4-Benzyl-6-bromo-2-(4-methoxy­phen­yl)-4H-imidazo[4,5-b]pyridine monohydrate

The imidazopyridine fused ring in the title compound, C20H16BrN3O·H2O, is coplanar with the aromatic ring at the 2-position [dihedral angle = 5.2 (1)°]. In the five-membered imidazo portion, the C—N bond whose C atom is also connected to the pyridine N atom has predominantly double-bond character [1.334 (2) Å] whereas the C—N bond whose atom is connected to the pyridine C atom has predominantly single-bond character [1.371 (2) Å]. The water mol­ecule engages in hydrogen bonding with the latter N atom; it is also connected to a symmetry-related water mol­ecule, generating a linear chain structure

From ∞1[(UO2)2O(MoO4)4]6− to ∞1[(UO2)2(MoO4)3(MoO5)]6− infinite chains in A6U2Mo4O21 (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure of Cs6[(UO2)2(MoO4)3(MoO5)]

A new caesium uranyl molybdate belonging to the M6U2Mo4O21 family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A6[(UO2)2O(MoO4)4], the caesium compound Cs6U2Mo4O21 should be written Cs6[(UO2)2(MoO4)3(MoO5)] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs6[(UO2)2(MoO4)3(MoO5)] crystallizes in the triclinic symmetry with space group P1̄ and a=10.4275(14) Å, b=15.075(2) Å, c=17.806(2) Å, α=70.72(1)°, β=80.38(1)° and γ=86.39(1)°, V=2604.7(6) Å3, Z=4, ρmes=5.02(2) g/cm3 and ρcal=5.08(3) g/cm3. A full-matrix least-squares refinement on the basis of F2 yielded R1=0.0464 and wR2=0.0950 for 596 parameters with 6964 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with Mo(Kα) radiation and a CCD detector. The crystal structure of Cs compound is characterized by ∞1[(UO2)2(MoO4)3(MoO5)]6− parallels chains built from U2O13 dimeric units, MoO4 tetrahedra and MoO5 square pyramids, whereas, Na, K and Rb compounds are characterized by ∞1[(UO2)2O(MoO4)4]6− parallel chains formulated simply of U2O13 units and MoO4 tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 61

Molten salt flux synthesis and crystal structure of a new open-framework uranyl phosphate Cs3(UO2)2(PO4)O2: Spectroscopic characterization and cationic mobility studies

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Synthesis, crystal structure, infrared and electrical conductivity of the layered rubidium uranate Rb₄U₅O₁₇

International audienceSingle crystals of a new layered rubidium uranate compound Rb4U5O17 have been synthesized by high-temperature solid-state reaction. The crystal structure was determined from single crystal X-ray diffraction data. The title compound crystallizes in the orthorhombic symmetry with space group Pbcn, and the following crystallographic data: a = 18.6762(9) Å, b = 7.0490(4) Å, c = 14.1207(7) Å and Z = 4. A full-matrix least-squares refinement on the basis of F2 yielded R1 = 0.031 and wR2=0.060 for 120 parameters with 2723 independent reflections with I ≥ 2σ(I) collected on a BRUKER X8 Apex II 4K diffractometer with Mo Kα radiation and a CCD detector. The crystal structure contains infinite corrugated layers [(UO2)5O7]4− parallel to (0 0 1), formed by the association by edge- and corner-sharing of (UO2)O5 pentagonal bipyramids and distorted (UO2)O4 square bipyramids. The alkaline cation Rb+ are localized between layers and ensured the cohesion of the structure. Conductivity measurements, between 200 and 700 °C, show an Arrhenius law evolution, with a better electrical conductivity than the two other uranates Rb9U9O31 and Rb2U2O7, recently characterized. Infrared spectroscopy measurements at room temperature have allowed the identification of the various modes of vibrations of the uranyl ions

A new uranyl niobate sheet in the cesium uranyl niobate Cs₉[(UO₂)₈O₄(NbO₅)(Nb₂O₈)₂]

International audienceA new cesium uranyl niobate, Cs9[(UO2)8O4(NbO5)(Nb2O8)2] or Cs9U8Nb5O41 has been synthesized by high-temperature solid-state reaction, using a mixture of U3O8, Cs2CO3 and Nb2O5. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) Å, b=14.933(2) Å, c=20.155(2) Å β=110.59(1)°, P21/c space group and Z=4. The crystal structure was refined to agreement factors R1=0.049 and wR2=0.089, calculated for 4660 unique observed reflections with I ≥ 2σ(I), collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector.In this structure the UO7 uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer ∞2[U8O36] corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb2O8 entities and NbO5 square pyramids, respectively, to form infinite uranyl niobate sheets ∞2[(UO2)8O4(NbO5)(Nb2O8)2]9- stacking along the [010] direction. The Nb2O8 entities result from two edge-shared NbO5 square pyramids. The Cs+ cations are localized between layers and ensured the cohesion of the structure.The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs+ cations to the infinite uranyl niobate layers and by the high density of these cations in the interlayer space without vacant site.Infrared spectroscopy investigated at room temperature in the frequency range 400–4000 cm−1, showed some characteristic bands of uranyl ion and niobium polyhedr