Novel monohydrogenphosphate sensor based on vanadyl salophen

A novel PVC-based membrane sensor based on vanadyl salophen (VNSP) for determination of trace amounts of monohydrogenphosphate (MHP) ions is introduced. The electrode revealed Nernstian response towards monohydrogenphosphate over the wide concentration range from 1.0×10⁻¹ to 1.0×10⁻⁶ M at the pH of 8.2. The effect of solvent mediator, cationic additives and amount of ion-carrier on the behavior of the sensor was investigated. The sensor shows a short response time (<20 s) in the whole concentration ranges. The selectivity of the electrode is very high, and it can be used for detection of trace amounts of monohydrogenphosphate in the presence of large amounts of other anions. The detection limit of the electrode was 5.0×10⁻⁷ M (48 ng/ml) and it could be used for 14 weeks without any measurable changes in the slope. The potentiometric selectivity coefficients data revealed negligible interference from 16 common anions. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer samples and, as an indicator electrode, in potentiometric titration of HPO₄²⁻ ion with barium nitrate.     

Construction of nonanuclear supramolecular structures from simple modular units

A porphyrazine based supramolecule with a nonanuclear structure has been prepared by the ready coordination of pyridine donor sites in octakis(4-pyridoxyethylthio)porphyrazinatomagnesium with vanadyl bis(acetylacetonate) and characterized by EPR spectroscopy.     

Cu4O12-Baugruppen aus planaren CuO4-Polygonen im Barium-Vanadyl-Oxocuprat(II)-phosphat Ba(VO)Cu4(PO4)4

Cu₄O₁₂ Groups Built of Square Planar CuO₄ Polygones in the Barium Vanadyl Oxocuprate(II) Phosphate Ba(VO)Cu₄(PO₄)₄ Single crystals of Ba(VO)Cu₄(PO₄)₄ have been prepared by solid state reactions just below the melting points of the reaction mixtures of BaP₂O₆, Cu₃(PO₄)₂, CuO, V₂O₅ and V₂O₃ in evacuated closed quartz glas tubes. The compound crystallizes with tetragonal symmetry, Space group D? P42₁2, a = 9.560(2), c = 7.160(2) Å, Z = 2. Special and new features of the crystal structure are to each other isolated Cu₄O₁₂ and (VO)(PO₄)₄ groups. The crystal chemistry of the Cu₄O₁₂ groups is discussed with respect to other compounds containing out of plane connected square planar MO₄ polygones.     

Spectral studies on VO ions in potassium thiourea bromide single crystals using EPR and optical absorption spectroscopy

Electron paramagnetic resonance (EPR) studies have been carried out on VO²⁺ ions doped in single crystals of ferroelectric material, potassium thiourea bromide (PTB) at room temperature and in the temperature range 103–343 K on X-band MW frequency. An isotropic octet spectrum characteristic of VO²⁺ ion was obtained due to the fast re-orientation of the VO²⁺ in PTB lattice, which exhibits glassy nature at certain range around room temperature. The temperature dependant EPR spectra of VO²⁺ ions in this host lattice has been attributed to the occurrence of multiple phase transitions due to the combined environment effects of KBr and thiourea materials in the single crystal. From the optical absorption spectrum, the crystal field splitting parameter Dq, tetragonal parameters Ds and Dt have been evaluated and discussed.     

Effect of calcination temperature on the structure of vanadium phosphorus oxide materials and their catalytic activity in the decomposition of 2-propanol

The synthesis of vanadyl phosphate by reaction of an alcoholic solution of V₂O₅ and o-H₃PO₄ has been studied. The solids obtained were investigated by various physico-chemical techniques as in situ X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) under inert atmosphere. The compounds have been further characterized by infrared and UV–Visible spectroscopies. The isopropanol conversion is carried out to evaluate the catalytic activity of the samples. The isopropanol conversion increases with the reaction temperature from 433 to 503 K for vanadyl phosphorus oxides calcined at a different temperature. However, the conversion attains 100% at 503 K, and the solid calcined at 973 K exhibits high selectivity towards propene (100% at 503 K).     

A PVC-based 1,8-diaminonaphthalen electrode for selective determination of vanadyl ion

A PVC membrane vanadyl (VO²⁺) ion-selective electrode was constructed using 1,8-diaminonaphthalen (DAN) as a neutral carrier. The electrode shows good Nernstian response for VO²⁺ ions over a wide concentration range (1.0×10⁻¹-1.0×10⁻⁵ M). The optimum composition of the membrane was 55 wt.% poly(vinylchloride), 35 wt.% 2-nitrophenyl octyl ether (NPOE), 5 wt.% ionophore, and 5 wt.% potassium tetrakis(p-chlorophenyl)borate (KTpClPB). It has relatively fast response time and can be used at least for 5 weeks without any considerable divergence in potentials. The proposed electrode revealed relatively good selectivity for VO²⁺ over wide variety of other metal ions. The electrode was used for the potentiometric titration of VO²⁺ ions with EDTA.     

Vanadyl Sulfate (VOSO4.3H2O). An Efficient Catalyst for Acylation of Alcohols and Phenols under Solvent Free Condition

Alcohols and phenols were efficiently acylated with acetic anhydride in the presence of vanadyl sulfate (VOSO₄.3H₂O) at room temperature in high yields.     

Synthesis,Electrochemical and Luminescence Studies of Nickel and Vanadium Complexes Containing Tetradentate Schiff Base Ligand with N2O2 Donor Atoms

A symmetrical tetradentate Schiff base ligand was derived by the condensation of ortho‐vanillin and thiourea in 2:1 molar ratio and adjusted pH. Nickel and vanadyl complexes were obtained using the template method by the reaction of ortho‐vanillin and thiourea with Ni(OAc)₂. 4H₂O and VO(acac)₂ (2:1:1 molar ratio) in absolute ethanol and adjusted pH. The Schiff base ligand and its complexes have been characterized by FT‐IR, ¹H NMR, UV/Vis, elemental analysis and conductometry measurements. In nickel and also vanadyl complexes the ligands were coordinated to the metals via the imine N and enolic O atoms. The complexes have been found to possess 1:1 metal to ligand stoichiometry and the molar conductance data revealed that the metal complexes were non‐electrolytes. The nickel and vanadyl complexes exhibited tetrahedral and square pyramidal coordination geometry, respectively. The emission spectra of the ligand and its complexes were studied in DMSO. Electrochemical properties of the ligand and its complexes were also investigated in the DMF solvent at the 150 mVs^‐1 scan rate. The ligand and its complexes showed irreversible processes at this scan rate.     

Electron Paramagnetic Resonance,Optical Spectra and DC Conductivity Studies of Vanadyl Doped Bi2O3 · BaO · B2O3 Glasses

Glasses with composition xBi₂O₃ ·(0.30 - x)BaO · 0.70B₂O₃ have been prepared in the range (0.00 ≤ x ≤ 0.15) containing 2.0 mol% of V₂O₅. Electron paramagnetic resonance (EPR), optical transmission and absorption spectra and DC conductivity of these glasses have been studied. The spin Hamiltonian parameters (SHP) of VO²⁺ ions, dipolar hyperfine coupling parameter P, Fermi contact interaction parameter K, and molecular orbital coefficients (α² and γ²) have been calculated. The SHP arc related with the theoretical optical basicity. A_th. The position of the absorption edge and the values of the optical band gap have also been reported. The effect of addition of Bi₂O₃ on the DC conductivity has also been studied.     

氧钒离子作用下人血红蛋白构象变化的动态过程及2,3-二磷酸甘油酸的影响

用停流分光光度计检测在有或无DPG结合时Hb与氧钒离子作用过程中自身荧光的变化,发现无DPG的Hb自身荧光只是一个单调的荧光猝灭过程.DPG结合于Hb后的荧光变化则先为荧光猝灭,转而缓慢增加.用氧钒离子结合引起的构象变化及DPG和DPG的水解产物3PGA所起的稳定Hb四级结构作用解释了上述过程.