排序方式: 共有132条查询结果,搜索用时 15 毫秒
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A supramolecular multiposition rotary device 总被引:1,自引:0,他引:1
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Brian D. Baker Cortés Dr. Mihaela Enache Dr. Kathrin Küster Florian Studener Dr. Tien-Lin Lee Nicolas Marets Prof. Dr. Véronique Bulach Prof. Dr. Mir Wais Hosseini Prof. Dr. Meike Stöhr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12430-12436
The self-assembly of a nickel-porphyrin derivative (Ni-DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni-DPPyP onto Au(111) gave rise to a close-packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two-dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close-packed network and post-deposition annealing at 423 K led to the formation of a Co-coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal-ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni-DPPyP molecule. 相似文献
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The Monoammoniate of Gallium Amide Fluoride, Ga(NH3)(NH2)F2 The oxidation of gallium metal with NH4F leads at 325 °C in the presence of indium to single crystals of Ga(NH2)F2 · NH3 [monoclinic, C2/m (no. 12), a = 1053.1(1), b = 557.4(1), c = 484.2(3) pm, β = 90.04(4)]. The crystal structure is built up from layers of corner-bridged [Ga(NH3)2F4] and [Ga(NH2)2F4] octahedra, respectively. The infrared spectrum proves the existence of the amide group in Ga(NH2)F2 · NH3. 相似文献
94.
The most important characteristic in building acoustics is the transmission loss which describes the insulation performance of a separating component. This quantity is defined by the ratio of inclined sound power to transmitted power. The transmission loss is usually measured in costly experimental set-ups of either real size facilities or down scaled test models. In order to reduce the effort and to gain further insight into the complex behavior of wave propagation in coupled structure-fluid systems, virtual test facilities using numerical methods (FEM) are established. An appropriate determination of the reverberation time is essential for obtaining good quality simulations. The results of the simulated transmission loss are presented and compared with common analytical prediction methods based on the transfer matrix method. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Comparing Ullmann Coupling on Noble Metal Surfaces: On‐Surface Polymerization of 1,3,6,8‐Tetrabromopyrene on Cu(111) and Au(111)
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Dr. Tuan Anh Pham Dr. Fei Song Dr. Manh‐Thuong Nguyen Dr. Zheshen Li Florian Studener Prof. Meike Stöhr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5937-5944
The on‐surface polymerization of 1,3,6,8‐tetrabromopyrene (Br4Py) on Cu(111) and Au(111) surfaces under ultrahigh vacuum conditions was investigated by a combination of scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Deposition of Br4Py on Cu(111) held at 300 K resulted in a spontaneous debromination reaction, generating the formation of a branched coordination polymer network stabilized by C?Cu?C bonds. After annealing at 473 K, the C?Cu?C bonds were converted to covalent C?C bonds, leading to the formation of a covalently linked molecular network of short oligomers. In contrast, highly ordered self‐assembled two‐dimensional (2D) patterns stabilized by both Br?Br halogen and Br?H hydrogen bonds were observed upon deposition of Br4Py on Au(111) held at 300 K. Subsequent annealing of the sample at 473 K led to a dissociation of the C?Br bonds and the formation of disordered metal‐coordinated molecular networks. Further annealing at 573 K resulted in the formation of covalently linked disordered networks. Importantly, we found that the chosen substrate not only plays an important role as catalyst for the Ullmann reaction, but also influences the formation of different types of intermolecular bonds and thus, determines the final polymer network morphology. DFT calculations further support our experimental findings obtained by STM and XPS and add complementary information on the reaction pathway of Br4Py on the different substrates. 相似文献
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Liang Fu Prof. Dr. Meike Niggemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6367-6370
The first transition‐metal‐free carboarylation of alkynes with commercial and readily available alcohols as alkylating agents was realized in the presence of an environmentally benign calcium catalyst. Thereby, a novel protocol for the one‐step synthesis of highly congested, all‐carbon tetrasubstituted alkenes, as incorporated in potentially bioactive, complex dihydronaphthalene, chromene and dihydroquinoline structures, is provided. The reaction features an unprecedented, particularly wide substrate scope, good functional‐group tolerance and simple experimental operation under mild reaction conditions. 相似文献
99.
Cyano‐Functionalized Triarylamines on Coinage Metal Surfaces: Interplay of Intermolecular and Molecule–Substrate Interactions
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Dr. Kathrin Müller Dr. Juan Carlos Moreno‐López Stefano Gottardi Ute Meinhardt Dr. Handan Yildirim Prof. Abdelkader Kara Dr. Milan Kivala Prof. Dr. Meike Stöhr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):581-589
The self‐assembly of cyano‐functionalized triarylamine derivatives on Cu(111), Ag(111) and Au(111) was studied by means of scanning tunnelling microscopy, low‐energy electron diffraction, X‐ray photoelectron spectroscopy and density functional theory calculations. Different bonding motifs, such as antiparallel dipolar coupling, hydrogen bonding and metal coordination, were observed. Whereas on Ag(111) only one hexagonally close‐packed pattern stabilized by hydrogen bonding is observed, on Au(111) two different partially porous phases are present at submonolayer coverage, stabilized by dipolar coupling, hydrogen bonding and metal coordination. In contrast to the self‐assembly on Ag(111) and Au(111), for which large islands are formed, on Cu(111), only small patches of hexagonally close‐packed networks stabilized by metal coordination and areas of disordered molecules are found. The significant variety in the molecular self‐assembly of the cyano‐functionalized triarylamine derivatives on these coinage metal surfaces is explained by differences in molecular mobility and the subtle interplay between intermolecular and molecule–substrate interactions. 相似文献