A new organic-inorganic hybrid based on dimeric [Mn2V22O64]10 − polyoxoanion as catalyst for oxidation of sulfides

A new organic-inorganic hybrid compound constructed from [Mn₂V₂₂O₆₄]^10 − units, H₆[(C₆H₄NO₂Cu(H₂O)₄)]₂[Mn₂V₂₂O₆₄]·28H₂O 1, has been synthesized and characterized by single-crystal X-ray diffraction, IR, powder X-ray diffraction (XPRD) and TG. Compound 1 is composed of dimeric [Mn₂V₂₂O₆₄]^10 − polyoxoanions, metal-organo fragments [(C₆H₄NO₂Cu(H₂O)₄)]^2 + and lattice water molecules. Moreover, a three-dimensional supramolecular structure is formed in 1 by the extensive hydrogen bond interaction among the terminal oxygen atoms of [Mn₂V₂₂O₆₄]^10 − anions, the coordinated waters of Cu^2 + ions and crystal water molecules. Compound 1 exhibits remarkable catalytic activity for the heterogeneous oxidation of sulfides under mild condition.     

A novel organic-inorganic hybrid polyoxometalate-based 3D framework constructed by organo-functionalized [As2W21O72(mal)2]18 − units and Ce3 + ions

A novel organic-inorganic hybrid polyoxometalate-based 3D framework K₅H₄{Ce₃(H₂O)₉[As₂W₂₁O₇₂(mal)₂]}·20H₂O (1) (mal = malic acid) has been synthesized by the metastable precursor [As₂W₁₉O₆₇(H₂O)]^14 −, which was further characterized by IR spectrum, thermogravimetric analysis (TGA), and X-ray single-crystal diffraction. Structural analysis revealed that 1 consists of the organo-functionalized [As₂W₂₁O₇₂(mal)₂]^18 − units linked together by the Ce^3 + ions resulting in 3D network-like architecture. Magnetic property studies indicate that obvious antiferromagnetic interactions exist in three Ce^3 + ions.     

A new organic-inorganic hybrid tetrameric polyoxometalate assembled by monovacant Dawson [α2-P2W17O61]10 − and trivalent cerium cations

A novel octa-nuclear cerium(III)-containing organic-inorganic hybrid polyoxometalate [N(CH₃)₄]₈H₁₆[{Ce(η¹-C₆H₅NO₂)₂(H₂O)₆[Ce(H₂O)₃(α₂-P₂W₁₇O₆₁)]}{Ce(η²-C₆H₅NO₂)₂(H₂O)₅[Ce(H₂O)(α₂-P₂W₁₇O₆₁)]}]₂·90H₂O (C₆H₅NO₂ = isonicotinic acid) (1) was obtained, which had been hydrothermally synthesized and characterized by IR spectrum, thermogravimetric analysis (TGA), and X-ray single-crystal diffraction. Structural analysis indicated at 1 is composed of four lacunary Dawson-type units [α₂-P₂W₁₇O₆₁]^10 − joined together by eight cerium cations forming an uncommon zigzag tetrameric structure with eight isonicotinic acids as the organic pendants coordinating to the cerium cations. Magnetic property studies indicate that obvious antiferromagnetic interactions exist in eight Ce^3 + cations.     

A novel 2D organic–inorganic hybrid based on [P2W18O62]6− polyoxoanion and Cu–bbi coordination polymers

A novel 2D compound based on Wells–Dawson polyoxometalates, [Cu₃(bbi)₆(P₂W₁₈O₆₂)] (bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) (1) has been hydrothermally synthesized and characterized by elemental analyse, IR, TG, PXRD and single crystal X-ray diffraction. In compound 1, each Cu²⁺ ion is connected with four adjacent Cu²⁺ ions by bbi ligands along four different directions and each bbi ligand is two-coordinated by two Cu²⁺ ions, which results in an unusual 2D interlink lock-liked layer. Interestingly, two kinds of macrocycles exist in the structure, in which six smaller 33-membered rings are placed end to end to form the larger ones (66-membered macrocycles). The [P₂W₁₈O₆₂]⁶⁻ polyoxoanions as bidentate ‘guest’ is incorporated into the larger macrocycles. These 2D layers are further packed into 3D framework through strong supramolecular interactions. Additionally, electrochemical and electrocatalysis behavior of 1-CPE have been studied in detail.     

Investigation of dielectric properties and microstructure of sintered 13·2Li2O − 67·6SiO2 − 14.49Al2O3 − 3·3TiO2 − 0.4BaO − 0.97ZnO glass-ceramics

Lithium aluminosilicate (LAS) is an interesting material for the electronics industry. The material has near zero water absorption, low dielectric constant, and low loss tangent. Therefore, this material is interesting for the packaging of radio frequency transmitters used under harsh conditions. In this study, LAS glass powders with different particle sizes were dry pressed. Densification, crystallization, microstructure and dielectric properties were studied during thermal treatments. The highest sintered density (about 97%) has been achieved with milled powder with a d₉₀ of about 6 μm. Investigation of the microstructure reveals that flaky rutile has formed in β-spodumene grain boundaries even though spherical rutile is observed inside of β-spodumene. Glass phase in grain boundaries contain mostly SiO₂, Al₂O₃ and ZnO. Impedance analysis showed that the dielectric constant is influenced by phase transformation and density. The formation of hexagonal LiAlSi₂O₆ increases the dielectric constant while transformation to tetragonal structure decreases the dielectric constant.     

A rare polyoxometalate based on mixed niobium-based polyoxoanions [GeNb18O54]14 − and [Nb3W3O19]5 −

Polyoxoniobate [GeNb₁₈O₅₄]^14 − and polyniobotungstate [Nb₃W₃O₁₉]^5 − are firstly found to co-crystallize at the same crystal to form a rare organic–inorganic hybrid polyoxometalate H[Cu(en)₂(H₂O)]₈[Cu(en)₂(H₂O)₂]₂{K₄[Cu(en)₂]₂[Cu(en)₂(GeNb₁₈O₅₄)]₂}[Nb₃W₃O₁₉]·32H₂O (1). Interestingly, in 1, the crescent-shaped polyoxoanions [GeNb₁₈O₅₄]^14 − can form dimeric secondary building units (SBUs) {[GeNb₁₈O₅₄]₂[K₂(H₂O)₅]₂} via the linkage of K⁺ cations. These dimeric SBUs can be further bridged by copper complexes to generate 1D infinite double strand chains with completely different isolated polyoxoanions [Nb₃W₃O₁₉]^5 − filling the gaps between chains.     

A new polyanion with Dawson-like constitution: [H2SeW18O60]6 −

A new tungstoselenite, [H₂SeW₁₈O₆₀]^6 −, was isolated under acidic medium conditions (pH = 1.7)with the monoprotonated ethylamine as cation. It represents the first example of Se-containing polyoxometalate with unusual Dawson-like construction and has fully been characterized both in solid state and in solution. The high-resolution ESI-MS confirmed that the polyanion at least contains two protons and its proton number can be up to six in solution.     

Hydrothermal synthesis,structure and properties of two new phosphomolybdates based on Strandberg-type {P2Mo5O23}6 − building units

Two inorganic–organic hybrid compounds based on Strandberg-type phosphomolybdates (abbreviated as {P₂Mo₅O₂₃}^6 −) complexes [H₃O]₂[Cu₂(Pyim)₂(H₂O)₃][P₂Mo₅O₂₃] · 6H₂O (1) and [Cu₃(Pyim)₃(H₂O)₄][P₂Mo₅O₂₃] · 7H₂O (2) were successfully synthesized at different pH values under hydrothermal conditions. Both 1 and 2 are based on the {P₂Mo₅O₂₃}^6 − clusters connected by copper complexes to generate one dimensional chain. The magnetic analyses of compounds 1 and 2 indicate antiferromagnetic interactions between copper ions.     

pH-dependent assembly of 1D–2D structures based on both {V10O28} and [NiMo6O24H6]4 − units: Synthesis,structure and magnetic properties

Two novel complexes [H₂N(CH₂CH₂)₂O]₄[Na(H₂O)₂{O(CH₂CH₂)₂NH₂}]₂[Na(H₂O)₄]₂[V₁₀O₂₈][NiMo₆O₂₄H₆]·8H₂O (1) and [H₂N(CH₂CH₂)₂O]₆[Na(H₂O)₃]₂[V₁₀O₂₈H₂][NiMo₆O₂₄H₆]·4H₂O (2) containing both isopolyvanadate {V₁₀O₂₈} and [NiMo₆O₂₄H₆]^4 − units have been synthesized and structurally characterized for the first time, showing that the pH value of the reaction plays a key role in structure control of self-assembled processes. Compound 1 exhibits a novel one-dimensional (1-D) chain-like structure consisting of Anderson-type [NiMo₆O₂₄H₆]^4 − and isopolyvanadate [V₁₀O₂₈]^6 − anions linked by Na⁺ ions. In compound 2 with the lower pH value, [NiMo₆O₂₄H₆]^4 − and [V₁₀O₂₈H₂]^4 − anions are bridged by [Na₂O₁₀] units to form the 2D extended layer. The magnetic properties of 1 and 2 are presented.     

Microstructure and electrical properties of relaxor (1 − x)[(K0.5Na0.5)0.95Li0.05](Nb0.95Sb0.05)O3–xBaTiO3 piezoelectric ceramics

In order to solve the low temperature stability of electrical properties in KNN-based ceramics, (1 ? x)[(K_0.5Na_0.5)_0.95Li_0.05](Nb_0.95Sb_0.05)O₃–xBaTiO₃ [(1 ? x)KNLNS–xBT] lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. The introduction of BT stabilizes the tetragonal phase of KNLNS ceramics at room temperature, results in a typical ferroelectric relaxor behavior, and shifts the polymorphic phase transition to below room temperature. Moreover, there is a strong BaTiO₃ concentration dependence of relaxor behavior and electrical properties, and the ceramic with x = 0.005 exhibits optimum electrical properties and typical relaxor behavior (d₃₃ = 269 pC/N, k_p = 0.50, ?_r = 1371, tan δ = 0.03, T_C ～ 349 °C and γ = 1.88024). These results indicate that the BT is an effective way to improve the temperature stability as well as the electrical properties of KNN-based ceramics.     

Remarkable effect of Co and Mn on the activity of Fe3 − xMxO4 promoted oxidation of organic contaminants in aqueous medium with H2O2

In this work substituted magnetites Fe_3 − xMn_xO₄ (x=0.21, 0.26 and 0.53), Fe_3 − xCo_xO₄ (x=0;0.19;0.38;0.75) and Fe_3 − xNi_xO₄ (x=0;0.10;0.28;0.54) have been used to promote two different reactions involving H₂O₂: (i) the oxidation of organic molecules namely phenol, hydroquinone and methylene blue dye in aqueous medium and (ii) the peroxide decomposition to O₂. The presence of Co or Mn in the magnetite structure strongly increased the rate of H₂O₂ decomposition and the oxidation of the organic molecules whereas the presence of Ni inhibited both reactions. Kinetic data and CEMS Mössbauer spectroscopy suggest that the H₂O₂ decomposition and the organic oxidation are competitive reactions involving oxidizing species generated by surface M²⁺ (M=Fe, Co or Mn).     

Two 1-D Krebs-type heteropolyoxotungstates based on [X2W21O72Na(OH)2]13 − (X = SbIII,BiIII) units

By the one-pot self-assembly reaction of simple materials under acidic aqueous solution, two 1-D chain Krebs-type heteropolyoxometalates [H₂N(CH₃)₂]₂Na₁₁[X₂W₂₁NaO₇₂(OH)₂]·34H₂O (X = Sb^III for 1, Bi^III for 2) have been successfully synthesized and structurally characterized by elemental analysis, IR spectra, UV spectra, thermogravimetric (TG) analysis and X-ray single-crystal diffraction. The most prominent structural feature of 1 and 2 is that both display an interesting 1-D chain alignment constructed from Krebs-type [X₂W₂₁NaO₇₂(OH)₂]^13 − fragments connected by sharing four W–O–W connectors, which is for the first time observed in the polyoxometalate chemistry. Additionally, the electrochemical properties of 1 and 2 have been studied in 0.5 mol L^− 1 Na₂SO₄ + H₂SO₄ supporting electrolyte.     

Organic–inorganic hybrid oxides: Structure and magnetic properties of [{Cu(terpy)}2Mo6O17(H2O)(O3PCH2NH2CH2PO3)2] · H2O,a bimetallic oxide constructed from novel {Mo6O17(H2O)(O3PCH2NH2CH2PO3)2}4− clusters

The hydrothermal reaction of MoO₃, CuSO₄ · 5H₂O, 2,2′:6′:2″-terpyridine (terpy) and bis-N,N-(methylphosphonic acid) amine (H₂O₃PCH₂NHCH₂PO₃H₂) provided blue crystals of the bimetallic oxide [{Cu(terpy)}₂Mo₆O₁₇(H₂O)(O₃PCH₂NH₂CH₂PO₃)₂] · H₂O (1 · H₂O). The three-dimensional structure of 1 is constructed from {Mo₆O₁₇(H₂O)(O₃PCH₂NH₂CH₂PO₃)₂}⁴⁻ clusters linked through {Cu(terpy)}²⁺ subunits. The cluster consists of three pairs of edge-sharing {MoO₆} octahedra linked through corner-sharing interactions into a {Mo₆O₆} ring. One phosphonate ligand spans the diameter of the ring, bridging four molybdenum sites and leaving at a pendant {PO} group at each terminus. The second diphosphonate ligand exploits one {–PO₃} unit to cap the hexamolybdate ring and bridge all six molybdenum sites while the second {–PO₃} terminus bridges two molybdenum sites, leaving a pendant {PO} unit. Crystal data: C₃₄H₄₅Cu₂Mo₆N₈O₃₅P₄: monoclinic, P2₁/n, a = 11.9431(7) Å, b = 17.382(1) Å, c = 27.524(2) Å, β = 90.429(1)°, V = 5713.7(6) Å³, Z = 4, D_calc = 2.270 g cm⁻³, R₁ = 0.0466.     

Synthesis and crystal structure of [nBu4N][Er(pic)4] · 5.5H2O: a new infrared emitter

The new erbium(III) complex of picolinic acid (Hpic), [ⁿBu₄N][Er(pic)₄] · 5.5H₂O, was synthesized and the crystal structure determined by single-crystal X-ray diffraction. The compound was further characterized using IR, Raman, ¹H NMR and elemental analysis. The picolinate ligands (pic⁻) are coordinated through N,O-chelation to the erbium cations, as shown by X-ray diffraction and spectroscopic results, leading to an eight coordinate complex. Photoluminescence measurements were performed for this compound which exhibits infrared emission.     

Etherification of n-butanol to di-n-butyl ether over H3PMo12 − xWxO40 (x = 0, 3, 6, 9, 12) Keggin and H6P2Mo18 − xWxO62 (x = 0, 3, 9, 15, 18) Wells–Dawson heteropolyacid catalysts

Etherification of n-butanol to di-n-butyl ether was carried out over H₃PMo_12 − xW_xO₄₀ (x = 0, 3, 6, 9, 12) Keggin and H₆P₂Mo_18 − xW_xO₆₂ (x = 0, 3, 9, 15, 18) Wells–Dawson heteropolyacid (HPA) catalysts. Acid strength of H₃PMo_12 − xW_xO₄₀ Keggin and H₆P₂Mo_18 − xW_xO₆₂ Wells–Dawson HPA catalysts was determined by NH₃-TPD (temperature-programmed desorption) measurements. The correlations between desorption peak temperature (acid strength) of the HPA catalysts and catalytic activity revealed that conversion of n-butanol and yield for di-n-butyl ether increased with increasing acid strength of the catalysts, regardless of the identity of HPA catalysts (without HPA structural sensitivity).     

Hydrothermal synthesis,crystal structure and physical properties of {[Gd(H2O)4(μ2-C6NO2H5)2Gd(H2O)4](μ3-C6NO2H4)2(ZnCl3)2} · 2H2O · 2Cl

A bimetallic 4f–3d tetranuclear complex {[Gd(H₂O)₄(μ₂-C₆NO₂H₅)₂Gd(H₂O)₄](μ₃-C₆NO₂H₄)₂(ZnCl₃)₂} · 2H₂O · 2Cl (1) has been synthesized via hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. Complex 1 is characterized by a tetranuclear Gd₂Zn₂ structure with the gadolinium and zinc atoms interconnected by isonicotinic acid ligands. The tetranuclear species of {[Gd(H₂O)₄(μ₂-C₆NO₂H₅)₂Gd(H₂O)₄](μ₃-C₆NO₂H₄)₂(ZnCl₃)₂} link to isolated chlorine ions and water molecules via π?π interactions and hydrogen bonds to yield a 3-D supramolecular framework. Photoluminescent investigation reveals that the title complex displays an emission in ultraviolet region. The solid-state diffuse reflectance spectra of 1 reveal the presence of a sharp optical gap of 3.66 eV.     

Luminescent and porous zinc complex with 2D → 3D parallel polycatenation based on a new rigid V-shaped pyridyl ligand

Entangled coordination polymers have attracted considerable interest due to their novel structures and potential applications. In this paper, one new 2D → 3D porous zinc coordination polymer {[Zn₂(DPDBT)₂(OBA)₂](H₂O)₃}_n (1) with parallel polycatenation was synthesized under solvothermal conditions based on 2,8-di(pyridin-4-yl)dibenzo[b,d]thiophene (DPDBT) ligand. In addition, complex 1 exhibits interesting solid-state photoluminescence and high thermal stability.     

A study on proton conduction in a layered metal–organic framework,Rb2(adp)[Zn2(ox)3]·3H2O (adp = adipic acid,ox2 − = oxalate)

We newly synthesized a metal–organic framework (MOF) Rb₂(adp)[Zn₂(ox)₃]·3H₂O (adp = adipic acid; ox^2 − = oxalate), where the rubidium ions, carboxylic acid groups, and water molecules are located in an interlayer space of a two-dimensional (2-D) oxalate-bridged network. The structure of this compound was determined using single-crystal X-ray diffraction analysis. Hydrated phases of this compound were examined using thermogravimetry and water vapor adsorption measurements. Proton conductivity in this MOF was investigated by alternating current impedance measurements. Systematic comparison with previously reported isomorphous 2-D compounds A₂(adp)[Zn₂(ox)₃]·3H₂O (A = NH₄ and K) showed that the difference in the ionic radii of the cations leads to a difference in activation energy of proton conductivity and that absence of NH₄⁺ ions causes a significant decrease in proton conductivity, even though the ionic radius of Rb⁺ (1.52 Å) is closer to that of NH₄⁺ (1.61 Å) than that of K⁺ (1.38 Å).     

Ultra-low temperature sintered (1–x)BaV2O6-xLiF ceramics for ULTCC and 5 G millimeter-wave antenna applications

(1–x)BaV₂O₆-xLiF (x = 0.025, 0.05, 0.10, 0.15) ceramics with an ultra-low sintering temperature of 475 °C were synthesized using the standard solid-state reaction method. The ceramics demonstrated a remarkable enhancement in the quality factor (Qf), reaching a maximum value of 16,800 GHz at x = 0.10, which is 5.6 times higher than that of pure BaV₂O₆ ceramics obtained in this work. A near-zero temperature coefficient of resonant frequency (τ_f = 1.44 ppm/°C) was simultaneously achieved, together with a dielectric constant ε_r of 11.54. Additionally, the chemical compatibility between the present ceramics and the Al electrode was confirmed. Moreover, a millimeter-wave antenna with an excellent S₁₁ value of −50.3 dB, and a large bandwidth of 3.44 GHz was fabricated using the 0.9BaV₂O₆-0.1LiF ceramic as the dielectric resonator. These results highlight the potential application prospects of (1–x)BaV₂O₆-xLiF ceramics in the ultra-low temperature co-fired ceramic technology and 5 G millimeter-wave antennas.