Hydrothermal syntheses and crystal structures of new cage-like mixed-valent polyoxovanadates

Three new cage-like mixed-valent polyoxovanadates [Ni(1,10'-phen)(3)](2)[V10O26] 1, [Zn(2,2'-biPY)(3)](3)[V15O36Cl](.)3H(2)O (2) and [Co(2,2'-biPY)(3)](3)[V15O36Cl](.)3H(2)O (3) have been hydrothermally synthesized for the first time and characterized by elemental analyses, IR, EPR spectra, TG analyses and single crystal X-ray diffraction. The polyoxoanion of I exhibits an interesting empty ellipsoidal [V-2(IV) V-8(V) O-26](4-) 'host' shell, while the oxo vanadium clusters of 2 and 3 possess a spherical [V-8(IV) V-7(V) O36Cl](6-) cage with a Cl- ion encapsulated. The structure-directing role of organic templates (1,10'-phen and 2,2'-bipy) on the formation of the polyoxoanion structures is discussed.

An unusual organic-inorganic chain-like hybrid complex [(CuCl)(2)(o-phen)](infinity) (o-phen=o-phenanthroline)

A novel organic-inorganic hybrid complex [(CuCl)(2) (o-phen)](infinity) 1 (o-phen = o-phenanthroline) has been hydrothermally synthesized and structurally characterized by elemental analyses, XPS spectrum, TG analysis, and single-crystal X-ray diffraction. Compound I crystallizes in the monoclinic system, space group P2(1)/n, a = 3.7285(7) Angstrom, b = 19.603(4) Angstrom, c = 16.757(3) Angstrom, beta = 95.83(3)degrees, V = 1218.4(4) Angstrom(3), Z = 4, lambda(MoKalpha) = 0.71073 Angstrom (R(F) = 0.0643 for 2559 reflections). Data were collected on an R-axis RAPID diffractometer at 293 K in the range of 1.60 < θ < 27.48degrees. The title compound exhibits a one-dimensional chain-like scaffolding constructed by the unusual [Cu3Cl3] hexagon motifs by, sharing opposite edges. Only Cu(1) sites of the [Cu3Cl3] hexagon are coordinated with N donors of o-phen groups. Furthermore, the three-dimensional supermolecular architecture is formed by C-H...Cl hydrogen bonds between o-phen groups and CuCl chains.

Study of electron transfer across the liquid/ice-like matrix interface by scanning electrochemical microscopy

In this work, we report the findings of a study on scanning electrochemical microscopy (SECM) to investigate the interfacial electron-transfer (ET) reaction between the 7,7,8,8-tetracyanoquinodimethane radical anion (TCNQ(.-)) in 1,2-dichloroethane and ferricyanide in an ice-like matrix (a mixture of insulting ice and conductive liquid) under low temperatures. Experimental results indicate that the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to a liquid/liquid interface at temperatures above -20 degreesC. Furthermore, imaging data show that the surface of the ice-like matrix is microscopically flat and physically stable and can be applied as either a conductive or an insulting substrate for SECM studies. Perchlorate ion was selected as the common ion in both phases, the concentrations of which controlled the interfacial potential difference. The effect of perchlorate concentration in the DCE phase on interfacial reactions has been studied in detail. The apparent heterogeneous rate constants for TCNQ(.-) oxidation by Fe(CN)(6)(3-) in another phase under different temperatures have been calculated by a best-fit analysis, where the experimental approach curves are compared with the theoretically derived relationships. Reaction rate data obey Butler-Volmer formulation before and after the freezing point, which is similar to most other known cases of ET reactions at liquid/liquid interfaces. However, there is a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase, which reflects the phase transition. At temperatures below -20 degreesC, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrix became an insulating one, which indicates that the aqueous phase is really a frozen phase.

Seed-mediated growth of large, monodisperse core-shell gold-silver nanoparticles with Ag-like optical properties

Large, monodisperse core-shell Au-Ag nanoparticles with Ag-like optical properties have been prepared by the seeding growth method in micellar media.

Electrocatalytic oxidation of NADH by rutin in biomembrane-like films on glassy carbon electrode

Stable lipid film was made by casting dipalmitoylphosphatidylcholine (DPPC) and rutin onto the surface of a glassy carbon (GC) electrode. The electrochemical behavior of rutin in the DPPC film was studied. The modified electrode coated with rutin gave quasi-reversible reduction-oxidation peak on cyclic voltammogram in the phosphate buffer (pH 7.4). The peak current did not decrease apparently after stored at 4 degreesC for 8 hours in refrigerator. This model of biological membrane was used to investigate the oxidation of dihydronicotinamide adenine dinucleotide (NADH) by rutin. Rutin in the film acts as a mediator. The modified electrode shows a great enhancement and the anodic peak potential was reduced by about 220 mV in the oxidation of 5 X 10(-3) mol L-1 NADN compared with that obtained at a bare glassy carbon electrode. (C) 2000 Elsevier Science S.A. All rights reserved.

The single crystal-like banded textures in the films of a thermotropic liquid crystalline poly(aryl ether ketone) containing a lateral chloro group

The banded textures in the films of a thermotropic liquid crystalline poly(aryl ether ketone) containing a lateral chloro group have been studied by means of transmission electron microscopy(TEM), electron diffraction(ED) and atomic force microscopy (AFM). The crystallization-induced Landed texture without external shear can be formed when the thin films were annealed at the temperature range(320-330 degrees C) of the liquid crystalline state from the melt, The results show that the banded regions have high orientation of single crystal based on the orthorhombic packing and the growing direction of the Lands is along the b axis of the crystals, This kind of single crystal-like bands is due to the different orientation of the packing molecular chains, The molecular chains of the dark bands in the bright field electron micrograph are perpendicular to the film plane, while the ones of the bright Lands are tilt along the b axis with the tilt angle upto +/-20 degrees.

Shear-induced spiral-like morphology of a main-chain liquid crystalline poly(aryl ether ketone)

The shear-induced spiral-like morphology of a main-chain thermotropic liquid crystalline poly(aryl ether ketone) is observed and characterized by means of polarizing light microscopy, atomic force microscopy, transmission electron microscopy and electron diffraction techniques. The spiral-like texture is formed during shearing in the temperature range of liquid crystalline to isotropic transition (335-340 degreesC), and dispersed discontinuously in the mosaic matrix. Electron diffraction results indicate that the spiral exhibits orthorhombic lateral packing of the crystals and homeotropic alignment of the molecules. The spiral formation process and possible affecting factors are discussed.

Host-guest-like thiamine-anion complexation in thiaminium bis(tetrafluoroborate)

In the title compound, 3-[(4-amino-2-methyl-5-pyrimidin-1-io)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium(2+) bis(tetrafluoroborate), C12H18N4OS2+. 2BF(4)(-), the divalent thiamine cation (in the F conformation) is associated with BF4- anions via two characteristic bridging interactions between the thiazolium and pyrimidinium rings, i.e. C-H . . . BF4- . . . pyrimidinium and N-H . . . BF4- . . . thiazolium interactions. Thiamine molecules are linked by N-H . . .O hydrogen bonds to form a helical chain structure.