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排序方式: 共有969条查询结果,搜索用时 46 毫秒
1.
Mariem Ghali Chaima Brahmi Mahmoud Benltifa Cyril Vaulot Aissam Airoudj Philippe Fioux Frédéric Dumur Corine Simonnet-Jégat Fabrice Morlet-Savary Salah Jellali Latifa Bousselmi Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2021,59(2):153-169
Different inorganic/organic photocomposites based on polyoxometalate (POM) nanoparticles have been developed for photocatalytic applications. Currently, polyoxometalate nanoparticles have been successfully in-situ embedded into an acrylate polymer network by photopolymerization upon mild visible light irradiation at 405 nm. The proposed POM/polymer photocomposites have been characterized using complementary techniques for a better understanding of their photocatalytic activity. Interestingly, the obtained photocomposites exhibit high rigidity, excellent thermal stability, a non-negligible porosity and new functionalities such as light reactivity and redox properties. Moreover, developed composites showed efficient catalytic activity for the color removal of aqueous solutions of erythrosine and rose Bengal under Light Emitting Diodes LED@375 nm irradiation reaching 80 and 90% as a final color removal, respectively. 相似文献
2.
Anthony Blanchard Flavien Melis Fabrice Gouanvé Jean-Matthieu Brouillat Eliane Espuche 《Journal of polymer science. Part A, Polymer chemistry》2021,59(1):70-83
The influences of the molar mass (low, medium, and high) and content of poly(vinyl alcohol) (PVOH) dispersed by melt-blending in an ethylene vinyl alcohol (EVOH) copolymer on the morphology, microstructure, thermal, mechanical, and oxygen barrier properties were investigated. Multilayer films with external low-density polyethylene layers and inner EVOH/PVOH blend layer and respective monolayer films were elaborated and characterized. EVOH/PVOH blends exhibited a good compatibility because of the initial presence of PVOH segments in EVOH. The detailed quantitative analysis of the morphology performed for all blends showed that the finest dispersion was obtained with the PVOH with the lowest molar mass. The properties of the films as a function of the PVOH content and its molar mass were determined herein. Significant improvement of barrier properties was obtained at moderated water activities (up to aw = 0.6) by using the PVOH with the lowest molar mass. Compared to the neat EVOH material, the oxygen permeability coefficients decreased by a factor 2 by adding 15 vol% PVOH while the thermal and mechanical properties remained similar. 相似文献
3.
Romain Bénéteau Anne Boussonnière Jean‐Christophe Rouaud Prof. Dr. Jacques Lebreton Dr. Jérôme Graton Prof. Dr. Denis Jacquemin Dr. Muriel Sebban Prof. Dr. Hassan Oulyadi Ghanem Hamdoun Dr. Amber N. Hancock Prof. Dr. Carl H. Schiesser Dr. Fabrice Dénès 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4809-4824
α‐Bromo aluminium acetals are suitable substrates for Ueno–Stork‐like radical cyclisations affording γ‐lactols and acid‐sensitive methylene‐γ‐lactols in high yields. The mechanistic study herein sets the scope and limitation of this reaction. The influence of the halide (or chalcogenide) atom X (X=Cl, Br, I, SPh, SePh) in the precursors α‐haloesters, as well as influence of the solvent and temperature was studied. The structure of the aluminium acetal intermediates resulting from the reduction of the corresponding α‐haloesters has been investigated by low‐temperature 13C‐INEPT diffusion‐ordered NMR spectroscopy (DOSY) experiments and quantum calculations, providing new insights into the structures of these thermally labile intermediates. Oxygen‐bridged dimeric structures with a planar Al2O2 ring are proposed for the least hindered aluminium acetals, while monomeric structures seem to prevail for the most hindered species. A comparison against the radical cyclisation of aluminium acetals derived from allyl and propargyl alcohols with the parent Ueno–Stork has been made at the BHandHLYP/6‐311++G(d,p) level of theory, highlighting mechanistic similarities and differences. 相似文献
4.
Naphthalic anhydride derivatives: Structural effects on their initiating abilities in radical and/or cationic photopolymerizations under visible light 下载免费PDF全文
Pu Xiao Frédéric Dumur Jing Zhang Bernadette Graff Fabrice Morlet‐Savary Jean Pierre Fouassier Didier Gigmes Jacques Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2015,53(24):2860-2866
Only one naphthalic anhydride derivative has been reported as light sensitive photoinitiator, this prompted us to further explore the possibility to prepare a new family of photoinitiators based on this scaffold. Therefore, eight naphthalic Naphthalic anhydride derivatives (ANH1‐ANH8) have been prepared and combined with an iodonium salt (and optionally N‐vinylcarbazole) or an amine (and optionally 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine) to initiate the cationic polymerization of epoxides and the free radical polymerization of acrylates under different irradiation sources, that is, very soft halogen lamp (~ 12 mW cm?2), laser diode at 405 nm (~1.5 mW cm?2) or blue LED centered at 455 nm (80 mW cm?2). The ANH6 based photoinitiating systems are particularly efficient for the cationic and the radical photopolymerizations, and even better than that of the well‐known camphorquinone based systems. The photochemical mechanisms associated with the chemical structure/photopolymerization efficiency relationships are studied by steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin‐trapping techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2860–2866 相似文献
5.
6.
Tomáš Čarný Dr. Ronan Rocaboy Dr. Antonin Clemenceau Prof. Dr. Olivier Baudoin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19142-19146
The 1,4-palladium shift strategy allows the functionalization of remote C−H bonds that are difficult to reach directly. Reported here is a domino reaction proceeding by C(sp3)−H activation, 1,4-palladium shift, and amino- or alkoxycarbonylation, which generates a variety of amides and esters bearing a quaternary β-carbon atom. Mechanistic studies showed that the aminocarbonylation of the σ-alkylpalladium intermediate arising from the palladium shift is fast using PPh3 as the ligand, and leads to the amide rather than the previously reported indanone product. 相似文献
7.
Jing Zhang Shuhui Wang Jacques Lalevée Fabrice Morlet-Savary Elizabeth S.-H. Lam Bernadette Graff Jing Liu Feiyue Xing Pu Xiao 《Journal of polymer science. Part A, Polymer chemistry》2020,58(6):792-802
The photoinitiation abilities of three 1,2-diketones [i.e., acenaphthenequinone ( ANPQ ), aceanthrenequinone ( AATQ ), and 9,10-phenanthrenequinone ( PANQ )]-based photoinitiating systems [PISs, with additives such as iodonium salt, N-vinylcarbazole (NVK), tertiary amine, and phenacyl bromide (R-Br)] for cationic photopolymerization and free-radical photopolymerization under the irradiation of ultraviolet (UV; 392 nm) or blue (455 nm) light-emitting diode (LED) bulb are investigated. All 1,2-diketones studied exhibit ground state absorption that match with the emission spectra of UV (392 nm) or blue LED (455 nm) better than that of the well-known blue-light-sensitive photoinitiator camphorquinone (CQ). In particular, AATQ /iodonium salt/NVK can show high photoinitiating ability (with epoxide conversion yield >70%) under the UV light irradiation due to the effect of NVK. In addition, 1,2-diketone/iodonium salt (and optional NVK) systems are capable of initiating free-radical photopolymerization of methacrylates, with conversions of 50–58%. Furthermore, some 1,2-diketone/tertiary amine (and optional R-Br) combinations are found to demonstrate high efficiency to initiate free-radical photopolymerization, and 71% of methacrylate conversion can be achieved with PANQ /tertiary amine/R-Br PIS. Some 1,2-ketone-based PISs can even exhibit higher efficiency than the CQ-based systems. The photochemical mechanism of the radical generation from the 1,2-diketone-based PISs is investigated and found to be consistent with the related photopolymerization efficiency. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 792–802 相似文献
8.
Dr. Miguel Cortijo Dr. Ángela Valentín-Pérez Dr. Andrei Rogalev Dr. Fabrice Wilhelm Dr. Philippe Sainctavit Dr. Patrick Rosa Dr. Elizabeth A. Hillard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(59):13363-13366
An original method for determining the handedness of individual non-centrosymmetric crystals in a mixture using a tightly-focused, circularly polarized X-ray beam is presented. The X-ray natural circular dichroism (XNCD) spectra recorded at the metal K-edge on selected crystals of [Δ-M(en)3](NO3)2 and [Λ-M(en)3](NO3)2 (M=CoII, NiII) show extrema at the metal pre-edge (7712 eV for Co, 8335 eV for Ni). A mapping of a collection of some 220 crystals was performed at the respective energies by using left and right circular polarizations. The difference in absorption for the two polarizations, being either negative or positive, directly yielded the handedness of the crystal volume probed by the beam. By using this technique, it was found that the addition of l -ascorbic acid during the synthesis of [Co(en)3](NO3)2 resulted in an enantiomeric enrichment of the Λ-isomer of 67±13 %, whereas the Ni analogue was similarly, but conversely, enriched in the Δ-isomer (65±22 %). 相似文献
9.
Pierre Thesmar Seemon Coomar Dr. Alessandro Prescimone Prof. Dr. Daniel Häussinger Prof. Dr. Dennis Gillingham Prof. Dr. Olivier Baudoin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15298-15312
This article provides a detailed report of our efforts to synthesize the dithiodiketopiperazine (DTP) natural products (−)-epicoccin G and (−)-rostratin A using a double C(sp3)−H activation strategy. The strategy's viability was first established on a model system lacking the C8/C8’ alcohols. Then, an efficient stereoselective route including an organocatalytic epoxidation was secured to access a key bis-triflate substrate. This bis-triflate served as the functional handles for the key transformation of the synthesis: a double C(sp3)−H activation. The successful double activation opened access to a common intermediate for both natural products in high overall yield and on a multigram scale. After several unsuccessful attempts, this intermediate was efficiently converted to (−)-epicoccin G and to the more challenging (−)-rostratin A via suitable oxidation/reduction and protecting group sequences, and via a final sulfuration that occurred in good yield and high diastereoselectivity. These efforts culminated in the synthesis of (−)-epicoccin G and (−)-rostratin A in high overall yields (19.6 % over 14 steps and 12.7 % over 17 steps, respectively), with the latter being obtained on a 500 mg scale. Toxicity assessments of these natural products and several analogues (including the newly synthesized epicoccin K) in the leukemia cell line K562 confirmed the importance of the disulfide bridge for activity and identified dianhydrorostratin A as a 20x more potent analogue. 相似文献
10.
Guanqi Wang Dr. Yohann Moreau Dr. Florian Berthiol Dr. Christian Philouze Dr. Olivier Jarjayes Prof. Fabrice Thomas 《欧洲无机化学杂志》2023,26(15):e202300223
The copper and nickel complexes of two tetradentate ligands derived from bis(aminophenol) and bis(phenol) architectures connected by an oxamate linker were isolated. Depending on the metal and ligand, the complex is isolated with either an intact (deprotonated) ligand ( 12− ), one-electron oxidized ligand ( 2− ) or quinone form ( 3 ). Surprisingly, the Mannich base is easier to oxidize than the amidophenol derivatives. The complexes were characterized by X-ray diffraction, cyclic voltammetry, UV-Vis-NIR and EPR spectroscopies. Complex 1 shows two reversible oxidation waves assigned to the successive iminosemiquinone/aminophenolate redox systems. Complex 2− shows an intense NIR feature, as well as an EPR signal at giso=2.043, consistent with a metallic contribution to the main ligand radical SOMO. Complex 3 shows the typical feature of an isolated Cu(II) complex. Spectro-electrochemistry coupled to DFT calculations demonstrate a ligand-centered oxidative redox chemistry for all the complexes. 相似文献