title: Structures of Plutonium(IV) and Uranium(VI) with N,N-Dialkyl Amides from Crystallography, X-ray Absorption Spectra, and Theoretical Calculations.
abstract: The structures of plutonium(IV) and uranium(VI) ions with a series of N,N-dialkyl amides ligands with linear and branched alkyl chains were elucidated from single-crystal X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and theoretical calculations. In the field of nuclear fuel reprocessing, N,N-dialkyl amides are alternative organic ligands to achieve the separation of uranium(VI) and plutonium(IV) from highly concentrated nitric acid solution. EXAFS analysis combined with XRD shows that the coordination structure of U(VI) is identical in the solution and in the solid state and is independent of the alkyl chain: two amide ligands and four bidentate nitrate ions coordinate the uranyl ion. With linear alkyl chain amides, Pu(IV) also adopt identical structures in the solid state and in solution with two amides and four bidentate nitrate ions. With branched alkyl chain amides, the coordination structure of Pu(IV) was more difficult to establish unambiguously from EXAFS. Density functional theory (DFT) calculations were consequently performed on a series of structures with different coordination modes. Structural parameters and Debye-Waller factors derived from the DFT calculations were used to compute EXAFS spectra without using fitting parameters. By using this methodology, it was possible to show that the branched alkyl chain amides form partly outer-sphere complexes with protonated ligands hydrogen bonded to nitrate ions.
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Eléonor
authors.initials: E
authors.lastname: Acher
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Yanis
authors.initials: Y
authors.lastname: Hacene Cherkaski
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dumas
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Tamain
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Guillaumont
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Boubals
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Guilhem
authors.initials: G
authors.lastname: Javierre
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, 01314 Dresden, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Hennig
authors.affiliation: Synchrotron SOLEIL , L'Orme des Merisiers, BP 48, St Aubin, 91192 Gif sur Yvette, France.
authors.forename: Pier Lorenzo
authors.initials: PL
authors.lastname: Solari
authors.affiliation: CEA Marcoule, Nuclear Energy Division, RadioChemistry & Processes Department, DRCP 30207 Bagnols-sur-Cèze, France Bagnols sur Cèze, France.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Charbonnel