Investigation of the luminescence of [UO₂X₄]^2- (X=Cl, Br) complexes in organic phase using time-resolved laser-induced fluorescence spectroscopy and quantum chemical simulations

Hanna Oher (1) , Thomas Vercouter (1) , Florent Réal (2) , Valérie Vallet (2)

1 SEARS - Service d'études analytiques et de réactivité des surfaces
2 PCMT - Physico-Chimie Moléculaire Théorique

The luminescence properties of the [UO₂Cl₄]^2- complex in an organic phase, especially the influence of large organic counter cations, have been studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and ab initio modeling. The experimental spectrum was assigned by vibronic Franck-Condon calculations on quantum chemical methods on the basis of a combination of relativistic density functional approaches. The shape of the luminescence spectrum of the uranyl tetrachloride complex is determined by symmetrical vibrations and geometrical change upon emission. The possible change in the luminescence properties depending on the first and second uranyl coordination spheres was predicted theoretically for the [UO₂Br₄]^2- and [R₄N]₂[UO₂Cl₄] ([R₄N] = [Bu₄N], [A336]) systems. The computations reveal that for U(VI), the second coordination sphere has little influence on the spectrum shape, making speciation of uranyl complexes with identical first coordination-sphere ligands tedious to discriminate. The computed structural changes agreed well with experimental trends; theoretical spectra and peak attributions are in a good accordance with TRLFS and magnetic circular dichroism (MCD) data respectively.

Domaines: Chimie théorique et/ou physique; Chimie-Physique [physics.chem-ph]; Chimie de coordination

Hanna Oher, Thomas Vercouter, Florent Réal, Valérie Vallet. Investigation of the luminescence of [UO₂X₄]^2- (X=Cl, Br) complexes in organic phase using time-resolved laser-induced fluorescence spectroscopy and quantum chemical simulations. Inorganic Chemistry, 2020, 59 (9), pp.5896-5906. ⟨10.1021/acs.inorgchem.9b03614⟩. ⟨hal-02407977⟩