We present a state-of-the-art computational study of the uranyl(vi) and uranyl(v) cation-cation interactions (dications) in aqueous solution. Reliable electronic structures of two interacting uranyl(vi) and uranyl(v) subunits as well as those of the uranyl(vi) and uranyl(v) clusters are presented for the first time. Our theoretical study elucidates the impact of cation-cation interactions on changes in the molecular structure as well as changes in vibrational and UV-Vis spectra of the bare uranyl(vi) and uranyl(v) moieties for different total spin-states and total charges of the dications.
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Controlled and sequential single-electron reduction of the uranyl dication.
Dalton Trans
October 2024
EaStCHEM School of Chemistry, Joseph Black Building, University of Edinburgh, Edinburgh EH9 3FJ, UK.
A flexible tripodal pyrrole-imine ligand (HL) has been used to facilitate the controlled and sequential single-electron reductions of the uranyl dication from the U(VI) oxidation state to U(V) and further to U(IV), processes that are important to understanding the reduction of uranyl and its environmental remediation. The uranyl(VI) complexes UO(HL)(sol) (sol = THF, py) were straightforwardly accessed by the transamination reaction of HL with UO{N(SiMe)}(THF) and adopt 'hangman' structures in which one of the pyrrole-imine arms is pendant. While deprotonation of this arm by LiN(SiMe) causes no change in uranyl oxidation state, single-electron reduction of uranyl(VI) to uranyl(V) occurred on addition of two equivalents of KN(SiMe) to UO(HL)(sol).
View Article and Find Full Text PDFEffects of coordinating heteroatoms on molecular structure, thermodynamic stability and redox behavior of uranyl(vi) complexes with pentadentate Schiff-base ligands.
RSC Adv
August 2022
Laboratory for Zero-Carbon Energy, Institute of Innovative Research, Tokyo Institute of Technology 2-12-1 N1-32, O-Okayama, Meguro-ku Tokyo 152-8550 Japan
Uranyl(vi) complexes with pentadentate NO-, NO- and NOS-donating Schiff base ligands, Bu,MeO-saldien-X (X = NH, O and S), were synthesized and thoroughly characterized by H NMR, IR, elemental analysis, and single crystal X-ray diffraction. The crystal structures of UO(Bu,MeO-saldien-X) showed that the U-X bond strength follows U-O ≈ U-NH > U-S. Conditional stability constants ( ) of UO(Bu,MeO-saldien-X) in ethanol were investigated to understand the effect of X on thermodynamic stability.
View Article and Find Full Text PDFDisproportionation of the Uranyl(V) Coordination Complexes in Aqueous Solution through Outer-Sphere Electron Transfer.
Inorg Chem
December 2021
Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
Among the linear actinyl(VI/V) cations, the uranyl(V) species are particularly intriguing because they are unstable and exhibit a unique behavior to undergo H promoted disproportionation in aqueous solution and form stable uranyl(VI) and U(IV) complexes. This study uses density functional theory (DFT) combined with the conductor-like polarizable continuum model approach to investigate [UO] to [UO] reduction free energies (RFEs) and explores the stability of uranyl(V) complexes in aqueous solution through computing disproportionation free energies (DFEs) for an outer-sphere electron transfer process. In addition to the aqua complex (U1), another three commonly encountered ligands such as chloride (U2), acetate (U3), and carbonate (U4) in aqueous environmental conditions are taken into account.
View Article and Find Full Text PDFEffects of Substituents on the Molecular Structure and Redox Behavior of Uranyl(V/VI) Complexes with NO-Donating Schiff Base Ligands.
Inorg Chem
August 2021
Laboratory for Zero-Carbon Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 N1-32, O-okayama, Meguro-ku, Tokyo 152-8550, Japan.
Uranyl(VI) complexes with pentadentate NO-donating Schiff base ligands having various substituents at the (R) and/or (R) positions on phenolate moieties, R,R-saldien, were synthesized and thoroughly characterized by H nuclear magnetic resonance, infrared, elemental analysis, and single-crystal X-ray diffraction. Molecular structures of UO(R,R-saldien) are more or less affected by the electron-donating or -withdrawing nature of the substituents. The redox behavior of all UO(R,R-saldien) complexes was investigated to understand how substituents introduced onto the ligand affect the redox behavior of these uranyl(VI) complexes.
View Article and Find Full Text PDFQuenching Mechanism of Uranyl(VI) by Chloride and Bromide in Aqueous and Non-Aqueous Solutions.
J Phys Chem A
May 2021
Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
A major hindrance in utilizing uranyl(VI) luminescence as a standard analytical tool, for example, in environmental monitoring or nuclear industries, is quenching by other ions such as halide ions, which are present in many relevant matrices of uranyl(VI) speciation. Here, we demonstrate through a combination of time-resolved laser-induced fluorescence spectroscopy, transient absorption spectroscopy, and quantum chemistry that coordinating solvent molecules play a crucial role in U(VI) halide luminescence quenching. We show that our previously suggested quenching mechanism based on an internal redox reaction of the 1:2-uranyl-halide-complex holds also true for bromide-induced quenching of uranyl(VI).
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