Density Functional Theory Investigation of the Redox Properties of Tricyclopentadienyl- and Phospholyluranium(IV) Chloride Complexes
Résumé
The redox behavior of tricyclopentadienyl- and phospholyluranium(IV) chloride complexes L3UCl with L = C5H5 (Cp), C5H4Me (MeCp), C5H4SiMe3 (TMSCp), C5H4tBu (tBuCp), C5Me5 (Cp*), and C4Me4P (tmp), has been investigated using relativistic density functional theory calculations, with the solvent being taken into account using the conductor-like screening model. A very good linear correlation (r2 = 0.99) has been obtained between the computed electron affinities of the L3UCl complexes and the experimental half-wave reduction potentials E1/2 related to the UIV/UIII redox systems. From a computational point of view, our study confirms the crucial importance of spin-orbit coupling and solvent corrections and the use of an extended basis set in order to achieve the best experiment-theory agreement. Considering oxidation of the uranium(IV) complexes, the instability of the uranium(V) derivatives [L3UCl]+ is revealed, in agreement with experimental electrochemical findings. The driving roles of both the electron-donating ability of the L ligand and the U 5f orbitals on the redox properties of the complexes are brought to light. Interestingly, we found and explained the excellent correlation between variations of the uranium Hirschfeld charges following UIV/UIII electron capture and E1/2. In addition, this work allowed one to estimate theoretically the half-wave reduction potential of [Cp*3UCl].