Excited states and luminescent properties of UO2F2 and its solvated complexes in aqueous solution

The electronic absorption and emission spectra of free UO2F2 and its water solvated complexes below 32,000 cm(-1) are investigated at the levels of ab initio CASPT2 and CCSD(T) with inclusion of scalar relativistic and spin-orbit coupling effects. The influence of the water coordination on the electronic spectra of UO2F2 is explored by investigating the excited states of solvated complexes (H2O)nUO2F2 (n = 1-3). In these uranyl complexes, water coordination is found to have appreciable influence on the (3)Δ (Ω = 1g) character of the luminescent state and on the electronic spectral shape. The simulated luminescence spectral curves based on the calculated spectral parameters of (H2O)nUO2F2 from CCSD(T) approach agree well with experimental spectra in aqueous solution at both near-liquid-helium temperature and room temperature. The possible luminescence spectra of free UO2F2 in gas phase are predicted on the basis of CASPT2 and CCSD(T) results, respectively, by considering three symmetric vibration modes. The effect of competition between spin-orbit coupling and ligand field repulsion on the luminescent state properties is discussed.