Preparation and Characterization of Chitosan Composite Membranes Crosslinked by Carboxyl-capped Poly（ethylene glycol）

In this study a series of chemically crosslinked chitosan/poly（ethylene glycol） （CS/PEG） composite membranes were prepared with PEG as a crosslinking reagent other than an additional blend. First, carboxyl-eapped poly（ethylene glycol） （HOOC-PEG-COOH） was synthesized. Dense CS/PEG composite membranes were then prepared by casting/evaporation of CS and HOOC-PEG-COOH mixture in acetic acid solution. Chitosan was chemically crosslinked due to the amidation between the carboxyl in HOOC-PEG-COOH and the amino in chitosan under heating, as confirmed by FTIR analysis. The hydrophilicity, water-resistance and mechanical properties of pure and crosslinked chitosan membranes were characterized, respectively. The results of water contact angle and water absorption showed that the hydrophilicity of chitosan membranes could be significantly improved, while no significant difference of weight loss between pure chitosan membranes and crosslinked ones was detected, indicating that composite membranes with amidation crosslinking possess excellent water resistanance ability. Moreover, the tensile strength of chitosan membranes could be significantly enhanced with the addition of certain amount of HOOC-PEG-COOH crosslinker, while the elongation at break didn＇t degrade at the same time. Additionally, the results of swelling behaviors in water at different pH suggested that the composite membranes were pH sensitive.     

Kinetics of Photocatalytic Degradation of Formic Acid over Silica Composite Films Based on Polyoxometalates

The composite films, XW11O39^n-/SiO2,(X refers to Si,Ge or P,respectively) were prepared by tetraethoxysilane (TEOS) hydrolysis sol-gel method via spin-coating technique. Formation of the composite films is due to strong chemical reaction of organic silanol group with the surface oxygen atoms of XW11O39^n-, resulted in the saturation of the surface of the lacunary polyoxometalates (POMs). Therefore,the coordination structural model of the films was proposed. As for the films, retention of the primary Keggin structure was confirmed by UV-vis, FT-IR spectra and MAS NMR. The surface morphology of the films was characterized by SEM, indicating that the film surface is relatively uniform, and the layer thickness is in the range of 250-350nm. Aqueous formic acid (FA) (0-20mmol/L) was degraded into CO2 and H2O by irradiating the films in the near-UV area. The results show that all the films have photocatalytic activities and the degradation reaction follows Langmuir-Hinshelwood first order kinetics.     

Novel 3-D Supramolecular Architectures Constructed from Zn^2＋ ions, Oxybis（4-benzoate） and Di（2-pyridyl）amine Ligands

Using the V-shaped oba dianions as bridging ligands and dpa molecules as terminal ligands, a new 1D helical coordination-polymeric chain, [Zn（oba）（dpa）]n [oba=oxybis（4-benzoate）, dpa=di（2-pyridyl）amine], was synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, UV-Vis and IR spectra, and TGA analysis. X-ray structural analysis revealed that, oba and dpa ligands played an important role in the self-assembly of the helical chains by providing potential supramolecular recognition sites for π-π aromatic stacking and hydrogen-bond interactions, resulting in the self-assembly of the （4,4） networks to give a 3-D supramolecular framework. The photoluminescence properties of the title compound were also investigated, showing intense blue photoluminescence properties at room temperature.     

Synthesis of Poly（N-vinylpyrrolidone） Nanofibers Containing Gold Nanoparticles via Electrospinning Technique

Poly(N-vinylpyrrolidone)(PVP)nanofibers containing gold nanoparticles were prepared by electrospinning method.This simple route was used to prepare composites on a large scale,and the syntheses are simple.The optical property of gold nanoparticles in PVP aqueous solution was investigated by UV-Visible absorption spectra.The morphology of the fibers and the distribution of particles were characterized by transmission electron microscopy.The structure of the composite was characterized by Fourier transform infrared spectroscopy.     

Crystal Structure, Thermal Decomposition Behavior and the Standard Molar Enthalpy of Formation of a Novel 3D Hydrogen- Bonded Supramolecular [Co（HnicO）2·（H2O）2]

Hydrothermal synthesis and X-ray characterized 3D supramolecular networks were constructed by [Co（HnicO）2·（H2O）2] （HnicOH=2-hydroxynicofinic acid） （1） as building block via abundant dimeric homomeric （N--H…O） and unusually cyclic tetrameric heteromeric （O-H…O） hydrogen-bonds. It is noted that there exist unusually linear metal-water chains comprised of tetrameric units linked by vertexes sharing cobalt centers through hydrogen-bonding. TG-DTG curves illustrated that thermal decomposition was completed by two steps, one is the loss of two terminal water molecules in the range of 156--234℃, and the other is the pyrolysis of HnicO ligand in the range of 234--730 ℃. The standard molar enthalpy of formation of the complex was determined to be （-1845.43± 2.77） kJ·mol^-1 by a rotary-bomb combustion calorimeter.     

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes Containing Benzoaza-15-crown-5

Three novel Schiff base cobalt（Ⅱ） complexes containing benzoaza-15-crown-5, CoL^1, CoL^2 and CoL^3 were synthesized and characterized, and these complexes were used in catalytic hydrolysis of carboxylic ester （PNPP, p-nitrophenyl picolinate） as mimic hydrolytic metalloenzyme. The analysis of specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved the key intermediates formed by PNPP with cobalt（Ⅱ） complexes. The CoL^3 bearing the electron withdrawing group shows better catalytic activity due to its stabilization effect on active species MLS^-. The catalytic mechanism of PNPP hydrolysis was also proposed. The kinetic parameter of PNPP catalytic hydrolysis has been calculated and the activation energy for the catalytic hydrolysis is 43.69, 39.76 and 35.44 kJ·mol^-1, respectively.     

A Novel Composite Electrode of Photocatalyst—TiO2／C Loading on the Surface of the Air （Oxygen） Electrode

The methods for preparing the H2O2 generating air (oxygen) electrode and the composite electrode of photocatalyst-TiO2/C loading on the surface of the air (oxygen) electrode were introduced.In the case of the composite electrode,the current efficiency of electro-generated H2O2 is higher than 80%(J≤15mA/cm^2).The degradation of aniline was used as an example to measure the influence of the composite electrode and compared with the system in which the air (oxygen) electrode and the photocatalyst-TiO2 were sqparated.The results confirmed that the composite electrode played an active role on accelerating the degradation rate of aniline.According to the measurement of the polarization curves of composite electrode and TiO2 photo anode,and of the adsorbing amount of aniline on the surface of the composite electrode,the principle of descending the recombination reta of photo-generated electron and hole and of enhancing the oxidation rate of organic molecule was described.The mechanism about the degradation of aniline was also discussed.     

Synthesis and Crystal Structure of a Novel Copper （Ⅱ） Complex with Acetylenedicarboxylate and 2, 2＇-Bipyridine

The title compound [Cu （ADC） （2, 2＇-bipy）]n （ADC = C2 （COO）2^2.） was prepared and characterized by elemental analysis, IR spectroscopy, X-ray analysis, respectively. The analysis of the crystal structure reveals that the copper atom is five-coordinated with two nitrogen atoms of 2, 2＇-bipy and three oxygen atoms of different acetylenedicarboxylate dianions. ADC as bridging ligands link the Cu （Ⅱ） ions, forming coordination polymer structure.     

Synthesis and Magnetic Properties of Fe（Ⅱ） and Nd（Ⅲ） Complexes of Poly（N-2-thiazolylacrylamide）

N-2-Thiazolylacrylamide （NTA） was polymerized by a radical route to obtain the polymer in good yield. The polymer with a pendent heterocyclic group is soluble in common organic solvents, which allow to prepare the corresponding metal complexes with higher loads easily. FTIR, ^1H NMR, elemental analysis, and energy-dispersive X-Ray spectroscopy （EDX） were applied to characterize these materials. The magnetic behavior of Fe（Ⅱ） and Nd（Ⅲ） complexes of poly（N-2-thiazolylacrylamide） was examined by a PPMS-9T magnetometer, exhibiting the characteristics of a soft ferromagnet. It is found that the Nd（Ⅲ） complex has an extremely high relative saturation magnetization of 35 emu/g.     

Synthesis, characterization and photocatalytic application of H3PW12O40/BiVO4 composite photocatalyst

A series of H3PW12O40/BiVO4 composite with different H3PW12O40 loadings were prepared using a hydrothermal and impregnation method. The prepared composites were characterized by XRD, Raman, SEM, XPS, and DRS techniques. The bandgap of the composite was narrower compared with the as-prepared pure BiVO4 . As a novel photocatalytic material, the photocatalytic performance of the H3PW12O40/BiVO4 composite was investigated by the degradation of methylene blue (MB) dye solution under visible light irradiation and compared with that of pure BiVO4 . The results revealed that the introduction of H3PW12O40 could improve the photocatalytic performance and different concentrations of H3PW12O40 resulted in different photocatalytic activities. The highest activity was obtained by the sample with a loading HPW concentration of 10 wt%. The reason for the enhanced photocatalytic activities of H3PW12O40/BiVO4 samples was also discussed in this paper. Moreover, the H3PW12O40/BiVO4 composites retained the catalytic activity after four repeated experiments.     

Preparation and StructuralCharacterization of RuII‐DMSO and RuIII‐DMSO‐substituted α‐Keggin‐type Phosphotungstates, [PW11O39RuIIDMSO]5– and [PW11O39RuIIIDMSO]4–, and Catalytic Activity for Water Oxidation

Ru^II‐ and Ru^III‐substituted α‐Keggin‐type phosphotungstates with a dimethyl sulfoxide (DMSO) ligand, [PW₁₁O₃₉Ru^IIDMSO]^5– ( 1 ) and [PW₁₁O₃₉Ru^IIIDMSO]^4– ( 2 ), were synthesized. Compound 1 was prepared by reaction of [PW₁₁O₃₉]^7– with [Ru^II(DMSO)₄]Cl₂ in water at 125 °C under hydrothermal conditions and was isolated as a cesium salt. Compound 2 was prepared by reaction of 1 with bromine in water at 60 °C and was isolated as a cesium salt. The compounds were characterized by cyclic voltammetry, elemental analysis, UV/Vis, IR,³¹P NMR, ¹⁸³W NMR, ¹H NMR, and XANES (Ru K‐edge and L₃‐edge)spectroscopic methods. Single crystal structural analysis of 1 revealed that Ru^II is incorporated in the α‐Keggin framework and coordinated by DMSO through a Ru–S bond. Cyclic voltammetry of 1 indicated that the incorporated Ru^II‐DMSO is reversibly oxidizable to the Ru^III‐DMSO derivative 2 . Compound 1 showed catalytic activity for water oxidation in the presence of cerium ammonium nitrate as an oxidant.     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Platinum‐Containing Polyoxometalates: syn‐ and anti‐[PtII2(α‐PW11O39)2]10− and Formation of the Metal–Metal‐Bonded di‐PtIII Derivatives

The first examples of dimeric, di‐Pt^II‐containing heteropolytungstates are reported. The two isomeric di‐platinum(II)‐containing 22‐tungsto‐2‐phosphates [anti‐Pt^II₂(α‐PW₁₁O₃₉)₂]^10? ( 1 a ) and [syn‐Pt^II₂(α‐PW₁₁O₃₉)₂]^10? ( 2 a ) were synthesized in aqueous pH 3.5 medium using one‐pot procedures. Polyanions 1 a and 2 a contain a core comprising two face‐on PtO₄ units, with a Pt???Pt distance of 2.9–3 Å. Both polyanions were investigated by single‐crystal XRD, IR, TGA, UV/Vis, ³¹P NMR, ESI‐MS, CID‐MS/MS, electrochemistry, and DFT. On the basis of DFT and electrochemistry, we demonstrated that the {Pt₂^II} moiety in 1 a and 2 a can undergo fully reversible two‐electron oxidation to {Pt₂^III}, accompanied by formation of a single Pt?Pt bond. Hence we have discovered the novel subclass of Pt^III‐containing heteropolytungstates.     

Visible‐Light‐Induced Water Oxidation Mediated by a Mononuclear‐Cobalt(II)‐Substituted Silicotungstate

A mononuclear‐cobalt(II)‐substituted silicotungstate, K₁₀[Co(H₂O)₂(γ‐SiW₁₀O₃₅)₂] ? 23 H₂O (POM‐ 1 ), has been evaluated as a light‐driven water‐oxidation catalyst. With in situ photogenerated [Ru(bpy)₃]³⁺ (bpy=2,2′‐bipyridine) as the oxidant, quite high catalytic turnover number (TON; 313), turnover frequency (TOF; 3.2 s^?1), and quantum yield (Φ_QY; 27 %) for oxygen evolution at pH 9.0 were acquired. Comparison experiments with its structural analogues, namely [Ni(H₂O)₂(γ‐SiW₁₀O₃₅)₂]^10? (POM‐ 2 ) and [Mn(H₂O)₂(γ‐SiW₁₀O₃₅)₂]^10? (POM‐ 3 ), gave the conclusion that the cobalt center in POM‐ 1 is the active site. The hydrolytic stability of the title polyoxometalate (POM) was confirmed by extensive experiments, including UV/Vis spectroscopy, linear sweep voltammetry (LSV), and cathodic adsorption stripping analysis (CASA). As the [Ru(bpy)₃]²⁺/visible light/sodium persulfate system was introduced, a POM–photosensitizer complex formed within minutes before visible‐light irradiation. It was demonstrated that this complex functioned as the active species, which remained intact after the oxygen‐evolution reaction. Multiple experimental parameters were investigated and the catalytic activity was also compared with the well‐studied POM‐based water‐oxidation catalysts (i.e., [Co₄(H₂O)₂(α‐PW₉O₃₄)₂]^10? (Co₄‐POM) and [Co^IIICo^II(H₂O)W₁₁O₃₉]^7? (Co₂‐POM)) under optimum conditions.     

Synthesis and properties of magnetite/poly (aniline‐co‐8‐amino‐2‐naphthalenesulfonic acid) (SPAN) nanocomposites

Composites were prepared by incorporating magnetite (Fe₃O₄) nanoparticles into the matrix of a sulfonated polyaniline (SPAN) [poly(aniline‐co‐8‐amino‐2‐naphthalenesulfonic acid) PANSA] through chemical oxidative polymerization of a mixture of aniline and 8‐amino‐2‐naphthalenesulfonic acid in the presence of magnetite nanoparticles. The composite, magnetite/SPAN(PANSA) was characterized by means of transmission electron microscopy (TEM), X‐ray diffraction (XRD), elemental analysis (EA), Fourier transform infrared (FT‐IR) spectra, UV‐vis spectroscopy, thermogravimetric analysis (TGA), conductivity and magnetic properties measurements. TEM image shows that magnetite nanoparticles were finely distributed into the SPAN matrix. XRD pattern of the nanocomposite reveals the presence of additional crystalline order through the appearance of a sharp peak at ～43° and 71°. Conductivity of the nanocomposite (0.23 S/cm) is much higher than pristine copolymer (1.97 × 10^?2 S/cm). The results of FT‐IR and UV‐visible spectroscopy reveal the presence of molecular level interactions between SO groups in SPAN and magnetite nanoparticles in the composite. Copyright © 2006 John Wiley & Sons, Ltd.     

A simple and safe method for the preparation of bis[2‐(2H‐tetrazol‐5‐yl)pyridinium] tetrachloridozincate(II)

In the title complex salt, (C₆H₆N₅)₂[ZnCl₄], the Zn^II cation is coordinated by four chloride ligands in a distorted tetrahedral geometry. The organic cations and complex anions are connected by N—H...Cl hydrogen bonds, leading to the formation of a three‐dimensional network. The title complex salt was synthesized by the reaction of sodium azide, pyridine‐2‐carbonitrile and ZnCl₂ in aqueous solution. The salt was characterized by elemental analysis and IR and UV–Vis spectroscopy.     

Synthesis,Spectral, Thermal and Biological Studies of Mn(II), Co(II), Ni(II) and Cu(II) Complexes with 1‐(((5‐Mercapto‐1H‐1,2,4‐triazol‐3‐yl)imino)‐methyl)naphthalene‐2‐ol

Mn(II), Co(II), Ni(II) and Cu(II) complexes of 5‐mercapto‐1,2,4‐triazol‐3‐imine‐2′‐hydroxynaphthaline have been synthesized and characterized by elemental analysis, IR, ¹H NMR, EI‐mass, UV‐Vis, and ESR (electron spin resonance) spectra, molar conductance, magnetic moment measurements, DC conductivity and thermogravimetric analysis. IR spectra confirm that the ligand molecule existed in both thione and thiole forms. The molar conductance values indicate the complexes are nonelectrolyte. The magnetic moment values of the complexes display paramagnetic behavior. All studies confirm the formation of an octahedral geometry for complex 1 and the other complexes have tetrahedral geometrical structures. The structures of the complexes have also been theoretically studied by using the molecular mechanic calculations by the hyperchem. 8.03 molecular modeling program which confirm the proposed structures. The Schiff‐base ligand and its metal complexes have also been screened for their antimicrobial activities.     

A novel inorganic–organic hybrid compound constructed from copper(II)-monosubstituted polyoxometalates and poly(amidoamine)

A novel inorganic–organic hybrid compound constructed from copper(II)-monosubstituted polyoxometalate Na₅PW₁₁Cu(H₂O)O₃₉ (PW₁₁Cu) and poly(amidoamine) (PAMAM) dendrimer was prepared at room temperature in an aqueous solution. The title compound PW₁₁Cu/PAMAM was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, indicating that the PW₁₁Cu was chemically anchored to PAMAM. The compound was first used as a bulk-modifier to fabricate a chemically modified carbon paste electrode (CPE) by direct mixing. The PW₁₁Cu/PAMAM bulk-modified CPE showed well-defined cyclic voltammograms with four redox couples in 0.2 M NaAc buffer solution and high electrocatalytic activity for the reduction of hydrogen peroxide and nitrite. Furthermore, the CPE revealed good stability due to the insolubility of the title compound and the interaction between PW₁₁Cu and PAMAM.     

Synthesis,structural features and biochemical activity assessment of N,N′‐bis‐(2‐mercaptophenylimine)‐2,5‐thiophenedicarboxaldehyde Schiff base and its Co(II), Ni(II), Cu(II) and Zn(II) complexes

The tetradentate Schiff base ligand (SB), N,N′‐bis‐(2‐mercaptophenylimine)‐2,5‐thiophenedicarboxaldehyde was prepared via condensation of 2,5‐thiophene‐dicarboxaldehyde with 2‐aminothiophenol in a 1:2 molar ratio by conventional method. Additionally, its Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized and fully characterized by elemental analysis, FT‐IR, ¹H NMR, ¹³C NMR, UV–Vis, ESR, ESI‐mass, conductivity and magnetic susceptibility measurements. Spectral studies suggested that, the Schiff base coordinate metal ions through the azomethine N‐ and deprotonated thiol S‐ atoms. Based on UV–Vis absorption and magnetic susceptibility data, tetrahedral geometry was assigned for both Co(II) and Zn(II) complexes, whereas on the other hand, square planar geometry for both Ni(II) and Cu(II) complexes. The Schiff base and its metal complexes were screened for their in vitro antimicrobial activity by minimum inhibitory concentration (MIC) method. Free radical scavenging activity of the novel compounds was determined by elimination of 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radicals. In addition, the interactions of the free ligand and its complexes with calf thymus DNA (CT‐DNA) were explored using absorption, emission and viscosity measurements techniques.     

In Situ Fabrication of Inorganic/Organic Hybrid Based on Cu/Co‐ZIF and Cu2O

We successfully fabricate a well‐defined inorganic/organic hybrid Cu₂O@Cu/Co‐ZIF (ZIF=zeolitic imidazolate frameworks) by use of growth of dual‐metal Cu/Co‐ZIF on the obtained Cu₂O hollow spheres. The key point of the strategy is coupling the in situ self‐sacrificing template. Cu₂O and the coordination of metal ions (Cu⁺ and Co²⁺) with 2‐methylimidazole. This new hybrid was characterized by powder X‐ray diffraction, (scanning) transmission electron microscopy, energy‐dispersive spectroscopy mapping, in situ FT‐IR spectroscopy, UV/Vis diffuse reflection spectroscopy, N₂ sorption measurements, and electron spin resonance. It was evidenced that Cu/Co‐ZIF nanocrystals have been assembled to continuous shells surrounding the Cu₂O cores as well as in the voids between layers and inner pores. Cu₂O@Cu/Co‐ZIF exhibits visible light responsiveness and holds potential as narrow band gap semiconductor and visible photocatalyst.