A single crystal X-ray diffraction and IR study of (NH4)2[(UO2)C2O4(CH3COO)2]

A single crystal X-ray diffraction study of (NH₄)₂[(UO₂)C₂O₄(CH₃COO)₂] was performed. The compound crystallizes in the monoclinic system; unit cell parameters (at 100 ± 2 K): a = 6.793(2), b = 18.866(6), c = 20.730(7) Å, β = 90.040(7)°, space group P2₁/c, Z = 8, V = 2656.5(14) ų, R = 0.0495. The main structural units of the crystals are mononuclear complexes [(UO₂)C₂O₄(CH₃COO)₂]^2? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^? and C₂O ₄ ^2? ) of uranyl complexes. The uranium-containing anions are linked with ammonium cations by electrostatic interactions and a system of hydrogen bonds. The results of the X-ray diffraction analysis of the compound are well consistent with the IR data.     

Synthesis and structure of Cs3[UO2(CH3COO)3]2(NCS)·H2O

The compound Cs₃[UO₂(CH₃COO)₃]₂(NCS)·H₂O (I) was synthesized and studied by IR spectroscopy and single crystal X-ray diffraction. Compound I crystallizes in the monoclinic system with the following unit cell parameters: a = 7.8286(9), b = 19.892(2), c = 20.050(2) Å, β = 94.527(2)°, space group P2₁/c, Z = 4, R = 0.0387. The uranium-containing structural units in crystals of I are mononuclear complexes [UO₂(CH₃COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?) of uranyl complexes.     

Synthesis and structure of (NH<Subscript>4</Subscript>)<Subscript>3</Subscript>[UO<Subscript>2</Subscript>(CH<Subscript>3</Subscript>COO)<Subscript>3</Subscript>]<Subscript>2</Subscript>(NCS)

The compound (NH₄)₃[UO₂(CH₃COO)₃]₂(NCS) (I) was synthesized and examined by single crystal X-ray diffraction analysis. The compound crystallizes in the rhombic system with the unit cell parameters a = 11.5546(4), b = 18.5548(7), c = 6.7222(3) Å, V = 1441.19(10) ų, space group P2₁2₁2, Z = 2, R = 0.0345. The uranium-containing structural units of crystals of I are isolated mononuclear groups [UO₂(CH₃COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?) of uranyl complexes. The specific features of packing of the uranium-containing complexes in the crystal structure are considered.     

A single crystal X-ray diffraction study of R[UO2(C2H5COO)3] (R = K or NH4)

A single crystal X-ray diffraction study of R[UO₂(C₂H₅COO)₃] [R = K (I) or NH₄ (II)] was performed. Both compounds crystallize in the cubic system, unit cell parameters for I: a = 11.4329(3) Å (at 100 K), space group P2₁3, Z = 4; for II: a = 11.60503(7) Å (at 123 K), space group P2₁3, Z = 4. The structures of crystals of I and II contain complex anions [UO₂(C₂H₅COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ of uranyl complexes (A = UO ₂ ²⁺ , B⁰¹ = C₂H₅COO^?). These anions are linked in a framework by electrostatic interactions with outer-sphere cations R and by hydrogen bonds (in case of II). The effect of the kind of carboxylate ion on structural features of R[UO₂L₃] (L is propionate or acetate ion) is discussed.     

Synthesis, structure, and properties of [Be(H2O)4][UO2(CH3COO)3]2

Crystals of previously unknown compound [Be(H₂O)₄][UO₂(CH₃COO)₃]₂ were prepared and studied by X-ray diffraction analysis. The compound crystallizes in the tetragonal system, unit cell parameters (at 100 K): a = 10.3647(3), c = 23.4127(8) Å, V = 2515.16(13) ų, space group I4₁/a, Z = 4, R = 0.0194. The structure consists of mononuclear complexes [Be(H₂O)₄]²⁺ and [UO₂(CH₃COO)₃]^? linked with each other by electrostatic interactions and hydrogen bonds formed by water molecules and O atoms of acetate anions. The compound was also studied by methods of thermal analysis and IR spectroscopy.     

A single crystal X-ray diffraction study of Na4(UO2)4(i-C4H9COO)11(NO3)·3H2O

Synthesis and the results of IR and single crystal X-ray diffraction study of Na₄(UO₂)₄(i-C₄H₉COO)₁₁·(NO₃)·3H₂O are reported. The crystals are monoclinic; the unit cell parameters at 100 K are as follows: a = 13.697(2), b = 20.285(3), c = 15.991(3) Å, β = 103.760(3)°, space group P2₁, Z = 2, R = 0.0650. The uraniumcontaining structural units are mononuclear moieties [UO₂(i-C₄H₉COO)₃]^? and [UO₂(NO₃)(i-C₄H₉COO)₂]^?, belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = i-C₄H₉COO^? and NO ₃ ^? ) of uranyl complexes. The IR data are consistent with the results of the single crystal X-ray diffraction study. The influence of the carboxylate ligand volume on the structure of Na[UO₂L₃]·nH₂O crystals (L = acetate, n-butyrate, isovalerate ion) is analyzed.     

Supramolecular templates for the synthesis of new nanostructured uranyl compounds: Crystal structure of [NH3(CH2)9NH3][(UO2)(SeO4)(SeO2OH)](NO3)

Crystals of a new uranyl selenate, [NH₃(CH₂)₉NH₃][(UO₂)(SeO₄)(SeO₂OH)](NO₃) (1), were prepared by isothermal evaporation from aqueous solution at room temperature. The crystal structure was solved by the direct method $ P\bar 1 $ , a = 10.7480(7), b = 13.8847(9), c = 14.6363(10) Å, α = 109.9600(10)°, β = 103.212(2)°, γ = 90.4090(10)°, V = 1990.0(2) ų, Z= 4) and refined to R ₁ = 0.0379 (wR ₂ = 0.0636) for 8515 reflections with ¦Fo¦ ≥ 4σ_F. The structure is based on [(UO₂)(SeO₄)(SeO₂OH)]-layers parallel to the (001) plane. In the structure of 1, there are two crystallographically independent 1,9-diammoniononane cations forming micelles in which the hydrocarbon chains are packed crosswise. The micelles are cylinders with an elliptical cross section and a rough surface. They are organized by the principle of hydrophilic and hydrophobic interactions. The cylinders are separated from each other by layers of triangular NO ₃ ^? groups. Compound 1 is an example of organic-inorganic composites with a unidimensional organic substructure in which the protonated chain-like diamine molecules arranged crosswise form cylindrical supramolecular templates.     

Reduction of U(VI) in laser liquids POCl3-SnCl4-235UO 2 2+ -Nd3+

U(IV) is irreversibly accumulated during synthesis of laser liquids POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ prepared from various initial Nd(III) and U(VI) compounds, irrespective of the way of their introduction. The rate of U(IV) accumulation in POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions increases with increasing UO ₂ ²⁺ and Nd³⁺ concentrations; for laser liquids with the Nd³⁺ luminescence lifetime τ > 150 μs the observed rate constant of U(IV) accumulation by the second-order reaction k ₂[U⁴⁺] is equal to (3 ± 1) × 10^?5 1 mol^?1 s^?1 at T = 380 K. U(IV) is accumulated during storage of POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions in hermetically sealed glass cells at room temperature and upon irradiation of solutions by xenon lamp light in the spectral region of UO ₂ ²⁺ absorption. The U(VI) reduction proceeds by chemical and photochemical activation of uranyl with formation of stable U⁴⁺ complexes with dichlorophosphate ions and also with Nd³⁺. Deactivation of the uranyl ion excitation with proton-and chlorine-containing impurities prevents U(VI) reduction.     

Synthesis and structure of crystals of UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>H<Subscript>5</Subscript>COO)<Subscript>2</Subscript>·1.5L (L = methylurea or <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>’-dimethylurea)

The compounds UO₂(C₂H₅COO)₂·1.5L, where L is methylurea (Meur) or N,N’-dimethylurea (s-Dmur), were synthesized and studied by IR spectroscopy and single crystal X-ray diffraction. Irrespective of the kind of amide L, the structure of the compounds consists of two mononuclear uranium-containing complexes: cationic [UO₂(prop)L₃]⁺ and anionic [UO₂(prop)₃]^–, where prop is propionate ion. Both compounds belong to crystal-chemical group AB⁰¹M₃¹+ AB⁰¹M₃⁰¹ (A = UO₂²⁺, B⁰¹ = prop^–, M¹ = L) of uranyl complexes. The composition of 15 stable uranyl complexes that can be formed in the UO₂²⁺, B⁰¹–prop^––L–H₂O system was predicted on the basis of the characteristics of the Voronoi–Dirichlet polyhedra from the standpoint of the 18-electron rule.     

Synthesis and crystal structure of a uranyl bichromate, [CH6N3]2[(UO2)(CrO4)(Cr2O7)](H2O)

Crystals of the first uranyl bichromate, [CH₆N₃]₂[(UO₂)(CrO₄)(Cr₂O₇)](H₂O), were obtained by evaporation from aqueous solutions. The compound crystallizes in the triclinic system, space group $P\bar 1$ , a = 7.1829(17), b = 9.304(3), c = 14.884(4) Å, α = 102.43(2)°, β = 97.98(2)°, γ = 101.07(2)°, V = 936.3(5) ų, Z = 2. The structure was solved by direct methods and refined by the full-matrix least-squares method to R ₁ = 0.064 (wR ₂ = 0.138) for 2225 reflections with |F _hkl | ≥ 4σ(|F _hkl |). The structure is based on infinite [(UO₂)(CrO₄)(Cr₂O₇)]^2? chains where [UO₇]^8? pentagonal bipyramids are linked by tridentate [Cr(1)O₄]^2? groups and [Cr₂O₇]^2? groups; these chains run along x axis and are oriented parallel to $(0\bar 11)$ . Trigonal [CH₆N₃]⁺ cations and water molecules are arranged between the chains.     

An X-ray diffraction study of Rb[UO2(SeO4)F]·H2O

An X-ray diffraction study of Rb[UO₂(SeO₄)F]·H₂O (I) was performed. The compound crystallizes in the rhombic system with the following unit cell parameters: a = 8.4753(6), b = 13.5234(9), c = 13.5296(9) Å, space group Pnma, Z = 8, V = 1550.7(2) ų; R = 0.0248. The principal structural units of crystals of I are [UO₂(SeO₄)F]^? layers belonging to crystal-chemical group AT³M² (A = UO ₂ ²⁺ , T³ = SeO ₄ ^2? , M² = F^?) of uranyl complexes. The uranium-containing layered units are combined via electrostatic interaction with Rb cations and via a system of hydrogen bonds involving outer-sphere water molecules.     

Liquid luminophores POCl3-SiCl4-235UO 2 2+ -Nd3+

Samples of liquid luminophores POCl₃-SiCl₄-Nd³⁺, POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ , and POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ Nd³⁺ were prepared for the first time. The physicochemical properties and absorption spectra of the samples were compared. The solubility of Nd and U(VI) compounds in the POCl₃ SiCl₄ binary solvent was examined. The Nd³⁺ concentration attains a maximum of 0.3 mM when Nd and U(VI) trifluoroacetates are jointly dissolved at the [POCl₃]/[SiCl₄] molar ratio of 6 8. The shapes of the absorption band of the Nd ions at 860–900 nm, corresponding to the ⁴ I _9/2 → ⁴ F _3/2 electronic transition, differ significantly in POCl₃-SiCl₄-Nd³⁺ and POCl₃-SnCl₄-Nd³⁺ solutions, and in POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions the band shape also depends on the type of the Nd and U(VI) compounds introduced. The near-IR region of the absorption spectra of POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ and POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions contains absorption bands of the OH groups. The band intensity is analyzed in relation to the characteristics of the solutions. The Nd³⁺ luminescence lifetime τ in the luminophores synthesized was estimated at 70–20 μs.     

Liquid phosphors POCl3-ZrCl4-235UO 2 2+ -Nd3+

Liquid phosphors POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ and POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ with concentrations of Nd³⁺ and UO ₂ ²⁺ of up to 0.75 and 0.12 M were prepared; the lifetime of the Nd³⁺ luminescence was up to 300 μs. The lifetime of the Nd³⁺ luminescence in POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions decreases with increasing neodymium concentration, and this decrease is more pronounced than that in POCl₃-ZrCl₄-Nd³⁺ solutions. At molar ratio [ZrCl₄]/[Nd³⁺] < 1.5, the luminescence lifetime sharply decreases with decreasing ZrCl₄ concentration. The intensity of the absorption bands of the OH groups observed in the near-IR range of the absorption spectra of POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions increases with increasing neodymium concentration. Upon storage of POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions for 2 years without contact with the environment, the intensity of the IR absorption bends of the OH groups gradually increases, whereas the lifetime of the Nd³⁺ luminescence decreases to 60-80 μs.     

Synthesis and crystal structure of a new uranyl selenite(IV)-selenate(VI), [C5H14N]4[(UO2)3(SeO4)4(HSeO3)(H2O)](H2SeO3)(HSeO4)

Crystals of a new uranyl selenite(IV)-selenate(VI), [C₅H₁₄N]₄[(UO₂)₃(SeO₄)₄(HSeO₃)(H₂O)]·(H₂SeO₃)(HSeO₄) were obtained by evaporation from aqueous solutions. The compound crystallizes in the triclinic system, space group $P\bar 1$ , a = 11.7068(9), b = 14.8165(12), c = 16.9766(15) Å, α = 73.899(6)°, β = 76.221(7)°, γ = 89.361(6)°, V = 2743.0(4) ų, Z = 2. The crystal structure was solved by direct methods and refined to R ₁ = 0.081 (wR ₂ = 0.150) for 6966 reflections with |F _hkl | ≥ 4σ(|F _hkl |). The structure is based on [(UO₂)₃(SeO₄)₄(HSeO₃)(H₂O)]^3? layers formed by joining uranyl pentagonal bipyramids, selenate tetrahedra, and selenite pyramids. The [HSe(VI)O₄]^? anions, [H₂Se(IV)O₃] molecules, and protonated methylbutylamine cations are arranged between the layers.     

Liquid phosphors POCl3-TiCl4-235UO 2 2+ -Nd3+: 2. Nd3+ luminescence lifetime

Lifetime of the Nd³⁺ luminescence in POCl₃-TiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions is almost independent of the concentrations of neodymium and uranyl ions; it attains the maximal value of 220 μs at [TiCl₄] = 0.20?0.35 M and increases with increasing synthesis time, reaching 220 μs at t = 40?60 min. Upon storage, the Nd³⁺ luminescence lifetime decreases by 20–30% in 2 months, and in 2 years it decreases to 60–80 μs in all the samples. Simultaneously with decreasing Nd³⁺ luminescence lifetime, multiple increase in the intensity of the absorption bands of the OH groups is observed in the near-IR range of the absorption spectra of POCl₃-TiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions.     

Mechanism of Np(VI) oxidation with ozone in alkaline solutions

Bubbling of an ozone-oxygen mixture containing 0.1?C0.5 vol % O₃ at a rate of 15?C20 l h^?1 through 13 ml of a 2 × 10^?5?1 × 10^?4 M solution of Np(VI) in 0.1 and 1 M LiOH leads to the formation of Np(VII). The initial rate increases approximately in proportion to [Np(VI)] and [O ₃ ^gas ]^0.5. Up to 80% of Np(VI) is oxidized at maximum. At the O₃ concentration in the gas phase increased to 1?C4 vol %, Np(VI) is oxidized completely. Under the same conditions, Np(VI) in a concentration of (1?C5) × 10^?3 M is oxidized to almost 100%. Analysis of published data and additional experiments on the reaction of O₃ with Np(VI) ions in LiOH solutions allow a conclusion that the ozonation involves the reactions O₃ + OH^? = HO ₂ ^? + O₂, O₃ + HO ₂ ^? + OH^? = O ₃ ^? + O ₂ ^? + H₂O, and O₃ + O ₂ ^? = O ₃ ^? + O₂, followed by O ₃ ^? + NpO₂(OH) ₄ ^2? = O₂ + NpO₄(OH) ₂ ^3? + H₂O. In addition, HO ₂ ^? reduces Np(VII) and Np(VI) and reacts with O ₃ ^? . Certain contribution is made by the reaction Np(VI) + O₃ = Np(VII) + O ₃ ^? . The dependence of the Np(VII) accumulation rate on [O ₃ ^gas ]^0.5 was interpreted in terms of the concept of a heterogeneous-catalytic process.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>(OH)(CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>)<Subscript>3</Subscript>]<Subscript>2</Subscript>(ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The complex [UO₂(OH)(CO(NH₂)₂)₃]₂(ClO₄)₂ (I) was synthesized. A single crystal X-ray diffraction study showed that compound I crystallizes in the triclinic system with the unit cell parameters a = 7.1410(2), b = 10.1097(2), c = 11.0240(4) Å, α = 104.648(1)°, β = 103.088(1)°, γ = 108.549(1)°, space group \(P\bar 1\), Z = 1, R = 0.0193. The uranium-containing structural units of the crystals are binuclear groups [UO₂(OH)· (CO(NH₂)₂)₃] ₂ ²⁺ belonging to crystal-chemical group AM²M ₃ ¹ [A = UO ₂ ²⁺ , M² = OH^?, M¹ = CO(NH₂)₂] of uranyl complexes. The crystal-chemical analysis of nonvalent interactions using the method of molecular Voronoi-Dirichlet polyhedra was performed, and the IR spectra of crystals of I were analyzed.     

Cation-cation interaction in mixed-valent An(IV)/Np(V) tribromoacetates [An(NpO2)(H2O)3(CBr3COO)5]·CBr3COOH·nH2O,An = Th(IV), Np(IV)

The structure of new mixed-valent An(IV)/Np(V) compounds [An(NpO₂)(H₂O)₃(CBr₃COO)₅]·CBr₃COOH·nH₂O, where An(IV) = Th and Np, was studied. Two independent Np(V) atoms have the coordination surrounding in the form of pentagonal bipyramids with the O atoms of NpO ₂ ⁺ dioxocations in apical positions; the equatorial planes of the bipyramids are constituted by the O atoms of five CBr₃COO^? ions. Two independent An(IV) atoms have the oxygen surrounding in the form of distorted tricapped trigonal prisms (CN = 9) constituted by the O atoms of four CBr₃COO^? ions, two NpO ₂ ⁺ cations, and three water molecules. Eight of ten independent CBr₃COO^? anions link the An⁴⁺ and NpO ₂ ⁺ cations in the bidentate bridging fashion into electrically neutral chains [An(NpO₂)(H₂O)₃(CBr₃COO)₅]n, and two CBr₃COO^? anions interact with two independent NpO ₂ ⁺ dioxocations in the monodentate fashion. CBr₃COOH and water molecules are located between the layers. In the [An(NpO₂)(H₂O)₃(CBr₃COO)₅]n chains, NpO ₂ ⁺ cations alternate with An⁴⁺ cations, and mixed-valent An(IV)/Np(V) cation-cation interaction arises, in which each NpO ₂ ⁺ cation acts as a bidentate ligand and An⁴⁺ acts as coordination center for two dioxocations. [Th(NpO₂)(H₂O)₃(CBr₃COO)₅]·CBr₃COOH·2H₂O is the first example of a Th(IV) compound in which cation-cation bonds with the NpO ₂ ⁺ ions are present.