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51.
Kun‐Li Wang Tseung‐Yuen Tseng Hung‐Lung Tsai Sheng‐Chieh Wu 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6861-6871
A series of poly(aryl ether)s were successfully prepared via aromatic nucleophilic substitution reaction from various bisphenols and a novel bipolar aryl difluoride monomer containing electron‐donor triphenylamine and electron‐acceptor 1,2,4‐triazole moieties. The poly(aryl ether)s exhibited excellent solubility in organic solvents such as dimethylformamide, chloroform, and tetrahydrofuran at room temperature. The poly(aryl ether)s showed high thermal stability with Td10 higher than 500 °C and glass transition temperatures (Tg) higher than 187 °C. The thin films of the poly(aryl ether)s indicated bistable resistive switching behavior with ON/OFF current ratios as high as 103. The switching on and switching off bias voltages of the poly(aryl ether)s were affected by the bisphenol moiety. The good resistive switching behavior of the poly(aryl ether)s made them promising candidates for future nonvolatile memory applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6861–6871, 2008 相似文献
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The reaction mechanisms as well as substituted effect and solvent effect of the enyne–allenes are investigated by Density Functional Theory (DFT) method and compared with the Myers–Saito and Schmittel reactions. The Myers–Saito reaction of non‐substituted enyne–allenes is kinetically and thermodynamically favored as compared to the Schmittel reaction; while the concerted [4 + 2] cycloaddition is only 1.32 kcal/mol higher than the C2? C7 cyclization and more exothermic (ΔRE = ?69.38 kcal/mol). For R1 = CH3 and t‐Bu, the increasing barrier of the C2? C7 cyclization is higher than that for the C2? C6 cyclization because of the steric effect, so the increased barrier of the [4 + 2] cycloaddition is affected by such substituted electron‐releasing group. Moreover, the strong steric effect of R1 = t‐Bu would shift the C2? C7 cyclization to the [4 + 2] cycloaddition. On the other hand, for R1 = Ph, NH2, O?, NO2, and CN substituents, the barrier of the C2? C6 cyclization would be more diminished than the C2? C7 cyclization due to strong mesomeric effect; the reaction path of C2? C7 cyclization would also shift to the [4 + 2] cycloaddition. The solvation does not lead to significant changes in the potential‐energy surface of the reaction except for the more polar surrounding solvent such as dimethyl sulfoxide (DMSO), or water. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
54.
Carmine Coluccini Yoke Mooi Ng Yves Ira A. Reyes Hsin-Yi Tiffany Chen Yit Lung Khung 《Molecules (Basel, Switzerland)》2020,25(22)
In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host–guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform. 相似文献
55.
Inside Back Cover: Selective Inhibition of Lysine‐Specific Demethylase 5A (KDM5A) Using a Rhodium(III) Complex for Triple‐Negative Breast Cancer Therapy (Angew. Chem. Int. Ed. 40/2018)
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Guan‐Jun Yang Wanhe Wang Dr. Simon Wing Fai Mok Chun Wu Betty Yuen Kwan Law Dr. Xiang‐Min Miao Ke‐Jia Wu Dr. Hai‐Jing Zhong Prof. Dr. Chun‐Yuen Wong Prof. Dr. Vincent Kam Wai Wong Prof. Dr. Dik‐Lung Ma Prof. Dr. Chung‐Hang Leung 《Angewandte Chemie (International ed. in English)》2018,57(40):13349-13349
56.
Reaction of alkyl, acetoxy, and silyl enol ethers of 3-(organosilyl)cyclohexanone with molecular dioxygen in toluene at 110 degrees C produced the corresponding conjugated enones in yields up to 88% yield. The reaction of the same type failed on replacement of the silyl group at the C-3 position with an isopropyl group. These results indicate the existence of an unprecedented silicon-induced ene-type reaction. Its reaction mechanism, generality, limitations, and exceptions are discussed. 相似文献
57.
Recently, Tobita et al. reported stoichiometric hydrosilylation reactions of acetone and acetonitrile with neutral hydrido(hydrosilylene)tungsten complexes Cp'(CO)2(H)W=Si(H)[C(SiMe(3))(3)] (Cp' = Cp*, C(5)Me(4)Et). The mechanisms of the hydrosilylation reactions of unsaturated compounds (ketone and nitrile) with the tungsten complexes have been investigated with the B(3)LYP density functional theory method. Four possible reaction mechanisms were studied. The results of the calculations indicate that the hydrosilylation of acetone proceeds via a metal hydride migration mechanism proposed by Tobita et al., while the hydrosilylation of nitrile occurs through a silyl migration mechanism, analogous to the modified Chalk-Harrod mechanism. The [2(sigma)+2(pi)] additions of various CX (CX = C=O or CN) multiple bonds with the Si-H bonds in the neutral complexes have very high barriers although similar additions were found feasible in other related cationic complexes. All the hydrosilylation reactions studied here give stable tungsten-silylene or tungsten-silyl products, which are not easily converted into the starting hydrido(hydrosilylene)tungsten complexes when reacting with a hydrosilane substrate molecule. Therefore, we predict that hydrosilylation of acetonitrile and acetone catalyzed by these tungsten complexes is difficult to achieve. 相似文献
58.
Chung LW Hayashi S Lundberg M Nakatsu T Kato H Morokuma K 《Journal of the American Chemical Society》2008,130(39):12880-12881
Firefly emission is a well-known efficient bioluminescence. However, the mystery of the efficient thermal generation of electronic excited states in firefly still remains unsolved, particularly at the atomic and molecular levels. We performed SA-CASSCF(12,12)/6-31G* and CASPT2(12,12)/6-31G*//SA-CASSCF(12,12)/6-31G* calculations to elucidate the reaction mechanism of bioluminescence from the firefly dioxetanone in the gas phase. Adiabatic transition state (TS) for the O-O bond cleavage and the minimum energy conical intersection (MECI) were located and characterized. The unique topology of MECI featuring a seam of a sloped conical intersection for the firefly dioxetanone, which was uncovered for the first time, emerges along the reaction pathway to provide a widely extended channel to diabatically access the excited-state from the ground state. 相似文献
59.
Synthesis of Blue‐, Green‐, Yellow‐, and Red‐Emitting Graphene‐Quantum‐Dot‐Based Nanomaterials with Excitation‐Independent Emission
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Chia‐Chun Ke Ya‐Chun Yang Wei‐Lung Tseng 《Particle & Particle Systems Characterization》2016,33(3):132-139
A one‐pot method is described for the preparation of graphene quantum dots/graphene oxide (GQDs/GO) hybrid composites with emission in the visible region, through heteroatom doping and hydroxyl‐radical‐induced decomposition of GO. The NH4OH‐ and thiourea‐mediated dissociation of H2O2 produces hydroxyl radicals. Treatment of GO with hydroxyl radicals results in the production of small‐sized GO sheets and GQDs, which self‐assemble to form GQDs/GO through strong π–π interactions. For example, the reaction of GO with a mixture of NH4OH and H2O2 for 40, 120, and 270 min generates yellow‐emitting GQDs/GO (Y‐GQDs/GO), green‐emitting GQDs/GO, and blue‐emitting GQDs, while red‐emitting GQDs/GO (R‐GQDs/GO) are prepared by incubating GO with a mixture of thiourea and H2O2. From the analysis of these four GQD‐based nanomaterials by transmission electron microscopy, atomic force microscopy, and fluorescence lifetime spectroscopy, it is found that this tunable fluorescence wavelength results from the differences in particle size. All four GQD‐based nanomaterials exhibit moderate quantum yields (1–10%), nanosecond fluorescence lifetimes, and excitation‐independent emissions. Except for R‐GQDs/GO, the other three GQD‐based nanomaterials are stable in a high‐concentration salt solution (e.g., 1.6 m NaCl) and under high‐power irradiation, enabling the sensitive (high‐temperature resolution and large activation energy) and reversible detection of temperature change. It is further demonstrated that Y‐GQD/GO can be used to image HeLa cells. 相似文献
60.
本文研究了江西波阳重晶石用煤高温还原的条件。找出了最佳还原温度为1050℃,最佳矿、煤配比为3.5:1、还原时间60min,以及原料粒度、炉内气氖和原料中杂质对还原化率的影响程度。对重晶石的还原机理也进行了讨论。 相似文献