A TDDFT and PCM-TDDFT studies on absorption spectra of N-substituted 1,8-naphthalimides dyes

The electronic absorption spectra of 39 N-substituted 1,8-naphthalimides dyes have been investigated in the framework of time-dependent density functional theory (TDDFT) and polariable continuum TDDFT (PCM-TDDFT). The B3LYP and PBE0 hybrid functionals together with 6-31+G(d) basis set were selected to calculate the excitation energies of 3-30 lowest-lying singlet excited states. Comparing the experimental spectra with calculated excitation energy, the mean absolute error (MAE) of TD-B3LYP/6-31+G(d) is 0.21 eV. Including solvent effect, the PCM-TD-B3LYP/6-31+G(d) provides a very high accuracy for compounds 1-5 (in cyclohexane) and 20-26 (in chloroform), but a larger error with 0.37-0.47 eV for compounds 6-19 and 27-39 (in DMF). The PBE0 hybrid functional provides a slight higher accuracy than B3LYP. The MAE is 0.28 eV for PCM-TD-B3LYP/6-31+G(d), and 0.21 eV for PCM-TD-PBE0/6-31+G(d), respectively. All calculation reveals that the maximum absorption band mainly results from the π → π∗ transition from HOMO to LUMO.