Showing papers on "Uranyl published in 1977"
TL;DR: The Gibbs free energies, enthalpies and entropies of 42 dissolved uranium species and 30 uranium-bearing solid phases have been critically evaluated from the literature and estimated when necessary for 25°C.
2,019 citations
TL;DR: In this paper, the quenching of uranyl luminescence by water molecules was satisfactorily interpreted by an electron transfer mechanism in terms of oxidation-reduction potentials of the uranyl ion and water molecule.
55 citations
TL;DR: In this paper, the luminescence lifetimes of uranyl aquo ion, 1:1 and 1:2 uranyl fluoro complexes were determined to be 2.4, 75 and 150 μs, respectively (25°C, 0.1 M HClO 4, μ = 1).
51 citations
TL;DR: In this paper, the existence of three phases in gamma uranium trioxide between 373°K and 77°K has been studied and the three phases are closely related and the transitions smooth and displacive.
50 citations
TL;DR: In this article, the crystal and molecular structure of uranyl diperchlorate heptahydrate, UO2[ClO4]2·7H2O, has been determined by single-crystal X-ray methods.
Abstract: The crystal and molecular structure of uranyl diperchlorate heptahydrate, UO2[ClO4]2·7H2O, has been determined by single-crystal X-ray methods. The crystals are orthorhombic, space group Pca21, with unit-cell dimensions a= 9.302(4), b= 14.692(6), and c= 10.842(5)A, Z= 4. 493 Reflections have been measured by a diffractometer and the structure solved by heavy-atom methods to R 0.046. The crystal contains [UO2(OH2)5]2+,2[ClO4]–, and 2H2O in each asymmetric unit, held together by hydrogen bonds. The uranium has pentagonal-bipyramidal co-ordination with U–O(uranyl) of 1.71 A(average), U–O(aqua) of 2.45 A(average), and O ⋯ O contacts of 2.88 A.
46 citations
TL;DR: In this article, the equilibrium in solution between tricarbonate and dicarbonates of the uranyl ion has been investigated, and it has been shown that these species are the only species of UO2(CO3)22− existing in solutions of sodium bicarbonately in the concentration range 003 M-015 M.
46 citations
TL;DR: In this article, the quenching reaction of uranyl luminescence by metal ions in a lower valence state such as Fe 2+, Tl + and Ce 3+ is diffusion-controlled and the dominant process of the reaction is concluded to be an electron transfer from quenchers to uranyl ion.
45 citations
TL;DR: In this paper, the reaction of the primary alcohols in the presence of titanium(IV) chloride or uranyl chloride was examined under several conditions, and a possible scheme for the reactions was suggested.
Abstract: α,β-Unsaturated carbonyl compounds and esters, cyclopropyl ketones, β-diketones, Schiff’s bases, and nitriles were irradiated in several alcohols in the presence of titanium(IV) chloride or uranyl chloride. In the titanium(IV) chloride-catalyzed reactions, the α-carbon atom of the primary alcohols underwent a bond formation, generally with the C=X (or C≡N) carbon atom of the substrates, while the bond formation occurred on a C=C carbon atom of the substrates in the uranyl chloride-catalyzed reactions. The reactions were examined under several conditions, and a possible scheme for the reactions was suggested.
36 citations
TL;DR: In this paper, the X-ray excited electron spectra from two uranium fluorides, UF 4 and K 2 UF 6, were analyzed by comparison with previously reported ESCA measurements on uranium oxides and uranyl compounds.
31 citations
TL;DR: In this paper, a series of dioxouranium(VI) complexes were synthesised with the tetradentate Schiff base ligands (N 2 O 2 donor set) obtained by the condensation of ethylenediamine with salicyladehyde(H 2 salen), acetylacetone (H 2 aaen) or benzoyl acetone (h 2 baen) and ter-dentate bases derived by condensing of Salicylaldehyde with glycine(glysal), o -aminophenol(APhSal) or 2
31 citations
TL;DR: In this paper, the tunnel effect theory of radiationless transitions is applied to the quenching of the uranyl ion excited state by aliphatic compounds, and the most important mechanism kinetically is suggested to involve chemical quench via hydrogen abstraction, and rates for these reactions are analysed theoretically.
Abstract: The tunnel-effect theory of radiationless transitions is applied to the quenching of the uranyl ion excited state by aliphatic compounds. The most important mechanism kinetically is suggested to involve chemical quenching via hydrogen abstraction, and rates for these reactions are analysed theoretically. Good agreement between theory and experiment is observed for a number of alcohols and ethers, and the reactions are suggested to possess considerable charge-transfer character. With t-butanol it is suggested that abstraction occurs preferentially from the hydroxylic hydrogen. Theoretical analysis of the rates of hydrogen abstraction from carboxylic acids suggests that the reaction geometry in this case may be different from the reaction with alcohols or ethers. The possibility that excited uranyl ion can abstract a hydrogen atom from water is examined, and theoretical evidence is presented to suggest that this is the main route for deactivation of uranyl ion lowest excited state in water at room temperature.
TL;DR: In this article, the authors characterized benzyltrimethyl-ammonium µ2-peroxo-bis[trichlorodioxouranate(VI)], containing one of the first examples of a complex containing a dioxygen molecule.
Abstract: The interaction in air of benzyltrimethylammonium chloride with uranyl sulphate in methanol solution, containing sulphuric acid, has provided a variety of products one of which we have now characterized as benzyltrimethyl-ammonium µ2-peroxo-bis[trichlorodioxouranate(VI)], containing one of the first examples of a complex containing a dioxygen molecule, bonding as a µ2-peroxo-linkage. The crystals are monoclinic, P21/c, with a= 8.869(5), b= 11.013(5), c= 25.60(1)A and β= 103.7(1)°. The asymmetric unit contains [N(PhCH2)Me3]2[UO2Cl3(O2)½], Z= 4. An automatic Weissenberg diffractometer was used to measure 2 442 independent reflections using MO-Kα, radiation at room temperature. The structure was refined by full-matrix least squares to R= 0.114 and R′= 0.072. The anion consists of two distorted coplanar Cl3O2 pentagons. They surround the uranyl groups which lie perpendicular to the plane of the pentagons and which are linked by a bridging oxygen molecule in which both oxygen atoms are equidistant from both uranium atoms.
TL;DR: The direct polarographic determination of uranium and iron in acetylacetone after extraction of the chelate from aqueous solution has been developed and it is found that both metal acetylacetonates are reduced more reversibly and at more positive potential than in the pure solvent.
TL;DR: In this article, the separation of iron(III), copper(II), and uranyl(II) ions from a series of salt solutions by chelating ion exchange on Duolite CS-346 resin by pH control is described.
TL;DR: The application of the Hydrolysis Process to the fabrication of (U, Pu)O 2 microspheres is described in this paper, where a uranium feed solution of high uranium concentration is prepared from concentrated uranyl nitrate-urea solution by adding solid hexa-methylentetramine.
TL;DR: In this article, the stability constants and enthalpies of thorium(IV)- and uranyl(VI)-malonate complexes were determined by potentiometric and calorimetric titrations in 1.00 M solutions of Na(ClO 4 ) at 25°C.
TL;DR: In this paper, the tripeptide glutathione complexes of different molar ratios were prepared and studied by IR, PMR, electronic absorption and circular dichroism spectra.
TL;DR: In this article, the dissolution of β-UO3 in acid and carbonate solutions has been studied as functions of stirring rate, hydrogen-ion concentration, carbonate concentration, various other cations and anions in solution, and temperature.
Abstract: The kinetics of dissolution of β-UO3 in acid and carbonate solutions have been studied as functions of stirring rate, hydrogen-ion concentration, carbonate concentration, various other cations and anions in solution, and temperature. The dissolution rates are: (i) independent of stirring rate, (ii) dependent on the 0.5 order in [H+] in acid solutrons and a substantially lower order in carbonate solutions; (iii) inhibited by the presence of cations in solution in the order Mg2+ > Li+ > Na+ > [NH4]+ > K+ Cs+ in acid solutions and Na+ > [NH4]+ > Cs+ K+ in carbonate solutions, the relative effects of the cations in the acid and carbonate solutions being very similar; (iv) increased by sulphate but unaffected by chloride, nitrate, and perchlorate ions in acid solutions; and (v) characterised by activation energies of ca. 12 kcal mol–1 in acid solutions and 15 kcal mol–1 in carbonate solutions. The observed kinetic data have been rationalised in terms of a charge-transfer (c.t.) mechanism, in which the transfer of charged complexes of the uranyl and oxide ions of the β-UO3 lattice across the electrochemical-potential barrier at the solid–solution phase boundary is the rate determining step during the dissolution reaction. In HCl, HClO4, and HNO3 the c.t. species are the uranyl and protonated oxide ions of the lattice, while in H2SO4 sulphatouranate complexes are also involved. In carbonate solution the dicarbonatouranate ion and the protonated oxide ion are the c.t. species. The β-UO3 dissolution reactions are interesting examples of c.t. kinetics since the oxide anions and uranyl cations of the β-UO3 lattice form complexes with the cations and anions in the solutions in the process of dissolution and these complex-formation reactions are mirrored in the rate expressions for dissolution.
TL;DR: The tetrahydrofuran complex of uranyl nitrate UO/sub 2/(NO/sub 3/)/sub 2/ 2C/sub 4/H/sub 8/O was prepared and its crystal structure was determined as discussed by the authors.
Abstract: The tetrahydrofuran complex of uranyl nitrate UO/sub 2/(NO/sub 3/)/sub 2/ 2C/sub 4/H/sub 8/O was prepared and its crystal structure was determined. Cell parameters of a = 9.412 (7) A, b = 12.649 (9) A, C = 7.237 (5) A, ..beta.. = 117.12 (6), and V = 766.8A were determined. The molecular structure was found to consist of a U atom on a center of symmetry coordinated to eight O atoms. The two uranyl O atoms were found to be perpendicular to the plane of the remaining coordinating O atoms. (BLM)
TL;DR: In this article, the preparation, physical and chemical properties of a variety of mononuclear and binuclear complexes containing Schiff base ligands derived from 3-formysalicylic acid and diamines are reported.
TL;DR: In this paper, the interaction between M 2 UO 2 Cl 4, n H 2 O (M = Rb, Cs) and O 2 (OH) 2 leads to new complexes M 2U 2 O 5 Cl 4, 2H 2 O.
TL;DR: In this article, the stability constants for complexes formed by uranyl ion with amino acids were determined by pH titrations at 31°C and μ = 0.1 (NaClO 4 ) in the pH rang 1.7-3.5.
TL;DR: In this article, the polarographic investigation of the reaction between uranyl and diethyldithiocarbamate ions in DMSO evidentiates two prevailing complex species: UO2(DEDTC)+ and UO 2(DDA)−3.
TL;DR: In this paper, the vibrational behavior of the Ca1-xSrxUO4 solid solutions suggests that two of these modes are conveniently described by internal motions of the uranyl group, viz. symmetric stretch (696 cm−1) and librational motions.
TL;DR: In this paper, the formation of uranyl ion complexes in DMSO was investigated using the polarographic method, and the 3:1 and 1:1 glycolate complexes gave distinct cathodic waves, while the 2.1 M tetrabutylammonium perchlorate was used as supporting electrolyte.