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991.
A general nonaqueous route to binary metal oxide nanocrystals involving a C-C bond cleavage 总被引:1,自引:0,他引:1
Pinna N Garnweitner G Antonietti M Niederberger M 《Journal of the American Chemical Society》2005,127(15):5608-5612
A widely applicable solvothermal route to nanocrystalline iron, indium, gallium, and zinc oxide based on the reaction between the corresponding metal acetylacetonate as metal oxide precursor and benzylamine as solvent and reactant is presented. Detailed XRD, TEM, and Raman studies prove that, with the exception of the iron oxide system, where a mixture of the two phases magnetite and maghemite is formed, only phase pure materials are obtained, gamma-Ga(2)O(3), zincite ZnO, and cubic In(2)O(3). The particle sizes lie in the range of 15-20 nm for the iron, 10-15 nm for the indium, 2.5-3.5 nm for gallium, and around 20 nm for zinc oxide. GC-MS analysis of the final reaction solution after removal of the nanoparticles showed that the composition is rather complex consisting of more than eight different organic compounds. Based on the fact that N-isopropylidenebenzylamine, 4-benzylamino-3-penten-2-one, and N-benzylacetamide were the main species found, we propose a detailed formation mechanism encompassing solvolysis of the acetylacetonate ligand, involving C-C bond cleavage, as well as ketimine and aldol-like condensation steps. 相似文献
992.
Stoichiometric powder mixtures CaO/WO3 and SrO/WO3 react tribochemically on grinding in a vibrating mill to CaWO4 and SrWO4, respectively. IR spectra, X-raydiffraction, DTA and solubilities indicate at least 70–80% CaWO4 are formed after periods of drinding of 50 hours, and 100% SrWO4 after periods of 15 hours. Observations on the behaviour of the ground samples on subsequent annealing contribute to the general solid-state reaction MO + WO3 → MWO4. 相似文献
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996.
Dipl.-Ing. Sabrina D. Püschmann Philipp Frühwirt Michael Pillinger Andreas Knöchl Marlene Mikusch Dr. Judith Radebner Dr. Ana Torvisco Prof. Roland C. Fischer Prof. Norbert Moszner Prof. Dr. Georg Gescheidt Dr. Michael Haas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3338-3347
Tetraacylgermanes are known as highly efficient photoinitiators. Herein, the synthesis of mixed tetraacylgermanes 4 a – c and 6 a – e with a nonsymmetric substitution pattern is presented. Germenolates are crucial intermediates of these new synthetic protocols. The synthesized compounds show increased solubility compared with symmetrically substituted tetraacylgermanes 1 a – d . Moreover, these mixed derivatives reveal broadened n–π* absorption bands, which enhance their photoactivity. Higher absorption of these new compounds at wavelengths above 450 nm causes efficient photobleaching when using an LED emitting at 470 nm. The quantum yields are in the range of 0.15–0.57, depending on the nature of the aroyl substituents. On the basis of these properties, mixed-functionalized tetraacylgermanes serve as ideal photoinitiators in various applications, especially in those requiring high penetration depth. The synthesized compounds were characterized by elemental analysis, IR spectroscopy, NMR and CIDNP spectroscopy, UV/Vis spectroscopy, photolysis experiments, and X-ray crystallography. The CIDNP data suggest that the germyl radicals generated from the new tetraacylgermanes preferentially add to the tail of the monomer butyl acrylate. In the case of 6 a – e only the mesitoyl groups are cleaved off, whereas for 4 a – c both the mesitoyl and the aroyl group are subject to α-cleavage. 相似文献
997.
Marcel Ritter Vincensius S. P. Oetama Daniel Schulze Katrin Muetzlaff Anja K. Meents Dr. Raphael A. Seidel Dr. Helmar Görls Prof. Dr. Matthias Westerhausen Prof. Dr. Wilhelm Boland Prof. Dr. Georg Pohnert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6205-6213
The degradation of chlorophyll, the omnipresent green pigment, has been investigated intensively over the last 30 years resulting in many elucidated tetrapyrrolic degradation products. With a comparison to the degradation of the structurally similar heme, we hereby propose a novel additional chlorophyll degradation mechanism to mono- and dipyrrolic products. This is the first proof of the occurrence of a family of mono- and dipyrrols in leaves that are previously only known as heme degradation products. This product family is also found in spit and feces of herbivores with specific metabolomic patterns reflecting the origin of the samples. Based on chromatographic and mass spectrometric evidence as well as on mechanistic considerations we also suggest several tentative new degradation products. One of them, dihydro BOX A, was fully confirmed as a novel natural product by synthesis and comparison of its spectroscopic data. 相似文献
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999.
Shai Rahimipour Georg Gescheidt Itzhak Bilkis Mati Fridkin Lev Weiner 《Applied magnetic resonance》2010,37(1-4):629-648
In this review article, the structure, properties, stability and biological application of redox-active quinones are presented. A series of quinoid molecules is evaluated in terms of their ability to act as electron-transfer active compounds using cyclovoltammetric, electron paramagnetic resonance (EPR) and spin-trapping techniques. Redox potentials and electron distribution of the intermediate radical anions are shown to be decisive factors for the generation of reactive oxygen species (ROS). Mechanisms of ROS generation in dark by biological electron-transfer reaction or under photoexcitation have been proposed and experimentally verified. For site-specific damage of tumors, some quinone derivatives were covalently bound with the luteinizing hormone-releasing hormone (LH–RH or GnRH) that produces specific complexes with receptors on the surface of cancer cells. The properties of obtained conjugates to be bound with the different lines of cancer cells (αT3-1, M2R, LNCaP) were tested. EPR was used for the estimation of efficacy of ROS production by the conjugates in solution and in the complex with cancer cells. The toxicity of these conjugates as well as their stability in the stimulated oxidative stress were tested. The proposed approach could be useful in creating a new family of addressed anticancer drugs, including compounds for the treatment of tumors by photodynamic therapy. 相似文献
1000.
Dr. Xin Chen Peter Denninger Dr. Tanja Stimpel-Lindner Prof. Erdmann Spiecker Prof. Georg S. Duesberg Dr. Claudia Backes Dr. Kathrin C. Knirsch Prof. Andreas Hirsch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6535-6544
Two-dimensional (2D) molybdenum disulfide (MoS2) holds great promise in electronic and optoelectronic applications owing to its unique structure and intriguing properties. The intrinsic defects such as sulfur vacancies (SVs) of MoS2 nanosheets are found to be detrimental to the device efficiency. To mitigate this problem, functionalization of 2D MoS2 using thiols has emerged as one of the key strategies for engineering defects. Herein, we demonstrate an approach to controllably engineer the SVs of chemically exfoliated MoS2 nanosheets using a series of substituted thiophenols in solution. The degree of functionalization can be tuned by varying the electron-withdrawing strength of substituents in thiophenols. We find that the intensity of 2LA(M) peak normalized to A1g peak strongly correlates to the degree of functionalization. Our results provide a spectroscopic indicator to monitor and quantify the defect engineering process. This method of MoS2 defect functionalization in solution also benefits the further exploration of defect-free MoS2 for a wide range of applications. 相似文献