Interplay between solvent models and predicted optical spectra: A TD-DFT study of 7-OH-coumarin

Using time-dependent density functional theory, we investigate the solvatochromic effects on the optical spectra of a typical hydroxy coumarin, considering its enol, keto, anionic and cationic forms. The absorption and fluorescence transitions energies have been computed within both the linear-response (LR) and the more refined state specific (SS) approaches, with explicit solvent molecules. These energies have also been used to compute 0–0 transitions and vibrationally resolved spectra. We show that the SS approach is mandatory to describe the solvent response due to the large increase of dipole moment upon the excitation while hydrogen bonds tune both absorption and emission energies.