Bridging the Transuranics with Uranium(IV) Sulfate Aqueous Species and Solid Phases

International audienceIsolating isomorphic compounds of tetravalent actinides (i.e., Th IV , U IV , Np IV , and Pu IV) improve our understanding of the bonding behavior across the series, in addition to their relationship with tetravalent transition metals (Zr and Hf) and lanthanides (Ce). Similarities between these tetravalent metals are particularly illuminated in their hydrolysis and condensation behavior in aqueous systems, leading to polynuclear clusters typified by the hexamer [M IV 6O4(OH)4] 12+ building block. Prior studies have shown the predominance and coexistence of smaller species for Th IV (monomers, dimers, and hexamers) and larger species for U IV , Np IV , and Pu IV (including 38-mers and 70-mers). We show here that aqueous uranium(IV) sulfate also displays behavior similar to that of Th IV (and Zr IV) in its isolated solid-phase and solution speciation. Two single-crystal X-ray structures are described: a dihydroxide-bridged dimer (U2) formulated as U2(OH)2(SO4)3(H2O)4 and a monomer-linked hexamer framework (U-U6) as (U(H2O)3.5)2U6O4(OH)4(SO4)10(H2O)9. These structures are similar to those previously described for Th IV. Moreover, cocrystallization of monomer and dimer and of dimer and monomer-hexamer phases for both Th IV (prior) and U IV (current) indicates the coexistence of these species in solution. Because it was not possible to effectively study the sulfate-rich solutions via X-ray scattering from which U2 and U-U6 crystallized, we provide a parallel solution speciation study in low sulfate conditions, as a function of the pH. Raman spectroscopy, UV-vis spectroscopy, and small-angle X-ray scattering of these show decreasing sulfate binding, increased hydrolysis, increased species size, and increased complexity, with increasing pH. This study describes a bridge across the first half the actinide series, highlighting U IV similarities to Th IV , in addition to the previously known similarities to the transuranic elements

Polyoxometalates-Functionalized Electrodes for (Photo)Electrocatalytic Applications: Recent Advances and Prospects

International audienceThis review is intended to provide an up-to-date and comprehensive description of recent advances since the mid-2010s in the elaboration and the involvement of polyoxometalates (POMs)-functionalized (photo)electrodes in (photo)electrocatalytic reactions. Focus has been essentially placed not only on reactions of high interest, such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and CO2 reduction reaction (CDRR) but also on other more "confidential " reactions (e.g., reduction of oxyanionic species and ascorbic acid oxidation). It is now well-known that POMs represent one class of fascinating compounds largely explored in inorganic chemistry, highlighted by the large number of complexes with structural, redox, and functional diversities which make them particularly attractive as efficient electrocatalysts for a wide range of significant multiredox reactions. The transposition of homogeneous electrocatalysis to (photo)electrode-supported electrocatalysis using POMs and its derivatives undoubtedly constitutes a really promising avenue toward the development of modern electrochemical devices, which could be of high interest for applications in chemical sensing, biosensing, electroanalysis, and solar driven fuel cells

Mixed Formate-Dicarboxylate Coordination Polymers with Tetravalent Uranium: Occurrence of Tetranuclear {U 4 O 4 } and Hexanuclear {U 6 O 4 (OH) 4 } Motifs

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Isolation of thorium benzoate polytypes with discrete ThO8 square antiprismatic units involved in chain-like assemblies

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Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

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Ex-Situ Kinetic Investigations of the Formation of the Poly-Oxo Cluster U38

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Chemistry of tetravalent actinide (U and Th) carboxylates: isolation of oxo/hydroxo polynuclear clusters

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Thorium Terephthalates Coordination Polymers Synthesized in Solvothermal DMF/H2O System

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Room temperature crystallization of trichlorodioxouranate [UO2Cl3(L)] species in molecular assemblies involving aliphatic dicarboxylate linkers

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Synthesis and Crystal Structure Characterization of Thorium Trimesate Coordination Polymers

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