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Xiao-Ming Chen

Publications and source records attributed to Xiao-Ming Chen.

17 recordsLinked to original sources
PubMed2003

Syntheses, structures, photoluminescence, and theoretical studies of a novel class of d10 metal complexes of 1H-[1,10]phenanthrolin-2-one.

A novel asymmetric monosubstituted 1,10-phenanthroline, Hophen.0.5 H(2)O (1, Hophen=1H-[1,10]phenanthrolin-2-one), was generated by a facile route, and a novel class of crystalline, d(10)-metal, monomeric or oligomeric complexes of this ligand, namely [Hg(ophen)(2)].4 H(2)O.CH(2)Cl(2) (2), [Cd(3)Cl(ophen)(5)].1.5 H(2)O.2 CH(2)Cl(2) (3), and [Zn(4)O(ophen)(4)(OAc)(2)].4H(2)O.2 CH(2)Cl(2) (4), were obtained by means of liquid diffusion, and were characterized by X-ray crystallography and photoluminescence studies. Complex 1 exhibits a hydrogen-bonded dimeric structure, 2 is a neutral monomeric complex, 3 has a trinuclear structure with the ophen ligand acting as a bridge through the ketone groups, and 4 features a tetranuclear Zn(4)O core that is consolidated further by bridging ophen and acetate ligands. All the complexes display photoluminescent properties in the blue/green region. The photoluminescent mechanisms were investigated by means of molecular orbital calculations, which showed that the photoluminescent properties are ligand-based and can be tuned upon ligation to different metal ions.

Aldose-Ketose Isomerases↗
PubMed2003

A novel, highly electrical conducting, single-component molecular material: [Ag2(ophen)2] (Hophen = 1H-[1,10]phenanthrolin-2-one).

This communication describes a highly conducting, single-component molecular material [Ag2(ophen)2] (Hophen = 1H-[1,10]phenanthrolin-2-one) based on very strong off-set pi-pi stacking interactions with an unusually short ring-to-ring distance of ca. 3.15 A between adjacent molecules and silver(I)-pi interactions with the Ag...C contact of 3.082 A between adjacent molecules. The title compound, having a room-temperature conductivity of 14 S cm-1, is structurally different from both the known conducting single-component molecular materials of transition-metal complexes with sulfur-containing pi-delocalized dithiolene ligands and the known conducting multicomponent organosilver(I) materials.

Journal Article↗
PubMed2003

Structural elucidation and antitumor activity of a fructan from Cyathula officinalis Kuan.

A fructan named CoPS3 was isolated from Cyathula officinalis Kuan. The structure of CoPS3 was determined by methylation, by the reductive-cleavage method combined with GC-MS analysis, and both 1D and 2D 1H and 13C NMR spectroscopy. These results show that CoPS3 is a graminans-type fructan that is comprised of a beta-D-fructofuranosyl backbone having residues linked (2-->1)- and (2-->6) with branches and an alpha-D-glucopyranose residue on the nonreducing end of the fructan chain. Each branch is terminated by a beta-D-Fruf residue. Bioassay showed that it could inhibit growth of Lewis pulmonary carcinoma implanted in mice.

Amaranthaceae↗
PubMed2003

A novel three-dimensional coordination polymer constructed with mixed-valence dimeric copper(I,II) units.

A novel three-dimensional coordination polymer with a mixed-valence localized copper(I,II) dimeric unit, [Cu2(4-pya)3]n (4-pya = 4-pyridinecarboxylate), was hydrothermally synthesized via a simultaneous in-situa redox and hydrolysis reaction of Cu(II) and 4-cyanopyridine and crystallographically characterized to be a twofold interpenetrated three-dimensional coordination network with a cubic [Cu16(4-pya)12] building unit.

Journal Article↗
PubMed2002

Synthesis and structural characterization of di- and tetranuclear zinc complexes with phenolate and carboxylate bridges. Correlations between 13C NMR chemical shifts and carboxylate binding modes.

Two di- and a tetranuclear zinc-carboxylate complexes with different coordination modes, [Zn(2)L(mu(1,3)-OAc)(2)](ClO(4)) (1), [Zn(2)L(mu(1,3)-Pro)(2)](ClO(4)) (2), and [Zn(2)L(mu(1,1)-HCO(2))(mu(1,3)-HCO(2))](2)(ClO(4))(2) (3) (where L = 2,6-bis(N-2-(2'-pyridylethyl)formimidoyl)-4-methylphenol, OAc = acetate, and Pro = propionate) have been synthesized. Their compositions and structures have been identified by elemental analyses, IR, NMR, and X-ray single-crystal diffraction. The cations in both 1 and 2 reveal that the two zinc ions are assembled by a phenolate and a pair of syn-syn mu(1,3)-carboxylate bridges with metal-metal distances of 3.281 and 3.331 A, respectively, and each polyhedron around the zinc ion is a slightly distorted trigonal bipyramid. Compound 3 is a tetranuclear complex consisting of two identical dinuclear subunits that connect to each other by the two formate groups. In each subunit, the pair of metal ions separated at 3.130(1) A is assembled by a phenolate oxygen from L, and a monodentate and a syn-syn bidentate formate bridges. The formate group displays a novel tridentate mode, namely, monodentate and syn-anti bidentate bridges. On the other hand, the solid-state (13)C NMR technique was employed to distinguish the different binding modes of acetate group in five-coordinate zinc complexes. The chemical shifts are as follows: chelating mode (ca. 184 ppm) > bidentate bridge (ca. 180 ppm) > monodentate bridge (ca. 176 ppm).

Journal Article↗
PubMed2002

Double-stranded helices and molecular zippers assembled from single-stranded coordination polymers directed by supramolecular interactions.

Using three nonlinear dicarboxylates, isophthalate (ipa), 4,4'-oxybis(benzoate) (oba), and ethylenedi(4-oxybenzoate) (eoba), we have prepared five neutral infinite copper(II) dicarboxylate coordination polymers containing lateral aromatic chelate ligands, namely [Cu(ipa)(2,2'-bpy)]n.2nH2O (1), [Cu2(ipa)2(phen)2H2O]n (2), [Cu(oba)(phen)]n (3), [Cu(oba)(2,2'-bpy)]n (4), and [Cu(eoba)(phen)]n (5; 2,2'-bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline) by hydrothermal synthesis. X-ray single-crystal structural analyses of these complexes reveal that the nonlinear flexible or V-shaped dicarboxylates can induce the helicity or flexuousity of the polymeric chains and aromatic chelate ligands are important in providing potential supramolecular recognition sites for pi-pi aromatic stacking interactions. An appropriate combination of the bridging dicarboxylate and aromatic chelate can induce a pair of single-stranded helical or flexuous chains to generate a double-stranded helix or molecular zipper through supramolecular interactions, respectively.

Journal Article↗
PubMed2002

The caudal periaqueductal gray participates in the activation of brown adipose tissue in rats.

To investigate the involvement of the periaqueductal gray (PAG) in the control of non-shivering thermogenesis, we tested the effects of electrical or chemical stimulation of the PAG on thermogenesis of brown adipose tissue (BAT) in urethane anesthetized rats. Electrical stimulation (0.1 mA, 33 Hz, 0.5 ms) or application of D,L-homocysteic acid (0.5 mM, 0.3 micro l) into the lateral region of the caudal PAG (cPAG) elicited BAT thermogenesis, measured as a rise in the local temperature of interscapular BAT. These results suggest that neurons in the cPAG send excitatory efferent signals for BAT thermogenesis.

Adipose Tissue, Brown↗
PubMed2002

Variation in the coordination mode of arenedisulfonates: syntheses and structural characterization of mononuclear and dinuclear cadmium(II) arenedisulfonate complexes with two- to zero-dimensional architectures.

Seven cadmium(II) arenedisulfonate compounds, namely [Cd(2,2'-bpy)(2)(H(2)O)(peds)].4H(2)O (1), [Cd(2)(2,2'-bpy)(4)(H(2)O)(2)(1,5nds)](1,5nds).4H(2)O (2), [Cd(cyclam)(1,5nds)](2) (3), ([Cd(inia)(2)(H(2)O)(2)(2,6nds)].4H(2)O)(n)(4), ([Cd(inia)(2)(H(2)O)(2)(bpds)].4H(2)O)(n)(5), ([Cd(2)(inia)(4)(H(2)O)(3)(peds)(2)].2H(2)O)(n)(6), and [Cd(1,5nds)(H(2)O)(2)](n) (7), where 2,2'-bpy = 2,2'-bipyridyl, cyclam = 1,4,8,11-tetraazacyclotetradecane, inia = isonicotinamide, nds = naphthalenedisulfonate, bpds = 4,4'-biphenyldisulfonate, and peds = 4,4'-phenyletherdisulfonate, have been obtained from aqueous solution by using similar procedures and structurally characterized by X-ray single-crystal diffraction, IR spectroscopy, and thermal gravimetric analysis. In 1, the peds anion coordinates as a monodentate ligand, leading to a mononuclear unit. In 2 and 3, the 1,5nds anions coordinate as mu(2)-bridging ligands in different modes, producing charged or neutral dinuclear clusters. In 4 and 5, 2,6nds and bpds behave as mu(2)-spacers, resulting in 1-dimensional polymers. While in 6, the peds acts both as terminal and bridging ligands with the SO(3)(-) groups being either monodentate or mu(2)-bridging, creating a knotted 1-dimensional polymer with dinuclear clusters as the repeating units. In 7, 1,5nds acts as a bridging ligand with each SO(3)(-) coordinated as a mu(2)-bridging group to adjacent Cd(II) centers, leading to a 2-dimensional polymer. Together with the reported ([Cu(en)(2)(1,5nds)].2H(2)O)(n) (8), all of the six possible coordination modes adopted by organodisulfonate anions, on the assumption that each SO(3)(-) group could be monodentate or mu(2)-bridging, are realized by introducing nitrogen-containing organic ligands as auxiliaries.

Journal Article↗
PubMed2002

Pseudo-polyrotaxane and beta-sheet layer-based three-dimensional coordination polymers constructed with silver salts and flexible pyridyl-type ligands.

A fascinating 3D pseudo-polyrotaxane architecture with 1D polymeric [Ag(bpp)](n) chains penetrating 2D (6,3) [Ag(2)(bpp)(2)(ox)](n) sheets and a 3D coordination network constructed with 2D infinite [Ag(ppa)](n) beta-sheetlike layers pillared by ox ligands (bpp = 1,3-bis(4-pyridyl)propane; ppa = N-(4-pyridinylmethyl)-4-pyridinecarboxamide; ox = oxalate) have been prepared by utilizing flexible pyridyl-type ligands and have been crystallographically characterized. Crystal data for 1: monoclinic, space group C2/c, a = 7.619(2) A, b = 19.781(4) A, c = 26.799(5) A, beta = 94.720(10) degrees, U = 4025.2(15) A(3), and Z = 4. Crystal data for 2: monoclinic, space group C2/c, a = 28.947(8) A, b = 8.617(3) A, c = 16.307(6) A, beta =121.07(1) degrees, U = 3484(2) A(3), and Z = 4.

Journal Article↗
PubMed2002

Polymeric (3-amino-2-chloropyridine)nitratosilver(I).

In the title compound [alternative name: poly[silver(I)-micro-(3-amino-2-chloropyridine)-micro-nitrato]], [Ag(NO(3))(C(5)H(5)ClN(2))](n) the Ag(I) atom is in an irregular AgN(2)O(3) geometry, surrounded by one pyridyl N atom [Ag-N 2.283 (5) A], one amine N atom [Ag-N 2.364 (6) A] and three O atoms from different nitrate ions [Ag-O 2.510 (6)-2.707 (6) A]. The Ag ions are bridged by the 3-amino-2-chloropyridine ligands into helical chains. Adjacent uniform chiral chains are further interlinked through the NO(3) bridges into an interesting two-dimensional coordination network in the solid.

Journal Article↗
PubMed2002

Interlocking of molecular rhombi into a 2D polyrotaxane network via pi-pi interactions. Crystal structure of [Cu2(bpa)2(phen)2(H2O)]2.2H2O (bpa2- = biphenyl-4,4'-dicarboxylate, phen = 1,10-phenanthroline).

In the solid state, interlocking of the lateral phen ligands at the acute angle sites of the molecular [Cu2(bpa)2-(phen)2(H2O)]2 rhombi via aromatic pi-pi stacking interactions into the cavities of the adjacent rhombi generates laminated polyrotaxanes that are further assembled into a 3D network via similar interactions between the phen ligands at the obtuse angle sites.

Journal Article↗
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.

Journal Article↗
PubMed2002

Tetra-mu-acetato-kappa2O:O'-bis[(4-phenylpyridine-kappaN)copper(II)].

The title compound, [Cu(2)(C(2)H(3)O(2))(4)(C(11)H(9)N)(2)] or [Cu(2)(MeCO(2))(4)(phpy)(2)] (phpy is 4-phenylpyridine), consists of centrosymmetric dimers in which the CuII atoms display a square-pyramidal CuO(4)N coordination, with four acetate O atoms in the basal plane [Cu-O 1.975 (3)-1.987 (3) A] and the phpy N atom in the apical position [Cu-N 2.150 (3) A]. The Cu atoms are 2.654 (1) A apart and are bridged by four acetate groups. The discrete dimers are extended into a three-dimensional supramolecular array through intermolecular pi-pi-stacking interactions.

Journal Article↗
PubMed2001

Di-mu-chloro-bis([2-[N,N-bis(2-aminoethyl)amino-kappa3N]ethylaminium]-copper(II)) bis(naphthalene-1,5-disulfonate) pentahydrate.

The title compound, [Cu2(C6H19N4)2Cl2](C10H6O6S2)2*5H2O, is comprised of discrete [Cu2(tren)2Cl2]2+ dimers [tren is 2-[N,N-bis(2-aminoethyl)amino]ethylaminium] and naphthalene-1,5-disulfonate anions. Two Cl- anions bridge two Cu(II) ions, each of which is also coordinated by two of the primary and the tertiary amino N atoms of the tren ligand, giving each metal atom a distorted square-pyramidal coordination geometry. The cation lies about an inversion centre and the asymmetric unit also has two independent anions lying about inversion centres.

Journal Article↗
PubMed1998

Clathration of Two-Dimensional Coordination Polymers: Synthesis and Structures of [M(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O and [Cu(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(4).(4,4'-H(2)Bpy) (M = Cd(II), Zn(II) and bpy = Bipyridine).

In the presence of guest 2,4'-bpy molecules or under acidic conditions, three compounds, [Cd(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O (1), [Zn(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O (2), and [Cu(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(4).(4,4'-H(2)bpy) (3), were obtained from the reactions of the metal salts and 4,4'-bpy in an EtOH-H(2)O mixture. 1 has a 2-D square-grid network structure, crystallizing in the monoclinic space group P2/n, with a = 13.231(3) Å, b = 11.669(2) Å, c = 15.019(3) Å, beta = 112.82(3) degrees, Z = 2; 2 is isomorphous with 1, crystallizing in the monoclinic space group P2/n, with a = 13.150(3) Å, b = 11.368(2) Å, c = 14.745(3) Å, beta = 110.60(3) degrees, Z = 2. The square grids superpose on each other into a channel structure, in which each layer consists of two pairs of shared edges, perfectly square-planar with an M(II) ion and a 4,4'-bpy at each corner and side, respectively. The square cavity has dimensions of 11.669(2) x 11.788(2) and 11.368(2) x 11.488(2) Å for 1 and 2, respectively. Every two guest 2,4'-bpy molecules are clathrated in each hydrophobic host cavity and are further stabilized by pi-pi stacking and hydrogen bonding interactions. The NMR spectra clearly confirm that both 1 and 2 contain 4,4'-bpy and 2,4'-bpy molecules in a 1:1 ratio, which have stacking interaction with each other in the solution. 3 crystallizes in the orthorhombic space group Ibam, with a = 11.1283(5) Å, b = 15.5927(8) Å, c = 22.3178(11) Å, Z = 4. 3 is made up of two-dimensional square [Cu(4)(4,4'-bpy)(4)] grids, where the square cavity has dimensions of 11.13 x 11.16 Å. Each [4,4'-H(2)bpy](2+) cation is clathrated in a square cavity and stacks with one pair of opposite edges of the host square cavity in an offset fashion with the face-to-face distance of ca. 3.95 Å. Within each cavity, the [4,4'-H(2)bpy](2+) cation forms twin three-center hydrogen bonds with two pairs of ClO(4)(-) anions. The results suggest that the guest 2,4'-bpy molecules and protonated [4,4'-H(2)bpy](2+) cations present in the reaction systems serve as structure-directing templates in the formation of the crystal structures and exclude self-inclusion of the networks having larger square cavities.

Journal Article↗