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991.
5-(1H-Tetrazol-1-yl)isophthalic acid (H(2)L) reacts with Cu(II) ion forming a new metal-organic framework {[CuL]·DMF·H(2)O}(∞) (1) (DMF = N,N-dimethylformamide), with a rutile-related type net topology. Compound 1 possesses a 3D structure with 1D channels that can be desolvated to yield a microporous material. Adsorption properties (N(2), H(2), O(2), CO(2), and CH(4)) of the desolvated solid [CuL] (1a) have been studied, and the results exhibit that 1a possesses fairly good capability of gas sorption for N(2), H(2), O(2), and CO(2) gases, with high selectivity ratios for O(2) over H(2) at 77 K and CO(2) over CH(4) at 195, 273, and 298 K. Furthermore, 1a has excellent O(2) uptake at 77 K and a remarkably high quantity of adsorption for CO(2) at room temperature (298 K) and atmospheric pressure, suggesting its potential applications in gas separation or purification. 相似文献
992.
A series of isomeric bis(chlorophthalimide)s (BCPIs) were conveniently prepared from 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, and mixtures thereof. Polymerization of BCPIs with bis(4-mercaptophenyl) sulfone (BMPS) proceeded smoothly in the presence of tributylamine, from which a class of isomeric poly(thioether ether sulfone imide)s (PTESIs) with inherent viscosities of 0.45-0.82 dL/g were obtained. The solubility, thermal stability, and mechanical properties of these polymers were characterized. Compared to the PTESIs derived from single BCPIs, i.e., 3,3′-, 3,4′-, or 4,4′-BCPIs, the PTESIs derived from mixed BCPIs showed better solubility and higher storage modulus. These PTESIs also demonstrated good thermal stability, giving only 5% weight loss at temperature of 490 °C in nitrogen atmosphere. The glass transition temperatures (Tgs) of these isomeric PTESIs were between 242 and 265 °C, and were increased with increasing of the ratio of 3-chlorophthalimide unit in the polymer backbone. 相似文献
993.
Xiu-Li Wang Bao-Kuan Chen Guo-Cheng Liu Hong-Yan Lin Hai-Liang Hu 《Journal of organometallic chemistry》2010,695(6):827-832
Three new 3-D inorganic-organic polyoxovanadate-based coordination polymers [M2(bbi)(V2O6)2(H2O)2] [M = Co (1), Mn (2)] and [Ni2(bbi)3V4O12]·4H2O (3) (bbi = 1,1-(1,4-butanediyl)bis(imidazole)) have been synthesized under hydrothermal condition and characterized by elemental analyses, IR spectra, TG and single crystal X-ray diffraction. The 3-D networks of compounds 1 and 2 are constructed from neutral {M2V4O12} [M = Co (1), Mn (2)] layers that are pillared via the coordination of organic ligands bbi to M sites. Compound 3 is a 3-D eight-connected network, in which each binuclear [Ni2O4N6] node linked with other eight adjacent nodes through two {V4O12}4− clusters and six bbi ligands. The electrochemical behaviors of 1-3 modified carbon paste electrodes (1-CPE, 2-CPE and 3-CPE) in 1 M H2SO4 aqueous solution have been reported. 相似文献
994.
A new noncentrosymmetric ferroborate crystal, K2Fe2B2O7, has been grown from high temperature melt. Structure solution from single crystal X-ray diffraction shows that the title compound crystallizes in a trigonal space group P321 with cell dimensions of a=8.7475(12) Å and c=8.5124(17) Å. In the structure, FeO4 tetrahedron shares its three basal oxygen atoms with BO3 triangles forming a two-dimensional layer in the ab plane and the layers are connected by the apical Fe-O bonds along the c direction. The crystal is transparent in the visible and near infrared region from 500 to 2000 nm with three pronounced absorption bands ascribed to d-d transitions of tetrahedrally coordinated Fe3+ ions. Though, structurally analog to K2Al2B2O7, the further twisting of the BO3 groups between adjacent layers reduces its optical nonlinearity to a second-harmonic generation intensity of about 0.4 times that of KDP. Spin-glass behavior is observed at 20 K which is probably due to geometrically magnetic frustration of the triangular Fe net in the ab plane. 相似文献
995.
High-performance liquid chromatography (HPLC) fingerprint has been commonly used in the quality control and assessment of herbal medicines, and two-dimensional (2D) fingerprint obtained by means of HPLC-diode array detector (HPLC/DAD) can provide higher reliability. In this paper, an approach to the analysis of the 2D HPLC/DAD fingerprints, which was based on digital image recognition techniques, was developed for the first time. First, wavelet transform was employed to eliminate noise signal in the 2D fingerprint, and then the 2D fingerprint was converted into grayscale image. Second, several features of the image were calculated, and hierarchical clustering. This approach was applied to the qualitative analysis of the different samples of coptis chinensis, and the clustering result of samples was all highly consistent with the real situation. Based on the densities in grayscale image, three components in standard samples were quantitative analyzed, and the obtained correlation coefficients between concentration and grayscale density were more than 0.999. Our study indicated that the analysis of the 2D HPLC/DAD fingerprint was successful based on the idea and techniques of digital image recognition techniques, and this proposed approach provided a new pathway for the analysis of two-dimensional spectrums. 相似文献
996.
Tianhui Hu Helou Xie Jianbo Xiao Hailiang Zhang Erqiang Chen 《Cellulose (London, England)》2010,17(3):547-558
A novel combined main-chain/side-chain liquid-crystalline polymer based on an ethyl cellulose main chain containing azobenzene
mesogens (AzoEC) was successfully synthesized. Molecular characterization of the resulting polymers with different degrees
of substitution (DS) was performed with proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). Thermal stability was investigated
by thermogravimetric analysis (TGA). The phase transitions and liquid-crystalline behavior of these polymers were investigated
by differential-scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The
results indicate that DS has substantial effect on the liquid-crystalline behavior of these polymers. AzoEC with low DS only
shows the cholesteric phase similar to ethyl cellulose (EC). However, when DS increases to a specific value, AzoEC begins
to show fascinating supramolecular structures. The supramolecular structure of AzoEC with maximum DS consisted of a large-scale
ordered lamellar structure formed by EC main chains and a small-scale ordered structure formed by azobenzene mesogens. 相似文献
997.
A novel inorganic-organic hybrid compound based on mixed-valence Wells-Dawson arsenotungstate and mixed-ligand Cu(I) units, Cu8I(imi)4(bpy)6(H2O)[As2VW2VW16VlO62]·2H2O (1) (bpy=4,4′-bipydine; imi=imidazole), has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, luminescent spectrum and single crystal X-ray diffraction. Single-crystal X-ray diffraction revealed that four terminal and three bridging oxygen atoms of the Wells-Dawson cluster are coordinated to Cu(I) ions and form an unprecedented hepta-supporting polyoxometalate. The functionalized arsenotungstates are further connected by two kinds of tridentate linkers, Imi-Cu-(bpy)-Cu-(bpy)-Cu-(bpy)-Cu-Imi and Imi-Cu-(bpy)-Cu-(bpy)-Cu-H2O, to construct a 3D framework with 46·64 topology. The hybrid material has an intense emission at about 397 nm. 相似文献
998.
Protein thiols contribute significantly to antioxidant defence and selective oxidation of cysteines is important in signal transduction even in sub-stress scenarios. However, cysteine is the second rarest residue in proteins and it can be difficult to target low-abundance thiol (-SH)-containing proteins in proteomic separations. Activated thiol sepharose (ATS) allows covalent selection of -SH-containing proteins which can then be recovered by reduction with mercaptoethanol or dithiothreitol. This is a robust method for enriching -SH-containing proteins. We have used ATS to estimate the percentage (by weight) of thiol-containing proteins in cell extracts from a range of biological sources: a bacterium, Escherichia coli; a fungus, Trichoderma harzianum; and a bivalve mollusc Mytilus edulis. -SH-containing proteins account for 2.52% (E. coli), 1.4% (T. harzianum) and 1.4% (M. edulis) of total protein. Exposure to pro-oxidants did not materially alter these values. On removal of low Mr thiols such as glutathione, the values for M. edulis did not significantly change but those for T. harzianum increased threefold. The two-dimensional electrophoresis profiles of ATS-selected proteins for each organism were compared in control and pro-oxidant-exposed preparations. This revealed that some proteins present in controls were absent in pro-oxidant-treated extracts which we attribute to thiol oxidation. ATS has significant potential in enrichment for -SH-containing proteins in redox proteomics. 相似文献
999.
This work exploited a sequential injection lab-on-valve (LOV) system for the determination of cadmium by anodic stripping voltammetry (ASV). A miniaturized electrochemical flow cell (EFC) was fabricated in LOV, in which a nafion coated bismuth film electrode was used as working electrode. The cadmium was electrodeposited on the electrode surface in bismuth solution, and measured with the subsequential stripping scan. Under optimal conditions, the proposed system responded linearly to cadmium concentrations in a range 2.0-100.0 μg L−1. The detection limit of this method was found to be 0.88 μg L−1. By loading a sample volume of 800 μL, a sampling frequency of 22 determinations h−1 was achieved. The repeatability expressed as relative standard derivation (R.S.D.) was 3.65% for 20 μg L−1 cadmium (n = 11). The established method was applied to analysis of trace cadmium in environmental water samples and the spiked recoveries were satisfactory. 相似文献
1000.
A series of tetrafluorophenyl-modified oligo(3,6-carbazole ethynylene)s (CfCzCf, CfCz2Cf, CfCz3Cf, (CfCz)2Cf, and Cf2CzCf2) were synthesized by a Pd/Cu-catalyzed Sonogashira coupling reaction and fully characterized. Their photophysical and electronic properties as well as their thermal stabilities were investigated. It is noteworthy that these tetrafluorophenyl modified compounds showed relative thermal stabilities and low-lying HOMO levels ranging from −5.54 to −5.60 eV, which might be the promising candidates for hole-transporting materials in OLEDs. 相似文献