Vanadium Chloride Research Articles

Metal Effects on Electronic Structures of Directly Linked Tribenzotetraazachlorin-Fullerene Conjugates

Mixed condensation of 1,2-dicyanofullerene (1) and 4,5-dibutyloxyphthalonitrile (2a) in the presence of vanadium(III) chloride (VCl3) in quinoline forms the hexabutyloxy-substituted tribenzotetraazachlorin (TBTAC) - fullerene (C60) vanadyl complex (3). UV-vis absorption and magnetic circular dichroism (MCD) spectroscopy demonstrated that 3 shows two intense Q-band components, whereas the previously reported nickel complex possessing the identical peripheral substituents (4) shows one intense and two medium-intense bands in the 600-800 nm region, indicating that the electronic mixing states of 3 are different from those of the nickel complex (4). The metal effects on electronic structures of the conjugates were interpreted using density functional theory (DFT) calculations.

Synthesis and modification of micro-and nanorods of vanadium oxides

A method for the gas-phase synthesis of single-crystalline micro-and nanorods of vanadium pentoxide (V2O5) has been developed based on the thermal decomposition of vanadium chloride vapor. Using this technique, it is possible to obtain separate micro-and nanorods (with thicknesses ranging from 50 nm to 5 μm and a length of up to 7 mm), planar arrays, and three-dimensional structures. The temperature dependence of the resistance of individual microrods of vanadium oxides in various degrees of oxidation has been measured.

Synthesis and X-ray structural characterization of tris( l-glycinato)vanadium(III) and trans-tetraquadichlorovanadium(III) chloride

Despite the importance of V III in biology, only three V III complexes of naturally occurring amino acids have been structurally characterized. We report the structure of the first vanadium complex incorporating a glycine ligand, [V(Gly) 3] · 2DMSO, which crystallizes in a monoclinic system with space group Cc, a = 8.9186(5) Å, b = 21.5347(9) Å, c = 9.9064(5) Å and β = 110.536(3)°. The X-ray structural data show the central V III metal octahedrally coordinated by three bidentate glycinato ligands arranged a mer configuration, with both Δ and Λ enantiomers present in the unit cell. The bulk sample was isolated as [V(Gly) 3] · DMSO · NaCl. Structural comparisons are made with the corresponding homoleptic glycinato complexes of Co III, Cr III and Ni II. The structure of trans-[V(OH 2) 4Cl 2]Cl · 2H 2O has also been re-determined. This latter complex crystallizes in a monoclinic system in the P2(1)/ c space group, a = 6.4381(9) Å, b = 6.3843(9) Å, c = 11.7980(17) Å and β = 98.057(2)°. The vanadium atom lies at a crystallographic inversion centre within the distorted octahedron formed by the four water and two chloride ligands.

Vanadium Complexes Possessing N2O2S2-Based Ligands: Highly Active Procatalysts for the Homopolymerization of Ethylene and Copolymerization of Ethylene/1-hexene

The family of ligands containing an N2O2S2 core, namely, 1,2-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)ethane (H2L1), 1,3-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)propane (H2L2), 1,4-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)butane (H2L3), and 1,2-di(3-Me-5-t-Bu-salicylaldamino-o-phenylthio)ethane (H2L4), have been prepared and complexed with a variety of vanadium chlorides and alkoxides to afford complexes of the form [V(X)L1] (X = O (1), Np-tol (2), Cl (3)), [V(O)(L2,3)] (L2 (4), L3 (5)), and [V(L4)] (6). Crystal structure determinations of H2L1 and H2L4 show the molecule to be centrosymmetric about the bridging ethane moiety, with structural determination of 1 and 3 revealing isostructural monomeric complexes in which the ligand chelates in such a way as to afford pseudo-octahedral coordination at the vanadium center. Prolonged reaction of H2L1 with [V(Np-tol)(OEt)3] led, via oxidative cleavage of the C-S bond, to the bimetallic complex [V2L1(3-Me,5-t-Bu-salicylaldimino-o-phenylthiolate)2] [VL'] (7), as characterized by single-crystal X-ray crystallography. 7 was also isolated from the reaction of H2L4 and [VO(On-Pr)3]. The ability of 1-7 to catalyze the homopolymerization of ethylene and the copolymerization of ethylene/1-hexene in the presence of dimethylaluminum chloride (DMAC) has been assessed: screening reveals that for ethylene homopolymerization 1-7 are all highly active (>1000 g/mmol.h.bar), with the highest activity (ca. 11 000 g/mmol.h.bar) observed using catalyst 3; the use of trimethyl aluminum (TMA) or methylaluminoxane (MAO) as the cocatalyst led only to poorly active systems producing negligible polymer. Analysis of the polyethylene produced showed high molecular weight linear polymers with narrow polydispersities. For ethylene/1-hexene copolymerization, activities as high as 1,190 g/mmol.h.bar were achieved (4); analysis of the copolymer indicated an incorporation of 1-hexene in the range of 5-13%.

Thermodynamics of the Formation of Vanadium(II) Complexes in Chloride Melts

Vanadium equilibrium potentials were determined in NaCl-KCl equimolar melts containing 0.018 - 8.02 wt.% of vanadium between 690 and 820 oC. It was found that only vanadium(II) ions are present in the equilibrium with the metal. The temperature dependence of E*V2+/V formal standard potential was determined. Enthalpy and entropy change of the formation of vanadium(II) chloride in NaCl-KCl melt were determined. Hypothetical values of enthalpy and entropy change of the formation of super-cooled liquid vanadium(II) chloride were calculated. Enthalpy and entropy of mixing of VCl2 and NaCl-KCl were estimated.

The role of nitric oxide in diabetes-induced changes of morphine tolerance in rats

Several neuroendocrine complications including diabetes change the morphine antinociception and the development of tolerance to the drug. Morphine antinociception was reduced significantly in morphine tolerant diabetic rats compared to the non-diabetic animals. The exact mechanism of this effect is not known. This study was performed to determine the role of nitric oxide (NO) on morphine tolerance in diabetic state. Nociceptive responses in alloxan-induced diabetic morphine tolerated rats were measured by the hot-plate test. The urinary nitric oxide level was measured spectrophotometrically with Griess reagent. For the conversion of nitrate to nitrite, vanadium chloride was used. The results showed that experimental diabetes increased morphine analgesia. Conversely, degree of tolerance to morphine was diminished in diabetic state. The urinary nitrite content in diabetic morphine tolerated rats was higher than non-diabetic groups. L-arginine significantly increased the NO production in diabetic morphine tolerated animals, whereas aminoguanidine decreased it. Appropriately, L-arginine increased the latency time of reaction to noxious stimuli in diabetic compared to non-diabetic rats. L-arginine-treated animals also showed more tolerance to morphine analgesia. As expected, aminoguanidine deducted the level of morphine tolerance in diabetic animals. It is suggested that NO has a modulatory role in the effects of diabetes on morphine analgesia and tolerance.

Piperazinium aquabis(oxalato)oxidovanadate(IV) dihydrate

The title compound, (C4H12N2)[V(C2O4)2O(H2O)]·2H2O, has been obtained by the reaction of vanadium(III) chloride with piperazinediium oxalate in aqueous solution. It shows distorted octahedral geometry [V=O = 1.6010 (12) Å and V—O = 1.9932 (12)–2.2176 (12) Å]]. The structure exhibits intermolecular N—H⋯O and C—H⋯O hydrogen bonds. The uncoordinated water mol­ecules contribute to the formation of the supra­molecular structure via O—H⋯O hydrogen bonds.

Synthesis, reactivity, and X-ray structural characterization of a vanadium(III) oxidation pre-catalyst, (CpP OEtCo)VCl 2(DMF)

Vanadium complexes are extensively used in the chemical industry as oxidation catalysts. During the course of our investigations into vanadium oxidation catalysis, the rich reactivity of a vanadium(III) scorpionate analogue complex, (CpP OEtCo)VCl 2(DMF) ( 1), was investigated. The octahedrally coordinated 1 was prepared by mixing vanadium(III) chloride with Na(CpP OEtCo) in DMF. The crystal structure of 1 has been determined through X-ray diffraction. Complex 1, C 20H 42Cl 2CoNO 10P 3V, crystallizes in the monoclinic space group P2 1/ c with a = 38.566(9) Å, b = 9.499(2) Å, c = 18.149(4) Å, and β = 100.485(4)° with Z = 8. Complex 1 was found to be an effective pre-catalyst for the oxidation of 3,5-di- tert-butylcatechol to 3,5-di- tert-butylquinone. The reactivity studies, oxidative catalytic ability, as well as X-ray structural characterization of (CpP OEtCo)VCl 2(DMF) will be discussed. ((CpP OEtCo) = [η 5-cyclopentadienyltris(diethylphosphito-κ 1P) cobaltate(III) −; DMF = N, N-dimethylformamide).

Vanadium(III) Chloride as an Effective Catalyst for the Pechmann Reaction.

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The Growth of Thermochromic VO2 Films on Glass by Atmospheric-Pressure CVD: A Comparative Study of Precursors, CVD Methodology, and Substrates

This paper briefly reviews previous work on the growth of thermochromic VO2 thin films on glass, and then examines and compares three different CVD approaches and two precursor systems for the production of these materials. It is found that atmospheric pressure (AP) CVD using vanadium(IV) chloride (VCl4) and H2O on commercial SiO2-precoated glass yields the smoothest films, with transition temperature (Tc) values of around 58 °C, while APCVD using vanadyl(IV) acetyl acetonate (VO(acac)2) on the same substrates produces slightly rougher films, which are more crystalline and possess a Tc with a value as low as 51.5 °C. Films grown using VO(acac)2 in a direct liquid-injection metal-organic (DLI-MO) CVD reactor exhibited considerably poorer thermochromic and morphological properties as compared with those grown by APCVD. These findings are discussed in terms of possible variations in growth mechanisms occurring during the three processes studied.

Use of Griess Reagent Containing Vanadium(III) for Post-Column Derivatization and Simultaneous Determination of Nitrite and Nitrate in Baby Food

An ion chromatographic method with post-column derivatization and spectrophotometric detection is presented for the determination of nitrate and nitrite (NOx) in baby food. NOx residues found naturally or added as preservatives were extracted from baby foods and determined by using ion chromatography with post-column derivatization and spectrophotometric detection. Nitrate was reduced to nitrite online by post-column reduction using vanadium(lll) chloride and heat. Nitrite reacted with Griess reagent to produce a dye that was detected at 525 nm. The use of V(III) and heat to promote the reduction of nitrate to nitrite online is a novel feature of this detection system. The determination of incurred NOx residues in samples by using AOAC Method 993.03 yielded results comparable to those obtained by ion chromatography with spectrophotometric detection. The toxic and carcinogenic metal cadmium used in the AOAC Method to reduce the nitrate to nitrite was avoided. The proposed method provides simultaneous determination of nitrate and nitrite. Average recoveries of nitrate and nitrite residues ranged from 82 to 107% for fortification levels of 25-400 ppm.

Vanadium(III) chloride as an effective catalyst for the Pechmann reaction

Good yields of substituted coumarins were obtained by a synthetic method involving the Pechmann reaction using vanadium(III)chloride (VCl3) reagent to effect this condensation under solvent-free conditions.

Determination of Total Nitrogen in River Water Based on Diazotization Coupling Reaction in the Presence of Vanadium Chloride after Oxidative Pretreatment with Peroxodisulfate

A convenient method was proposed for the spectrophotometric determination of total nitrogen in sewage and river-water samples. Each water sample was taken into glass bottles with screw caps and then heated at 120°C for 30 min after the addition of potassium peroxodisulfate, by which nitrogen-containing compounds were quantitatively oxidized into nitrate. The determination of the resulting nitrate was performed by measuring the absorbance at 540 nm after a diazotization coupling reaction of N -naphthylethylenediamine and sulfanylamide in the presence of nitrite generated from the reduction of nitrate with vanadium chloride. The proposed method could be applied to the determination of total nitrogen in sewage and river-water samples. Analytical data obtained by the proposed method were highly correlated to those determined by the UV method (JIS method). The sensitivity of the proposed method is superior to those of spectrophotometric methods reported so far.

A Mild and Efficient Tetrahydropyranylation and Detetrahydropyranylation of Alcohols and Phenols by VCl3

Vanadium chloride is found to be an efficient catalyst for the tetrahydropyranylation and detetrahydropyranylation of various alcohols and phenols, giving good yields at room temperature and short reaction times.

Synthesis of nanocrystalline VN via thermal liquid–solid reaction

Nanocrystalline vanadium nitride (VN) was prepared by a direct thermal liquid–solid reaction between vanadium chloride (VCl 4) and sodium azide (NaN 3) at 600 °C. Characterized by XRD, TEM, XPS and PL, the composition and morphology of the product were confirmed. The possible reaction mechanism was also discussed.

Vanadium-Catalyzed Pinacol Coupling Reaction in Water

A catalytic pinacol coupling using water as a solvent was performed by a catalytic amount of vanadium(III) chloride and metallic Al as a co-reductant. A combination forms a binary catalytic system, being in sharp contrast to the reaction in organic solvent, which requires a chlorosilane as an additive. Various aromatic aldehydes underwent the reductive coupling to give the corresponding 1,2-diols in moderate to good yields.

Vanadium(III) chloride: A mild and efficient catalyst for the chemoselective deprotection of acetonides

Acetonides are selectively cleaved at room temperature by a catalytic amount of VCl 3 in methanol to furnish the corresponding diols under mild conditions. Other hydroxyl protecting groups such as TBDMS, TBDPS, Ac, THP, Bn, prenyl, allyl present in the substrate were intact under the reaction conditions.

Increased Serum Nitrite/Nitrate (NOx) and Malondialdehyde (MDA) Levels During Alcohol Withdrawal in Alcoholic Patients

Serum nitrite/nitrate (NOx) and malondialdehyde (MDA) levels of 40 male alcoholic patients and 14 healthy male controls were investigated. Severity of alcohol withdrawal in alcoholic patients was evaluated by using the Clinical Institute Withdrawal Assessment for Alcohol (CIWA-Ar) scale just before taking the blood samples. NOx levels in serum samples were determined based on the reduction of nitrate to nitrite by vanadium chloride. MDA levels were also determined spectrophotometrically at 540 nm. The total CIWA-Ar score of alcohol-withdrawn patients was found to be 17.7. NOx and MDA levels were significantly increased in alcoholics during alcohol withdrawal as compared to control subjects. In conclusion, we observed increased serum NOx levels and lipid peroxidation during alcohol withdrawal in alcoholic patients.

Autoregulatory Role of Endothelium-derived Nitric Oxide (NO) on Lipopolysaccharide-induced Vascular Inducible NO Synthase Expression and Function

Nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) is responsible for sepsis-induced hypotension and plays a major contributory role in the ensuing multiorgan failure. The present study aimed to elucidate the role of endothelial NO in lipopolysaccharide (LPS)-induced iNOS expression, in isolated rat aortic rings. Exposure to LPS (1 mug/ml, 5 h) resulted in a reversal of phenylephrine precontracted tone in aortic rings (70.7 +/- 3.2%). This relaxation was associated with iNOS expression and NF-kappaB activation. Positive immunoreactivity for iNOS protein was localized in medial and adventitial layers of LPS-treated aortic rings. Removal of the endothelium rendered aortic rings resistant to LPS-induced relaxation (8.9 +/- 4.5%). Western blotting of these rings demonstrated an absence of iNOS expression. However, treatment of endothelium-denuded rings with the NO donor, diethylamine-NONOate (0.1 mum), restored LPS-induced relaxation (61.6 +/- 6.6%) and iNOS expression to levels comparable with arteries with intact endothelium. Blockade of endothelial NOS (eNOS) activation using geldanamycin and radicicol, inhibitors of heat shock protein 90, in endothelium-intact arteries suppressed both LPS-induced relaxation and LPS-induced iNOS expression (9.0 +/- 8.0% and 2.0 +/- 6.2%, respectively). Moreover, LPS treatment (12.5 mg/kg, intravenous, 15 h) of wild-type mice resulted in profound elevation of plasma [NO(x)] measurements that were reduced by approximately 50% in eNOS knock-out animals. Furthermore, LPS-induced changes in vascular reactivity and iNOS expression evident in wild-type tissues were profoundly suppressed in tissues taken from eNOS knockout animals. Together, these data suggest that eNOS-derived NO, in part via activation of NF-kappaB, regulates iNOS-induction by LPS. This study provides the first demonstration of a proinflammatory role of vascular eNOS in sepsis.

Formation of VN from VCl4 and NH(SiMe3)2 by APCVD − a Potential Solar Control Coating

AbstractVanadium nitride thin films have been synthesised by the reaction of vanadium(IV) chloride with hexamethyldisilazane (HMDS) under atmospheric pressure (AP)CVD conditions at 300−550 °C. The films deposited have good optical characteristics and low electrical resistivities. These films were not scratched off the glass substrate by a steel stylus and were not degraded by immersion in a range of solvents. X‐ray diffraction showed an NaCl‐type cubic cell with a = 4.102(1)−4.127(1) Å, dependent on the sample. X‐ray photoelectron spectroscopy shows that the films have a V/N ratio close to unity. For comparison, films were also deposited by the APCVD reaction of VOCl3 with HMDS. These films consist of mixed phases of vanadium oxynitride and V2O3. The VN films show properties suitable for use as solar control coatings. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)