Predictions of optical excitations in transition-metal complexes with time dependent-density functional theory: Influence of basis sets

The calculation of the absorption spectra of four families of transition-metal complexes (Ni(CO)(4), MnO4-, MF6 (M = Cr, Mo, W) and CpM(CO)(2) (M = Rh, Ir)) has been undertaken to unravel the influence of basis sets onto excitation energies, oscillator strengths, and assignments. Three among the most common pseudopotentials, with the corresponding valence basis sets, and two all-electron basis sets have been used for the metal center description in the framework of the time dependent Density Functional Theory (TD-DFT). Our results show that this approach does not particularly depend on the basis set used on the metal atoms. Furthermore, the chosen functional PBE0 provides transitions in good agreement with experiments, and it provides an accuracy of about 0.3 eV, comparable to that of refined post-Hartree-Fock methods.