Browse
Submit Data
Databases
API
Help

Dataset Information

25 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Crystal structure of [UO₂(NH₃)₅]NO₃·NH₃.

ABSTRACT: Penta-ammine dioxide uranium(V) nitrate ammonia (1/1), [UO₂(NH₃)₅]NO₃·NH₃, was obtained in the form of yellow crystals from the reaction of caesium uranyl nitrate, Cs[UO₂(NO₃)₃], and uranium tetra-fluoride, UF₄, in dry liquid ammonia. The [UO₂]⁺ cation is coordinated by five ammine ligands. The resulting [UO₂(NH₃)₅] coordination polyhedron is best described as a penta-gonal bipyramid with the O atoms forming the apices. In the crystal, numerous N-H?N and N-H?O hydrogen bonds are present between the cation, anion and solvent mol-ecules, leading to a three-dimensional network.

SUBMITTER: Woidy P

PROVIDER: S-EPMC5137591 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Crystal structure of [UO2(NH3)5]NO3·NH3.

Woidy Patrick P Kraus Florian F

Acta crystallographica. Section E, Crystallographic communications 20161101 Pt 12

Penta-ammine dioxide uranium(V) nitrate ammonia (1/1), [UO2(NH3)5]NO3·NH3, was obtained in the form of yellow crystals from the reaction of caesium uranyl nitrate, Cs[UO2(NO3)3], and uranium tetra-fluoride, UF4, in dry liquid ammonia. The [UO2]+ cation is coordinated by five ammine ligands. The resulting [UO2(NH3)5] coordination polyhedron is b ...[more]

PMID: 27980813

Similar Datasets

Coffinite formation from UO2+x.

Project description:Most of the highly radioactive spent nuclear fuel (SNF) around the world is destined for final disposal in deep-mined geological repositories. At the end of the fuel's useful life in a reactor, about 96% of the SNF is still UO2. Thus, the behaviour of UO2 in SNF must be understood and evaluated under the weathering conditions of geologic disposal, which extend to periods of hundreds of thousands of years. There is ample evidence from nature that many uranium deposits have experienced conditions for which the formation of coffinite, USiO4, has been favoured over uraninite, UO2+x, during subsequent alteration events. Thus, coffinite is an important alteration product of the UO2 in SNF. Here, we present the first evidence of the formation of coffinite on the surface of UO2 at the time scale of laboratory experiments in a solution saturated with respect to amorphous silica at pH = 9, room temperature and under anoxic conditions.

| S-EPMC7376029 | biostudies-literature

Crystal Structure Formation of CH₃NH₃PbI3-xClx Perovskite.

Project description:Inorganic-organic hydride perovskites bring the hope for fabricating low-cost and large-scale solar cells. At the beginning of the research, two open questions were raised: the hysteresis effect and the role of chloride. The presence of chloride significantly improves the crystallization and charge transfer property of the perovskite. However, though the long held debate over of the existence of chloride in the perovskite seems to have now come to a conclusion, no prior work has been carried out focusing on the role of chloride on the electronic performance and the crystallization of the perovskite. Furthermore, current reports on the crystal structure of the perovskite are rather confusing. This article analyzes the role of chloride in CH₃NH₃PbI3-xClx on the crystal orientation and provides a new explanation about the (110)-oriented growth of CH₃NH₃PbI₃ and CH₃NH₃PbI3-xClx.

| S-EPMC5456724 | biostudies-other

Synthesis and crystal structure of 4-fluoro-benzyl-ammonium di-hydrogen phosphate, [FC6H4CH2NH3]H2PO4.

Project description:The asymmetric unit of the title salt, [p-FC6H4CH2NH3]+·H2PO4-, contains one 4-fluoro-benzyl-ammonium cation and one di-hydrogen phosphate anion. In the crystal, the H2PO4- anions are linked by O-H?O hydrogen bonds to build corrugated layers extending parallel to the ab plane. The FC6H4CH2NH3+ cations lie between these anionic layers to maximize the electrostatic inter-actions and are linked to the H2PO4- anions through N-H?O hydrogen bonds, forming a three-dimensional supra-molecular network. Two hydrogen atoms belonging to the di-hydrogen phosphate anion are statistically occupied due to disorder along the OH?HO direction.

| S-EPMC5137615 | biostudies-literature

Crystal structure of the uranyl arsenate mineral hugelite, Pb2(UO2)3O2(AsO4)2(H2O)5, revisited: a correct unit cell, twinning and hydrogen bonding.

Project description:Revisiting the structure of uranyl arsenate mineral hügelite provided some corrections to the available structural data. The previous twinning model (by reticular merohedry) in hügelite has been corrected. Twinning of the monoclinic unit cell [a = 7.0189 (7) Å, b = 17.1374 (10) Å, c = 8.1310 (10) Å and β = 108.904 (10)°], which can be expressed as a mirror in [100], leads to a pseudo-orthorhombic unit cell (a = 7.019 Å, b = 17.137 Å, c = 61.539 Å and β = 90.02°), which is eight times larger, with respect to the unit-cell volume, than a real cell. Moreover, the unit cell of chosen here and the unit cell given by the previous structure description both lead to the same supercell. A new structure refinement undertaken on an untwinned crystal of hügelite resulted in R = 4.82% for 12 864 reflections with Iobs > 3σ(I) and GOF = 1.12. The hydrogen-bonding scheme has been proposed for hügelite for the first time.

| S-EPMC8182802 | biostudies-literature

Thermodynamic model of the oxidation of Ln-doped UO2.

Project description:Ln-doped UO2 is often considered as a model system of spent nuclear fuel (SNF) helping to reveal effects of fission and activation products on its chemical stability. Comparing thermodynamics of UO2-UO3 and LnO1.5-UO2-UO3 systems provides a means to understand the phenomenon of an increased resistivity of Ln-doped UO2 to oxidation in air relative to pure UO2. Here a thermodynamic model is developed and is applied to investigate detailed phase changes occurring along the oxidation of Ln-doped fluorite to U3O8. The study proposes that an enhanced resistivity to oxidation of Ln-doped UO2 is likely caused by a thermodynamically driven partitioning of Ln between a fluorite-type phase and a U3O8 polymorph, which at ambient temperatures becomes hindered by slow diffusion.

| S-EPMC10589314 | biostudies-literature

Atomic-scale imaging of CH3NH3PbI3 structure and its decomposition pathway.

Project description:Understanding the atomic structure and structural instability of organic-inorganic hybrid perovskites is the key to appreciate their remarkable photoelectric properties and understand failure mechanism. Here, using low-dose imaging technique by direct-detection electron-counting camera in a transmission electron microscope, we investigate the atomic structure and decomposition pathway of CH3NH3PbI3 (MAPbI3) at the atomic scale. We successfully image the atomic structure of perovskite in real space under ultra-low electron dose condition, and observe a two-step decomposition process, i.e., initial loss of MA+ followed by the collapse of perovskite structure into 6H-PbI2 with their critical threshold doses also determined. Interestingly, an intermediate phase (MA0.5PbI3) with locally ordered vacancies can robustly exist before perovskite collapses, enlightening strategies for prevention and recovery of perovskite structure during the degradation. Associated with the structure evolution, the bandgap gradually increases from ~1.6 eV to ~2.1 eV. In addition, it is found that C-N bonds can be readily destroyed under irradiation, releasing NH3 and HI and leaving hydrocarbons. These findings enhance our understanding of the photoelectric properties and failure mechanism of MAPbI3, providing potential strategies into material optimization.

| S-EPMC8448763 | biostudies-literature

Crystal structure of the complex of 2,4,6-tri-ethyl-1,3,5-tris-[(4-methyl-1H-indazol-1-yl)meth-yl]-benzene with NH4PF6.

Project description:The complex of 2,4,6-tri-ethyl-1,3,5-tris-[(4-methyl-1H-indazol-1-yl)meth-yl]-benz-ene with ammonium hexa-fluorophosphate, C39H42N6·NH4 +·PF6 -, crystallizes in the monoclinic space group P21 with two mol-ecules of the receptor, two NH4 + and two PF6 - ions in the asymmetric unit. In each of the complexes the ammonium ion resides in the cavity of the receptor mol-ecule and is fixed in its position by three N-H⋯N bonds, while the remaining hydrogen atom of the cation acts as a bifurcated binding site for N-H⋯F bonding to the counter-anion. The crystal is composed of one-dimensional supra-molecular aggregates extending along the a-axis direction.

| S-EPMC9361362 | biostudies-literature

Nanoscale mechanism of UO2 formation through uranium reduction by magnetite.

Project description:Uranium (U) is a ubiquitous element in the Earth's crust at ~2 ppm. In anoxic environments, soluble hexavalent uranium (U(VI)) is reduced and immobilized. The underlying reduction mechanism is unknown but likely of critical importance to explain the geochemical behavior of U. Here, we tackle the mechanism of reduction of U(VI) by the mixed-valence iron oxide, magnetite. Through high-end spectroscopic and microscopic tools, we demonstrate that the reduction proceeds first through surface-associated U(VI) to form pentavalent U, U(V). U(V) persists on the surface of magnetite and is further reduced to tetravalent UO2 as nanocrystals (~1-2 nm) with random orientations inside nanowires. Through nanoparticle re-orientation and coalescence, the nanowires collapse into ordered UO2 nanoclusters. This work provides evidence for a transient U nanowire structure that may have implications for uranium isotope fractionation as well as for the molecular-scale understanding of nuclear waste temporal evolution and the reductive remediation of uranium contamination.

| S-EPMC7417540 | biostudies-literature

Defect segregation facilitates oxygen transport at fluorite UO2 grain boundaries.

Project description:An important challenge for modelling transport in materials for energy applications is that in most applications they are polycrystalline, and hence it is critical to understand the properties in the presence of grain boundaries. Moreover, most grain boundaries are not pristine stoichiometric interfaces and hence dopants are likely to play a significant role. In this paper, we describe our recent work on using atomistic molecular dynamics simulations to model the effect of doped grain boundaries on oxygen transport of fluorite structured UO2. UO2, much like other fluorite grain boundaries, are found to be sinks for oxygen vacancy segregation relative to the grain interior, thus facilitating oxygen transport. Fission products further enhance diffusivity via strong interactions between the impurities and oxygen defects. Doping produces a striking structural alteration in the Σ5 class of grain boundaries that enhances oxygen diffusivity even further. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'.

| S-EPMC6635626 | biostudies-literature

Single crystal structure, vibrational spectroscopy, gas sorption and antimicrobial properties of a new inorganic acidic diphosphates material (NH4)2Mg(H2P2O7)2•2H2O.

Project description:We report on the successful synthesis of diammonium magnesium dihydrogendiphosphate (V) dihydrate compound (NH4)2Mg(H2P2O7)2•2H2O using a wet chemical route. Single crystal X-ray diffraction analysis and micro Raman spectroscopy are employed to characterize the compound. We demonstrate, using a multidisciplinary approach, that this compound is ideal for carbon dioxide (CO2) capture in addition to other anthropogenic gasses. We show here -from both an experimental as well as from a density functional theory (DFT) calculations routes- the potential for adopting this compound into domestic air-conditioning units (ACUs). From these experiments, the resistance to bacterial growth is also investigated, which is critical for the adoption of this compound in ACUs. Our compound exhibits a higher methane (CH4) sorptivity as compared to CO2 at 25?°C and 45?°C under pressures up to 50 bars. Furthermore, DFT electronic structure calculations are used to compute the main structural and electronic properties of the compound, taking into consideration the characteristics of the identified pores as a function of the progressive CO2 vs. CH4 loadings. Finally, the antibacterial assay reveals a strong antibacterial activity against the tested Gram-positive and Gram-negative bacteria, with a large zone of inhibition against the tested E. Coli, S. Aureus and K. Pneumonia.

| S-EPMC7264148 | biostudies-literature