Facile preparation of ZnTiO3 ceramic powders in sodium/potassium chloride melts

A facile molten salt synthesis route was developed to prepare ZnTiO3 ceramic powders with simple oxides ZnO and TiO2 using sodium and potassium chloride eutectic salts as flux. The role of calcination temperature and time and the amount of salt addition to ZnTiO3 formation was investigated by thermogravimetry-differential thermal analysis, X-ray diffraction and Fourier transformation-infrared spectroscopy measurements. Pure hexagonal phase of ZnTiO3 could be obtained from the mixture of the simple oxides and the chlorides (50 mol% KCl, 20 times to oxides in molar ratio) heating at 800 degrees C for 6 h. The scanning electron microscopy images revealed the products were hexagonal sheets of about 1-3 mu m size. Increasing the amount of salt aids in reducing the crystal sizes of final ceramic powders because of diluting the solution.

Direct oxidation of benzene to phenol on manganese pyrophosphate with hydrogen peroxide

A solid catalyst manganese pyrophosphate based on non-sieves to oxidize benzene to phenol with oxidant hydrogen peroxide has shown good conversion with good selectivity in CH3CN at 65 degrees C investigating water contact angle data of three manganese salts, it is found manganese pyrophosphate has certain repulsive water character. It is further to be confirmed by benzene and phenol adsorption experiments onto catalyst surface by GC. With benzene/H2O2 ratio of 1, the benzene conversion of 13.8% with phenol selectivity of 85.0% was achieved. It is noteworthy that no any products are obtained using manganese pyrophosphate as catalyst in the oxidation of phenol in CH3CN solvent.

Syntheses and properties of polyimides derived from diamines containing 2,5-disubstituted pyridine group

A Series of novel homo- and copolyimides containing pyridine units were prepared from the heteroaromatic diamines, 2,5-bis (4-aminophenyl) pyridine and 2-(4aminophenyl)-5-aminopyridine, with pyromelltic dianhydride (PMDA), and 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidizaton method. The poly(amic acid) precursors have inherent viscosities of 1.60-9.64 dL/g (c = 0.5 g/dL in DMAC, 30 degrees C) and all of them can be cast and thermally converted into flexible and tough polyimide films. All of the polyimides show excellent thermal stability and mechanical properties. The polyimides have 10% weight loss temperature in the range of 548-598 degrees C in air. The glass transition temperatures of the PMDA-based samples are in the range of 395-438 degrees C, while the BPDA-based polyimides show two glass transition temperatures (T(g)1 and T(g)2), ranging from 268 to 353 degrees C and from 395 to 418 degrees C, respectively. The flexible films possess tensile modulus in the range of 3.42-6.39 GPa, strength in the range of 112-363 MPa and an elongation at break in the range of 1.2-69%. The strong reflection peaks in the wide-angle X-ray diffraction patterns indicate that the polyimides have a high packing density and crystallinity.

Syntheses and properties of novel polyimides derived from 2-(4-aminophenyl)-5-aminopyrimidine

2-(4-Aminophenyl)-5-aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo- and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97-4.38 dL/g (c = 0.5 g/dL, in DMAc, 30 degrees C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307-434 degrees C and the 10% weight loss temperature is in the range of 556-609 degrees C under air. The polyimide films possess strength at break in the range of 185-271 MPa, elongations at break in the range of 6.8-51%, and tensile modulus in the range of 3.5-6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance.

New neutral nickel(II) complexes bearing pyrrole-imine chelate ligands: synthesis, structure and norbornene polymerization behavior

New neutral nickel(II) complexes bearing nonsymmetric bidentate pyrrole-imine chelate ligands (4a-d), [2-(ArNCH)C4H3N]Ni(PPh3)Ph [Ar=2,6-diisopropylphenyl (a), 2-methyl-6-isopropylphenyl (b), 2,6-diethylphenyl (c), 2-tert-butylphenyl (d)], have been prepared in good yields from the sodium salts of the corresponding ligands and trans-Ni(PPh3)(2)(Ph)Cl, and the structure of complex 4a has been confirmed by X-ray crystallographic analysis. These neutral Ni(II) complexes were investigated as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display very high activities and produce great mass polymers. Catalyst activity of up to 4.2 x 10(7) g (mol Ni h)(-1) and the viscosity-average molecular weight of polymer of up to 9.2 x 10(5) g mol(-1) were observed. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of reaction parameters such as Al-Ni ratio, norbornene-catalyst ratio, monomer concentration, polymerization reaction temperature and time.

Anion coordination and molecular assembly in C2-substituted thiamine-anion systems: effects of the anion and molecular conformation

The compounds (het)(PtCl6)2H(2)O 1, (het)(HgI4).H2O 2 (het = 2-(alpha-hydroxyethyl)thiamine) and (hpt)(Hg2Br6) 3 (hpt = 2-(alpha-hydroxypropyl)thiamine) have been prepared and structurally characterized by X-ray crystallography in order to study the influence of the anion and molecular conformation on the formation of supramolecular architectures that adsorb anionic species. Both het and hpt molecules adopt the usual S conformation for C2-substituted thiamine but differ from the F conformation for C2-free thiamine derivatives. Two types of characteristic ligand-anion complexation are observed, being of the forms C(6')-H...anion...thiazolium-ring (in 1 and 2) and N(4'1)-H...anion...thiazolium-ring (in 3). The reaction of het with PtCl62- or HgI42- gives a 1-D double-chain in 1, consisting of two hydrogen-bonded het chains, which are cross-linked by anions through hydrogen bonding and anion...aromatic-ring interactions, or a cationic 3-D framework in 2 formed by the stacking of hydrogen-bonded sheets with anion-and-water-filled channels. In the case of 3, hydrogen-bonded hpt dimers and HgBr62- anions form alternate cation-anion columns. A comparison with the cases of C2-free thiamine-anion complexes indicates that the change in molecular conformation results in novel supramolecular assemblies in 1 and 2 and an analogous architecture in 3, which also depends on the nature of the anions.

Hydrothermal synthesis, structure, and characterization of two one-dimensional chainlike hybrid complexes [(CuX)(2)(o-phen)](infinity) (X = Br, Cl; o-phen = o-phenanthroline)

Two novel organic-inorganic hybrid complexes [(CuX)(2)(o-phen)](infinity) (X = Br (1), Cl (2); o-phen = o-phenanthroline) have been synthesized hydrothermally and characterized structurally by elemental analyses, IR, ESR, XPS spectrum, TG analyses and single-crystal X-ray diffraction. Both title compounds exhibit novel one-dimensional chainlike copper halide scaffolding constructed by the unusual [Cu3X3] hexagon motifs by sharing opposite edges, where a single Cu site of each [Cu3X3] hexagon is chelated with N donors of o-phen group. To our knowledge, such basic o-phen-copper halide skeleton has not been reported hitherto. Moreover, TG analyses indicate that both title compounds possess high thermal stability.

Novel, highly active binuclear 2,5-disubstituted Amino-p-benzoquinone-nickel(II) ethylene polymerization catalysts

Reaction of salts of the 2,5-disubstituted amino-p-benzoquinone bridging ligand (la-e) with trans-bis(triphenylphosphane)phenylnickel(II) chloride results in the binuclear complexes 2a-e, which show high activities for ethylene polymerization without any cocatalysts. High-molecular-weight, moderately branched polyethylene of broad molecular-weight distribution was obtained.

Synthesis and structural characterization of a new molecule-based complex constructed from dodecamolybdophosphoric acid and imidazole

A new compound, (CH5N2)(3)(PMo12O40CH4N23H2O)-C-.-H-. (1), was synthesized and structurally characterized by elemental analyses, IR spectra, UV spectra, NMR spectra and ESR spectra. This is, to our knowledge, the first example of an imidazole-polyoxometalate species. The compound was recrystallized from N,N-dimethylformamide (DMF), and then black block-like crystals of (C3H5N2)(4)((PMoMo11O40)-Mo-V-O-VI)(.)4C(3)H(7)NO(.) 2H(2)O (2), were obtained. It crystallizes in a triclinic space group P (1) over bar with n=12.423(3) Angstrom, b=12.666(3) Angstrom, c=13.341(3) Angstrom, alpha=70.56(3)degrees, beta=71.16(3)degrees, gamma=64.18(3)degrees, V= 1742.3(6) Angstrom(3), Z=1, R1 = 0.0585, wR2 = 0.1885. An X-ray crystallographic study showed that the crystal structure is constructed by electrostatic attractions and hydrogen bonds between a dodecamolybdophosphoric anion and an imidazole. The imidazole and DMF molecules occupy cavities in a polyoxometalate lattice ordered along a c-axis. The structure of (2) is similar to that of (1) from a comparison of both IR spectra and TGA Curves.

Ultrafine fibers electrospun from biodegradable polymers

Biodegradable poly(I-lactide) (PLLA) and poly(e-caprolactone) (PCL) were electrospun into ultrafine fibers. The technological parameters influencing the spinning process and morphology of the fibers obtained were examined. These parameters included solvent composition, addition of certain organic salts, molecular weight and concentration of the polymers, capillary diameter, air ventilation, and pressure imposed on the surface of the solution as well as electrostatic field. By properly choosing and adjusting these parameters, submicron PLLA and PCL fibers with a narrow diameter distribution were prepared. Scanning electronic microscopy was used to observe the morphology and diameter size of the fibers.

Synergistic extraction of zinc(II) by mixtures of primary amine N1923 and Cyanex272

The extraction of zinc(II) and cadmium(II) from chloride solution by mixtures of primary amine N1923 and Cyanex272 (HA) was studied. The synergistic effect was observed for the extraction of zinc(II) while no synergistic effect for cadmium(II), which makes it possible to separate zine(II) and cadmium(II) with the mixtures. The results showed that zinc(II) was extracted as (RNH3Cl)(3) . ZnCIA instead of ZnA(2) . 2HA which was extracted by Cyanex272 alone. The extraction mechanism was discussed and the formation constants and thermodynamic functions were determined. The separation factors between zinc(II) and cadmium(II) were calculated.

High-sensitivity molecular mass determination of lysozyme prior to MALDI-MS

Sodium dodecyl sulfate(SDS) is a powerful solubilizing detergent which is often used during the separation of highly complex protein mixtures by one- or two-dimensional (2D) gel electrophoresis. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a widely used technique for mass spectrometric analysis of some protein molecules compared to other techniques. But the presence of SDS or some salts usually leads to signal deterioration when using MALDI-MS. A method for using nitrocellulose membrane as the solid-phase carrier combined with n-octyl-beta-D-glucopyranoside in the matrix highly enhances the sensitivity of the molecular mass determination of lysozyme. This technique has the advantage that the signal-to-noise of the molecular weight profile is improved compared with the mass spectrum and the profile is relatively easy to interpret.

Citrate-gel synthesis and luminescent properties of ZnGa2O4 doped with Mn2+ and EU3+

By using inorganic salts as raw materials and citric acid as complexing agent, spinel oxide ZnGa2O4 and Mn2+, Eu3+-doped ZnGa2O4 phosphor powders were prepared by a citrate-gel process. X-ray diffraction (XRD), TG-DTA, FT-IR. and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500 degreesC and pure ZnGa2O4 phase is obtained at 700 degreesC, which agrees well with the results of TG-DTA and FT-IR. In the crystalline ZnGa2O4, the Eu shows its characteristic red (615 nm, D-5(0)-F-7(2)) emission with a quenching concentration of 5 mol% (of Ga3+), and the Mn shows green emission (505 nm, T, A,) with a quenching concentration of 0.1 mol% (of Zn2+). The luminescence mechanism of ZnGa2O4:Mn2+/Eu3+ is presented.

Hydrothermal synthesis and crystal structure of a hybrid material based on [Co-4(phen)(8)(H2O)(2)(HPO3)(2)](4+) and a highly reduced polyoxoanion

An unusual composite hybrid material [Co-4 (phen)(8) (H2O)(2) (HPO3)(2)](H3O)(3) [PMo8VI V-4(IV) O-40 ((VO)-O-IV) 2] 1 (phen = 1,10-phenanthroline) has been hydrothermally synthesized from a mixture of NH4VO3, Na2MoO4.2H(2)O, CoCl2.6H(2)O, phen, H3PO3 and water. It was characterized by elemental analysis, IR, UV-vis, XPS, EPR, TG and single crystal X-ray diffraction. The title compound is constructed from the organic-inorganic hybrid [Co-4(phen)(8)(H2O)(2) (HPO3)(2)](4+) and highly reduced bi-capped pseudo-Keggin [(PMo8V4O40)-V-VI-O-IV ((VO)-O-IV)(2)](7-) polyoxoanions The structure exhibits an extended 2D network through hydrogen bonds among cations, anions and H2O, combining polyoxometalates with metal phosphonates for the first time.

Interactions of thiamine monophosphate (TMP) with one- and two-dimensional polymeric halogenomercurate anions. Crystal structures of (TMP)(Hg2Br5)center dot 0.5H(2)O and (TMP)(2)(Hg3I8)

An investigation into the interactions between thiamine monophosphate (TMP) and anions has resulted in the preparation and X-ray characterization of the compounds (TMP)(Hg2Br5).0.5H(2)O (1) and (TMP)(2)(Hg3I8) (2). In each compound the TMP molecule exists as a monovalent cation in the usual F conformation. The halogenomercurate anions occur in two-dimensional (2-D) network in 1 or one-dimensional (1-D) chain in 2. In both 1 and 2, the structures consist of alternating cationic sheets of the hydrogen-bonded TMP molecules and anionic sheets of the polymeric halogenomercurate anions. The TMP molecule binds to the polymeric anions through the characteristic 'anion bridge I', C(2)-H..X...pyrimidinium (X = Br in 1 and 1 in 2), and electrostatic interactions between electropositive S(1) and halogen atoms. The 'anion bridge II' of the type N(4'1)-H...X...thiazolium (X = phosphate group) plays a role in stabilizing the molecular conformation. The biological implication of the host-guest-like complexation between TMP and polymeric anions is discussed.