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排序方式: 共有361条查询结果,搜索用时 119 毫秒
351.
Polystyrene nanoparticles doped with a luminescent europium complex, Eu(tta)(3)phen, are prepared by miniemulsion polymerization. The influence of the complex on the miniemulsion polymerization is investigated by the systematic variation of the initial concentration of Eu(tta)(3)phen from 2 to 7 wt% relatively to styrene. A maximum doping level of about 2% by weight in the final particles can be achieved. At higher doping levels, destabilization of the miniemulsion leads to a loss of reproducibility with respect to both the degree of conversion and the final Eu content of the particles. Doped nanoparticles of varying diameter, ranging from 19 to 94 nm, are successfully prepared. Steady-state and time-resolved luminescence measurements indicate that the luminescence properties of Eu(tta)(3)phen in the doped latexes are unchanged from those found in THF solution. Aqueous dispersions of the doped particles exhibit characteristic red emission under UV light irradiation. The luminescence intensity increases linearly with Eu(tta)(3)phen content, indicating the absence of self-quenching despite the relatively high local concentrations within the particles. 相似文献
352.
A readily available pincer ruthenium(II) complex catalyzes the selective monoalkylation of (hetero)aromatic amines with a wide range of primary alcohols (including pyridine-, furan-, and thiophene-substituted alcohols) with high efficiency when used in low catalyst loadings (1 mol %). Tertiary amine formation via polyalkylation does not occur, making this ruthenium system an excellent catalyst for the synthesis of sec-amines. 相似文献
353.
Levine DR Caruso A Siegler MA Tovar JD 《Chemical communications (Cambridge, England)》2012,48(50):6256-6258
The synthesis of new boron-containing acenes (meta-B-entacenes) is reported. These compounds exhibit slightly non-planar core geometries with blue-shifted spectral properties and more negative electrochemical reduction potentials relative to known para isomers. Polarizable π-extended architectures were realized via cross-coupling procedures with chloro-functionalized precursors. 相似文献
354.
Sanguinet L Pozzo JL Guillaume M Champagne B Castet F Ducasse L Maury E Soulié J Mançois F Adamietz F Rodriguez V 《The journal of physical chemistry. B》2006,110(22):10672-10682
This paper presents a series of acidoswitchable NLO-phores combining the 9-methylbenzimidazolo[2,3-b]oxazolidine core with various pi systems such as phenylethenyl, phenylethynyl, and naphthylethenyl. All the prepared derivatives are shown to display acidochromic behavior at ambient temperature. The remarkable contrast in the NLO response along the reversible transformations observed in HRS experiments is rationalized by high level theoretical calculations. 相似文献
355.
Area preserving diffeomorphisms of the 2-disk which are Identity near the boundary form a group which can be equipped, using theL
2-norm on its Lie algebra, with a right invariant metric. In this paper we give a lower bound on the distance between diffeomorphisms which is invariant under area preserving changes of coordinates and which improves the lower bound induced by the Calabi invariant. In the case of renormalizable and infinitely renormalizable maps, our estimate can be improved and computed. 相似文献
356.
Poly(1,6‐hexane‐9,9,9′,9′,9″,9″‐hexahexyl‐7,2′;7′,2″‐terfluorene‐2,7″‐dicarboxylate) (PTFHHC6) has been synthesized and characterized. This polymer exhibits strong emission in the blue range, both in solution (quantum yield of 76%) and in the solid state. Moreover, PTFHHC6 presents some advantages over other polyfluorene derivatives since its solid‐state fluorescence spectrum does not show any excimer formation and does not vary upon thermal treatment. Electrochemical measurements have revealed a reversible p‐n dopable polymer. This aromatic polyester shows promising optical and electrical properties for the development of blue light‐emitting diodes. 相似文献
357.
Maxime Artault Thomas Cantin Mélissa Longuet Kassandra Vitse Christ Daniel Matatu Mbengo Frédéric Guégan Bastien Michelet Agnès Martin-Mingot Sébastien Thibaudeau 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202316458
Here we report a method to reorganize the core structure of aliphatic unsaturated nitrogen-containing substrates exploiting polyprotonation in superacid solutions. The superelectrophilic activation of N-isopropyl systems allows for the selective formal Csp3−H activation/cyclization or homologation / functionalization of nitrogen-containing substrates. This study also reveals that this skeletal reorganization can be controlled through protonation interplay. The mechanism of this process involves an original sequence of C−N bond cleavage, isopropyl cation generation and subsequent C−N bond and C−C bond formation. This was demonstrated through in situ NMR analysis and labelling experiments, also confirmed by DFT calculations. 相似文献
358.
Kim Anh Nguyen Emilie Lesur Maxime Ribéraud Antoine Sallustrau Davide Audisio Frédéric Taran 《Helvetica chimica acta》2023,106(3):e202200187
The synthesis of four clickable sydnone-heptamethine cyanine derivatives is described in this article. The synthetic route is based on a palladium-cross coupling reactions of sydnone boronates affording the desired sydnone-cyanine conjugates in only five steps. These compounds were shown to react smoothly with cyclooctynes to form the corresponding pyrazoles clicked products quantitatively at room temperature and with rate constants up to 18 m −1 ⋅ s−1, affording interesting new tools for biorthogonal fluorescent labelling of (bio)molecules. Fluorescence properties of both sydnone- and pyrazole-cyanines are described, as well. 相似文献
359.
Alexandre Labiche Augustin Malandain Maxime Molins Dr. Frédéric Taran Dr. Davide Audisio 《Angewandte Chemie (International ed. in English)》2023,62(36):e202303535
In contrast to stable and natural abundant carbon-12, the synthesis of organic molecules with carbon (radio)isotopes must be conceived and optimized in order to navigate through the hurdles of radiochemical requirements, such as high costs of the starting materials, harsh conditions and radioactive waste generation. In addition, it must initiate from the small cohort of available C-labeled building blocks. For long time, multi-step approaches have represented the sole available patterns. On the other side, the development of chemical reactions based on the reversible cleavage of C−C bonds might offer new opportunities and reshape retrosynthetic analysis in radiosynthesis. This review aims to provide a short survey on the recently emerged carbon isotope exchange technologies that provide effective opportunity for late-stage labeling. At present, such strategies have relied on the use of primary and easily accessible radiolabeled C1-building blocks, such as carbon dioxide, carbon monoxide and cyanides, while the activation principles have been based on thermal, photocatalytic, metal-catalyzed and biocatalytic processes. 相似文献
360.
Maxime Robin Stephane Mialhe Valerie Pique Robert Faure Jean‐Pierre Galy 《ChemInform》2002,33(38):153-153