Arene-Bridged Diuranium Complexes: Inverted Sandwiches Supported by δ Backbonding

The paper describes the Rossendorf beamline (ROBL) built by the Forschungszentrum Rossendorf at the ESRF. ROBL comprises two different and independently operating experimental stations: a radiochemistry laboratory for X-ray absorption spectroscopy of non-sealed radioactive samples and a general purpose materials research station for X-ray diffraction and reflectometry mainly of thin films and interfaces modified by ion beam techniques.

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ROBL – a CRG beamline for radiochemistry and materials research at the ESRF

Different inner-sphere coordination environments are observed for the uranyl nitrate complexes formed with octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide and tributyl phosphate in dodecane and in the hydrophobic ionic liquids (ILs) [C4mim][PF6] and [C8mim][N(SO2CF3)2]. Qualitative differences in the coordination environment of the extracted uranyl species are implied by changes in peak intensity patterns and locations for uranyl UV−visible spectral bands when the solvent is changed. EXAFS data for uranyl complexes in dodecane solutions is consistent with hexagonal bipyramidal coordination and the existence of UO2(NO3)2(CMPO)2. In contrast, the complexes formed when uranyl is transferred from aqueous nitric acid solutions into the ILs exhibit an average equatorial coordination number of approximately 4.5. Liquid/liquid extraction results for uranyl in both ILs indicate a net stoichiometry of UO2(NO3)(CMPO)+. The concentration of the IL cation in the aqueous phase increases in proportion to the a...

Uranyl Coordination Environment in Hydrophobic Ionic Liquids: An in Situ Investigation

Actinide speciation using X-ray absorption fine structure spectroscopy

Pentavalent uranium chemistry: synthetic pursuit of a rare oxidation state.

XAS study of actinide and lanthanide solvent extraction compounds—I. UO2(NO3)2(TIBP)2 and UO2(NO3)2(TBP)2 (with TIBP = tri-isobutylphosphate and TBP = tributylphosphate)

Xas study of actinide solvent extraction compounds. ii: UO2(NO3)2(L)2 (with L=tri-isobutylphosphate, tri-n-butylphosphate, trimethylphosphate and triphenylphosphate)

X-ray Absorption Spectroscopy (XAS) has been used to study monocyclooctatetraene compounds of oxidation states IV and V. An updated version of ab initio code FEFF, FEFF7.0 has been tested at the L3 edge of uranium in order to extract reliable phases and amplitudes. EXAFS best fit structural parameters have shown the lengthening of the U-Ligand distances with the increasing electronic charge of the complex. XANES at the L3 and M5 edges shows the screening effect of the additional 5/ electron when the oxidation state of U varies from V to IV.

R. Guillaumont

Papers

XAS study of actinide and lanthanide solvent extraction compounds—I. UO2(NO3)2(TIBP)2 and UO2(NO3)2(TBP)2 (with TIBP = tri-isobutylphosphate and TBP = tributylphosphate)

Xas study of actinide solvent extraction compounds. ii: UO2(NO3)2(L)2 (with L=tri-isobutylphosphate, tri-n-butylphosphate, trimethylphosphate and triphenylphosphate)

X-ray absorption spectroscopy of organouranium compounds in the (+v) and (+iv) oxidation states