Uranium migration through the Swiss Opalinus Clay varies on the metre scale in response to differences of the stability constant of the aqueous, ternary uranyl complex Ca₂UO₂(CO₃)₃

The simulation of uranium migration through the Swiss Opalinus Clay is used as an example to quantify the influence of varying values of a stability constant in the underlying thermodynamic database on the migration lengths for the repository scale. Values for the stability constant of the neutral, ternary uranyl complex Ca2UO2(CO3)3 differ in literature by up to one order of magnitude. Within the studied geochemical system, either the neutral or the anionic complex CaUO2(CO3)32- is the predominant one, depending on the chosen value for the neutral complex. This leads to a changed interaction with the diffuse double layers (DDL) enveloping the clay minerals and thus can potentially influence the diffusive transport of uranium. Hence, two identical scenarios only differing in the value for the stability constant of the Ca2UO2(CO3)3 complex were applied in order to quantify and compare the migration lengths of uranium on the host rock scale (50 m) after a simulation time of one million years. We ran multi-component diffusion simulations for the shaly and sandy facies in the Opalinus Clay. A difference in the stability constant of 1.33 log units changes the migration lengths by 5 to 7 m for the sandy and shaly facies, respectively. The deviation is caused by the anion exclusion effect. However, with a maximum diffusion distance of 22 m, the influence of the stability constant of the Ca2UO2(CO3)3 complex on uranium migration in the Opalinus Clay is negligible on the host rock scale.

Broadening the scope of uranyl photoreactivity: The oxidation of a uranyl complex anion in solid-state materials

Reported are the syntheses, structural characterizations and luminescence properties of three novel [UO2Cl4]2 bearing compounds containing substituted 1,1’-dialkyl-4,4’-bipyridinum dications (i.e. viologens). These compounds undergo photoinduced luminescence quenching upon exposure to UV radiation. Kinetic analyses indicate the degree of quenching follows a second-order rate law with a rate constant dependent on viologen substituent. This phenomenon is proposed to involve the formal transfer of one electron from the [UO2Cl4]2- to the viologen species. This proposed mechanism is supported through a series of calculations and computational work including Rehm-Weller analysis, time-dependent density functional theory (TD-DFT), and density of states (DOS). This work constitutes the first study of an oxidized uranyl complex anion which expands the conventional understanding of uranyl photoreactivity.

Spectroscopic properties, molecular structure, anticancer and antimicrobial evaluation of some new moxifloxacin metal complexes in the presence of 1,10-phenanthroline

New series of Y(III), Zr(IV), Pd(II), La(III) and U(VI) complexes with moxifloxacin (MOX) and 1,10-phenanthroline (Phen) were synthesized and the chelation behaviours have been investigated. The complexes were characterized using elemental analysis, molar conductance, magnetic properties, thermal studies and various spectral techniques such as FT-IR, UV-Vis, 1H NMR and mass spectra. The kinetic and thermodynamic parameters (E*, ΔH*, ΔS* and ΔG*) were calculated using Coats-Redfern and Horowitz-Metzeger methods. The bond length and force constant, F(U=O), for the uranyl complex was calculated. The DFT calculations were carried out to understand the optimized molecular geometry for the compounds. The calculated data indicated that Pd(II) complex with smaller energy gap value (∆E = 0.136 au) is more reactive than all compounds and La(III) complex with greater energy gap (∆E = 0.192 au) is less reactive. All studied compounds are treated as soft (η = 0.068-0.096) except MOX treated as hard (η = 0.16). The HOMO of all complexes is localized on MOX (100%) without any density on the Phen (0%) except Pd(II) complex, the HOMO is localized on Phen (61%). The LUMO in U(VI) complex is localized mainly on the U(VI) ion (63%), and in the Y(III) complex is localized mainly on Phen (89%). The cytotoxic activities against MCF-7, HCT-116 and the antimicrobial activity were tested. KEY WORDS: Moxifloxacin, 1,10-Phenanthroline, Spectroscopy, Thermal analysis, DFT, Antitumor agents Bull. Chem. Soc. Ethiop. 2020, 34(2), 295-312 DOI: https://dx.doi.org/10.4314/bcse.v34i2.8

Sulfur-substituted uranyl stabilized by fluoride ligands: matrix preparation of U(O)(S)F2via oxidation of U(0) by SOF2

A neutral sulfur-substituted uranyl complex [U(O)(S)F2] in which the SUO2+ moiety is stabilized by electron withdrawing fluoride ligands was prepared via oxidation of U(0) by SOF2 in cryogenic matrixes.

Structural and computational characterization of a bridging zwitterionic-amidoxime uranyl complex

A bridging (μ2) neutral zwitterionic amidoxime binding mode previously unobserved between amidoximes and uranyl is reported and compared to other uranyl amidoxime complexes.

Correction: UO22+-mediated ring contraction of pyrihexaphyrin: synthesis of a contracted expanded porphyrin-uranyl complex

Correction for ‘UO22+-mediated ring contraction of pyrihexaphyrin: synthesis of a contracted expanded porphyrin-uranyl complex’ by James T. Brewster et al., Chem. Sci., 2019, 10, 5596–5602.