Phosphan-, Phosphit- und Phosphido-Komplexe des Vanadiums(V)

Phosphane, Phosphite, Phosphido, Complexes of Vanadium(V) Complex formation of tert-butylimidovanadium(V)trichloride ( 1 ) with phosphanes und phosphites has been studied. Syntheses of phosphidovanadium(V) compounds ^tC₄H₉N?VCp(NH^tC₄H₉)[P(SiMe₃)₂] and ^tC₄H₉N?VCp(NⁱProp₂)(PR₂) (R?SiMe₃, Ph) are described starting from the corresponding chlorovanadium(V) complexes. The reaction of 1 with silver hexafluorophosphate yields a bis(fluoro)phosphidovanadium(IV complex [(μ-PF₂)₂V₂Cl₂)(N^tC₄H₉)₂]; as primary intermediate product of the unknown redox reaction a cationic vanadium(V) complex [^tC₄H₉N?VCl₂ · PPh₃]⁺PF₆^? has been isolated. 1 reacts with an excess of diisopropylamine forming ^tC₄H₉N?V(NⁱProp₂)Cl₂ ( 16 ); in addition the following diisopropylamido-tert-butylimidovanadium(V) compounds ^tC₄H₉N?VCp(NⁱProp₂)Cl ( 3 ) and ^tC₄H₉N?V(NⁱProp₂)X₂ (X?CH₂CMe₃, O^tC₄H₉, CH₃COO) has been prepared. All compounds obtained are characterized by ¹H, ⁵¹V, ³¹P NMR spectroscopy. The X-ray diffraction analysis of 16 and 3 indicate a planar coordination sphere of the amido nitrogen atom.     

Kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium

The kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium has been carried out. The reaction is first order with respect to vanadium(V) and the substrate and is acid catalysed.Hammett acidity function (H ₀) andBunnett hypothesis have been applied. The formation of free radicals during the course of the reaction has been indicated. A probable reaction mechanism is proposed.

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Die Kinetik der Oxidation von Ethyldigol mit Vanadium(V) in wäßrigem saurem Medium

Zusammenfassung Es wurde die Kinetik der Oxidation von Ethyldigol mittels Vanadium(V) in wäßriger saurer Lösung untersucht. Die Reaktion ist erster Ordnung bezüglich Vanadium(V) und Substrat und ist säurekatalysiert. Es wurden dieHammett-Aciditätsfunktion (H ₀) und dieBunnett-Hypothese angewandt. Die Bildung von freien Radikalen während der Reaktion konnte bestätigt werden. Es wird ein Reaktionsmechanismus vorgeschlagen.

     

RP-HPLC study of redox equilibria in vanadium-PAR binary and ternary systems: Direct determination of vanadium in steel

The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C₁₈ column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H₂O₂-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH₂OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH₂OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel.     

Trinuclear Schiff base complexes with uranium(V) and copper(II) or zinc(II) ions

Treatment of the uranium(IV) complexes [{ML¹(py)}₂U^IV] (M = Cu, Zn; L¹ = N,N′-bis(3-hydroxysalicylidene)-1,3-propanediamine) with silver nitrate in pyridine led to the formation of the corresponding cationic uranium(V) species which were found to be thermally unstable and were converted back into the parent U^IV complexes; no electron transfer was observed in solution between the U^IV and U^V compounds. In the crystals of [{ML¹(py)}₂U^IV][{ML¹(py)}₂U^V][NO₃], the neutral U^IV and cationic U^V species are clearly identified by the distinct U–O distances. Similar reaction of [{ZnL²(py)}₂U^IV] [L² = N,N′-bis(3-hydroxysalicylidene)-1,4-butanediamine] with AgNO₃ gave crystals of [{ZnL²(py)}U^V{ZnL²(py)₂}][NO₃] but the copper counterpart was not isolated. Crystals of [{ZnL¹(py)}₂U^V][OTf] · THF (OTf = OSO₂CF₃) were obtained fortuitously from the reaction of [Zn(H₂L¹)] and U(OTf)₃.     

Determination of chikusetsusaponin V and chikusetsusaponin IV in rat plasma by liquid chromatography–mass spectrometry and its application to a preliminary pharmacokinetic study

A sensitive liquid chromatography–electrospray ionization–mass spectrometry method has been developed and validated for determination of two major bioactive saponins in rat plasma after oral administration of saponins extracted from Rhizoma Panacis Japonici, including chikusetsusaponin V and chikusetsusaponin IV for the first time. Akebia saponin D was used as the internal standard (IS). Plasma samples were prepared by protein precipitation with methanol. A Phenomenex C₁₈ column (150 × 4.6 mm, 4 µm) was used as the analytical column with a mobile phase of acetonitrile and 0.05% aqueous formic acid. Mass spectrometric detection was achieved by single quadrupole mass spectrometer equipped with an electrospray ionization interface operating in negative ionization mode. Calibration curves showed good linearity over the concentration range of 5–500 ng/mL for the two analytes in rat plasma. The lower limit of quantification was 5 ng/mL. The intra‐ and inter‐batch precisions were within 10.3% and accuracy ranged from ?3.9 to 5.4%. The method was validated and successfully applied to the preliminary pharmacokinetic study of chikusetsusaponin V and chikusetsusaponin IV in rat plasma after oral administration of saponins extracted from Rhizoma Panacis Japonici. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,crystal structure and photo-induced isomerization of [ N,N ′- bis (4-fluorobenzylidene) ethylenediamine]bromo(triphenylphosphine)copper(I) complex

Abstract

The electrochemical behavior of VOQ₂OH or [VOQ₂-OVOQ₂] (Q = 8-hydroxyquinohnate anion) has been investigated by cyclic voltammetry in acetonitnie solutions. Although both species exist simultaneously at every condition analyzed, they can be clearly differentiated by this method. The effect of trace amounts of water on the electrochemical behavior is also discussed.     

A multi-object image segmentation C–V model based on region division and gradient guide

The Chan–Vese (C–V) model is an ineffective method for processing images in which the intensity is inhomogeneous. This is especially true for multi-object segmentation, in which the target may be missed or excessively segmented. In addition, for images with rich texture information, the processing speed of the C–V is slow. To overcome these problems, this paper proposes an effective multi-object C–V segmentation model based on region division and gradient guide. First, a rapid initial contour search is conducted using Otsu’s method. This contour line becomes the initial contour for our multi-object segmentation C–V model based on a gradient guide. To achieve the multi-object segmentation the image is then converted to a single level set whose evolution is controlled using an adaptive gradient. The feasibility of the proposed model is analyzed theoretically, and a number of simulation experiments are conducted to validate its effectiveness.     

Synthesis,characterization and application of alumina/ vanadium pentoxide nanocomposit by sol–gel method

In this work, we report the preparation of Al₂O₃/V₂O₅ nanocomposit using vanadium and aluminum nitrate by sol–gel method. Characterization of nanocomposit was carried out by powder X‐ray diffractometry (XRD), Fourier transform infrared (FT‐IR), scanning electron microscopy (SEM), Energy‐Dispersive X‐ray (EDX) and UV spectroscopy. Then, applicability of the synthesized nanocomposit was tested as a nanocatalyst for the synthesis of diindolyl oxindole derivatives, an important class of potentially bioactive compounds. The products were obtained in good to high yields from one‐pot three‐component condensation of isatin with indole. Also, this nanocatalyst has been reused several times, without observable loss of activity.     

Synthesis of V5+‐doped Ag/AgCl photocatalysts with enhanced visible light photocatalytic activity

V⁵⁺‐doped Ag/AgCl photocatalysts were prepared via the ion exchange method. The catalysts were characterized using X‐ray diffractometry, transmission electron microscopy, and energy‐dispersive X‐ray, X‐ray photoelectron, Fourier transform infrared and ultraviolet–visible spectroscopies. The V⁵⁺‐doped Ag/AgCl photocatalysts show much higher photocatalytic activities than Ag/AgCl under visible light irradiation for methyl orange (MO) decomposition. Especially, the 2.0 wt% V⁵⁺‐doped Ag/AgCl photocatalyst shows the highest photocatalytic activity and also high stability after five cycles. The MO degradation rate during each cycle is almost maintained at 97%. Electron spin resonance spectroscopy and radical trapping experiments reveal that holes play an important role in the photocatalytic process.     

RFID在音圈振膜自动化生产线中的应用

本文针对音圈振膜自动化生产线所选用的RFID系统进行了软硬件设计,详细介绍了V680系列的RFID系统。并在Sysmac Studio编程软件中对其进行通信测试,最后对上游工位下来的载体进行数据采集并将采集到的数据嵌入到本工作站实现相应的动作。