Photochemistry of f-element ions

Published data on photochemical reactions of f-element compounds, namely, uranyl ion and lanthanide and actinide ions, are surveyed and analyzed. The types of reactions of photoexcited ions, reaction mechanisms, and analytical applications of the photochemical methods for the separation, isolation, and determination of f-elements are considered.     

Spectral Properties of Uranyl Nitrate Complexes with Tertiary Aliphatic Phosphine Oxides

The IR and Raman vibrational spectra of a number of uranyl nitrate complexes with tertiary aliphatic phosphine oxides in a solid phase and solutions have been investigated. It is found that the spectral characteristics of these complexes are independent of the state of aggregation of the substance. From the analysis of experimental and predicted data on vibrational spectra and application of the spectral signs of coordination of the NO₃ ^– ligand a conclusion is drawn on the formation of insular type structures. It is established that the presence of neutral organophosphorus ligands in the composition of the complexes does not exert any effect on the applicability of the spectral criteria of coordination of the nitrate acidoligand.     

Metal-Carboxyl Helical Chain Secondary Units Supported Ion-Exchangeable Anionic Uranyl–Organic Framework

As a less explored avenue, actinide-based metal-organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an azobenzenetetracarboxylate-based anionic MOF supported by uranyl–carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain-type building unit is reported for the first time in uranyl-based MOFs. Structural analysis reveals that the formation of helical chain secondary units can be attributed to restricted equatorial coordination of rigid flat azobenzene ligand to uranyl centres. Meanwhile, this newly-synthesized anionic material has been used to remove Eu³⁺ ions, as a non-radioactive surrogate of Am³⁺ ion, through an ion-exchange process with [(CH₃)₂NH₂]⁺ ions in its open channels, as evidenced by a combination of ¹H NMR spectroscopy, EDS and PXRD.     

Pb(UO2)(V2O7), a novel lead uranyl divanadate

A new lead uranyl divanadate, PbUO₂(V₂O₇), has been synthesized by high temperature solid-state reaction and its crystal structure was solved by direct methods using single-crystal X-ray diffraction data. It crystallizes in the monoclinic system with space group P2₁/n and following cell parameters: a=6.9212(9) Å, b=9.6523(13) Å, c=11.7881(16) Å, β=91.74(1)°, V=787.01(2) Å³, Z=4, ρ_mes=5.82(3), ρ_cal=5.83(1) g/cm³. A full-matrix least-squares refinement on the basis of F² yielded R₁=0.029 and wR₂=0.064 for 2136 independent reflections with I>2σ(I) collected with a Bruker AXS diffractometer (MoKα radiation). The crystal structure of PbUO₂(V₂O₇) consists of a tri-dimensional framework resulting from the association of V₂O₇ divanadate units formed by two VO₄ tetrahedra sharing corner and UO₇ uranyl pentagonal bipyramids and creating one-dimensional elliptic channels occupied by the Pb²⁺ ions. In PbUO₂(V₂O₇), infinite ribbons of four pentagons wide are formed which can be deduced from the sheets with Uranophane type anion-topology that occurs, for example, in the uranyl divanadate (UO₂)₂(V₂O₇), by replacement of half-U atoms of the edge-shared UO₇ pentagonal bipyramids by Pb atoms. Infrared spectroscopy was investigated at room temperature in the frequency range 400-4000 cm⁻¹, showing some characteristic bands of uranyl ion and of VO₄ tetrahedra.     

Cluster model for complex compounds of hexavalent uranium

We have studied the regular patterns of the change in the electronic transition frequency in low-temperature luminescence spectra of uranyl trinitrate and tetranitrate crystals with alkali metal cations or an NH ₄ ⁺ group as the outer-sphere cations, as a function of the ionization potential of the latter. An analogous study was carried out as a function of the ratio of the concentrations of impurity and matrix for different cations in mixed crystals and solid solutions. Analysis of the results obtained, together with available crystallographic data, allowed us to propose a cluster model for the uranyl complex. The observed regular patterns are also explained from the standpoint of statistical thermodynamics. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 588–591, September–October, 2006.     

Solute activity coefficients in dilute aqueous electrolyte mixtures. III. The ternary system HClO4+UO2(ClO4)2+H2O at 25°C

Isopiestic vapor pressure comparison measurements were conducted with the three-component system HClO₄+UO₂(ClO₄)₂+H₂O in the concentration range between I=0.05 and 1.9m. Analysis of the mixture composition and concentration dependence of the osmotic coefficients with the Scatchard neutral-electrolyte and ion-component methods and with the Pitzer ioncomponent methods gave equally satisfactory results. Prediction of the observed osmotic coefficients by two-component approximations was satisfactory, and the data agreed well with values estimated with a model based on the osmolal fraction. A fair concordance was also found between predicted solute activity coefficients from simple models and values derived from complete treatments which included interaction terms.     

正辛烷为稀释剂不对称N-甲基-N-辛基烷基酰胺萃取铀(Ⅵ)的研究(英)

The extraction of uranyl nitrate was studied with newly synthesized unsymmetrical alkylamides, Nmethyl-N-octyloctylamide (MOOA), N-methyl-N-octyldecanamide (MODA), and N-methyl-N-octyldodecanamide (MODOA), employing n-octane as diluent. The effect of the concentrations of nitric acid, sodium nitrate and extractants on the extraction was investigated and the extraction mechanism was suggested. The effect of temperature on the extraction was also studied and the related thermodynamic functions were calculated. The extracted species were characterized by FTIR spectrometry。     

N、N′-二乙基-N、N′-二苯基脲的萃取性能和二硝酸二(N、N′-二乙基-N、N′-二苯基脲)合铀酰(Ⅱ)配合物的合成、结构研究

The extraction behavior of N,N′-diethyl-N,N′-dibenzenyl-urea (DEDBU) to Uranium(Ⅵ) and Thorium(Ⅳ) from nitric acid solution was studied by using xylene as diluent. The effects of aqueous HNO₃ concentration and ex-tractant concentration on the extraction distribution ratio of U(Ⅵ) and Th(Ⅳ) were studied, and the results show that the extraction behavior of the extractant to U(Ⅵ) is similar to tributyl phosphate (TBP), the solvation numbers for DEDBU and TBP are two, respectively. Under the experiment condition, the extractant does not show the extraction behavior to Th(Ⅳ), this result exhibits that the extractant has good application to separate U(Ⅵ) and Th(Ⅳ). The crystal structure of the complex UO₂(NO₃)₂[CH₂(CH₂)₂CONC₈H₁₇]₂ was determined by single crystal X-ray diffraction. Crystal data: C₂₄H₄₆N₄O₁₀U, triclinic, space group , a = 8.662(2)?, b= 10.07(2)?, c= 10.895(3)?, α = 103.77(2)°, β = 92.01(2)°, γ = 96.23(2)°, V= 915.7(4)?³, M_r = 934.78, Z= 1, D_c= 1.695 g·cm^-3, F(000) = 462, μ = 4.495mm-1, R= 0.0250, wR= 0.0591, observed reflec-tions 3566 (I>2σ(I)).The central uranyl ions is coordinated by six oxygen atoms, two of them are from the carbonyl groups of N,N′-diethyl-N,N′-dibenzenyl-urea molecules, and the other four are from two nitrate groups.