排序方式: 共有49条查询结果,搜索用时 578 毫秒
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Lukas Englert Andreas Stoy Dr. Merle Arrowsmith Dr. Jonas H. Muessig Melanie Thaler Andrea Deißenberger Alena Häfner Dr. Julian Böhnke Dr. Florian Hupp Dr. Jens Seufert Dr. Jan Mies Dr. Alexander Damme Dr. Theresa Dellermann Kai Hammond Dr. Thomas Kupfer Dr. Krzysztof Radacki Torsten Thiess Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8612-8622
A series of 22 new bis(phosphine), bis(carbene), and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X=Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X=Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopy, elemental analysis, and, for 20 of these compounds, single-crystal X-ray diffraction, revealing an unexpected variation in the bonding motifs. In addition to the classical B2X4L2 diborane(4) bis-adducts, certain more sterically demanding carbene ligands induce a halide displacement which led to the first halide-bridged monocationic diboron species, [B2X3L2]A (A=BCl4, Br, I). Furthermore, low-temperature 1:1 reactions of B2Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR spectra and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed. 相似文献
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Back Cover: Tailoring Large Pores of Porphyrin Networks on Ag(111) by Metal–Organic Coordination (Chem. Eur. J. 43/2016)
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Saranyan Vijayaraghavan Dr. David Ecija Dr. Willi Auwärter Sushobhan Joshi Dr. Knud Seufert Dr. Mateusz Drach Damian Nieckarz Dr. Paweł Szabelski Dr. Claudia Aurisicchio Prof. Dr. Davide Bonifazi Prof. Dr. Johannes V. Barth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14143-14150
The formation of 2D surface‐confined supramolecular porous networks is scientifically and technologically appealing, notably for hosting guest species and confinement phenomena. In this study, we report a scanning tunneling microscopy (STM) study of the self‐assembly of a tripod molecule specifically equipped with pyridyl functional groups to steer a simultaneous expression of lateral pyridyl–pyridyl interactions and Cu–pyridyl coordination bonds. The assembly protocols yield a new class of porous open assemblies, the formation of which is driven by multiple interactions. The tripod forms a purely porous organic network on Ag(111), phase α, in which the presence of the pyridyl groups is crucial for porosity, as confirmed by molecular dynamics and Monte Carlo simulations. Additional deposition of Cu dramatically alters this scenario. For submonolayer coverage, three different porous phases coexist (i.e., β, γ, and δ). Phases β and γ are chiral and exhibit a simultaneous expression of lateral pyridyl–pyridyl interactions and twofold Cu–pyridyl linkages, whereas phase δ is just stabilized by twofold Cu–pyridyl bonds. An increase in the lateral molecular coverage results in a rise in molecular pressure, which leads to the formation of a new porous phase (ε), only coexisting with phase α and stabilized by a simultaneous expression of lateral pyridyl–pyridyl interactions and threefold Cu–pyridyl bonds. Our results will open new avenues to create complex porous networks on surfaces by exploiting components specifically designed for molecular recognition through multiple interactions. 相似文献
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The pikromycin polyketide synthase (PKS) is unique in its ability to generate both 12 and 14 membered ring macrolactones. As such, dissection of the molecular basis for controlling metabolic diversity in this system remains an important objective for understanding modular PKS function and expanding chemical diversity. Here, we describe a series of experiments designed to probe the importance of the protein-protein interaction that occurs between the final two monomodules, PikAIII (module 5) and PikAIV (module 6), for the production of the 12 membered ring macrolactone 10-deoxymethynolide. The results obtained from these in vitro studies demonstrate that PikAIII and PikAIV generate the 12 membered ring macrocycle most efficiently when engaged in their native protein-protein interaction. Accordingly, the data are consistent with PikAIV adopting an alternative conformation that enables the terminal thioesterase domain to directly off-load the PikAIII-bound hexaketide intermediate for macrocyclization. 相似文献
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K. P. Jochum H.-J. Laue H. M. Seufert A. W. Hofmann 《Analytical and bioanalytical chemistry》1994,350(10-11):642-644
Isotope dilution measurements of geological reference materials are described using a newly developed multi-ion counting (MIC) system for a spark source mass spectrometer. Compared with the conventional photoplate detection system, there are considerably improved analytical features of the MIC system, especially the high sensitivity which leads to short measuring times of 1 min to 1 h for trace element analysis on the μg/g — ng/g level. 相似文献
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The cyclopentadienylboranes I–XI have been synthesized by the reaction of halogenoboranes with cyclopentadienyl-trimethylsilanes, -trimethylstannanes and -lithium compounds. Substitution reactions at the boron atom in III and VIII with tetramethylstannane and dimethylamine lead to the cyclopentadienylboranes XII–XV. The structures of I–XV have been investigated by 1H-, 13C- and 11B-n.m.r. measurements. The 5-trimethylsilyl-cyclopentadienylboranes show a dynamic behaviour due to sigmatropic rearrangements. The influence of a boryl ligand on the speed of these rearrangements is discussed. 相似文献
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Summary In order to avoid the influence of sample heterogeneity, matrix effects and the non-availability of well analyzed standard samples on the precision and the accuracy of spark source mass spectrometric analysis, metal and silicate samples are dissolved chemically. For quantitative analysis, isotope dilution and calibration with standard solutions are used, whereby a precision of better than ±3% and ±8%, respectively, is obtained. This development has improved the precision by about a factor of 3 and increased the reliability of the analysis.
Verbesserung der Genauigkeit und der Richtigkeit der funken-massenspektrometrischen Analyse durch chemisches Auflösen der Probe und Anwendung der Isotopenverdünnungsmethode
Zusammenfassung Um den Einfluß der Probenheterogenität, von Matrixeffekten und des Fehlens von gut analysierten Standardproben auf die Genauigkeit und Richtigkeit der funken-massenspektrometrischen Analyse zu vermeiden, sind metallische und silicatische Proben chemisch gelöst worden. Zur quantitativen Analyse wird die Isotopenverdünnungsmethode und eine Eichung mit Standardlösungen verwendet, wobei eine Genauigkeit von besser als ±3% bzw. ±8% erreicht wird. Diese Entwicklung hat die Genauigkeit gegenüber der direkten Methode um einen Faktor von ungefähr 3 verbessert und die Zuverlässigkeit der Analyse erhöht.相似文献