The n → π* transition in nitroso compounds: A TD-DFT study

The visible spectra of a series of various nitroso dyes have been evaluated by using time-dependent density functional theory approach and explicitly taking into account bulk solvent effects. Using the PBE0 functional with the 6-311++G(3d,3p) atomic basis set, the agreement between theoretical and experimental n → π* transition energies is excellent for all nitroso species. The mean absolute error is limited to 0.05 eV and the maximal deviation is 0.21 eV for a set of 22 cases. As a blind test, we have predicted the absorption spectra for unknown species, in order to assess the impact of the atom bound to the NO group.