Reliable modeling of the electronic spectra of realistic uranium complexes

Abstract

We present an EOMCCSD (equation of motion coupled cluster with singles and doubles) study of excited states of the small [UO2](2+) and [UO2](+) model systems as well as the larger U(VI)O2(saldien) complex. In addition, the triples contribution within the EOMCCSDT and CR-EOMCCSD(T) (completely renormalized EOMCCSD with non-iterative triples) approaches for the [UO2](2+) and [UO2](+) systems as well as the active-space variant of the CR-EOMCCSD(T) method-CR-EOMCCSd(t)-for the U(VI)O2(saldien) molecule are investigated. The coupled cluster data were employed as benchmark to choose the "best" appropriate exchange-correlation functional for subsequent time-dependent density functional (TD-DFT) studies on the transition energies for closed-shell species. Furthermore, the influence of the saldien ligands on the electronic structure and excitation energies of the [UO2](+) molecule is discussed. The electronic excitations as well as their oscillator dipole strengths modeled with TD-DFT approach using the CAM-B3LYP exchange-correlation functional for the [U(V)O2(saldien)](-) with explicit inclusion of two dimethyl sulfoxide molecules are in good agreement with the experimental data of Takao et al. [Inorg. Chem. 49, 2349 (2010)].