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排序方式: 共有251条查询结果,搜索用时 15 毫秒
1.
在氢化丁苯共聚物13C-NMR谱脂肪碳部分谱带归属的基础上,根据各谱带的主要来源,推导出六个二单元浓度的计算公式。计算出二单元、一单元的相对含量,各结构单元的数均序列长度、嵌段含量和其它结构参数。加氢前后的1H-和13C-NMR谱的组成计算结果基本一致。初步探讨了作为粘度指数改进剂的氢化丁苯共聚物微观结构与性能的关系,为合成提供了依据。 相似文献
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Reaction schemes have been developed that lead to clusters having the topology of the PN cluster of nitrogenase. The single cubane clusters [(Tp)MFe3S4Cl3]z (M = Mo, z = 1-; M = V, z = 2-) react with PEt3 to give [(Tp)MFe3S4(PEt3)3]1+, which are reduced to the neutral edge-bridged double cubanes [(Tp)2M2Fe6S8(PEt3)4] with highly reduced (2[MFe3S4]1+) cores. Reaction of these clusters in acetonitrile with (Et4N)(HS) results in the formation of [(Tp)2Mo2Fe6S9(SH)2]3- and [(Tp)2V2Fe6S9(SH)2]4-. X-ray structures of the Et4N+ salts reveal the bridging pattern M2Fe6(mu2-S)2(mu3-S)6(mu6-S) in which two cuboidal MFe3(mu3-S)3 units share the common bridge atom mu6-S and are externally bridged by two mu2-S atoms. The M sites possess trigonal octahedral, and the Fe sites, distorted tetrahedral coordination. Hydrosulfide ligands and sulfide atoms simulate terminal cysteinate ligation and mu2 bridges, respectively, in the protein-bound cluster Fe8S7(mu2-SCys)2(SCys)4. The synthetic clusters have the same bridging pattern as the PN cluster and approach congruency with it. These clusters are the first molecular topological analogues of a PN cluster. Like the latter, they are substantially reduced (majority of Fe(II)). 相似文献
3.
Dr. Zheng-Guang Wu Xiang-Ji Liao Li Yuan Prof. Yi Wang Prof. You-Xuan Zheng Prof. Jing-Lin Zuo Prof. Yi Pan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(25):5694-5700
Click chemistry focuses on the development of highly selective reactions using simple precursors for the exquisite synthesis of molecules. Undisputedly, the CuI-catalyzed azide–alkyne cycloaddition (CuAAC) is one of the most valuable examples of click chemistry, but it suffers from some limitations as it requires additional reducing agents and ligands as well as cytotoxic copper. Here, we demonstrate a novel strategy for the azide–alkyne cycloaddition reaction that involves a photoredox electron-transfer radical mechanism instead of the traditional metal-catalyzed coordination process. This newly developed photocatalyzed azide–alkyne cycloaddition reaction can be performed under mild conditions at room temperature in the presence of air and visible light and shows good functional group tolerance, excellent atom economy, high yields of up to 99 %, and absolute regioselectivity, affording a variety of 1,4-disubstituted 1,2,3-triazole derivatives, including bioactive molecules and pharmaceuticals. The use of a recyclable photocatalyst, solar energy, and water as solvent makes this photocatalytic system sustainable and environmentally friendly. Moreover, the azide–alkyne cycloaddition reaction could be photocatalyzed in the presence of a metal-free catalyst with excellent regioselectivity, which represents an important development for click chemistry and should find versatile applications in organic synthesis, chemical biology, and materials science. 相似文献
4.
Xiao-Bo Ma Jing-Lin Zhang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):227-231
Abstract The condensation of N-phenyl-N′-(2-hydroxylphenyl)urea or N-phenyl-N′-(2-aminophenyl)urea with tris(dia1kylamino)phosphine afforded derivatives of 4,5-benzo-1,3,2-oxaza (or diaza)-phospholane which formed intramolecular hydrogen bond. The cleavage of the amide bond to give N,N-dialky1-N′-phenylurea together with polymers of 1,3,2-benzodiazaphosphole was observed in the latter reaction. 相似文献
5.
Xiao-Bo Ma Jing-Lin Zhang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):233-237
Abstract 1,3,2-Diazaphosphetidin-4-one derivatives were synthesized. Their 1H NMR signals at ambient temperature displaed a broad doublet which eventually coalesced before becoming sharp upon warming, and the 13C NMR spectra also showed that the α-and β-carbons of the dialkylamino group were non-equivalent. The phenomena were ascribed to restricted rotation about the exocyclic P—N bond. 相似文献
6.
Jing-Lin Zhang And Jin-Qiao Lu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract 2-(N2-O,O-Dialkylthiophosphoryl)hydrazinobenzothiazole (I) could be synthesized with satisfactory yields from the reaction of 2-hydrazinobenzothiazole with thiophosphoryl chlorides. At higher temperature bis(dialkoxy)thiophosphoryl derivatives (11) were given. 相似文献
7.
旨在研究无线传感器与执行器网络(WSANs)中节点失效情况下恢复执行器(actor)节点服务的算法. 首先说明了WSANs中的实时覆盖模型, 证明WSANs覆盖恢复问题是NP难问题, 给出了近似求解方案. 在此基础上, 提出了一种基于六边形蜂巢结构的移动容错算法HMFR用于恢复失效actor节点, HMFR 算法在限制网络初始部署的条件下拥有很好的性能. 通过实验与现有的恢复算法进行比较, 发现HMFR算法在actor覆盖sensor节点数和移动距离方面有更好的性能. 相似文献
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