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Xian-Ming Zhang

Publications and source records attributed to Xian-Ming Zhang.

14 recordsLinked to original sources
PubMed2007

Structural and electronic properties of hetero-transition-metal Keggin anions: a DFT Study of alpha/beta-[XW12O40]n- (X = CrVI, VV, TiIV, FeIII, CoIII, NiIII, CoII, and ZnII) relative stability.

Density functional theory calculations have been carried out to investigate the electronic structures and the alpha/beta relative stability of Keggin-typed [XW(12)O(40)]n- anions with transition metal as heteroatom X (X = Cr(VI), V(V), Ti(IV), Fe(III), Co(III), Ni(III), Co(II) and Zn(II)). Nice agreement in geometries between computation and experiment has been obtained, and the higher stability of the alpha isomer over the beta one has been confirmed. Structural parameter analysis reveals that the {M(3)O(13)} triads in both alpha and beta isomers contract considerably with the increase of the negative anionic charge, while the overall size of both isomers shrinks only slightly. Fragment molecular orbital analysis shows that except alpha/beta-[TiW(12)O(40)]4-, the electronic structures of Keggin anions can be described by the insertion of the e and/or t2 orbital of XO4n- into the frontier orbitals of W(12)O(36) cage, and this leads to the specific redox property, which is different from that of the Keggin anions with main-group elements as heteroatoms. Energy decomposition analysis shows that the enhanced intrinsic stability of the alpha isomer in Td arrangement of W(12)O(36) shell and the larger deformation of the alpha over the beta isomer are two dominating factors and contribute oppositely to the alpha/beta relative stability.

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PubMed2006

Two mixed-valence vanadium(III,IV) phosphonoacetates with 16-ring channels: H2(DABCO)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O and H2(PIP)[V(IVO)(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O.

Two isostructural mixed-valence vanadium phosphonoacetates H2(DABCO)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O (1) and H2(PIP)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O (2) have been synthesized. They crystallize in the orthorhombic space group Pnna with a = 7.0479(10) A, b = 15.307(2) A, and c = 17.537(3) A for 1 and a = 7.0465(9) A, b = 15.646(2) A, and c = 17.396(2) A for 2. X-ray single-crystal diffraction reveals that 1 and 2 have a three-dimensional open framework featuring 16-ring ellipsoid channels that are filled with doubly protonated 1,4-diazabicyclo[2,2,2]octanium/piperazinium cations and water molecules. According to the classification in metal-organic frameworks, 1 and 2 contain infinite (-O-V-)(infinity) chains that are cross-linked by "metalloligand" [VO(H2O)(O3PCH2CO2)2](4-) into a 3-D net of the sra topology. The temperature dependence of the magnetic susceptibility of 1 shows that the chi(m)T value in the range of 60-320 K is constant of 1.105 cm3 K mol(-1)/V2 unit, and upon further cooling, the chi(m)T value rapidly increases to 1.81 cm3 K mol(-1) at 2 K. The corresponding effective magnetic moment (mu(eff))/V2 unit varies from 2.97 mu(B) at 320 K to 3.80 mu(B) at 2 K. The magnetic data in the range of 2-320 K follow the Curie-Weiss law with C = 1.074 cm3 K mol(-1) and Theta= -1.34 K.

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PubMed2006

Diversity of coordination architecture of metal 4,5-dicarboxyimidazole.

Seven complexes of metal 4,5-dicarboxyimidazole acid (H3dcbi), namely, [Cd(H2dcbi)2(H2O)3].H2O (1.alpha), [Cd(H2dcbi)2(H2O)2].2H2O (1.beta), [Cd(H2dcbi)2(H2O)2].2H2O (1.gamma), [Cd(H2dcbi)2(H2O)2] (2), [Cd(Hdcbi)(H2O)] (3), [Cd5(Hdcbi)2(dcbi)2(H2O)].XH2O (4), [Cd2(Hdcbi)(C2O4)] (5), [Ag5(Hdcbi)2(CN)] (6), and [Mn(Hdcbi)(H2O)] (7), have been hydro(solvo)thermally synthesized by fine control over synthetic conditions such as stoichiometry, solvent, and pH value. X-ray single-crystal structural analyses reveal that they have rich structural chemistry ranging from mononuclear (1), one-dimensional (2), and two-dimensional (3 and 7) to three-dimensional (4-6), among which 1 crystallizes in three types (alpha, beta, and gamma) of polymorphs. Seven coordination modes of H(n)dcbi ranging from monodentate to mu5 have been observed, among which four modes are found first. The coordination geometries of the Cd(II) sites vary from five-coordinate trigonal bipyramid and square pyramid, six-coordinate octahedron to seven-coordinate pentagonal bipyramid. Analyses of the synthetic conditions and structures of the Cd(II) complexes show that the influences of the solvent and the metal-to-ligand molar ratio are very important to the products and coordination modes of H(n)dcbi (n =0, 1, 2). Studies of the coordination modes of H(n)dcbi and the structures of the Cd(II) complexes also reveal that the singly deprotonated H2dcbi generally coordinates in the monodentate imidazole-N or N,O-chelate mode to result in mononuclear structures, the doubly deprotonated Hdcbi coordinates in the mu2, mu3, or mu4 mode to generate one-dimensional or two-dimensional structures, and the triply deprotonated dcbi can coordinate in the mu5 mode to form three-dimensional structures. The cyanide was in situ formed via C-C bond cleavage of acetonitrile during the preparation of 6, which adopts a rare mu4-kC,kC:kN,kN mode to bridge four Ag(I) ions. The microporous three-dimensional framework of 4 is maintained after the removal of the guest molecules. Compounds 1-5 show strong violet emissions with maxima around 380 nm, tentatively attributed to the ligand-centered transition.

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PubMed2006

Syntheses and structures of metal tetrazole coordination polymers.

Two salts and seven copper(I/II) and silver(I) coordination polymers containing tetrazolyl ligands have been hydro(solvo)thermal synthesized by metal salts, NaN3 and various nitriles generated via [2 + 3] cycloaddition reactions of organonitriles and sodium azide. The study also shows that in some cases the azide can play a dual role in the in situ syntheses of metal tetrazole complexes, namely, starting material for tetrazole ligand and co-ligand in the tetrazole-based coordination complexes. Compounds and are simple salts of ammonium and sodium 5-methyltetrazolate. Compound has a 3-D framework with intersecting channel and unprecedented (4(9).6(6)) topology constructed from mixed-valent Cu8 clusters. Compounds and are isomorphous, and have 3-D organic-inorganic frameworks constructed by [M2(mtta)]+ (Hmtta = 5-methyltetrazole) ribbon and [M2(N3)]+ (M = Cu, Ag) layer two types of structural motifs, which contains an mu(4)-1,1,1,3 azide. Compound is a 3-D four-connected chiral complex with (4(2).8(4))(Cu)(4(2).8(2).10(2))(tta) topology. The structure of consists of 2-D three-connected layers that are linked by ligand-unsupported Ag(I)...Ag(I) interactions to form a 3-D supramolecular array. Compound shows a 3-D chiral framework containing tetrahedrally and linearly coordinated Ag(I) ions and mu3- and mu4-two types of 5-propyltetrazolate. Compound has a 2-D layered structure formed by linkage of [Ag(tetrazolyl)] ribbons via C-C and N-Ag bonds. Magnetic measurement confirmed that there are two Cu(II) ions and six Cu(I) ions per Cu8 unit consistent with a mixed-valent Cu(I,II) complex.

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PubMed2005

Cuprophilicity-induced cocrystallization of [Cu2(4,4'-bpy)(CN)2]n sheets and [Cu(SCN)]n chains into a 3-D pseudopolyrotaxane.

The cocrystallization of [Cu(SCN)]n chains and [Cu2(4,4'-bpy)(CN)2]n (4,4'-bpy = 4,4'-bipyridine) layers generated a 3-D pseudopolyrotaxane compound, [Cu2(4,4'-bpy)(CN)2].[Cu(SCN)] (1), which can also be viewed as a 3-D network constructed by linkages of 2-D sheets and 1-D chains via unsupported CuI-CuI interactions. The CuI-CuI contact of 2.651(4) A in 1 is the shortest unsupported CuI-CuI distance documented to date, indicating cuprophilic attractions.

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PubMed2005

A twelve-connected Cu6S4 cluster-based coordination polymer.

Hydrothermal reaction of Cu(MeCO2)2, (4-pyridylthio)acetic acid, and NH4SCN resulted in a metal-organic framework [Cu3(4-pyridinethiolate)2(CN)] which has twelve-connected face-centered cubic topology with Cu6S4 clusters as nodes.

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PubMed2005

Hydrothermal syntheses and structures of two mixed-valence copper(I,II) 2-pyrazinecarboxylate coordination polymers.

Replacement of linear ligand L in Cu(I)XL system (X = halide or pseudohalide; L = 4,4'-bipyridine or pyrazine) by neutral species Cu(pzc)2(H2O)x (pzc = 2-pyrazinecarboxylate) resulted in mixed-valence Cu(I,II) coordination polymers [Cu2(pzc)2Br(H2O)]n (1) and [Cu3(pzc)2(CN)2(H2O)2 x 2H2O]n (2). Complex 1 has two-dimensional (4,4) topological layer constructed by [CuBr]n chains and Cu(pzc)2(H2O) species, while 2 has a three-dimensional framework formed by linkage of two-dimensional (6,3) layers via ligand-unsupported Cu(I)-Cu(I) interactions. The two-dimensional (6,3) layer in 2 is constructed by zigzag [CuCN]n chains and Cu(pzc)2(H2O)2 species. Cyanides in 2 were produced by oxidative desulfation of SCN- anions.

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PubMed2004

Apoptosis of murine melanoma B16-BL6 cells induced by quercetin targeting mitochondria, inhibiting expression of PKC-alpha and translocating PKC-delta.

PURPOSE: In our previous study, quercetin was found to induce apoptosis of murine melanoma B16-BL6 cells. The cellular and molecular mechanism of quercetin-induced apoptosis was investigated in the present study. METHODS: Nuclear morphology was determined by fluorescence microscopy. DNA fragmentation was analyzed by electrophoresis and quantified by the diphenylamine method. The transmembrane potential of mitochondria was measured by flow cytometry. Bcl-2, Bcl-X(L), PKC-alpha, PKC-beta, and PKC-delta were detected by Western blotting. Caspase activity was determined spectrophotometrically. RESULTS: Quercetin induced the condensation of nuclei of B16-BL6 cells in a dose-dependent pattern as visualized by Hoechst 33258 and propidium iodide dying. Phorbol 12-myristate 13-acetate (PMA), a PKC activator, significantly enhanced apoptosis induced by quercetin, while doxorubicin, a PKC inhibitor, markedly decreased it. Both PMA and doxorubicin showed a consistent effect on the fragmentation of nuclear DNA caused by various dosages of quercetin. Quercetin dose-dependently led to loss of the mitochondrial membrane potential, which was also significantly reinforced or antagonized by PMA and doxorubicin, respectively. Moreover, PMA showed reinforcement, while doxorubicin showed significant antagonization, of the quercetin-mediated decrease in the expression of Bcl-2. Quercetin promoted caspase-3 activity in a dose-dependent manner, which was also regulated by PMA and doxorubicin with a pattern similar to that seen in their effect on apoptosis, mitochondrial membrane potential and Bcl-2 expression, but none of these were directly affected by PMA and doxorubicin. Free fatty acid and chlorpromazine, a PKC activator and inhibitor, respectively, did not interfere with these effects of quercetin. B16-BL6 cells expressed PKC-alpha, PKC-beta, and PKC-delta. Quercetin dose-dependently inhibited the expression of PKC-alpha but not that of PKC-beta and PKC-delta. Doxorubicin almost completely blocked the effect of quercetin on the expression of PKC-alpha. Quercetin was also involved in the translocation of PKC-delta from the cytosol to the nucleus. PMA enhanced the effect of quercetin on the translocation of PKC-delta. CONCLUSIONS: These results indicate that quercetin induced apoptosis of murine melanoma B16-BL6 cells by injuring their mitochondria, increasing the activity of caspase-3, inhibiting the expression of Bcl-2 and PKC-alpha, and inducing the translocation of PKC-delta. Doxorubicin inhibited these effects of quercetin by blocking the decreased expression of PKC-alpha induced by quercetin while PMA increased these effects by enhancing the translocation of PKC-delta induced by quercetin.

Animals↗
PubMed2004

In situ formation of meso-2,2'-oxydisuccinate via intermolecular dehydration coupling of D,L-malic acid: first coordination polymer of 2,2'-oxydisuccinate involving ether oxygen coordination: [Cd2(meso-odsc)(H2O)].

The first coordination polymer of 2,2'-oxydisuccinate, [Cd(2)(meso-odsc)(H(2)O)](odsc =meso-2,2'-oxydisuccinate), was hydrothermally synthesized from CdSO(4) and D,L-malic acid; X-ray crystallography shows that the D,L-malic acid was transformed in situ into meso-odsc via intermolecular dehydration coupling.

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PubMed2003

Quercetin inhibits the invasion of murine melanoma B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway.

PURPOSE: On the basis of the inhibitory effect of quercetin on the invasion of melanoma B16-BL6 cells previously reported by us, the mechanisms of quercetin-mediated inhibition of invasion were further investigated in the present study. METHODS: The ability of B16-BL6 cells to invade and migrate was evaluated in terms of the numbers of cells penetrating a reconstituted basement membrane in the Transwell coculture system. The relative levels and activities of matrix metalloproteinase-9 (MMP-9) and MMP-2 were determined by gelatin zymography and quantified using LabWorks 4.0 software. RESULTS: The quercetin-mediated inhibition of invasion was partially blocked by phorbol-12,13-dibutyrate (PDB), a PKC (protein kinase C) activator, and by doxorubicin, a PKC inhibitor. Only the proforms of MMP-9 (92 kDa) and MMP-2 (72 kDa) were detected by gelatin zymography. Quercetin dose-dependently decreased the gelatinolytic activity of pro-MMP-9. Doxorubicin also markedly reversed the quercetin-induced decrease. Quercetin showed a dose-dependent antagonism of increases in gelatinolytic activity of pro-MMP-9 induced by PDB and free fatty acid (another PKC activator). CONCLUSIONS: Together with the report that quercetin directly reduces PKC activity, the results reported here suggest that quercetin may inhibit the invasion of B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway.

Animals↗
PubMed2003

Oxidation of ferulic acid by Momordica charantia peroxidase and related anti-inflammation activity changes.

Plant peroxidases were found to play an important role in plant physiology such as the metabolism and transformation of small complexes. In the present research, a novel Momordica charantia peroxidase (MCP) from fruits was purified to electrophoretic homogeneity by combining consecutive treatment of ammonium sulfate fractionation, ion exchange chromatography on DEAE-Sepharose FF, affinity chromatography on concanavalin A (Con A) Sepharose and gel filtration on Sephadex G-150. The physical and chemical characters of MCP were also investigated. MCP catalyzed the oxidation of ferulic acid (FA) to dehydrodimer (FA-2) in aqueous acetone system at pH 5.0. Its structure was identified by spectral analyses including IR, 1H-, 13C-NMR and electrospray ionization mass spectroscopy (ESI-MS). The anti-inflammatory activities of FA, FA-2 and other derivatives were examined. FA-2 significantly inhibited the release of proinflammatory factors such as TNF-alpha, NO and proliferation of spleen cells induced by phytohemagglutinin (PHA) and Con A and promoted a greater DNA fragmentation of spleen cells than that of other complexes. These results suggested that MCP as a tool enzyme transformed some complexes such as FA to more active derivatives, and that FA-2 was a potential inhibitor on inflammation through interference with immune response in the process of inflammation, which maybe was associated with apoptosis of immune related cells induced by FA-2.

Animals↗
PubMed2002

Syntheses, crystal structures, and physical properties of dinuclear copper(I) and tetranuclear mixed-valence copper(I,II) complexes with hydroxylated bipyridyl-like ligands.

Four copper complexes with hydroxylated bipyridyl-like ligands, namely [Cu(2)(ophen)(2)] (1), [Cu(4)(ophen)(4)(tp)] (2), [Cu(4)(obpy)(4)(tp)] (3), and [Cu(4)(obpy)(4)(dpdc)].2H(2)O (4), (Hophen=2-hydroxy-1,10-phenanthroline, Hobpy=6-hydroxy-2,2'-bipyridine, tp=terephthalate, dpdc=diphenyl-4,4'-dicarboxylate) have been synthesized hydrothermally. X-ray single-crystal structural analyses of these complexes reveal that 1,10-phenanthroline (phen) or 2,2'-bipyridine (bpy) ligands are hydroxylated into ophen or obpy during the reaction, which provides structural evidence for the long-time argued Gillard mechanism. The dinuclear copper(I) complex 1 has three supramolecular isomers in the solid state, in which short copper-copper distances (2.66-2.68 A) indicate weak metal-metal bonding interactions. Each of the mixed-valence copper(i,ii) complexes 2-4 consists of a pair of [Cu(2)(ophen)(2)](+) or [Cu(2)(obpy)(2)](+) fragments bridged by a dicarboxylate ligand into a neutral tetranuclear dumbbell structure. Dinuclear 1 is an intermediate in the formation of 2 and can be converted into 2 in the presence of additional copper(II) salt and tp ligands under hydrothermal conditions. In addition to the ophen-centered pi-->pi* excited-state emission, 1 shows strong emissions at ambient temperature, which may be tentatively assigned as an admixture of copper-centered d-->s,p and MLCT excited states.

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