Theoretical study on the excited states of heteroarene chromophores: Comparison of calculated and experimental values

We compare the absorption/emission energies of three heteroaromatic chromophores, indoles, benzofurazans and coumarins, both experimentally and theoretically. First we used TDDFT and SAC-CI methods to calculate S0 → S1 vertical excitation energies corresponding to the absorptions. The excitation energies obtained by the SAC-CI method were superior to those obtained by the TDDFT method, as well as being consistent with those experimentally obtained. We thus applied the SAC-CI method to estimate the emission energies of these chromophores on the basis of the CIS- or TDDFT-optimized excited-state structures. We found a good and consistent agreement of the CIS-structure-based values with the experimental values, whereas the TDDFT-structure based values showed less good agreement.