JRP CALL information
Supported By

European Commission

Short description of the work
During this stay, the work done at HZDR-IRE was dedicated to the synthesis and the characterization of new neptunium-based coordination polymers, involving new neptunium crystal chemistry. The synthesis with 4,4’-biphenyldicaboxilic acid (H2-bpdc) in dimethylformamide (DMF) leaded to the crystallization of very nice octahedral crystals. Crystal data were collected and analyzed during this stay at HZDR-IRE. The corresponding structure revealed for the first time the isolation of the hexanuclear cluster An6O8 with neptunium in a solid state. During this stay, the same inorganic building unit was also stabilized with other carboxylate-based ligands (terephthalate and 2,6-naphtalendicarboxylate). The structural determination of these two solids is still in progress. We also analyzed the stabilization of new neptunium based clusters, from oxygen-free aqueous solutions with phthalic and mellitic acids as organic ligand precursors. We isolated two new compounds, showing also new neptunium crystal chemistries (infinite chains and layers). Based on the obtained data, several publications are expected and the manuscript will be prepared by early 2016.

Main visitor contact data
Name: christophe Volkringer
Organisation: Université de Lille

JRP Identification
JRP nr: TALI-CO5-18
JRP title: Synthesis and characterization of polymer and cluster complexes of tetravalent neptunium (Np(IV))
JRP scope: Scope 2: Actinide in the geological environment

Visited Associated Pooled Facility
Visited APF during the stay: HZDR - IRE
Name of the APF Contact Person: Harald Foerstendorf

Other APF and organisation involved in the JRP
Other organisations involved:
Other APF involved in the project: HZDR - IRE

Description of the work done at the associated pooled facility
Start date of the stay: 10/25/2015
End date of the stay: 11/12/2015
Quantity of access: 18
Access Unit: Days

Other APF visitors of the JRP during the stay
Visitor 2: Nicolas MARTIN (Université de lille)

During this stay, the work done at HZDR-IRE was dedicated to the synthesis and the structural characterization of the giant poly-oxo cluster Np38. Such type of complexes were already mentioned in the literature for uranium and plutonium but was never observed with neptunium. Our synthesis approach was based on the synthesis of U38, using a combination of tetrachloride actinide salt, benzoic acid, tetrahydrofuran and a small amount of water. In the case of neptunium, the syntheses were adapted to NpCl4 (Neptunium tetrachloride). The first attempt of Np38 synthesis gave very small crystals similar to those observed with uranium (octahedron), but too small for a single crystal X-ray diffraction (SC-XRD) analysis. Therefore, we optimized the synthesis parameters (mainly reaction time, amount of water) to improve the size and the quality of the crystals. This approach leaded to the production of Np38 crystals, good enough for SC-XRD and crystal data were collected during this stay at HZDR-IRE. The structure of Np38 was successfully solved shortly after this stay. Based on the obtained data, a manuscript is currently being prepared for publication.