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Although hydrogen peroxide (H2O2) has been highly used in nuclear chemistry for more than 75 years, the preparation and literature description of tetravalent actinide peroxides remain surprisingly scarce. A new insight is given in this topic through the synthesis and thorough structural characterization of a new peroxo compound of Pu(IV). [ABSTRACT FROM AUTHOR]

The extraction of ruthenium by tri-n-butyl phosphate (TBP) is an issue for the PUREX process. The addition of 50 mM of 2,2ʹ-bipyridine (BIPY) reveals that ruthenium can be maintained in 3 M HNO3 aqueous solution after heating at 90°C for 4 hours. The Ru-BIPY complex was characterized using UV-Visible and Raman spectroscopies, and single crystal X-Ray diffraction. These technics are in agreement with a 1:2 complex formation in HNO3 medium. The selectivity toward uranium was studied by solvent extraction experiments: the BIPY ligand is still able to maintain ruthenium in the aqueous phase whereas uranium is still extracted. [ABSTRACT FROM AUTHOR]

Actinide +VI complexes (AnVI =UVI , NpVI and PuVI) with dipicolinic acid derivatives were synthesized and characterized by powder XRD, SQUID magnetometry and NMR spectroscopy. In addition, NpVI and PuVI complexes were described by first principles CAS based and two‐component spin‐restricted DFT methods. The analysis of the 1H paramagnetic NMR chemical shifts for all protons of the ligands according to the X‐rays structures shows that the Fermi contact contribution is negligible in agreement with spin density determined by unrestricted DFT. The magnetic susceptibility tensor is determined by combining SQUID, pNMR shifts and Evans' method. The SO‐RASPT2 results fit well the experimental magnetic susceptibility and pNMR chemical shifts. The role of the counterions in the solid phase is pointed out; their presence impacts the magnetic properties of the NpVI complex. The temperature dependence of the pNMR chemical shifts has a strong 1/T contribution, contrarily to Bleaney's theory for lanthanide complexes. The fitting of the temperature dependence of the pNMR chemical shifts and SQUID magnetic susceptibility by a two‐Kramers‐doublet model for the NpVI complex and a non‐Kramers‐doublet model for the PuVI complex allows for the experimental evaluation of energy gaps and magnetic moments of the paramagnetic center. [ABSTRACT FROM AUTHOR]

The [AnIV(DPA)3]2− series with An = Th, U, Np, Pu has been synthesized and characterized using SC-XRD and vibrational spectroscopy. First principles calculations were performed, the total electron density is analyzed using the Quantum Theory of Atoms in Molecules. Crystal field parameters and strength parameters are deduced following a previous work on the LnIII analog series e.g. [J. Jung et al., Chem. – Eur. J., 2019, 25, 15112]. The trends in the parameters along the series are compared to the LnIII complexes. They evidence larger covalent interactions and larger J mixing. [ABSTRACT FROM AUTHOR]

Attempts to synthesize plutonium(IV) silicate, PuSiO4, have been made on the basis of results recently reported in the literature for CeSiO4, ThSiO4, and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4via applying the conditions reported for thorium and uranium, an efficient method of PuSiO4 synthesis was established by applying the conditions optimized for the CeSiO4 system. This method was based on the slow oxidation of plutonium(III) silicate reactants under hydrothermal conditions at 150 °C in hydrochloric acid (pH = 3–4). These results shed new light on the potential behavior of plutonium in reductive environments, highlighting the representative nature of cerium surrogates when studying plutonium under such conditions and providing some important pieces of information regarding plutonium chemistry in silicate solutions. [ABSTRACT FROM AUTHOR]

Three tetravalent actinide (AnIV) hexanuclear clusters with the octahedral core [An6(OH)4O4]12+ (AnIV=UIV, NpIV, PuIV) were structurally characterized in the solid state and in aqueous solution by using single-crystal X-ray diffraction, X-ray absorption, IR, Raman, and UV/Vis spectroscopy. The observed structure, [An6(OH)4O4(H2O)8(HDOTA)4] ⋅HCl/HNO3 ⋅ n H2O (An=U( I), Np( II), Pu( III)), consists of a AnIV hexanuclear pseudo-octahedral cluster stabilized by DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) ligands. The six actinide atoms are connected through alternate μ3-O2− and μ3-OH− groups. Extended X-ray absorption fine structure (EXAFS) investigations combined with UV/Vis spectroscopy provide evidence for the same local structure in moderate acidic and neutral aqueous solutions. The synthesis mechanism was partially elucidated and the main physicochemical properties (pH range stability, solubility, and protonation constant) of the cluster were determined. The results underline the importance of: 1) considering such polynuclear species in thermodynamic models, and 2) competing reactions between hydrolysis and complexation. It is interesting to note that the same synthesis route with thorium(IV) led to the formation of a dimer, Th2(H2O)10(H2DOTA)2 ⋅4 NO3 ⋅ x H2O ( IV), which contrasts to the structure of the other AnIV hexamers. [ABSTRACT FROM AUTHOR]

Two crystal growth methods dedicated to very low solubilityactinidecoordination polymers have been developed and applied to the synthesisof mixed actinide(IV)–actinide(IV) or actinide(IV)–actinide(III)oxalate single crystals of a size (typically 100–300 μm)suitable for isolating them and examining their crystal structure.These methods have been optimized on mixed systems composed of U(IV)and lanthanide (surrogate of trivalent actinides) and then assessedon U(IV)–Am(III), Pu(IV)–Am(III), and U(IV)–Pu(IV)mixtures. Three types of single crystals characterized by differentstructures have been obtained according to the synthesis and the chemicalconditions. This is the first time that these well-known or recentlydiscovered key compounds are formed by crystal growth methods specificallydeveloped for actinide crystal handling (i.e., in glove boxes), thusenabling direct structural studies on transuranium element systemsand acquisition of basic data. Characterization by X-ray diffraction,UV–visible solid spectroscopy, thermal ionization mass spectroscopy(TIMS), energy-dispersive X-ray spectroscopy (EDS), and inductivelycoupled plasma atomic emission spectroscopy (ICP-AES) demonstratesthe potentialities and complementarity of the two crystal growth methodsfor obtaining the targeted mixed oxalates (actinide oxidation stateand presence of both metallic ions in the crystal). More generally,this development opens broad prospects for single crystal synthesisof novel actinide organic frameworks and their structural description. [ABSTRACT FROM AUTHOR]

Actinide +IV complexes (An IV = Th IV , U IV , Np IV , and Pu IV ) with two dipicolinic acid derivatives (DPA and Et-DPA) have been studied by 1 H and 13 C NMR spectroscopies and first-principles calculations. The Fermi contact and dipolar contributions to the actinide-induced shifts (AIS) are evaluated from a temperature dependence analysis, combined with ab initio results. It allows an experimental estimation of the axial anisotropy of the magnetic susceptibility Δχ ax and of the hyperfine coupling constants of the NMR-active nuclei. Due to the compactness of the coordination sphere, the magnetic anisotropy of the paramagnetic center is small, and this makes the contact contribution to be the dominant one, even on the remote atoms. The sign of the hyperfine coupling constants and related spin densities is alternating on the nuclei of the ligand cycle, denoting a preponderant spin polarization mechanism. This is well reproduced by unrestricted density functional theory (DFT) calculations. Those values are furthermore slightly decreasing in the actinide series, which indicates a small decrease of the covalency from U IV to Pu IV .

Actinide +VI complexes ( A n V I = U V I , N p V I and P u V I ) with dipicolinic acid derivatives were synthesized and characterized by powder XRD, SQUID magnetometry and NMR spectroscopy. In addition, N p V I and P u V I complexes were described by first principles CAS based and two-component spin-restricted DFT methods. The analysis of the 1 H paramagnetic NMR chemical shifts for all protons of the ligands according to the X-rays structures shows that the Fermi contact contribution is negligible in agreement with spin density determined by unrestricted DFT. The magnetic susceptibility tensor is determined by combining SQUID, pNMR shifts and Evans' method. The SO-RASPT2 results fit well the experimental magnetic susceptibility and pNMR chemical shifts. The role of the counterions in the solid phase is pointed out; their presence impacts the magnetic properties of the N p V I complex. The temperature dependence of the pNMR chemical shifts has a strong 1 / T contribution, contrarily to Bleaney's theory for lanthanide complexes. The fitting of the temperature dependence of the pNMR chemical shifts and SQUID magnetic susceptibility by a two-Kramers-doublet model for the N p V I complex and a non-Kramers-doublet model for the P u V I complex allows for the experimental evaluation of energy gaps and magnetic moments of the paramagnetic center., (© 2021 Wiley-VCH GmbH.)

The [AnIV(DPA)3]2- series with An = Th, U, Np, Pu has been synthesized and characterized using SC-XRD and vibrational spectroscopy. First principles calculations were performed, the total electron density is analyzed using the Quantum Theory of Atoms in Molecules. Crystal field parameters and strength parameters are deduced following a previous work on the LnIII analog series e.g. [J. Jung et al., Chem. - Eur. J., 2019, 25, 15112]. The trends in the parameters along the series are compared to the LnIII complexes. They evidence larger covalent interactions and larger J mixing.

Attempts to synthesize plutonium(iv) silicate, PuSiO4, have been made on the basis of results recently reported in the literature for CeSiO4, ThSiO4, and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4via applying the conditions reported for thorium and uranium, an efficient method of PuSiO4 synthesis was established by applying the conditions optimized for the CeSiO4 system. This method was based on the slow oxidation of plutonium(iii) silicate reactants under hydrothermal conditions at 150 °C in hydrochloric acid (pH = 3-4). These results shed new light on the potential behavior of plutonium in reductive environments, highlighting the representative nature of cerium surrogates when studying plutonium under such conditions and providing some important pieces of information regarding plutonium chemistry in silicate solutions.