Oxo Peroxo Glycolato Complexesof Vanadium (V). Crystal Structureof (NBu4)2[V2O2(O2)2(C2H2O3)2]ċH2O

Summary.  Oxo peroxo glycolato complexes of vanadium(V) (M ₂[V₂O₂(O₂)₂(C₂H₂O₃)₂]ċnH₂O (n=0, 1; M=NBu₄ ⁺ (1), K⁺ (2), NH₄ ⁺ (3), Cs⁺ (4), NPr₄ ⁺ (5)) as well as (NBu₄)₂[V₂O₄(C₂H₂O₃)₂]ċ H₂O (6) have been prepared and characterized by spectroscopic methods. X-Ray structure analysis of 1 revealed the presence of dinuclear [V₂O₂(O₂)₂(C₂H₂O₃)₂]²⁻ anions with a (chemical structure) bridging core and six coordinated vanadium(V) atoms in a distorted pentagonal pyramidal array. Received July 12, 1999. Accepted (revised) October 28, 1999     

Phase Equilibria in the System V2O5–Fe8V10W16O85 and Some Properties of the Fe8V10W16O85 Phase

A phase diagram of the V₂O₅–Fe₈V₁₀W₁₆O₈₅ system were carried out using XRD and DTA methods. In addition, an indexing of Fe₈V₁₀W₁₆O₈₅ powder diffraction pattern was made and its basic crystallographic parameters were determined. Finally, the phase was studied using IR spectroscopy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation and Characterization of Cu3V2O7(OH)2·2H2O Hollow Spheres from NazV6O16·3HzO Nanobelts

Monoclinic Cu3V2O7(OH)2·2H2O(copper polyvanadate) hollow spheres were prepared with Na2V6O16·3H2O nanobelts as V-precursor by hydrothermal method.The purity and structure of the products were characterized by X-ray powder diffraction(XRD),Fourier transform infrared(FTIR) spectroscopy,Raman spectroscopy,thermogravimetric analysis(TGA) and X-ray photoelecton spectroscopy(XPS).The morphology and size were observed by scanning electron microscopy(SEM).We found that the Kagomé staircase-structural copper polyvanadate hollow spheres with an average diameter of 7 μm could be easily synthesized via the reaction of Na2V6O16·3H2O nanobelts with sufficient copper sulfate.The dielectric property of the copper polyvanadate demonstrates that dielectric loss hardly changes when the frequency of applied electric field is higher than 100 kHz.The formation process of the hollow spheres is discussed in detail by the observation of a series of products prepared for different reaction time.     

Formation of crystalline Na2V6O16·3H2O ribbons into belts and rings

Single-crystalline nanobelts and nanorings of Na(2)V(6)O(16)·3H(2)O structures have been facilely synthesized through a direct hydrothermal reaction between NaVO(3) and H(3)PO(4), without the addition of any harmful solvents or surfactants. The analytical techniques of scanning electron microscopy, transmission electron microscopy (TEM), powder X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, Fourier transform infrared, high-resolution TEM, and selected-area electron diffraction have been used to characterize the morphology, composition, and structure of the synthesized products. The Na(2)V(6)O(16)·3H(2)O nanobelts are up to several hundreds of micrometers in length and 100-300 nm in thickness, and for nanorings, the diameters are 4.5-6.5 μm. H(3)PO(4) plays a key role in maintaining the pH of the solution as well as producing PO(4)(3-) ions in solution. The chemical reactions and a possible growth mechanism involved in the formation of Na(2)V(6)O(16)·3H(2)O nanobelts and nanorings are briefly discussed.     

Hydrothermal Synthesis and Characterization of [V_(16)O_(38)(Cl)][Cu(enMe)_2]_(3.5)·2H_2O Containing {V_(16)O_(38)} Cluster

IntroductionBasedonarelativelylargenumberofdifferenttypesofbuildingblockswhichcorrespondtopolyhe dron {VOx} (x =4 ,5 ,6 ) ,polyoxovanadatesshowanextraordinaryvarietyofstructures ,suchascage ,basket ,belt ,ballandbarrelstructures[1— 5] .Further more,these polyoxovanadatesexhibita pronouncedtendencytoformcage likestructureswhichmayen capsulateneutralmoleculesaswellasionicguests ,afeaturesharedbysomeisopolyanionssuchas [V18O4 2·(H2 O) ]12 - [6 ] ,[H4 V18O4 2 (X) ]9- (X =Cl- ,Br- ,I- ) [2 ,…     

Role of the V(V)/ 1O2Complex in Oxidative Reactions in the H2O2/V(V)/AcOH System: Oxidation of Alkenes and Anthracenes

Anthracene and its alkyl derivatives undergo oxidation in the V^(V)/H₂O₂/AcOH system via a nonradical mechanism through the intermediate formation of the vanadium(V) complex with singlet dioxygen as a ligand. The ¹O₂molecule is transferred from this complex to an unsaturated substrate. The free singlet dioxygen ¹O₂(¹ _g ) is almost inactive toward anthracene in AcOH solution. Consequently, the vanadium(V) complex with singlet dioxygen is the only oxidant species active in the reaction. The ratio between the rate constant of the reaction of this complex with 2-ethylanthracene and the rate constant of its deactivation is an order of magnitude greater than the ratio between the rate constant of the reaction of dissolved free singlet dioxygen with the same substrate and the rate constant of its deactivation (physical quenching).     

Antimonato polyoxovanadates with structure directing transition metal complexes: pseudopolymorphic {Ni(dien)2}3[V15Sb6O42(H2O)]·nH2O compounds and {Ni(dien)2}4[V16Sb4O42(H2O)

Three new poloxovanadates were synthesized under solvothermal conditions and were structurally characterized. The two compounds with composition {Ni(dien)(2)}(3)[V(15)Sb(6)O(42)(H(2)O)]·nH(2)O (n = 12 and 8; dien = bis(2-aminoethyl)amine or diethylenetriamine) are pseudopolymorphs crystallizing in different space groups. The compounds were obtained by applying identical reaction slurries but using different reaction temperatures. Both compounds feature the [V(15)Sb(6)O(42)(H(2)O)](6-) anion which is the antimony analogue to the single molecule magnet [V(15)As(6)O(42)(H(2)O)](6-). Crystal data: 1 tetragonal space group P4, a = 46.9378(3), c = 16.51300(10) ? and V = 36380.7(4) ?(3). 2 rhombohedral space group R3c with a = 23.0517(4), c = 28.6216(5) ? and V = 13171.3(4) ?(3). In 1 several unusual short inter-cluster Sb···O contacts lead to the formation of three different super-clusters with composition V(60)Sb(24)O(168). The 12 unique {Ni(dien)(2)}(2+) complexes adopt all three possible configurations. In 2 the special arrangement of the {Ni(dien)(2)}(2+) complexes around the cluster anion prevents inter-cluster Sb···O contacts. The main structural motif of the third compound {Ni(dien)(2)}(4)[V(16)Sb(4)O(42)(H(2)O)] (3) is the [V(16)Sb(4)O(42)(H(2)O)](8-) cluster anion consisting of two perpendicular eight-membered rings of VO(5) pyramids. Two additional VO(5) polyhedra are located on opposite sides. Crystal data: 3 triclinic space group P1 = 13.5159(4), b = 14.2497(5), c = 14.9419(4) ?, α = 98.322(2), β = 114.080(2), γ = 110.130(2)° and V = 2326.35(12) ?(3).     

Co(2,2'-bipy)(H2O)V2O6的合成及其晶体结构

以Co(NO3)2,2,2'-联吡啶(2,2'-bipy)及NaVO3为原料,采用水热法于200 ℃合成了一种新的有机-无机杂化材料--Co(2,2'-bipy)(H2O)V2O6(1),其结构经IR,热重分析及X-射线单晶衍射表征.结果表明,1属于单钭晶系,空间群为P21/c,晶胞参数为:a=7.855 6(3)(A),b=21.056 2(5)(A),c=9.552 1(6)A,α=90.000°,β=110.236(5)°,γ=90.000°,V=1 423.65(8)(A)3,Z=2,Dc=2.126 g·cm-3,μ(Mo Kα)=2.548mm-1,R1=0.058 6,wR2=0.093 5.1为一种二维层状结构,由[VO4]四面体通过共顶点构成的一维钒氧链,链与链之间以[Co(2,2'-bipy)(H2O)]2 基团连接而成.     

Zn3(OH)2V2O7·2H2O纳米片的水热制备

采用硝酸锌、五氧化二钒和氢氧化钠作为反应物,通过一个简单的CTAB辅助的水热方法制备了Zn3(OH)2V2O7·2H2O纳米片.运用XRD,ICP-AES,FTIR,HRTEM,EDS,FE-SEM对产物的晶相和形貌进行了表征.结果表明CTAB在控制产物的形貌、尺寸分布和自组装过程中起着关键作用.同时我们研究了产物的晶体生长行为和自组装过程.     

High-performance (NH4)2V6O16·0.9H2O nanobelts modified with reduced graphene oxide for aqueous zinc ion batteries

Ammonium vanadate has been considered as a competitive high-performance cathode material for aqueous Zn-ion batteries. However, it still suffers from insufficient rate capability and poor cyclability due to the low electronic conductivity. Herein, (NH₄)₂V₆O₁₆·0.9H₂O nanobelts with reduced graphene oxide (RGO) modification are synthesized by one-step hydrothermal reaction. Benefiting from the addition of RGO, an excellent electrochemical performance of (NH₄)₂V₆O₁₆·0.9H₂O@RGO nanobelts can be obtained. The (NH₄)₂V₆O₁₆·0.9H₂O@RGO displays a high-rate capacity and a high energy density of 386 Wh/kg at 72 W/kg. In particular, after 1000 cycles at 5 A/g, the capacity remains at 322 mAh/g with 92.8% capacity retention. In addition, the key reaction mechanisms of reversible Zn²⁺insertion/extraction in (NH₄)₂V₆O₁₆·0.9H₂O@RGO are clarified.     

Single-molecule magnetism behavior of [Mn12O12(O2CR)16(H2O)4]2− salts

(PPh₄)₂[Mn₁₂O₁₂(O₂CCHCl₂)₁₆(H₂O)₄] (3) has been prepared by the two-electron reduction of [Mn₁₂O₁₂(O₂CCHCl₂)₁₆(H₂O)₄] (2) using iodide. Crystallization from CH₂Cl₂/hexanes yields a mixture of two crystal forms, 3·4CH₂Cl₂·H₂O (3a) and 36CH₂Cl₂ (3b), which are triclinic and monoclinic, respectively. They are both trapped valence 2Mn(II), 6Mn(III), 4Mn(IV). DC magnetization data for dried, unsolvated 3 in 1.80–4.00 K and 10–70 kG ranges were fit to give S=10, D=−0.28 cm⁻¹, g=2.00. Frequency-dependent out-of-phase (χ″_M) signals in AC susceptibility studies on crystalline sample of 3a and 3b combined with DC relaxation decay data were fit to the Arrhenius equation to give an effective energy barrier of U_eff=18.5 and 30.3 K, respectively. Magnetization vs. DC field sweeps on single crystals of 3a and 3b gave hysteresis loops containing steps due to quantum tunneling of magnetization (QTM). The step separations yielded ∣D∣/g values of 0.087 and 0.14 cm⁻¹, and consequently U=20 and 39 K (for g=2) for 3a and 3b, respectively, suggesting that the differences in U_eff are primarily caused by changes to D. This work demonstrates the sensitivity of the magnetic properties of [Mn₁₂]²⁻ single-molecule magnets to subtle differences in their environment.     

Synthesis and structure of two molybdovanadates containing coordinatively bound oxalato ligands: (NH4)6[Mo6V2O24(C2O4)2]·6H2O and (NH4)4[H2Mo2V2O12(C2O4)2]·2H2O

The compounds (NH₄)₆[Mo₆V₂O₂₄(C₂O₄)₂]·6H₂O (I) and (NH₄)₄[H₂Mo₂V₂O₁₂(C₂O₄)₂]·2H₂O (II) have been prepared from molybdenum(VI) oxide and ammonium vanadate in aqueous solution through the addition of ammonium oxalate, and their structures determined by X-ray structure analysis. Whereas the molybdovanadate anion [Mo₆V₂O₂₄(C₂O₄)₂]⁶⁻ found in (I) consists of six MoO₆ and two VO₆ edge-sharing octahedra of the γ-[Mo₈O₂₆]⁴⁻ type structure, the tetranuclear anion [H₂Mo₂V₂O₁₂(C₂O₄)₂]⁴⁻ of (II) adopts the structure with a M₄O₁₆ core. Both complexes contain bidentate oxalato ligands bonded to the vanadium ions. In both crystal structures the molybdovanadate anions are mutually hydrogen bonded by ammonium ions and water molecules.     

V2O5负载量对V2O5/Al2O3氧化活化正庚烷催化裂解反应的影响

采用X射线衍射, 低温氮气吸脱附, 氨气程序升温脱附和吡啶吸附红外光谱分析方法对不同活性组分负载量V2O5/Al2O3的性质进行了表征. 根据表面VOx单元密度, 推测V2O5负载量为20%-25% (w)对应着V2O5/Al2O3表面达单层覆盖状态; V2O5的负载使Al2O3表面Lewis酸量减少, 并出现Br?nsted酸, 对应着氧化态VOx单元中的V―OH; 随着负载量的增加, Brφnsted酸量增加至负载量为20%时达到最大值. 对V2O5/Al2O3中活性组分负载量对其氧化活化正庚烷催化裂解反应的影响进行了考察. 结果表明, 在V2O5负载量为20%-25%时,V2O5/Al2O3的引入对正庚烷在HZSM-5平衡剂上催化裂解反应的促进作用最明显, 此时VOx单元在V2O5/Al2O3表面形成单层覆盖状态, 可提供最大量的表面晶格氧, 因而对正庚烷具有最强的氧化活化作用; V2O5负载量继续增加形成体相的V2O5和AlVO4, 不利于晶格氧参与正庚烷的转化, 因而反应性能有所下降.     

Phase diagram and IR spectral investigations of the 2TeO2 · V2O5Li2O · V2O5 · 2TeO2 system

By means of X-ray phase analysis, IR spectroscopy, and DTA, the system 2TeO₂ · V₂O₅Li₂O · V₂O₅ · 2TeO₂ was investigated and its phase diagram was constructed. The formation of a new compound with composition Li₂O · 3V₂O₅ · 6TeO₂, melting incongruently was documented. A comparison of the bands in the IR spectrum was made. Stable glasses in the whole range of concentrations were prepared. From the IR spectra of the glasses, the corresponding crystallization products, and the data of known crystal structures, a model of the short-range order in the glasses was proposed.     

K3[Fe3.26V0.74(OH)O(PO4)4(H2O)2]·2H2O: a synthetic leucophosphite

A new iron(III)/vanadium(III) phosphate, K₃[Fe_3.26V_0.74(OH)O(PO₄)₄(H₂O)₂]·2H₂O (1), has been obtained by hydrothermal synthesis and characterized by single crystal X-ray diffraction, Scanning electron microscopy–energy dispersive X-ray spectroscopy, Inductively coupled plasma atomic emission spectroscopy (ICP), thermogravimetric analysis, and FTIR spectroscopy. Single crystal X-ray diffraction reveals a 3D open framework (monoclinic, space group P2₁/n, a?=?9.6391(7)?Å, b?=?9.8063(7)?Å, c?=?9.7268(7)?Å, β?=?100.71(1)°, and V?=?903.38(11)?ų). This structure presents Fe^III and V^III in a 4.4?:?1?M ratio with the metal ions in two different crystallographic sites. Both metallic centers have distorted octahedral environments, linked by PO₄ tetrahedra, forming channels along the a-axis. The asymmetric unit of K₃[Fe_3.26V_0.74(OH)O(PO₄)₄(H₂O)₂]·2H₂O presents a {M₄(OH)O(PO₄)₄(H₂O)₂}^3? anionic entity, charge balanced by three K⁺, which are located within the channels. It is also possible to distinguish M₄O₂ units whose M^III polyhedra are linked by vertex and edges.     

Hydrothermal Synthesis and Crystal Structure of a New Supramolecular Channel Framework Based on Cu Complexes and Polyoxovanadate:[Cu(Ⅰ)(phen)2]5[HV15O36(Cl)]0.65[H3V16O38(Cl)]0.35·2H2O

A new compound [Cu(Ⅰ)(phen)2]5[HV15O36(Cl)]0.65[H3V16O38(Cl)]0.35·2H2O 1(phen = 1,10'-phenanthroline) has been prepared from the hydrothermal reaction of V2O5, CuCl,3:1:1:0.5:2.5:1400. Compound 1 crystallizes in the space group P42212 of the tetragonal system with a = b = 21.5009(8), c = 28.401(2) (A), V = 13129.5(12) (A)3, Z = 4, Dc = 1.800 g/cm3,μ(MoKα) =1.932 mm-1, λ.(MoKα) = 0.71073 (A), F(000) = 7063.4, C120H81.20ClCu5N20O38.7V15.35, Mr = 3557.58,the final R = 0.0594 and wR= 0.1320 for 7761 observed reflections (1 ＞ 2σ(Ⅰ)). Structure analysis shows that 1 exhibits a 3D channel framework formed by the supramolecular assembly of Cu complexes and polyoxovanadate clusters via intermolecular hydrogen bonding, and the channels contain Cu complexes. Other characterizations by elemental analysis, XPS, IR, XRD and thermal analysis are also described.     

V2O5/γ-Al2O3和V2O5/SiO2负载型催化剂对异丁烷的催化脱氢性能

V2O5/γ-Al2O3和V2O5/SiO2负载型催化剂对异丁烷的催化脱氢性能;V2O5/γ-Al2O3; V2O5/SiO2; 异丁烷; 脱氢     

负载型复合半导体V2O5-TiO2/SiO2表面V2O5和TiO2的相互修饰作用

 采用表面改性法制备了负载型复合半导体材料V2O5-TiO2/SiO2,并用X射线衍射、比表面积测定、拉曼光谱、程序升温还原和紫外-可见漫反射光谱等技术对固体材料的结构和光响应性能进行了表征. 结果表明,V2O5和TiO2在负载型复合半导体V2O5-TiO2/SiO2表面有相互修饰的作用. 一方面,V2O5能扩展TiO2的光响应范围,使TiO2的吸光区域由紫外光区拓宽至可见光区,从而提高了复合半导体对光能的利用率; 另一方面,TiO2则有助于提高V2O5在载体表面的分散程度,抑制VOx的聚合,减小V2O5的微晶尺寸,提高固体材料的能隙值和氧化还原能力.     

Synthesis and Crystal Structure of Two Decavanadates Cluster Metal Complexes: [Co(H2O)6]2[H2V10O28]·6H2O and (NH4)2[Ca(H2O)7]2[V10O28]

Two new decavanadate metal complexes, [Co(H₂O)₆]₂[H₂V₁₀O₂₈]·6H₂O (1) and (NH₄)₂[Ca(H₂O)₇]₂[V₁₀O₂₈] (2), have been synthesized under hydrothermal condition by using chlorhydric acid as the initiator at 120 °C. The aqueous NaVO₃ solution with an aqueous solution of CoCl₂·6H₂O were used for generating 1 and aqueous CaCl₂·2H₂O and NH₄VO₃ solution were employed for creating 2. Compound 1 consisted of discrete hexa-aqua-cobalt [Co(H₂O)₆]²⁺ cations, [H₂V₁₀O₂₈]⁴⁻ anions and non-coordination water molecules. Compound 2 were composed of hepta-aqua-calcium [Ca(H₂O)₇]²⁺ cations, ammonium NH₄ ⁺ and [V₁₀O₂₈]⁶⁻ anion. For compound 2, the distorted pentagonal bipyramid [Ca(H₂O)₇]²⁺ is uncommon. In the crystal lattice, hydrogen bonds played an important role on connecting cations, anions and non-coordinated water molecules to form the three-dimensional network.