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91.
Dr. Masato Ohashi Ryohei Doi Prof. Dr. Sensuke Ogoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):2040-2048
This report describes the first Pd0‐catalyzed cross‐coupling of hexafluorobenzene (C6F6) with diarylzinc compounds to give a variety of pentafluorophenyl arenes. This reaction could be applied to other perfluoroarenes, such as octafluorotoluene, pentafluoropyridine, and perfluoronaphthalene, to give the corresponding polyfluorinated coupling products. The optimal ligand in this catalytic reaction was PCy3, and lithium iodide was indispensable as an additive for the coupling reaction. One of the roles of lithium iodide in this catalytic reaction was to promote the oxidative addition of one C?F bond of C6F6 to palladium. Stoichiometric reactions revealed that an expected oxidative‐addition product, trans‐[Pd(C6F5)I(PCy3)2], generated from the reaction of [Pd(PCy3)2] with C6F6 in the presence of lithium iodide, was not involved in the catalytic cycle. Instead, a transient three‐coordinate, monophosphine‐ligated species, [Pd(C6F5)I(PCy3)], emerged as a potential intermediate in the catalytic cycle. Therefore, we isolated a novel PdII complex, [Pd(C6F5)I(PCy3)(py)], in which pyridine (py) acted as a labile ligand to generate the transient species. In fact, in the presence of lithium iodide, this PdII complex was found to react smoothly with diphenylzinc to give the desired pentafluorophenyl benzene, whereas the same reaction conducted in the absence of lithium iodide resulted in a decreased yield of pentafluorophenyl benzene, which indicated that the other role of lithium iodide was to enhance the reactivity of the organozinc species during the transmetalation step. 相似文献
92.
Dr. Ryohei Yasukuni Prof. Nordin Félidj Dr. Leïla Boubekeur-Lecaque Stéphanie Lau-Truong Prof. Jean Aubard 《Chemphyschem》2020,21(22):2614-2619
Localized surface plasmon resonance (LSPR) excitation on the photochromic reaction of a diarylethene derivative (DE) was studied by surface enhanced Raman scattering (SERS). UV and visible light irradiations transform reversibly DE between open-form (OF) and closed-form (CF) isomers, respectively. A mixture of PMMA and DE (either OF or CF isomer) was spin-coated onto gold nanorods (GNRs) arrays, designed by electron beam lithography, with two localized surface plasmon resonances (LSPR) at distinct wavelengths, due to their anisotropy. The photochromic reaction rates from CF to OF isomers, under LSPR excitation, were monitored from SERS spectral changes under different polarizations, on the same GNR substrate to compare the effect of LSPR field strength. It appears that the photoisomerization rate was faster when LSPR was excited with the polarization parallel to the GNR long axis. The present results highlight a potential genuine mechanism, from near field LSPR excitation, involved in the photochromic enhancement of diarylethene photochromes. 相似文献
93.
94.
王益 《高校应用数学学报(英文版)》2006,21(4):418-428
Symbolic dynamics of cellular automata is introduced by coarse-graining the temporal evolution orbits. Evolution languages are defined. By using the theory of formal languages and automata, the complexity of evolution languages of the elementary cellular automaton of rule 146 is studied and it is proved that its width 1-evolution language is regular, but for every n ≥ 2 its width n-evolution language is not context-free but context-sensitive. Also, the same results hold for the equivalent (under conjugation) elementary cellular automaton of rule 182. 相似文献
95.
Yoshio Kobayashi Tsukasa Shirochi Takafumi Maeda Yusuke Yasuda Toshiaki Morita 《Surface and interface analysis : SIA》2013,45(9):1424-1428
This paper describes a metal–metal bonding technique using metallic Cu nanoparticles prepared in aqueous solution. A colloid solution of metallic Cu particles with a size of 54 ± 15 nm was prepared by reducing Cu2+ (0.01 M (CH3COO)2Cu) with hydrazine (0.6 M) in the presence of stabilizers (5 × 10?4 M citric acid and 5 × 10?3 M cetyltrimethylammonium bromide) in water at room temperature in air. Discs made of metallic materials (Cu, Ni/Cu, or Ag/Ni/Cu) were successfully bonded under annealing at 400 °C and pressurizing at 1.2 MPa for 5 min in H2 gas with help of the metallic Cu particle powder. Shear strength required for separating the bonded discs was 27.9 ± 3.9 for Cu discs, 28.1 ± 4.1 for Ni/Cu discs, and 13.8 ± 2.6 MPa for Ag/Ni/Cu discs. Epitaxial crystal growth promotes on the discs with a good matching for the lattice constants between metallic nanoparticles and metallic disc surfaces, which leads to strong bonding. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
96.
0Introduction Anelectronicpackageisgenerallyconstructedwithanactivesiliconchip,mountisland,gold wires,leadframesandsoldersasshowninFig.1(a).Toprotectfromtheenvironment,thesilicon chipisusuallyencapsulatedinresin.SincethesematerialshavedifferentCTE(coeffic… 相似文献
97.
Dose-dependent inhibition of ultrasound-induced cell killing and free radical production by carbon dioxide 总被引:9,自引:0,他引:9
Previous studies have shown that if a solution for cell suspension is saturated with CO(2), ultrasound-induced in vitro cell killing and free-radical production are inhibited. However, the dose dependency of this observation has not been explored. Here, we used NaHCO(3) and HCl to produce a predictable concentration of CO(2) within the culture medium. Using 1 MHz continuous wave 4 W/cm(2) ultrasound, we sonicated U937 cells suspension for 1 min at 37 degrees C with CO(2) at different concentrations. At 2 mM, reduced cell killing was observed that further decreased with increasing CO(2) concentration until 100% protection was attained at 20 mM. Ultrasound-induced free-radical production was significantly decreased at 1 mM and became undetectable at 2 mM CO(2). This finding shows that CO(2)-mediated inhibition is concentration dependent and that the threshold for free-radical production is one order of magnitude higher than the threshold for cell killing induced by ultrasound. In addition, it also cautions researchers when adding acids and acid-based agents to a culture medium, which almost always contains NaHCO(3), in experiments related to the bioeffects of ultrasound. 相似文献
98.
The transition temperatures between high- and low-spin states of the assembled spin-crossover complexes, Fe(NCX)2(bpa)2(guest) (X = S, Se, BH3; bpa = 1,2-bis(4-pyridyl)ethane; guest = biphenyl, 2-nitrobiphenyl, diphenylmethane, or 1,4-dichlorobenzene), were compared with the Mössbauer parameters. The transition temperature increases when the QS value of FeII high-spin state becomes small. The transition temperature also increases by changing the anion from NCS to NCSe and then to NCBH3. 相似文献
99.
100.
We discuss how the spectral changes of quarkonia at T
c can reflect the ‘critical’ behaviour of QCD phase transition. Starting from the temperature dependencies of the energy density
and pressure from lattice QCD calculation, we extract the temperature dependencies of the scalar and spin-2 gluon condensates
near T
c. We also parametrize these changes into the electric and magnetic condensate near T
c. While the magnetic condensate hardly changes across T
c, we find that the electric condensate increases abruptly above T
c. Similar abrupt change is also seen in the scalar condensate. Using the QCD second-order Stark effect and QCD sum rules,
we show that these sudden changes induce equally abrupt changes in the mass and width of J/ψ, both of which are larger than 100 MeV at slightly above T
c.
相似文献