ИСТИНА

The vibronic structure of absorption and emission spectra bears a lot of information, which can hardly be extracted directly via immediate processing of experimental data. Computer simulation of vibronic spectra can help one to analyze the contributions of different factors. The nature of absorption bandshapes of dibenzoylmethanatoboron difluoride (DBMBF2) dye substituted in ortho-, meta-, and para-positions of the phenyl ring is investigated using DFT and TD-DFT with the range-separated hybrid CAM-B3LYP functional and the 6-311G(d,p) basis set. The solvent effects are taken into account within the polarized continuum model. The vibronic bandshape is simulated using time-dependent linear coupling model with vertical gradient approach through an original code. For flexible chromophores, the spectra of individual conformers are summed up with Boltzmann factors. It is shown that the long-wavelength absorption band shape of DBMBF2 derivatives is determined by three factors: the relative statistical weights of conformers with different electronic absorption patterns, the relative position and intensity of the second low-energy electronic transition, and the vibronic structure of individual electronic peaks. The simulated spectra of the dyes in study are in a good agreement with the available experimental data and explain the observed spectral features.