Excitation energies for anionic drugs predicted by PBE0, TPSS and τHCTH density functionals

Abstract

Numerous benchmarking studies dealing with TD-DFT calculated excitation energies for neutral molecules are reported in the scientific literature. However, charged species, both anionic and cationic, have received much less attention from this point of view. Against this background, here we report a comparative study of calculated excitation energies corresponding to the vertical singlet-singlet electronic transitions for a set of 96 anionic compounds containing basic well-known small-sized drugs and essential medicines. The objective of the work was to check the accuracy provided by one hybrid functional (PBE0), and two meta-GGA functionals (TPSS and τHCTH) in reproducing the experimental maximum absorption wavelengths. Computed data have been compared to available experimental data found in the literature. For the selected set of anions, it is shown that the two meta-GGA functionals performs similar to PBE0, with a slight advantage of TPSS density functional, which offers better values than PBE0 for mean signed-error and mean absolute error.