On the absorption spectra of recently synthesized carbonyl dyes: TD-DFT insights

The development of theoretical schemes allowing for efficient reproduction of the features of electronically excited states remains a challenging task. In that framework, time-dependent density functional theory (TD-DFT) has emerged as an efficient approach for reproducing and understanding the UV/visible spectra of large solvated molecules. In this paper, we investigate the ground and excited-state properties of two carbonyl dyes presenting very similar structures but possessing absorption peaks differing by both their transition energies and their band shapes. Using a global (PBE0) and a range-separated hybrid (CAM-B3LYP), we obtain consistent conclusions demonstrating, for this couple of dyes, the necessity to go beyond the vertical TD-DFT approximation even for a qualitative interpretation. These simulations are striking examples of the interest of using more refined theoretical schemes for correctly evaluating the transition energies of specific carbonyl dyes.