Crystal structure of a trigonal polymorph of aquadioxidobis(pentane-2,4-dionato-κ2 O,O′)uranium(VI)

The title compound, [UO2(acac)2(H2O)] consists of a uranyl(VI) unit ([O=U=O]2+) coordinated to two monoanionic acetylacetonate (acac, C5H7O2) ligands and one water molecule. The asymmetric unit includes a one-half of a uranium atom, one oxido ion, one-half of a water molecule and one acac ligand. The coordination about the uranium atom is distorted pentagonal–bipyramidal. The acac ligands and Ow atom comprise the equatorial plane, while the uranyl O atoms occupy the axial positions. Intermolecular hydrogen bonding between complexes results in the formation of two-dimensional hexagonal void channels along the c-axis direction with a diameter of 6.7 Å. The monoclinic (P21/c space group) polymorph was reported by Alcock & Flanders [(1987). Acta Cryst. C43, 1480–1483].

Direct Ionization Cross Sections of Uranium Atom By Electron Impact

A theoretical model for electron impact ionization cross section has been found to be reliable for wide range of atoms is applied in this paper to the Uranium atom. A modified Kim binary encounter Bethe (BEB) method and modified Khare BEB method is employed for calculating electron impact ionization cross sections. The present results so obtained are compared with experimental as well as theoretical results known to the best of our knowledge.

Ab initio structure solution of proteins at atomic resolution using charge-flipping techniques and cloud computing

Large protein structures at atomic resolution can be solved in minutes using charge-flipping techniques operating on hundreds of virtual machines (computers) on the Amazon Web Services cloud-computing platform driven by the computer programs TOPAS or TOPAS-Academic at a small financial cost. The speed of operation has allowed charge-flipping techniques to be investigated and modified, leading to two strategies that can solve a large range of difficult protein structures at atomic resolution. Techniques include the use of space-group symmetry restraints on the electron density as well as increasing the intensity of a randomly chosen high-intensity electron-density peak. It is also shown that the use of symmetry restraints increases the chance of finding a solution for low-resolution data. Finally, a flipping strategy that negates `uranium atom solutions' has been developed for structures that exhibit such solutions during charge flipping.

Synthesis and crystal structure of triethylammonium hexabromidouranate(IV) dichloromethane monosolvate

Triethylammonium hexabromidouranate(IV) dichloromethane monosolvate, [(C2H5)3NH]2[UBr6]·CH2Cl2, was obtained in the form of dark-brown crystals from the reaction of uranium pentabromide with NEt3 and ethylene glycol in dichloromethane at low temperature. During the progress of the reaction, the reduction of uranium(V) to uranium(IV) was observed, whose associated oxidation product could not be identified. The uranium atom of the [UBr6]2– anion is coordinated by six bromido ligands in the shape of an octahedron. Between cations, anion and solvent molecules of crystallization, numerous C—H...Hal hydrogen-bond-like interactions are present, leading to a three-dimensional network structure.