Parametric method for computing the structure of the excited states and the vibronic spectra of complex molecules. Absorption and fluorescence spectra of perylene

The structures of the perylene molecule in the first excited 1(1)B(2u) state and the band shape (vibrational structure) of its fluorescence and absorption spectra are computed by the parametric method. A fragmentary approach and the molecular fragments (H) > C = with the parameters obtained for acenes and polyenes are used to form molecular models ire the excited state. It is shown that a model that corresponds to the choice of fragments with the parameters of acenes is the most optimal. The theoretical spectra satisfactorily reproduce both qualitatively and quantitatively, the basic specific features of the vibrational structure of the experimental spectra. calculation results show high degree of transfer of the parameters of the method in a series of related molecules not only for acenes with "linear" arrangement of the rings (benzene, naphthalene, anthracene, etc.) but also for more complex structures (perylene). It is shown that the parametric method developed is efficient for predicting the vibronic spectra and the structure of the excited states of complex molecules.