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|All Authors / Contributors:||
Sandrine Hilaire; Eric Simoni; Université de Paris-Sud. Faculté des Sciences d'Orsay (Essonne).
|Description:||228 p. : ill. ; 30 cm.|
|Responsibility:||Sandrine Hilaire ; sous la direction de [Eric Simoni].|
Early actinides (U, Np, Pu, Am) in a high oxidation state show a particular linear structure in bonding with pi-donor ligands (O, NR, ...). The diminution of the charge on the metallic centre due to the electronic donation from the equatorial and axial ligands allow the existence of high oxidation states for the light actinide. The particularity of the actinide stands in the fact that An 5f orbitals can take part in chemical bonding because of a partial delocalisation. In order to understand this behaviour, a study of the electronic and the geometric structure is undertaken using both theorical and experimental approaches : - Modelling of geometry and IR vibrational frequencies of compounds with formula AnO2L2n+(H2O)3 (An= U(VI) 5f0, Np(V) 5f2, Np(VI) 5f1 and Np(VII) 5f°, L=CI-, Br-, F-, CO32- and OH-) were performed by the density functional theory (DFT) using Gaussian and ADF software. Bond population and molecular orbitals composition were essentially studied. - Hydroxide, carbonate and oxalate of Neptunium (+V) and (+VI) were synthesized with the aim to study the electronic properties by different experimental way: magnetism susceptibility (SQUID), Mossbauer, XPS measurements and vibrationals spectroscopy's. - Uranium studies are focused on the water free compounds UO2Cl2(THF)3, UO2(OPPh3)4(Otf)2 and UO2(OTf)2, exhibiting more covalent bonds in the equatorial plane.