Brahim Ayed

Na1.72Mn3.28(AsO4)3

The single crystal of sodium manganese arsenate (1.72/3.28/12), Na1.72Mn3.28(AsO4)3, used for analysis was prepared by solid-state reaction at 1073 K. The compound crystallizes in the monoclinic system in space group C2/c. The structure consists of a complex network of edge-sharing MnO6 octahedral chains, linked together by AsO4 tetrahedra, forming two distinct channels, one containing Na+ cations and the other occupied statistically by Mn+ and Na+ cations.

Two Novel Compounds Built Up of Decavanadate Clusters and Transition-Metal Complexes: Synthesis and Structure

Two inorganic compounds entitled tetrasodium hexaaquacobalt decavanadate tetraco-sahydrate,(I), and diammonium bis[hexaaquamanganese] decavanadate tetrahydrate,(II), have been isolated by conventional solution method and structurally characterized by single-crystal X-ray diffraction methods, scanning electron microscopy, IR spectra, thermal analyses and cyclic voltammetry measurements. They crystallize with triclinic (P-1) symmetry and consists of a centrosymmetric [V10O28]6− anion. The Co2+ and Mn2+ cations in (I) and (II) respectively are octahedrally coordinated by six water molecules. Compound (I) also contains a polymeric linear array of edge-sharing [Na(OH2)6]+ and [Co(OH2)6]2+ octahedra and compound (II) exhibit a catenary structure consisting of [V10O28]6− anions linked to [Mn(OH2)6]2+ and NH4+via hydrogen bonds.

Two new inorganic-organic hybrid materials based on inorganic cluster, [X2Mo18O62]6− (X=P, As)

AbstractTwo new inorganic-organic hybrid materials based on heteropolyoxometalates, (C4H10N)6(P2 Mo18O62).4H2O I, and (C4H10N)6(As2Mo18O62).4H2O II, where C4H10N is protonated pyrrolidine have been synthesized and structurally characterized by physic-chemical methods. Single-crystal X-ray diffraction method, infrared, ultraviolet spectroscopy, Thermogravimetricanalysis andcyclic voltammetry measurements of the title hybrid materials indicate that there are hydrogen bond interaction between O atoms of the heteropolyoxometalates and water molecules as well as the N and O atoms of the organic compound. The molecular structures of synthesized hybrid materials contain discrete entities of pyrrolidinumion and water molecules surround every [X2Mo18O62]6− anion over the extended crystalline network that the [X2Mo18O62]6− anion retains its “Dawson structure”. Crystal data: I monoclinic, space group P21/a, a = 13,453(1) Å, b = 24,046 (1) Å, c = 24,119(1) β = 97,99(1)°, V = 7726,30(5) Å3 and Z = 4; II monoclinic, space group P21/a, a = 13.4900(1) Å, 24.0900(1) Å, 24.2740(1) Å, β = 98.320(1)°, V = 7805.40(7) Å3 and Z = 4. Graphical AbstractTwo new inorganic-organic hybrid materials based on the inorganic cluster, [X2Mo18O62]6- (X = P, As), crystallize in monoclinic space group P21/a.

K2.6Nb11.6O30: a novel tetragonal bronze structure

K2.6Nb11.6O30, Mr = 1659.33 g ⋅ mol−1, crystallizes in the tetragonal system, space group P4/mbm, Z = 1. The lattice parameters are a = 12.549(3) Å, c = 3.978(2) Å, V = 626.4(4) Å3, Dx_{x} = 4.398 g ⋅ cm−3. The crystal structure was solved and refined from 413 independent reflections, obtained by X-ray diffraction on a single crystal. The final R index and weighted Rw index are 0.0500 and 0.1178, respectively. The three-dimensional network of K2.6Nb11.6O30 is similar to that of tetragonal tungsten bronze with K and Nb partially occupying the interstitial pentagonal and trigonal sites. The most interest of this structure is the planar pentagonal coordination of Nb atoms.

A novel organic-inorganic hybrid based on Anderson-type polyoxometalate: H(C5N5H5)2(C5N5H6)2[Al(OH6)Mo6O18]·10H2O

A new organic-inorganic hybrid compound, H(C5N5H5)2(C5N5H6)2[Al(OH6)Mo6O18]·10H2O, has been synthesized and structurally characterized by single crystal X-ray diffraction, elemental analyses, IR, UV-Vis spectra and thermogravimetric analyses. This compound crystallized in the triclinic system, space group P-1, with a = 8.033(5) Å, b = 9.960(4) Å, c = 16.797(7) Å, α = 73.43(3)°, β = 87.85(1)°, γ = 81.47(1)° and Z = 1. The crystal structure can be described by infinite polyanions [Al(OH)6Mo6O18]3− organized in layers parallel to the c-direction alternating with organic cations associated in ribbons spreading along the b-direction. Multiple hydrogen bonds originating from amine, hydroxyl groups and water molecules connect different components of the lattice.

A new sodium dimangnesium trivanadate, NaMg2V3O10

A single crystal of NaMg2V3O10 has been prepared by solid-state reaction at 1173 K. The [Mg2(V3O10)]− anions are built up from edge-sharing MgO6 octahedra to form [Mg4O18] units, which are linked to each other by trivanadate groups (V3O10). The Na+ ions are located in the tunnel space.

Synthesis and structural characterization of new inorganic–organic hybrid: arsenomolybdate compound with cytosinium cations

New organic–inorganic hybrid compound, with formula (C4H6N3O)6[(HAsO4)2Mo6O19]⋅7H2O, was prepared and characterized by IR and UV–visible spectroscopies and X-ray diffraction techniques. Thermal analysis was performed to study their thermal stability. The crystal structure of the title compound (triclinic, space group P − 1, Z = 2) was determined by X-ray diffraction. The compound contains the polyanion [(HAsO4)2Mo6O19]6−, which consists of the six molybdenum octahedral grouped into two parts consisting of four edge-sharing octahedral and two face-sharing octahedral, respectively, these two parts are connected by two corner-sharing O atoms to form a bent Mo6 ring. The polyanion framework derives from the Strandberg type and it is a new isomer. The cytosinium cations (Cyt+) are embedded in the channels and interact with the inorganic framework by way of N–H ⋯ O and O–H ⋯ O hydrogen bonds. Furthermore, the electrochemical property of this compound has been studied.

Crystal structure, vibrational studies, optical properties, and Hirshfeld surface analysis of (C5H6N5)2[Cr2O7]

Abstract Single crystals of a new organic–inorganic compound, (C5H6N5)2Cr2O7 (1), adeninium dichromate, were grown by the slow evaporation technique and characterized by X-ray diffraction, infrared absorption, and the optical properties were also investigated by UV-vis absorption spectroscopy. The compound crystallizes in the triclinic system and P-1 space group with a = 11.6850(2) Å, b = 11.7531(5) Å, c = 14.5603(7) Å, α = 83.956(3)°, β = 70.481(4)°, γ = 61.863(2)°, V = 1658.70(12) Å3. The structure of the compound consists of four adeninium, (C5H5N2)+, cations, and two dichromate dianions with all the atoms situated in general positions. Each dichromate anion is formed by two tetrahedral CrO4 joined through shared O atoms and are linked to the cations with several weak hydrogen bonding interactions resulting in an extended network. 3-D Hirshfeld surface analysis and 2-D fingerprint plots indicate that the packing is dominated by H⋯O/O⋯H and H⋯N/N⋯H contacts.

Dawson-type polyoxometalate nanoclusters confined in a carbon nanotube matrix as efficient redox mediators for enzymatic glucose biofuel cell anodes and glucose biosensors

Two new inorganic-organic hybrid materials based on heteropolyoxometalates (POMs): (C4H10N)6[P2Mo18O62]·4H2O (P2Mo18) and (C6H8NO)4[H2P2W18O62]·6H2O (P2W18) are reported as mediators for electron transfer between FAD-dependent glucose dehydrogenase (FAD-GDH) and a multiwalled carbon nanotube (MWCNT) matrix for glucose biofuel cell and biosensor applications. These polyoxometalates were chosen due to their promising redox behavior in a potential range for mediated electron transfer with the glucose oxidizing enzyme, FAD-GDH. P2Mo18 and P2W18 were immobilized on 1-pyrenemethylamine (PMA) functionalized MWCNT deposits. After immobilization of FAD-GDH, the P2W18-modified MWCNT electrode demonstrated mediated electron transfer and provided a catalytic current density of 0.34 mA cm-2 at 0.2 V vs SCE with an open circuit potential (OCP) of -0.08 V vs SCE. A 10-fold increase in catalytic current to 4.7 mA cm-2 at 0.2 V vs SCE and a slightly lower OCP of -0.10 V vs SCE was observed for an equivalent electrode modified with P2Mo18.The apparent superiority of P2Mo18 is related, at least in part, to its improved incorporation in the MWCNT matrix compared to P2W18. Both POM-modified bioanodes showed exceptional stabilities with 45% of their initial performances remaining after 15 days. The mediated electron transfer capacities of the POMs were also evaluated in a glucose sensor setup and showed very satisfying performances for glucose detection, including a sensitivity of 0.198 mA mol L-1 cm-2, a satisfying linear range between 1 mmol L-1 and 20 mmol L-1, and good reproducibility for the P2Mo18 electrode.