Uranyl complexes with acetophenone oxime

The interaction of uranyl compounds with acetophenone oxime has been studied. Mixed-ligand uranyl acetophenone oximates have been synthesized. X-ray crystallography shows that, in single crystals of [UO₂(C₈H₈NO)₂{(CH₃)₂SO}₂] and [UO₂(C₈H₈NO)(NO₃){(CH₃)₂SO}₂], acetophenone oxime is coordinated to uranyl as a bidentate chelating ligand.     

Uranyl aquahydroxylaminate complexes

Uranylaqua complexes with N-methyl-, N-ethyl-, N-isopropyl-, and N,N-dimethylhydroxylamines were studied. The structure of [UO₂{(CH₃)₂NO}₂(H₂O)₂] was determined by X-ray crystallography. The N, N -dimethylhydroxylaminate ion is coordinated to uranyl through the nitrogen and oxygen atoms with the formation of a three-membered chelate ring.     

Uranyl complexes with 1,2-cycloheptanedione dioxime

Uranyl compounds with 1,2-cycloheptanedione dioxime (heptoxime) have been studied. Partial isomerization of the ligand takes place upon the formation of aqua complexes. The coordination modes of heptoxime in uranyl complexes were established by X-ray crystallography on [(UO₂)₂(C₇H₁₀N₂O₂)₂{(CH₃)₂SO}₃] single crystals: cis-(E,E)tetradentate chelating bridging and cis-(E,Z)pentadentate chelating bridging.     

Uranyl complexes with methyl derivatives of alicyclic dioximes

A reaction of uranyl dioxalate complexes with methyl derivatives of alicyclic ??-dioximes, 3-methyl-1,2-cyclohexanedione dioxime and 3-methyl-1,2-cyclopentanedione dioxime, was studied. The structure of (CN₃H₆)₄[(UO₂)₂(C₆H₈N₂O₂)(CO₃)(C₂O₄)₂] · (C₆H₁₀N₂O₂) · 2H₂O and NH₄(CN₃H₆)₃[(UO₂)₂(C₇H₁₀N₂O₂)(CO₃)(C₂O₄)₂] · 2H₂O based on binuclear complex anions with carbonate-dioximate fragment was studied by X-ray diffraction.     

Uranyl complexes of n-alkanediaminotetra-acetic acids

The uranyl complexes of n-propanediaminetetra-acetic acid, n-butanediaminetetra-acetic acid and n-hexanediaminetetra-acetic acid have been studied by potentiometry, with computer evaluation of the titration data by the MINIQUAD program. Stability constants of the 1:1 and 2:1 metal:ligand chelates have been determined as well as the respective hydrolysis and polymerization constants at 25 degrees in 0.10M and 1.00M KNO(3). The influence of the length of the alkane chain of the ligands on the complexes formed is discussed.     

Uranyl complexes of alpha-carboxypolymethylenediaminetetra-acetic acids

The uranyl complexes of N,N,N',N'-tetrakis(carboxymethyl)-2,3-diaminopropionic acid, N,N,N',N'-tetrakis(carboxymethyl)diaminobutyric acid, N,N,N',N'-tetrakis(carboxymethyl)ornithine and N,N,N',N'-tetrakiscarboxymethyl)lysine have been studied by potentiometry, with computer evaluation of the titration data by the MINIQUAD program. Stability constants of the 1:1 and 2:1 metal:ligand chelates have been determined as well as the hydrolysis and polymerization constants at 25 degrees in 0.1M potassium nitrate. Results are compared with those obtained for the uranyl complexes of the corresponding members of the series of the polymethylenediaminetetra-acetic acids.     

Studies on uranyl complexes-III Uranyl complexes of edta

The uranyl complexes of EDTA have been studied by potentiometry ; stability constants of the 1:1 and 2:1 (metal to ligand) chelates have been determined, as well as the respective hydrolysis and polymerization constants. Possible structures for these species are discussed. To account for the abnormally high stability of UO(2)(H(2)O)HL-, hydrogen bonding between a protonated nitrogen atom of the ligand and one oxygen atom of UO(2)(2+) is suggested.     

Uranyl complexes with di-2-pyridyl ketone and di-2-pyridyl sulphide

Uranyl complexes of the type UO₂L_nX₂, where L is di-2-pyridyl ketone or di-2-pyridyl sulphide and n = 2 (X = Cl, NCS, ClO₄) or n = 1 (X = NO₃), have been prepared and characterized by elemental analyses, molar conductivity and thermoanalytical measurements.IR spectral data suggest that both ligands in all complexes act as bidentate chelating agents through the two nitrogen atoms. Alcoholation of the carbonyl group occurs in the complexes of di-2-pyridyl ketone obtained from alcoholic media.Conductivity measurements indicate that the thiocyanate and nitrate complexes are non electrolytes in MeNO₂ solution whereas the perchlorate complexes are 1:2 electrolytes.     

Uranyl and lanthanide complexes of the 1,2-dipyridylethylene isomers

Several new complexes of lanthanide(III) and uranyl cations with 1,2-di-(4-pyridyl)ethylene and 1-(3-pyridyl)-2-(4-pyridyl)ethylene have been prepared and characterized by elemental and thermal analyses, conductivity measurements and IR spectra. IR spectra show that the diimine acts generally as a bidentate bridging ligand; however, there is some evidence that complexes with the diimine monodentate to the cation are also formed. Enthalpy change and “activation energy” values for the thermal dissociation reaction of the lanthanide nitrate complexes show a periodic trend along the lanthanide series.     

Thermal decomposition of metal complexes: III. Uranyl nitrate adducts with N-donor ligands

The thermal decomposition of some uranyl nitrate adducts with neutral N-donor ligands was investigated in order to correlate the “activation energy” , E^*₂, of the first step, whose shape depends on the kind of the neutral ligand, with the anti-symmetric stretching vibration ν₃ of the O—U—O group. The linear relationship

was found.Some considerations about the identification of the symmetric stretching band ν₁ have been drawn.     

Uranyl sequestration: synthesis and structural characterization of uranyl complexes with a tetradentate methylterephthalamide ligand

Uranyl complexes of a bis(methylterephthalamide) ligand (LH(4)) have been synthesized and characterized by X-ray crystallography. The structure is an unexpected [Me(4)N](8)[L(UO(2))](4) tetramer, formed via coordination of the two MeTAM units of L to two uranyl moieties. Addition of KOH to the tetramer gave the corresponding monomeric uranyl methoxide species [Me(4)N]K(2)[LUO(2)(OMe)].     

Uranyl Phosphonates with Multiple Uranyl Coordination Geometries and Low Temperature Phase Transition

Two new uranium(Ⅵ) phosphonate compounds,namely K8[N(C2H5)4]2(UO2)17(H2O)4[CH2(PO3)2]8[CH2(PO3)(PO3H)]4·16(H2O) (1) and[N(C2H5)4]4(H3O)2(UO2)10[CH2(PO3)2]5[CH2(...     

Uranyl complexes with diamide ligands: a quantum mechanics study of chelating properties in the gas phase

We report a quantum mechanical study on the complexes of UO(2)(2+) with diamide ligands L of malonamide and succinamide type, respectively, forming 6- and 7-chelate rings in their bidentate coordination to uranium. The main aims are to (i) assess how strong the chelate effect is (i.e., the preference for bi- versus monodentate binding modes of L), (ii) compare these ligands as a function of the chelate ring size, and (iii) assess the role of neutralizing counterions. For this purpose, we consider UO(2)L(2+), UO(2)L(2)(2+), UO(2)L(3)(2+), and UO(2)X(2)L type complexes with X(-) = Cl(-) versus NO(3)(-). Hartree-Fock and DFT calculations lead to similar trends and reveal the importance of saturation and steric repulsions ("strain") in the first coordination sphere. In the unsaturated UO(2)L(2+), UO(2)L(2)(2+), and UO(2)Cl(2)L complexes, the 7-ring chelate is preferred over the 6-ring chelate, and bidentate coordination is preferred over the monodentate one. However, in the saturated UO(2)(NO(3))(2)L complexes, the 6- and 7-chelating ligands have similar binding energies, and for a given ligand, the mono- and bidentate binding modes are quasi-isoenergetic. These conclusions are confirmed by the calculations of free energies of complexation in the gas phase. In condensed phases, the monodentate form of UO(2)X(2)L complexes should be further stabilized by coordination of additional ligands, as well as by interactions (e.g., hydrogen bonding) of the "free" carbonyl oxygen, leading to an enthalpic preference for this form, compared to the bidentate one. We also considered an isodesmic reaction exchanging one bidentate ligand L with two monoamide analogues, which reveals that the latter are clearly preferred (by 23-14 kcal/mol at the HF level and 24-12 kcal/mol at the DFT level). Thus, in the gas phase, the studied bidentate ligands are enthalpically disfavored, compared to bis-monodentate analogues. The contrast with trends observed in solution hints at the importance of "long range" forces (e.g., second shell interactions) and entropy effects on the chelate effect in condensed phases.     

Uranyl compounds and complexes: Electronic structure,chemical bonding and spectral properties

The electronic structure of solid compounds -UO₃, Cs₂UO₂CL₄, UO₂F₄ and complexes UO ₂ ²⁺ and UO₂(NO₃)₂ · 2H₂O has been studied by the cluster discrete variational DV X method in Dirac-Slater and Hartree-Fock-Slater approximation. The analysis of relativistic effects in the electronic structure of uranyl compounds was based on the comparison of non-relativistic and relativistic DV results. The interpretation of X-ray photoelectron spectra of -UO₃ and Cs₂UO₂Cl₄ basing on the MO model is given. The various electronic states contributions to the chemical bonding in uranyl compounds are investigated.     

Uranyl α-dioximates with neutral ligands

The interaction of uranyl compounds with different α-dioximes has been studied. Uranyl complexes with glyoxime, methylglyoxime, dimethylglyoxime, and 1,2-cyclohexanedionedioxime have been synthesized. The X-ray diffraction study of single crystals of [UO₂(C₃H₅N₂O₂)₂{(NH₂)₂CO}₂], [UO₂(C₆H₉N₂O₂)₂(H₂O)₂] · H₂O, [UO₂(C₆H₉N₂O₂)₂(H₂O)₂] · 6H₂O, and [UO₂(C₆H₉N₂O₂)₂(H₂O)₂]₂(CH₃CONH₂)₂ · 6H₂O showed a bidentate cyclic coordination of α-dioximes to the central atom through only one oxime group     

Polarography of Uranyl Complex with Chromotropic Acid

The polarography characteristic of uranyl ion in chromotropic acid solution was investigated systematically over the pH range 2.0 to 10.0 with ligand concentrations varying from 0.010 M to 0.200 M. At pH 5.5, the one-electron reversible reduction waves were obtained. The temperature coefficient of the half-wave potential was obtained to be ?0.32 mV per degree and the mean value of i_d/h^1/2 is 0.340 ± 0.003. The electrode reaction is UO₂(HA)₂^4? + c = UO₂(HA)^2? + HA^3? Where pH 5.5, an irreversible and diffusion-controlled wave was obtained. The diffusion coefficients and kinetic parameters of complex species were determined by deducing instantaneous equations.     

The solution chemistry of ethylmethylglyoxime : Part I. The proton complex

The solubility of ethylmethylglyoxime (EMG) was studied as a function of pH. The solubility K_sl in 0.1 M aqueous solution is 0.0132 ±0.0006 M. The distribution constants K_Dl of EMG between various organic solvents and 0.1 M aqueous solution were found to be —0.47 for chloroform, —0.51 for benzene, —1.10 for carbon tetrachloride and —1.83 for hexane. The acid dissociation constants were determined from potentiometric titrations; the values pK_a1=10.51 and pK_a2=12.02 were obtaining by fitting the experimental data to normalized curves. The UV spectra of 5·10^-5M EMG solutions of varying pH were measured between 210 and 290 nm. It is shown that H₂A has an absorption maximum at 226 nm and HA^-and A^2- have absorption maxima at nearly the same wavelengths, i.e. 258 and 266 nm, respectively. The spectra of HA^- and A^2- have approximately the same form. The data are compared with those of dimethylglyoxime (DMG). The distribution constants (org/aq) are 4–5 times higher for EMG. The acid dissociation constants are about the same for EMG and DMG, but EMG is more soluble in water than DMG (13.2 and 5.0 mmoles/l, respectively). The UV spectra of EMG and DMG are very similar.     

Closing Uranyl Polyoxometalate Capsules with Bismuth and Lead Polyoxocations

Uranyl polyoxometalate clusters are both fundamentally fascinating and potentially relevant to nuclear energy applications. With only ten years of development, there is still much to be discovered about heterometal derivatives and aqueous speciation and behavior. Herein, we show that it is possible to encapsulate the polyoxocations [Bi₆O₈]²⁺ and [Pb₈O₆]⁴⁺ in [(UO₂)(O₂)(OH)]₂₄^24? (denoted Bi@U₂₄ and Pb@U₂₄) in pure form and high yields despite the fact that under aqueous conditions, these compounds are stable on opposite ends of the pH scale. Moreover, [Pb₈O₆]⁴⁺ is a formerly unknown Pb^II polynuclear species, both in solution and in the solid state. Raman spectroscopic and mass spectrometric analysis of the reaction solutions revealed the very rapid assembly of the nested clusters, driven by bismuth‐ or lead‐promoted decomposition of excess peroxide, which inhibits U₂₄ formation. Experimental and simulated small‐angle X‐ray scattering data of Bi@U₂₄ and Pb@U₂₄ solutions revealed that this technique is very sensitive not only to the size and shape of the clusters, but also to the encapsulated species.