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Single crystals of four novel uranyl selenate and selenite-selenate oxysalts with protonated ethylamine molecules, (C 2 H 8 N) 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](H 2 O) ( I ), (C 2 H 8 N) 3 [(UO 2 )(SeO 4 ) 2 (HSeO 4 )] ( II ), (C 2 H 8 N)[(UO 2 )(SeO 4 )(HSeO 3 )] ( III ), and (C 2 H 8 N)(H 3 O)[(UO 2 )(SeO 4 ) 2 (H 2 O)] ( IV ) have been prepared by isothermal evaporation from aqueous solutions. Uranyl-containing 1D and 2D units have been investigated using topological approach and information-based complexity measurements that demonstrate the evolution of structural units and the increase of topological complexity with the decrease of H 2 O content. [ABSTRACT FROM AUTHOR]

The novel uranyl sulfate templated by protonated guanidinium molecules was obtained from aqueous solution under ambient conditions. Its crystal structure was determined by the single crystal X-ray diffraction analysis and evaluated using a topological approach and information-based complexity calculations. The Se-for-S substitution resulted in a symmetry breaking (from orthorhombic in sulfate to monoclinic in selenate) due to the rearrangement of oxygen atoms, so the resulting symmetry is a consequence of interplay between the template-substructure interactions and size of the tetrahedral cation. [ABSTRACT FROM AUTHOR]

Crystals of the title compound are prepared by evaporation of aqueous solutions of Na2SO4 and NaF at 25 °C. [ABSTRACT FROM AUTHOR]

Single crystals of seven novel uranyl oxysalts of selenium with protonated methylamine molecules, [C 2 H 8 N] 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)] ( I ), [C 2 H 8 N] 2 [(UO 2 ) 2 (SeO 4 ) 3 (H 2 O)] ( II ), [C 4 H 15 N 3 ][H 3 O] 0.5 [(UO 2 ) 2 (SeO 4 ) 2.93 (SeO 3 ) 0.07 (H 2 O)](NO 3 ) 0.5 ( III ), [C 2 H 8 N] 3 [H 5 O 2 ][(UO 2 ) 2 (SeO 4 ) 3 (H 2 O) 2 ] 2 (H 2 O) 5 ( IV ), [C 2 H 8 N] 2 [H 3 O][(UO 2 ) 3 (SeO 4 ) 4 (HSeO 3 )(H 2 O)](H 2 SeO 3 ) 0.2 ( V ), [C 4 H 12 N] 3 [H 3 O][(UO 2 ) 3 (SeO 4 ) 5 (H 2 O)] ( VI ), and [C 2 H 8 N] 3 (C 2 H 7 N)[(UO 2 ) 3 (SeO 4 ) 4 (HSeO 3 )(H 2 O)] ( VII ) have been prepared by isothermal evaporation from aqueous solutions. Their crystal structures have been solved by direct methods and their uranyl selenate and selenite–selenate units investigated using black-and-white graphs from the viewpoints of topology of interpolyhedral linkages and isomeric variations. The crystal structure of IV is based upon complex layers with unique topology, which has not been observed previously in uranyl selenates. Investigations of the statistics and local distribution of the U–O br –Se bond angles demonstrates that shorter angles associate with undulations, whereas larger angles correspond to planar areas of the uranyl selenite layers. [ABSTRACT FROM AUTHOR]

Single crystals of two new uranyl selenates K3 (H3O)[(UO2)4 (SeO4)6 (H2O) 4]·5H2O (I) and K2.5(no)(NO3)0.5[(UO2)2(SeO4)3 (H2O)]·4H2O (II) have been prepared by room-temperature evaporation from aqueous solution of uranyl nitrate, selenic acid, potassium carbonate and (for the compound I) carbamide. The crystal structure of I has been solved by direct me-thods [monoclinic, P21/m, a = 12.001(3), b = 13.613(3), c = 13.753(3) Å, β = 109.187(4)°, V = 2122.0(8) ų= and Z = 2] and refined to R1 = 0.029 (wR2 = 0.084) for 4865 reflections with |Fo| ≥ 4σF using least-square methods. The crystal structure of II has been solved by direct methods [monoclinic, C2/c, a = 20.290(4), b = 10.380(2), c = 21.436(4) Å, β = 103.446(3)°, V= 4391.0( 13) ų and Z=4] and refined to R1 = 0.027 (wR2, = 0.066) for 7944 reflections with |Fo| ≥ 4σF using least-square techniques. The structures of I and II are based upon the [(UO2)2 (SeO4)3 (H2O) 2]2- and [(UO2)2 (SeO4)3 (H2O)]2-layers, respectively, consisting of UO7 pentagonal bipyramids sharing comers with SeO4 tetrahedra. Potassium cations induce curvature of the uranyl selenate layers, which is mediated by the interlayer water molecules, hydronium ions and nitrate groups. The topology of the 2D units in the structtire of I is novel for the structural chemistry of uranyl selenates. [ABSTRACT FROM AUTHOR]

Single crystals of Cs2[(UO2)2(CrO4)3] ( 1) were obtained by hydrothermal synthesis. The structure of 1 is based upon 2-dimensional uranyl chromate layers with the composition [(UO2)2(CrO4)3]2-. The cesium atoms are located in the interlayer under 'bulbs' centered at the Cr(2)O4 tetrahedra. The thermal behavior of 1 was studied in air. The diffraction maxima of 1 gradually disappear at approximately 450 °C. At this temperature, peaks of Cs2[(UO2)2(Cr2O8)] ( 2) appear indicating reduction of Cr6+ to Cr5+. Thermal expansion of 1 and 2 is anisotropic. Thermal expansion of the crystal structure of 1 in the [001] direction is greater than that in the other directions, while thermal expansion in the ab plane is uniform. Thermal expansion of 2 is strongly anisotropic as well with the higher expansion along the direction approximately perpendicular to the layers (along the a axis). The high-temperature study demonstrates that stable uranyl compounds with Cr5+ may form not only from hydrothermal aqueous solutions, but also as a result of high-temperature solid-state reactions. [ABSTRACT FROM AUTHOR]

Two novel uranyl-selenate oxysalts templated by the electroneutral 12-crown-4 and 15-crown-5 molecules are obtained from aqueous solutions under ambient conditions. The arrangement of organic molecules between the uranyl-selenate layers is provided only by means of protonated water molecule complexes. [ABSTRACT FROM AUTHOR]

The structure of a novel mixed-valent chromiumuranyl compound, (C3NH10)10[(UO2)13(Cr125+O42)(Cr6+O4)6(H2O)6]-(H2O)6 (1), obtained by the combination of a hydro-thermal method and evaporation from aqueous solutions with isopropylammonium, contains uranyl chromate hemispheres with lateral dimensions of 18.9 × 18.5 Å2 and a height of about 8 Å. The hemispheres are centered by a UO8 hexagonal bipyramid surrounded by six dimers of Cr5+O5 square pyramids, UO7 pentagonal bipyramids, and Cr6+O4 tetrahedra. The hemispheres are linked into two-dimensional layers so that two adjacent hemispheres are oriented in opposite directions relative to the plane of the layer. From a topological point of view, the hemispheres have the formula U21Cr23 and can be considered as derivatives of nanospherical cluster U26Cr36 composed of three-, four-, and five-membered rings. [ABSTRACT FROM AUTHOR]