排序方式: 共有132条查询结果,搜索用时 15 毫秒
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Marian Rauser Raphael Eckert Max Gerbershagen Meike Niggemann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6785-6789
A rare reductive coupling of nitro compounds with organohalides has been realized. The reaction is initiated by a partial reduction of the nitro group to a nitrenoid intermediate. Therefore, not only aromatic but also aliphatic nitro compounds are efficiently transformed into monoalkylated amines, with organohalides as the alkylating agent. Given the innate reactivity of the nitrenoid, a catalyst is not required, resulting in a high tolerance for aryl halide substituents in both starting materials. 相似文献
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Meike Niggemann 《Nachrichten aus der Chemie》2007,55(10):1053-1054
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Charan Krishna Nichenametla Jesus Calvo Stefan Riedel Lukas Gerlich Meike Hindenberg Sergej Novikov Alexander Burkov Primož Kozelj Raul Cardoso-Gil Maik Wagner-Reetz 《无机化学与普通化学杂志》2020,646(14):1231-1237
Abstract . We report on semi-metallic cobalt monosilicide (CoSi) as a CMOS-compatible thermoelectric (TE) material and discuss the effect of n- and p-type dopants on its transport properties. Thin films of CoSi are developed using chemical vapor deposition tools and subsequent rapid thermal processing. Film properties such as microstructure, crystallinity and elemental distribution are studied via electron microscopy, X-ray diffraction and time-of-flight secondary ion mass spectroscopy. Doping silicon with boron prior to silicidation impedes the Co-Si diffusion process, while phosphorus atoms distribute uniformly in silicides with no voids or agglomerations. CoSi makes a suitable n-type TE candidate and provides an alternative to Si or SiGe materials. Transport properties of undoped CoSi exhibit a linear dependence within the investigated temperature window, whereas dopants in CoSi increase the number of electron carriers that contribute to charge transport and thereby influence the Seebeck coefficient. Thus, TE characteristics of thin CoSi films can be tuned via (i) the type of dopants used and/or (ii) varying the residual silicon thickness post silicidation. 相似文献
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Johannes M. Scheiger Chatrawee Direksilp Patricia Falkenstein Dr. Alexander Welle Dr. Meike Koenig Stefan Heissler Prof. Dr. Jörg Matysik Prof. Dr. Pavel A. Levkin Prof. Dr. Patrick Theato 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18798-18804
Sulfur as a side product of natural gas and oil refining is an underused resource. Converting landfilled sulfur waste into materials merges the ecological imperative of resource efficiency with economic considerations. A strategy to convert sulfur into polymeric materials is the inverse vulcanization reaction of sulfur with alkenes. However, the materials formed are of limited applicability, because they need to be cured at high temperatures (>130 °C) for many hours. Herein, we report the reaction of elemental sulfur with styrylethyltrimethoxysilane. Marrying the inverse vulcanization and silane chemistry yielded high sulfur content polysilanes, which could be cured via room temperature polycondensation to obtain coated surfaces, particles, and crosslinked materials. The polycondensation was triggered by hydrolysis of poly(sulfur-r-styrylethyltrimethoxysilane) (poly(Sn-r-StyTMS) under mild conditions (HCl, pH 4). For the first time, an inverse vulcanization polymer could be conveniently coated and mildly cured via post-polycondensation. Silica microparticles coated with the high sulfur content polymer could improve their Hg2+ ion remediation capability. 相似文献
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Glöggler S Müller R Colell J Emondts M Dabrowski M Blümich B Appelt S 《Physical chemistry chemical physics : PCCP》2011,13(30):13759-13764
Signal Amplification by Reversible-Exchange (SABRE) is a method of hyperpolarizing substrates by polarization transfer from para-hydrogen without hydrogenation. Here, we demonstrate that this method can be applied to hyperpolarize small amounts of all proteinogenic amino acids and some chosen peptides down to the nanomole regime and can be detected in a single scan in low-magnetic fields down to 0.25 mT (10 kHz proton frequency). An outstanding feature is that depending on the chemical state of the used catalyst and the investigated amino acid or peptide, hyperpolarized hydrogen-deuterium gas is formed, which was detected with (1)H and (2)H NMR spectroscopy at low magnetic fields of B(0) = 3.9 mT (166 kHz proton frequency) and 3.2 mT (20 kHz deuterium frequency). 相似文献
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Dr. Jeanne‐Marie Begouin Prof. Dr. Meike Niggemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8030-8041
Recently, Lewis acidic calcium salts bearing weakly coordinating anions such as Ca(NTf2)2, Ca(OTf)2, CaF2 and Ca[OCH(CF3)2]2 have been discovered as catalysts for the transformation of alcohols, olefins and carbonyl compounds. High stability towards air and moisture, selectivity and high reactivity under mild reaction conditions render these catalysts a sustainable and mild alternative to transition metals, rare‐earth metals or strong Brønsted acids. 相似文献
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Meike Spexard Dominik Immeln Christian Thöing Tilman Kottke 《Vibrational Spectroscopy》2011,57(2):282-287
Flavins play a key role as redox cofactors of enzymes involved in important metabolic processes. Moreover, they undergo photochemical reactions as chromophores in sensors of blue light or magnetic field in many organisms. The reaction mechanisms of flavoproteins have been investigated by infrared spectroscopy and theoretical studies. However, basic information on flavins in the infrared spectral range has been missing, such as absorption spectra in water and absorption coefficients. Here, the cofactors flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) were investigated in aqueous medium by Fourier transform infrared spectroscopy. Transmission and attenuated total reflection (ATR) configuration were employed in direct comparison. Absorption spectra in the range of 920–1800 cm−1 were determined after accurate subtraction of the contributions from the water vibrations. The important carbonyl vibrations were resolved at 1661 and 1712 cm−1. The absorption spectra may serve as a reference for theoretical and experimental studies on the effect of the microenvironment on the flavin cofactor. Furthermore, the molar absorption coefficient of FAD at 1547 cm−1 was determined to 2200 L mol−1 cm−1 with an integral absorption coefficient of ∼50,000 L mol−1 cm−2. These values are prerequisite for the determination of reaction yields in flavoproteins from reaction-induced difference spectra. 相似文献