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991.
Xiaolong Wan Jiadong Hu Dongyang Xu Yang Shang Yanxia Zhen Chenchen Hu Fan Xiao Yu-Peng He Yisheng Lai Weiqing Xie 《Tetrahedron letters》2017,58(12):1090-1093
A Re2O7 catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture. 相似文献
992.
Effect of halogen bonding on supramolecular assembly and photophysical properties of diaryl oxalates
Dong-En Wu Yang-Hui Luo Man-Ning Wang Qing-Ling Liu Gao-Ju Wen Ling-Jun Zhu Chang-Po Fan Bai-Wang Sun 《Structural chemistry》2017,28(6):1731-1742
In order to determine the effect of halogen bonding on supramolecular assemblies and photophysical properties of diaryl oxalates, diaryl oxalate itself and its derivatives with fluorine, chlorine, bromine, and iodine substituents in the p-position of phenyl rings were studied and compared. Their single-crystal structures were studied by geometrical analysis and theoretical calculation. The study reveals that different halogen bonds are formed with respect to different halogen atoms, such as C…F and X…X (bromine and iodine atoms) interactions, and molecular stacking modes would be affected by halogen bonds directly. Comparative studies of photophysical properties in dilute solution and solid state indicate that halogen substitutions would not affect the emission processes of diaryl oxalates in dilute solution; this is not the case for their solid state. This work has demonstrated that halogen bonds play an important role in regulating structures and photophysical properties of diaryl oxalates. 相似文献
993.
994.
Hui-Lu Wu Ke Li Tao Sun Fan Kou Fei Jia Jing-Kun Yuan Bin Liu Bao-Liang Qi 《Transition Metal Chemistry》2011,36(1):21-28
Tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and its two complexes, [Mn(Mentb)(DMF)(H2O)](pic)2
1 and [Zn(Mentb)(pic)](pic) 2 (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray
diffraction revealed that the two complexes have different structures. In complex 1, the coordination sphere around Mn(II) is distorted octahedral, whereas in complex 2 the coordination sphere around Zn(II) is distorted trigonal bipyramidal. The DNA-binding properties of the free ligand and
its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest
that the ligand and its two complexes bind to DNA via an intercalation binding mode, and their binding affinity for DNA follows
the order 1 > 2 > ligand. 相似文献
995.
Gold(I)‐Catalyzed Diazo Coupling: Strategy towards Alkene Formation and Tandem Benzannulation 下载免费PDF全文
Daming Zhang Guangyang Xu Dong Ding Chenghao Zhu Dr. Jian Li Prof. Dr. Jiangtao Sun 《Angewandte Chemie (International ed. in English)》2014,53(41):11070-11074
A gold(I)‐catalyzed cross‐coupling of diazo compounds to afford tetrasubstituted alkenes has been developed by taking advantage of a trivial electronic difference between two diazo substrates. A N‐heterocyclic‐carbene‐derived gold complex is the most effective catalyst for this transformation. Based on this new strategy, a gold(I)‐initiated benzannulation has been achieved through a tandem reaction involving a diazo cross‐coupling, 6π electrocyclization, and oxidative aromatization. 相似文献
996.
Copper‐Catalyzed NH Insertion and Oxidative Aromatization Cascade: Facile Synthesis of 2‐Arylaminophenols 下载免费PDF全文
Dong Ding Xiaobing Lv Dr. Jian Li Guangyang Xu Dr. Bing Ma Prof. Dr. Jiangtao Sun 《化学:亚洲杂志》2014,9(6):1539-1542
A copper‐catalyzed cascade reaction of N‐H insertion and oxidative aromatization has been developed. 2‐Arylaminophenols have been prepared in moderate to high yields from the diazo substrates. Moreover, this newly established methodology allows efficient access to natural 1‐oxygenated carbazole alkaloids, such as glycozolicine and murrayafoline A. 相似文献
997.
Fabrication of Predominantly Mn4+‐Doped TiO2 Nanoparticles under Equilibrium Conditions and Their Application as Visible‐Light Photocatalyts 下载免费PDF全文
Lijie Wang Jiajie Fan Zetan Cao Dr. Yichao Zheng Zhiqiang Yao Prof. Guosheng Shao Prof. Junhua Hu 《化学:亚洲杂志》2014,9(7):1904-1912
The chemical state of a transition‐metal dopant in TiO2 can intrinsically determine the performance of the doped material in applications such as photocatalysis and photovoltaics. In this study, manganese‐doped TiO2 is fabricated by a near‐equilibrium process, in which the TiO2 precursor powder precipitates from a hydrothermally obtained transparent mother solution. The doping level and subsequent thermal treatment influence the morphology and crystallization of the TiO2 samples. FTIR spectroscopy and X‐ray photoelectron spectroscopy analyses indicate that the manganese dopant is substitutionally incorporated by replacing Ti4+ cations. The absorption band edge can be gradually shifted to 1.8 eV by increasing the nominal manganese content to 10 at %. Manganese atoms doped into the titanium lattice are associated with the dominant 4+ valence oxidation state, which introduces two curved, intermediate bands within the band gap and results in a significant enhancement in photoabsorption and the quantity of photogenerated hydroxyl radicals. Additionally, the high photocatalytic performance of manganese‐doped TiO2 is also attributed to the low oxygen content, owing to the equilibrium fabrication conditions. This work provides an important strategy to control the chemical and defect states of dopants by using an equilibrium fabrication process. 相似文献
998.
Simultaneous determination of ten organophosphate pesticide residues in fruits by gas chromatography coupled with magnetic separation 下载免费PDF全文
In this study, γ‐Fe2O3/chitosan magnetic microspheres were synthesized and evaluated by X‐ray diffraction, SEM, thermogravimetric analysis, and static and kinetic adsorption experiments. Results showed that the magnetic microspheres exhibited good adsorption ability, and offered fast kinetics for the adsorption of trichlorfon, methamidophos, malathion, methyl parathion, dimethoate, omethoate, phosphamidon, phorate, isocarbophos, and chlorpyrifos. Based on magnetic separation, a simple method of magnetic SPE coupled to GC for the simultaneous determination of ten trace organophosphate pesticide residues was developed. Under the optimal conditions, the enrichment factor for ten organophosphorus pesticides was 10.1–364.7 and linear range was 0.001–10.0 mg/L. The LOD (S/N = 3) of the method for the ten pesticides was 0.31–3.59 μg/kg. The RSD for three replicate extractions of spiked samples was between 2.5 and 6.3%. The pear and apple samples spiked with ten organophosphate pesticides at 20 and 200 μg/kg levels were extracted and determined by this method with good recoveries ranging from 79.9 to 98.7%. Moreover, the method has been successfully applied for the determination of the ten organophosphate pesticide residues in peach samples. 相似文献
999.
Dongxu Zhao Yichun Liu Dezhen Shen Youming Lu Jiying Zhang X.W. Fan 《Journal of Sol-Gel Science and Technology》2002,23(3):231-234
The Mg
x
Zn1–x
O alloy thin films were synthesized on Si and quartz substrates by the sol-gel deposition method. The transmittance and cathodoluminescence spectra of the Mg0.05Zn0.95O and Mg0.15Zn0.85O nanoparticle films were obtained at room temperature. It was found that the bandgap of Mg0.05Zn0.95O and Mg0.15Zn0.85O films is as large as 3.72 eV and 3.79 eV, respectively. The ultraviolet emission peaks are located at 376 nm and 370 nm, respectively, for the samples annealed at 600°C. When the annealing temperature is elevated to 1000°C, the band-gap decreases to 3.42 eV and an emission line related to the deep-level defect appears at 500 nm. The mechanism behind these phenomena is discussed. 相似文献
1000.
The fluorescence of the water-soluble anionic conjugated polymer, poly[lithium 5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene] (MBL-PPV), is quenched in dilute aqueous solution by cytochrome c, a small, naturally occurring electron-transfer protein. The large value obtained for the Stern-Volmer constant (K(sv) = 3.2 x 10(8) at pH 7.4, and approximately 10(9) in acidic solutions) is attributed to a combination of two factors: (1) facile ET between the luminescent semiconducting polymer and the protein and (2) the Columb attraction between the oppositely charged polyelectrolytes. This system shows significant potential for biosensor applications. 相似文献