Tetravalent Vanadium Research Articles

The oxidation of NADH by tetravalent vanadium

Vanadyl (V (IV)) salts autoxidize in neutral aqueous solution yielding O 2 − plus vanadate (V (V)) and these, in turn, cause the oxidation of NADH, by a free radical chain reaction. This oxidation of NADH was inhibited by superoxide dismutase, but not by a scavenger of HO.. When H 2O 2 was present V (IV)) caused rapid oxidation of NADH by a process which was unaffected by superoxide dismutase but was inhibited by a scavenger of HO.. This appeared to be dependent upon reduction of H 2O 2 to OH − plus HO., by V (IV)), followed by oxidation of NADH by HO.. Since there are reductants, within cells, capable of reducing V (V)) to V (IV), these reactions are likely to contribute to the toxicity of vanadate.

Vanadyl ions increase the order parameter of plasma membranes without changing the rotational relaxation time

Differential polarized phase fluorometry of 1,6-diphenyl-1,3,5-hexatriene showed that vanadyl ions (VO 2+) increased its limiting anisotropy (order parameter) in crude plasma membranes from brown adipose tissue of the golden hamster ( Mesocricetus auratus). This was about 10 3 times larger than the effect of Ca 2+ and was several times greater than the action of Co 2+. Vanadate anions were without any effect. During the membrane treatment with VO 2+, the rotational relaxational time of diphenylhexatriene did not change. This results suggest a possible positive influence of tetravalent vanadium on the stability of cell membranes.

Thermal decomposition of the solvent-extracted metal complexes with high molecular weight amines

Organic solutions from the extractions of divalent manganese, cobalt, copper and zinc, trivalent gallium, indium and thallium, tetravalent vanadium and zirconium, and hexavalent uranium and molybdenum with trioctylamine (TOA, R 3N) and trioctylmethylammonium chloride (TOMAC, R 3R′NCl) in benzene were heated in vacua to prepare benzene-free complexes. The resulting complexes were examined by thermogravimetry and differential thermal analysis under an atmosphere of nitrogen, and their thermally decomposed products, such as volatile matters and residues, by gas chromatography, X-ray diffraction and infrared spectroscopy. Consequently, the thermal decomposition process of these complexes is discussed and the structure of the complexes is proposed on the basis of the results obtained.

The composition of asphaltenes and resins of West Siberian petroleums

ESR and X-ray diffraction analysis was used to examine asphaltene and resin samples of West Siberia. Experiments were carried out to simulate the effect of catagenesis on resin and asphaltene composition. Processes of thermocatalytic transformations of crude oil in the deposit were found to have no marked effect on asphaltene and resin composition. Transformation of the organic input at sedimentation was assumed to be the main factor determining the qualitative and quantitative composition of crude oil resins and asphaltenes of West Siberia. Petroleums formed from organic matter, accumulating under reducing conditions, contain more asphaltenes and resins, they include much tetravalent vanadium and the asphaltenes have abundant paramagnetic centres. Petroleums formed from oxidized organic matter contain very little asphaltene low concentrations of paramagnetic centers, and little tetravalent vanadium. Resins of these petroleums are rich in oxygen. High levels of asphalt-resin matter in petroleums is related to the presence in the initial organic progenitors of polyunsaturated fatty acids and various nitrogen- and sulfur-containing compounds.

Characterization of silica-supported vanadium species. Interactions with methanol and ammonia adsorbates studied by electron spin–echo modulation spectrometry

The interactions of deuterons in CH3OD and CD3OH adsorbates on V2O5/SiO2 catalysts have been analysed by electron spin–echo modulation (e.s.e.m.) spectrometry. The best fit to the experimental data indicates that the tetravalent vanadium interacts with three methanol molecules with V—DOMe= 0.27 and V—D3CMe= 0.35 nm in the first coordination sphere and with two farther methanol molecules at V—D3CMe= 0.45 nm. Fast Fourier transform of the time domain e.s.e.m. data for samples with adsorbed ND3 clearly shows a strong interaction between vanadium and nitrogen.

Tetravalent vanadium in CaF 2 and SrF 2 crystals: An EPR study

An EPR study of tetravalent vanadium centers created by room temperature X-irradiation in CaF 2 and SrF 2 is presented. The production efficiency of these centers is enhanced by previous annealing of the samples at 1000 K in air. The symmetry of V 4+ ions is tetragonal and its EPR spectrum can be described by an axial spin Hamiltonian including a Zeeman and hyperfine term with S = 1 2 and I = 7 2 (corresponding to 51V nuclei). The following values for the spin Hamiltonian parameters are obtained g ∥ = 1.947 ± 0.002, g ⊥ = 1.935 ± 0.005, A ∥ = 500 ± 5 MHz, A ⊥ = 150 ± 10 MHz in the case of SrF 2 and g ∥ = 1.945 ± 0.002, A ∥ = 505 ± 5 MHz and A ⊥ < 200 MHz, in the case of CaF 2. A model for the center including an interstitial O 2− ion is tentatively proposed.

Inhibition of (Na,K)-ATPase by tetravalent vanadium.

Vanadyl, the tetravalent state of vanadium and a divalent cation, VO2+, was a relatively powerful inhibitor of highly purified membrane-bound sodium and potassium ion transport adenosine triphosphatase. The sensitivity of the ATPase activity to vanadyl characteristically correlated positively with the specific activity of the enzyme preparation. Inhibition ranged from nearly complete inhibition at less than 5 microM vanadyl for some of the purest fractions (specific activity approximately 45 mumol/min/mg of protein) to no observable inhibition at 300 microM vanadyl in one crude preparation of the enzyme with a specific activity of 10 mumol/min/mg of protein. The level of free vanadyl was reduced by incubation with these membranes, but this reduction was not sufficient to account for the low sensitivity to vanadyl observed in crude preparations. A reduction in specific activity by partial inactivation of a sensitive preparation by treatment with FeCl3 and ascorbate reduced its sensitivity to vanadyl. Anionic ligands of the enzyme, vanadate or ATP, increased the rate of recovery from inhibition after chelation of free vanadyl. At pH 6.1, the inhibition was characteristically fully reversible (t1/2 approximately 10 min), whereas at pH 8.1 it was stable for hours. The degree and stability of enzyme inhibition by vanadyl increased for several hours during incubation of the vanadyl-enzyme mixture, and at pH 6.1 the properties of the inhibitor itself also changed with time. Preincubation of the ion at that pH for 5 h before addition of the enzyme produced a more stable inhibition. The time- and pH-dependent changes in the degree and stability of enzyme inhibition probably relate to the complex chemistry of the vanadyl ion in solution.

Aqueous Redox Polymerization of Acrylonitrile Initiated by Systems Based on Tervalent and Tetravalent Vanadium in Combination with N-Bromosuccinimide as the Oxidant

Abstract The kinetics of polymerization of acrylonitrile (AN) initiated by the systems V(IV)/N-bromosuccinimide (NBS) and V(HI)/NBS have been investigated in aqueous acid media in the 25–35°C range. Evidence for Michaelis-Menten kinetics is obtained from oxidation data with the system V(IV)/NBS. Rates of polymerization varied as [AN]3/2, [NBS]½, and [Vn+]½, where n = 3 or 4. The retardation of oxidation as well as polymerization by increasing [H+] results from protonation of NBS which inhibits complexation. A mechanism involving formation of a complex between the reductant metal ion and oxidant followed by its reaction with AN to generate initiating radicals, coupled with mutual termination of growing radicals, accounts for the kinetics of polymerization.

The effect of chelating agents on vanadium distribution in the rat body and on uptake by human erythrocytes.

Pentavalent vanadium (V5) as Na48VO3 was given i.p. to male Wistar rats at a dose of 5 mumol/kg in order to study its organ distribution pattern. Two days after injection, kidneys reached a V level of about 28 nmol/g wet weight, followed in decreasing order by spleen, liver, bone, blood plasma, testis, lung, erythrocytes and brain in control rats. A similar distribution pattern was seen after injection of tetravalent vanadium (V4) given as 48VOSO4. Two chelators, desferrioxamine B (Desferal) or Ca-Na3-diethylene triamine pentaacetic acid (DTPA), were given i.p. 24 h after the vanadium injections to different groups of rats at two dosage levels, 30 and 100 mumol/kg. Desferal (30 mumol/kg) reduced the vanadium content of the kidney by 17%, of the liver by 0%, and of the lung by 7%. The corresponding figures for the effect of DTPA (30 mumol/kg) were 7%, plus 15%, and 0%, respectively. At 100 mumol/kg, Desferal reduced the same organ levels by 20%, 26%, and 25%, respectively, and DTPA by 9%, 18%, and 25%, respectively. Both chelators raised faecal excretion at the low level, and both urinary and faecal excretion at the high level. Spleen and bone seemed to bind vanadium to a higher degree than the other organs under examination. Human erythrocytes, when incubated with 48VOSO4 (V4) or Na48VO3 (V5), were found to accumulate nearly the double amount of V5 as compared to V4. Glutathione (GSH) which is the main reducing substance within the erythrocytes, reduced the uptake of V5 to the V4 level when incubated together with GSH before addition to the cell suspension. Pretreating the erythrocytes with diethyl-maleate (DEM) which blocks the reducing SH groups of intracellular GSH, also reduced the uptake of V5. This may indicate a GSH dependent reduction of V5 to V4 within the erythrocytes. Four chelators, among them Desferal and DTPA, were found to reduce the cellbound amount of vanadium, either by extracting vanadium as V4, or by inhibiting uptake by the red blood cells.

Studies on Electronic Spectrum and Electron Spin Resonance of Vanadium(IV) Complexes with Organophosphorus Compounds and High Molecular Weight Amines

Abstract In the extraction of vanadium(IV) from aqueous solutions containing hydrochloric acid and/or a mixture of hydrochloric acid and lithium chloride by bis(2-ethylhexyl) hydrogenphosphate (DEHPA; HX), trioctylmethylammonium chloride (Aliquat-336), trioctylamine (TOA), trioctylphosphine oxide (TOPO) and tributyl phosphate (TBP), the complexes formed in the organic phases have been examined by spectrophotometry and electron spin resonance spectroscopy. It is found that in the extraction by DEHPA, the vanadium in the organic phase exists as the monomeric species, VO(X2H)2, or the polymeric one, (VOX2)n, and that in the extractions by Aliquat-336, TOA, TOPO, and TBP, tetravalent vanadium complexes are stable in the organic phases extracted from a mixed solution of hydrochloric acid and lithium chloride, while complexes containing pentavalent vanadium and VOV4+ ions are formed in the organic phases extracted from hydrochloric acid solutions.

Kinetics of SO2 oxidation on K2S2O7−V2O5 catalyst in non-steady conditions

Studies of SO2 oxidation on a molten component of vanadium catalysts in non-steadystate conditions indicates that the kinetics agree fairly well with an oxidation-reduction mechanism. In the low temperature range (<790 K) tetravalent vanadium can be partially crystallized.

Synthesis and properties of covalent tri- and tetravalent vanadium

Reactions of VCl 3 · 3 THF with RMgX (R  Ph, CH 2SiMe 3, C 6F 5) in various ratios have been studied. The stable compounds R 3V · THF (R  CH 2SiMe 3, C 6F 5) were obtained. The chemical properties of R 3V · THF, R 4V · 2 L (R  CH 2Ph, L  Et 2O; R  C 6F 5, L  THF) and (Me 3SiCH 2) 4V were investigated. Cleavage of the vanadium-carbonium σ-bond occurs in reactions with H 2O, HCl and HgCl 2. The insertion of carbon dioxide into the vanadiumcarbon σ-bond was investigated. A scheme for the derivatives of tri- and tetravalent vanadium is proposed. Oxidative addition to (C 6F 5) 3V · THF by Ph 3CCl and VCl 3 · 3THF was also studied.

Studies on the high-pressure reaction of Er 2O 3 and VO 2

The reaction of erbium sesquioxide (Er 2O 3) and vanadium dioxide (VO 2) at 50 kbar and 30 kbar pressures and 1400°C were studied. In the course of the reaction, tetravalent vanadium ions were reduced to the trivalent state and erbium vanadites (ErVO 3) were obtained. The crystal structures of the products were examined by an x-ray diffraction analysis. At 50 kbar, a vaterite-type (μ-CaCO 3) compound isostructural with ErBO 3, which belonged to a hexagonal system, and at 30 kbar, a calcite-type vanadite belonging to a rhombohedral (pseudo-hexagonal) system were obtained. In the case of the reaction of erbium sesquioxide and vanadium trioxide (V 2O 3) at high pressure, a perovskite-type erbium vanadite was obtained. The magnetic properties of the compounds were studied.

Synthese sous haute pression d'oxygene d'une forme dense ordonne´e de FeVO 4 et mise en evidence d'une varie´te´allotropique de structure CrVO 4

Abstract A new dense form of iron vanadate Fe 3+V 5+O 4 has been synthesized under high pressure high temperature conditions in a sealed platinum capsule. This phase cristallizes in a structure of monoclinic wolframite NiWO 4 type. The dense form of αPbO 2 type previously described by Young and Schwartz was shown to be probably a reduced form of composition Fe 1− x V 1+ x O 4 containing some tetravalent vanadium. This disordered phase was also obtained when runs were performed in unsealed capsules. The monoclinic form undergoes at 570°C an irreversible transformation to the form stable at normal pressure conditions, while the disordered form of αPbO 2 type transforms at about 540°C into intermediate form of Cr 3+V 5+O 4 type. The range of stability of this phase is very narrow and at about 570°C it transforms to the normal triclinic form.

Synthése sons Haute Pressiori d'Oxygène d'une Forme Dense Ordonée FeVO 4 et Mise en Evidence dune Variété Allotropique de Structure CrVO 4

Abstract A new dense form of iron vanadate Fe 3+ V 5+ O 4 has been synthesized under high pressure high temperature conditions in a sealed platinum capsule. This phase cristallizes in a structure of monoclinic wolframite NiWO 4 type. The dense form of αPbO 2 type previously described by Young and Schwartz was shown to be probably a reduced form of composition Fe 1− x V 1+ x O 4 containing some tetravalent vanadium. This disordered phase was also obtained when runs were performed in unsealed capsules. The monoclinic form undergoes at 570°C an irreversible transformation to the form stable at normal pressure conditions, while the disordered form of αPbO 2 type transforms at about 540°C into intermediate form of Cr 3+ V 5+ O 4 type. The range of stability of this phase is very narrow and at about 570°C it transforms to the normal triclinic form.

Hyperfine, Superhyperfine, and Quadrupole Interactions forV4+in Tetragonal GeO2

Single crystals of vanadium-doped tetragonal Ge${\mathrm{O}}_{2}$ have been studied at 300 and 92 K by electron-spin resonance. The observed spectra are attributed to tetravalent vanadium ions ($3{d}^{1}$) substitutional at the two inequivalent cation sites. With the choice of axes $\stackrel{\ensuremath{\rightarrow}}{\mathrm{x}}\ensuremath{\parallel}[\overline{1}10]$, $\stackrel{\ensuremath{\rightarrow}}{\mathrm{y}}\ensuremath{\parallel}[001]$, and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{z}}\ensuremath{\parallel}[110]$, the spin-Hamiltonian parameters obtained at 300 K from the hyperfine, super-hyperfine, and forbidden-transition spectra are ${g}_{x}=1.9467$, ${g}_{y}=1.9211$, ${g}_{z}=1.9638$; ${A}_{x}=18.48\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${A}_{y}=37.27\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${A}_{z}=134.63\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$; ${P}_{x}=\ensuremath{-}0.44\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${P}_{y}=\ensuremath{-}0.35\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${P}_{z}=+0.79\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$; ${A}_{\mathrm{ax}}=8.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${A}_{\mathrm{ay}}=8.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${A}_{\mathrm{az}}=8.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, where the last tensor corresponds to a shf interaction with a ${\mathrm{Ge}}^{73}$ nucleus at one of the nearest cation sites along the $c$ axis. Weaker interactions with other neighboring cations were also observed. On the basis of a molecular-orbital treatment of the unpaired spin, ligand-orbital-admixture coefficients were determined from these experimental results and from previously reported results ${\mathrm{V}}^{4+}$ in tetragonal Ti${\mathrm{O}}_{2}$ and Sn${\mathrm{O}}_{2}$. It is determined that the probability of finding the unpaired electron on the vanadium ion is about 0.71, while the probabilities for delocalization onto the anions and cations are about 0.27 and 0.02, respectively.

Spectra of V(II), V(III), V(IV) and V(V) in 5.6 molar phosphoric acid

The spectra of di, tri, tetra and pentavalent vanadium were measured in 5.6 molar H 3PO 4 media for the range of 10,000–53,000 cm −1. V(II) spectra were resolved into bands at 11,400,17,100 and 25,600 cm −1 with residues at 14,300 and 21,900 cm −1. The bands are probably due to 4 A 2 g → 4 T 2 g , 4 T 1 g ( F) and 4 T 1 g ( P) in an octahedral configuration. Residues are probably due to spin forbidden 4 A 2 g → 2 T 1 g , 2 E g transitions. For V(III), strong bonds were found at 15,150 and 23,250 cm −1 that can be attributed to 3 T 1 g → 3 T 2 g , 3 T 1 g in an approximately octahedral configuration. Weaker bands were found at 11,300 and 17,850 cm −1 that can be assigned to spin forbidden 3T 1 g → 1 E 1, 1 T 2 g and 1 A 1 g . In tetravalent vanadium, d-d transitions were found at 12,000, 13,400 and 14,800 cm −1 that can be assigned to 2 B 2 → 2 E( I), 2 B 1 and 2 A 1. The charge transfer spectra of V(V) showed transitions at 27,500, 34,750 and 51,000 cm −1. The V(V) charge transfer spectra may be used as evidence that the 41,00 cm −1 transition for V(IV) is probably a charge transfer rather than a d-d transition.

Paramagnetic Resonance of Interstitial V4+ in TiO2

The effects of various technological processes on the electronic structure of vanadium-doped TiO2 crystals have been studied. The EPR spectra give clear evidence that by suitable thermal treatment in a reducing atmosphere the tetravalent vanadium ions can be transferred from the substitutional to the interstitial positions. The four inequivalent spectra corresponding to the four interstitial octahedra have been analyzed and interpreted in terms of a microscopical model. The measured values of the components of the g-tensor and hyperfine interaction tensor are: gx = 1.9865 ± 0.0005, | Ax | = 45.4 ± 0.5 × 10−4 cm−1; gy = 1.9930 ± 0.0005, | Ay | = 60.5 ± 0.5 × 10−4 cm−1; gz = 1.9407 ± 0.0005, | Az | = 111.4 ± 0.5 × 10−4 cm−1. The linewidth was found to be approximately 2.8 G. The intensity of the absorption lines is one-tenth of the intensity of the original resonance of the substitutional V4+. The deviation of the axes of the magnetic coordinate systems of the four nonequivalent ions with respect to the substitutional sites was found to be φ = ± 10° (± 0.5°).

Quadrupole moment of vanadium-51: forbidden lines in EPR of oxovanadium(IV)

The first measurements of sign and magnitude of quadrupole coupling in tetravalent vanadium are obtained from forbidden EPR lines in crystal. For VO 2+ in Pd(C 6H 5COCHCOCH 3) 2, e 2 qQ = 24 ± 16 MHz; for VW 5O 4− 19 in Na 2(CH 3NH 3) 2V 2W 4O 19·6H 2O, e 2 qQ = −8 ± 1 MHz. These values support Q ≈ −0.10 ± 0.06 b for 15V.

Growth effects of vanadium in the rat.

Vanadium is necessary for growing rats raised inside trace elementcontrolled, all plastic isolators on a highly purified amino acid diet. Addifion of vanadium to the diet enhances growth by over 40 percent. A nearly optimum effect is obtained with 10 micrograms of vanadium per 100 grams of diet in (0.1 part per million), supplied in the form of sodium orthovanadate, as seen from series of tests with levels ranging from 1 to 5 micrograms per 100 grams of diet. Different vanadium compounds show different potencies: sodium orthovanadate was effective, metavanadate less active, and pyrovanadate without activity. Tetravalent vanadium, supplied as vanadyl sulfate or acetate, was utilized but produced smaller responses. The amounts of vanadium required are those normally found in tissues and nutrients.