Study on the role of SBA-15 in the oxidative dehydrogenation of n-butane over vanadia catalyst using density functional theory

The first step in the mechanism of n-butane oxidative dehydrogenation (ODH) on a V₄O₁₀ cluster and V₄O₁₀ supported SBA-15 is examined using DFT method. The activation and adsorption energies, oxidation state of V atoms are calculated. Over V₄O₁₀ the obtained results indicate that the activation of C-H bond of methylene group can occur at both the terminal and the bridging oxygen atoms with similar barrier (21.5–22.5 kcal mol^?1). The role of SBA-15 (with and without modification by Al) in n-butane adsorption step has been studied in detail. SBA-15 itself has mild effect on the reaction process, but the substitution of silicon atoms by aluminum atoms results in an active supporter for V₂O₅ in ODH reaction. In that, the ratio of Si/Al will decide the direction of initial interaction steps between n-butane and catalyst surface and it will result in the selectivity of the reaction products.

Novel examples of hybrid organic–inorganic solids based on building blocks

New hybrid organic/inorganic copper oxovanadium compounds of composition [Cu(dpa)₂]₄V₄O₁₂ (1), Cu₂(bipy)₂V₄O₁₂ (2), and Cu₂(bipy)₂V₆O₁₇ (3), which crystallize in the monoclinic 1, 2 and triclinic 3 symmetry, respectively, were obtained by soft hydrothermal routes. The first two structures present isolated [V₄O₁₂]⁴⁻ anionic units, the structure of 3 exhibits the same [V₄O₁₂]⁴⁻ cycles coupled by V₂O₅ dimeric bridges propagated as an infinite chain along the c-direction 3. For compound 1, the copper(I) centers are bonded to four nitrogen atoms with a distorted tetrahedral geometry. For compounds 2 and 3, the copper(II) centers are square pyramidal with two nitrogen atoms from the neutral diimine ligand and three oxygen atoms from the oxovanadium sub-unit. In all the compounds described herein, the vanadium ions are as V(V), occupying solely tetrahedral sites.     

A fresh look into VO(salen) chemistry: synthesis, spectroscopy, electrochemistry and crystal structure of [VO(salen)(H2O)]Br · 0.5 CH3CN

The reaction of V^IVO(salen) with [Et₄N][SnBr₃] in air proceeds via an initial reduction to give a [V^III (salen)]⁺ intermediate, which is then oxidised to dark green [V^VO(salen)(H₂O)]Br, 1. As determined by X-ray crystallography, 1 in the solid state contains hexacoordinate vanadium. ⁵¹V NMR spectra indicate that dissociation of the aqua ligand occurs to give a pentacoordinated [V^VO(salen)] cation in methanol-d₄ solution, while in DMSO-d₆ solutions, coordination of the solvent occurs to give [V^VO(salen)(DMSO-d₆)]⁺. The colour of 1 can be accounted for by O_oxo → V^V and phenolate → V^V LMCTs. Results from this study have led to the re-assignment of LMCTs and V-N and V-O_phenolate stretching frequencies in the IR spectrum. Cyclic voltammetry of 1 indicates three redox processes. The first is typical of [VO(salen)]/[VO(salen)]⁺ couple and the other two are bromide oxidations.     

Mechanistic Insights of Zn2+ Storage in Sodium Vanadates

Rechargeable aqueous zinc‐ion batteries (ZIBs) with high safety and low‐cost are highly desirable for grid‐scale energy storage, yet the energy storage mechanisms in the current cathode materials are still complicated and unclear. Hence, several sodium vanadates with NaV₃O₈‐type layered structure (e.g., Na₅V₁₂O₃₂ and HNaV₆O₁₆·4H₂O) and β‐Na_0.33V₂O₅‐type tunneled structure (e.g., Na_0.76V₆O₁₅) are constructed and the storage/release behaviors of Zn²⁺ ions are deeply investigated in these two typical structures. It should be mentioned that the 2D layered Na₅V₁₂O₃₂ and HNaV₆O₁₆·4H₂O with more effective path for Zn²⁺ diffusion exhibit higher ion diffusion coefficients than that of tunneled Na_0.76V₆O₁₅. As a result, Na₅V₁₂O₃₂ delivers higher capacity than that of Na_0.76V₆O₁₅, and a long‐term cyclic performance up to 2000 cycles at 4.0 A g^?1 in spite of its capacity fading. This work provides a new perspective of Zn²⁺ storage mechanism in aqueous ZIB systems.     

Structural and EPR/ENDOR/ESEEM spectroscopic investigations of a vanadomolybdate Keggin-type polyoxometalate in organic solvent

An EPR spectrum of as synthesized [G.A. Tsigdinos, C.J. Hallada, Inorg. Chem. 7 (1968) 437-441], orange colored, H₅PV₂Mo₁₀O₄₀ polyoxometalate showed the presence of a reduced vanadium(IV) addenda atom. Surprisingly, further ³¹P ENDOR (electron-nuclear double resonance) measurements indicated the absence of a phosphorous heteroatom leading to the suggestion that H₅V^VV^IVMo₁₁O₄₀ exists as a previously unrecognized impurity in the typically synthesized H₅PV₂Mo₁₀O₄₀ compound. H_5/4PV^VO₄V^IV/VMo₁₁O₃₆ was then synthesized in low yield (0.8 mol%) by omitting the addition of phosphate in a typical H₅PV₂Mo₁₀O₄₀ preparation. The molecular formulation and structure was supported by X-ray crystallography, infrared and mass spectrometry. Further use of EPR/ENDOR/ESEEM (electron-spin echo envelope modulation) allowed the formulation of [V^VV^IVMo₁₁O₄₀]⁵⁻ as [V^VO₄V^IVMo₁₁O₃₆]⁵⁻. Accordingly, the polyoxometalate has a heteroatom core with 11 molybdenum addenda and one VO²⁺ moiety at the polyoxometalate surface. The redox potential and the catalytic activity of the new vanadomolybdate polyoxometalate compound were essentially identical to the often-studied H₅PV₂Mo₁₀O₄₀ polyoxometalate isomeric mixture.     

Respiratory syncytial virus infection reduces lung inflammation and fibrosis in mice exposed to vanadium pentoxide

Background

Vanadium pentoxide (V₂O₅) exposure is a cause of occupational bronchitis and airway fibrosis. Respiratory syncytial virus (RSV) is a ubiquitous pathogen that causes airway inflammation. It is unknown whether individuals with pre-existing respiratory viral infection are susceptible to V₂O₅-induced bronchitis. We hypothesized that respiratory viral infection will exacerbate vanadium-induced lung fibrosis.

Methods

In this study we investigated the effect of RSV pre- or post-exposure to V₂O₅ in male AKR mice. Mice were pre-exposed by intranasal aspiration to RSV or media vehicle prior to intranasal aspiration of V₂O₅ or saline vehicle at day 1 or day 7. A parallel group of mice were treated first with V₂O₅ or saline vehicle at day 1 and day 7 then post-exposed to RSV or media vehicle at day 8.

Results

V₂O₅-induced airway inflammation and fibrosis were decreased by RSV pre- or post-exposure. Real time quantitative RT-PCR showed that V₂O₅ significantly increased lung mRNAs encoding pro-fibrogenic growth factors (TGF-β1, CTGF, PDGF-C) and collagen (Col1A2), but also increased mRNAs encoding anti-fibrogenic type I interferons (IFN-α, -β) and IFN-inducible chemokines (CXCL9 and CXCL10). RSV pre- or post-exposure caused a significantly reduced mRNAs of pro-fibrogenic growth factors and collagen, yet reduced RNA levels of anti-fibrogenic interferons and CXC chemokines.

Conclusions

Collectively these data suggest that RSV infection reduces the severity of V₂O₅-induced fibrosis by suppressing growth factors and collagen genes. However, RSV suppression of V₂O₅-induced IFNs and IFN-inducible chemokines suggests that viral infection also suppresses the innate immune response that normally serves to resolve V₂O₅-induced fibrosis.     

Micro‐ and Nano‐Structured Vanadium Pentoxide (V2O5) for Electrodes of Lithium‐Ion Batteries

Vanadium pentoxide (V₂O₅) has played important roles in lithium‐ion batteries due to its unique crystalline structure. To assist researchers understanding the roles this material plays, a comprehensive and critical review is conducted based on about 250 publications. Here, we report basics and applications of micro‐ and nano‐materials of V₂O₅ and V₂O₅‐based composites. The comparative and statistical analysis leads to the discovery of several interesting phenomena. The V₂O₅ electrodes with two lithium ions have a favorable capacity performance with reversible phase formation. The excellent capacity retention is displayed in the V₂O₅ electrodes with one lithium ion inserted. In the case of three lithium ions insertion, it was found that the irreversible formation of the phase ω in Li_xV₂O₅ leads to its control. In addition, effects of additives on electrode performance, circuitry models of performance, as well as reaction routes are studied. Two unprecedented concepts of the “high capacity band” and “empirical total capacity retention” are proposed though the comprehensive statistical analysis of the reviewed data. This review provides a comprehensive collection of information of state‐of‐the‐art and recent advancement in V₂O₅ and V₂O₅‐based composite materials for electrodes. Researchers could use the information to design and develop advanced electrodes for future batteries.     

Insulin-enhancing activity of a dinuclear vanadium complex: 5-chloro-salicylaldhyde ethylenediamine oxovanadium(V) and its permeability and cytotoxicity

A new insulin-enhancing oxovanadium complex 5-chloro-salicylaldhyde ethylenediamine oxovanadium (V) ([V₂O₂(μ-O)₂L₂]) has been synthesized. The complex was characterized by a variety of physical methods, including X-ray crystallography. The X-ray diffraction analysis show a dinuclear complex of two six-coordinate vanadium centers doubly bridged by the oxygen atoms of the Schiff base ligand with a V₂O₂ diamond core. The complex was administered intragastrically to STZ-diabetic rats for 2 weeks. The biological activity results show that the complex at the dose of 10.0 and 20.0 mg V kg^− 1, could significantly decrease the blood glucose level and ameliorate impaired glucose tolerance in STZ-diabetic rats. That results suggested that the complex exerts an antidiabetic effect in STZ-diabetic rats. Furthermore, the complex ([V₂O₂(μ-O)₂L₂]) had permeability above 10^− 5 cm/s. The experimental results suggested that the vanadium complex permeates via a passive diffusion mechanism. It was also suggested the complex with salen-type ligands has good lipophilic properties and better oral administration. The cytotoxicity of the complex ([V₂O₂(μ-O)₂L₂]) on Caco-2 cells was measured by a decrease of cell viability using the MTT assay suggesting that the chlorine atom at C4 of complex [V₂O₂(μ-O)₂L₂] increased cytotoxicity for vanadium complexes.     

Decavanadate protonation degrees in aqueous solution

Aqueous solutions of vanadium(V) have been prepared at different OH⁻ vs. vanadium concentrations from both decavanadic acid and metavanadate solutions. These solutions have been extracted with an excess of tetraheptylammonium bromide in benzene. The bromide displaced has been determined in order to gain information on the average charge of the extracting species already known to be variously protonated decavanadate anions. The addition of a constant excess of supporting electrolytes has been avoided, as it is known it could affect the position of equilibria.Besides the already well known H₂V₁₀O₂₈⁴⁻, HV₁₀ O₂₈⁵⁻ and V₁₀O₂₈⁶⁻ species, strong evidence has also been obtained for the existence of H₃V₁₀O₂₈³⁻.Moreover, a slow disproportionation of V₁₀O₂₈⁶⁻ into HV₁₀O₂₈⁵⁻ and V₂O₇⁴⁻ (or HVO₄²⁻) during a first stage, and then into metavanadate, resulted.Therefore, H₆V₁₀O₂₈ proves a strong acid as triprotic instead of tetraprotic, as reported in the literature. Inconsistent results are almost certainly due to the high ionic media usually employed.     

The first vanadate oxide phase containing two types of modified metal centers: {Mn(2,2-bpy)}[{VO2(2,2-bpy)}(VO3)(V2O6)] (2,2-bpy=2,2-bipyridine)

An unprecedented hybrid vanadate, {Mn^II(2,2^′-bpy)}[{V^VO₂(2,2^′-bpy)}(V^VO₃)(V^V₂O₆)], has been hydrothermally synthesized from the reaction of V₂O₅, 2,2^′-bipyridine, and MnCl₂. It has been characterized by IR, XPS, TGA and single-crystal X-ray diffraction. The structure of the title compound is constructed from left-handed and right-handed V-O helical chains linked through modified binuclear {Mn(2,2^′-bpy)V^VO₄(2,2^′-bpy)} moieties into a double helical structure.     

Nanoparticles Encapsulated in Porous Carbon Matrix Coated on Carbon Fibers: An Ultrastable Cathode for Li‐Ion Batteries

Nanostructured V₂O₅ is emerging as a new cathode material for lithium ion batteries for its distinctly high theoretic capacity over the current commercial cathodes. The main challenges associated with nanostructured V₂O₅ cathodes are structural degradation, instability of the solid‐electrolyte interface layer, and poor electron conductance, which lead to low capacity and rapid decay of cyclic stability. Here, a novel composite structure of V₂O₅ nanoparticles encapsulated in 3D networked porous carbon matrix coated on carbon fibers (V₂O₅/3DC‐CFs) is reported that effectively addresses the mentioned problems. Remarkably, the V₂O₅/3DC‐CF electrode exhibits excellent overall lithium‐storage performance, including high Coulombic efficiency, excellent specific capacity, outstanding cycling stability and rate property. A reversible capacity of ≈183 mA h g^?1 is obtained at a high current density of 10 C, and the battery retains 185 mA h g^?1 after 5000 cycles, which shows the best cycling stability reported to date among all reported cathodes of lithium ion batteries as per the knowledge. The outstanding overall properties of the V₂O₅/3DC‐CF composite make it a promising cathode material of lithium ion batteries for the power‐intensive energy storage applications.     

Organic-inorganic hybrid materials: Ligand influences on the structural chemistry of copper-vanadates

Hydrothermal reactions were used in the preparation of a series of bimetallic organic-inorganic hybrid materials of the M(II)/V_xO_y/organonitrogen ligand class. Compound 1, [{Cu₂(bpa)₂(C₂O₄)}₂V₄O₁₂]·H₂O, is molecular, while [{Cu(terpy)}₂V₆O₁₇] (2), [Cu₂(bpyrm)V₄O₁₂] (4) and [{Cu(phen)(H₂O)₂}VOF₄(H₂O)]·2H₂O (5) are two-dimensional, three-dimensional and one-dimensional, respectively (bpa = 2,2′-bipyridylamine; terpy = 2,2′:6,2″-terpyridine; bpyrm = 2,2′-bipyrimidine; phen = 1,10-phenanthroline). In contrast to the 2-D structure of 2, the Ni(II) analogue [{Ni(terpy)}₂V₄O₁₂]·2H₂O (3) is one-dimensional. The {V₄O₁₂}⁴⁻ cluster is a building block of structures 1, 3, and 4 while 2 is constructed from {V₆O₁₇}⁴⁻ rings.     

The role of central command in ventilatory control during static exercise

The role of central command in the respiratory response to 15 min of rhythmic-static (isometric) exercise was studied in humans. Voluntary exercise (VE) was compared with electrically induced exercise (EE) at three different work intensities, i.e. 5%, 15% and 25% of maximal voluntary contraction. A group of 12 volunteers participated in the study and each of them performed six sessions. A session consisted of at least 5 min rest, 15 min rhythmic-static single leg exercise (4 s contraction/12 s relaxation) and at least 5 min recovery. Force, minute ventilation (V _E) and oxygen uptake (VO₂) were measured. In EE, both V _E and VO₂ increased continuously during the entire exercise period after an initial rapid increase at all three work intensities. Correlation between VE and VO₂ was highly significant during EE. During all three work intensities of VE, VE and VO₂ achieved a steady-state after the initial increase. During VE, VE did not correlate as closely with VO₂ as during EE. All these findings indicate that central command was not imperative for an adequate ventilatory response to exercise within all three work intensities investigated. Without the influence of central command, correlation between VE and VO₂ was even better than during VE.     

Effect of Vanadium Pentoxide on the Incorporation of (2-14C)-Acetate into Fungal Lipids

Mycelia of Glomerella cingulata grown in the presence of vanadium pentoxide (V₂O₅), incorporated many times less (2-¹⁴C)-acetate into their lipids than mycelia of the same organism grown in the absence of V₂O₅. All neutral and polar lipid fractions investigated were affected. These data suggested that V₂O₅ depressed lipid biosynthesis in G. cingulata.     

Polyoxometalate cluster [V12B18O60H6] functionalized with the copper(II) bis-ethylenediamine complex

Three compounds based on the polyoxometalate building block [V₁₂B₁₈O₆₀H₆], (Na)₁₀[(H₂O)V₁₂B₁₈O₆₀H₆]·18H₂O (1), Na₈[Cu(en)₂]₂[V₁₂B₁₈O₆₀H₆](NO₃)₂·14.7H₂O (2), Na₇[Cu(en)₂]₂[V₁₂B₁₈O₆₀H₆](NO₃)·15.5H₂O (3), (en = ethylenediamine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis and TGA. Compound 1 consists of polyoxovanadium borate [V₁₂B₁₈O₆₀H₆] clusters which are surrounded by sodium countercations in octahedral sites, stabilized by electrostatic interactions with the oxygen atoms of both vanadium and boron centres. However, compounds 2 and 3 correspond to more complicated structures, constructed from the same polyoxometalate clusters, which are interconnected by [Cu(en)₂]²⁺ moieties via the terminal oxygen atoms of the polyoxoanions, generating one-dimensional structures. The functionalization of this polyoxovanadium borate cluster has been obtained by the use of [Cu(en)₂]²⁺ complex ions, thus demonstrating the capacity of the terminal oxygen atoms of the cluster to bind transition metal centres. The structural stability of the [V₁₂B₁₈O₆₀H₆] cluster permits the formation of functionalized polyoxometalate clusters, generating various crystalline lattices.     

A Flexible Quasi‐Solid‐State Asymmetric Electrochemical Capacitor Based on Hierarchical Porous V2O5 Nanosheets on Carbon Nanofibers

The development of 3D nanoarchitectures on flexible current collectors has emerged as an effective strategy for preparing advanced portable and wearable power sources. Herein, a flexible and efficient electrode is demonstrated based on electrospun carbon fibers (ECF) substrate with elaborately designed hierarchical porous V₂O₅ nanosheets (V₂O₅–ECF). The unique configuration of V₂O₅–ECF composite film fully enables utilization of the synergistic effects from both high electrochemical performance of V₂O₅ and excellent conductivity of ECF, endowing the films to be an excellent electrode for flexible and lightweight electrochemical capacitors (ECs). Benefiting from their intriguing structural features, V₂O₅–ECF and ECF films, directly used as electrodes for flexible asymmetric quasi‐solid‐state electrochemical capacitors, achieve superior flexibility and reliability, enhanced energy/power density, and outstanding cycling stability. Moreover, the ability to power light‐emitting diodes (LED) also indicates the feasibility for practical use. Therefore, it is believed that this novel design may find promising application in flexible devices in future.     

Two dumbbell-like polyoxometalates constructed from capped molybdovanadate and transition metal complexes

Self assembly of NaVO₃, Na₂MoO₄·2H₂O and NiCl₂·6H₂O with the assistance of organic liginds under hydrothermal conditions results in two molybdovanadates [Ni(enMe)₂]₄{[Ni(enMe)₂(H₂O)]₂[Ni(enMe)₂][(V^VMo^VI₈V₄^IVO₄₀)(V^IVO)₂]₂}·10H₂O (1) and [Ni(enMe)₂]₅{[Ni(enMe)₂]₂[(V^VMo^VI₄Mo^V₄V₄^IVO₄₀)(V^IVO)₄]₂}·2H₂O (2), (enMe = 1,2-diaminopropane), which have been characterized by single crystal X-ray diffraction analysis, IR spectroscopy, and elemental analysis. Both of the two compounds exhibit dumbbell-like structures constructed from capped polyoxomolybdovanadates and [Ni(enMe)₂]²⁺ complexes. Polyoxoxanion 1 is composed of two bicapped Keggin-type anions [(V^VMo₈V₄^IVO₄₀)(V^IVO)₂]⁷⁻, one [Ni(enMe)₂]²⁺ bridging fragment and two decorated nickel(II) complexes. Polyxoxanion 2 consists of two tetracapped molybdenum-vanadium polyoxoanions [(V^VMo^VI₄Mo^V₄V₄^IVO₄₀)(V^IVO)₄]⁷⁻, one [Ni(enMe)₂]²⁺ bridging fragment and a nickel(II) decorated fragment. Polyxoxanions 1 and 2 are further linked to form three-dimensional supramolecular networks through extensive hydrogen bonding interactions. In addition, photocatalysis properties of these two compounds have been investigated.     

Infrared and raman study of matrix isolated M(SO2) molecules. The structure of the molecular ion SO2−

The IR and Raman spectra of Cs(SO₂), K(SO₂) and Na(SO₂) molecules were studied by ³²S/³⁴S and ¹⁶O/¹⁸O isotopic substitution technique. These molecules have a planar ring configuration of C_2v symmetry with the OSO angle equal to 109°±5° and the SO bond length of 0.149±0.001 nm. The alkali metal atom interacts symmetrically with the oxygen atoms of the SO₂⁻ group. The doubling observed for the vibrations of Cs(S¹⁶O¹⁸O) was attributed to a matrix effect.     

Hydrothermal synthesis and structural characterization of bimetallic organic-inorganic hybrid materials: Copper vanadate-1,4-Carboxy-phenylphosphonate phases

The hydrothermal reactions of V₂O₅, a copper(II) source, 1,4-carboxy-phenylphosphonic acid, a bidentate organonitrogen ligand and HF provided a series of bimetallic organic-inorganic hybrid materials. [Cu(bpy)VO₂(O₂CC₆H₄PO₃)] (1) is one-dimensional, while [Cu(bpa)VO(OH)(O₂CC₆H₄PO₃)] (2) and [Cu(phen)V₂O₄F(O₂CC₆H₄PO₃)] (3) are two-dimensional. In the absence of V₂O₅, a number of copper-organophosphonates were isolated. Compound 4 [Cu(phen)(H₂O)(O₂CC₆H₄PO₃H)] is one-dimensional while [Cu₃(bpy)₂(O₂CC₆H₄PO₃)₂] (5) is two-dimensional. Molecular structures were observed for [CuF(bpy)(H₂O)(HO₂CC₆H₄PO₃H)] (6) and [Cu(bpa)(O₂CC₆H₄PO₃H)]·3H₂O (7·3H₂O).