deceptively similar to the corresponding results for classical band‐limited functions, the methods of proof are much more involved. On the one hand, we use the oscillation method from sampling theory and frame‐theoretic methods; on the other hand, we need the precise spectral theory of Sturm‐Liouville operators and the scattering theory of one‐dimensional Schrödinger operators. © 2017 Wiley Periodicals, Inc. 相似文献
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Monobromoferrocene (1) was obtained in 95% yield from ferrocene via lithiation with tert-BuLi/KO-tert-Bu and bromination with dibromotetrachloroethane. Starting from 1 mixtures of 1,2-dibromoferrocene (2) and apparently unreacted 1 (ranging from 80:20 to 50:50, depending on the reaction conditions) can be obtained via a lithiation- zincation- bromination sequence. These mixtures can be transferred directly with a tenfold excess of Lithium-tetramethylpiperidinide, followed by bromination with 1,1,2,2-tetrabromoethane to pentabromoferrocene (3), in an overall yield of 36% starting from ferrocene. The molecular structures of 3 and of 1,2,3-tribromoferrocene (4) have been determined by X-Ray diffraction. 相似文献
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