Effect of the fluorine substitution in ethyl groups of 1,4-distyrylbenzene on the fine structure fluorescence and fluorescence excitation spectra

Abstract

The fine-structure fluorescence and fluorescence excitation spectra of conjugated chain compounds, 1,4-distyrylbenzene (DSB) and its fluorine-substituted derivative α,ω-1,4-distyrylbenzene, have been obtained by the Shpolskii method in an n-octane matrix at a temperature of 4.2 K. These spectra have been simulated by representing the band of each of the vibronic transitions as the sum of a zero-phonon line and a phonon wing with the corresponding parameters, such as the half-widths of the spectral lines and the Debye-Waller factors. Based on this simulation, the relative intensities of vibronic transitions have been determined and the frequencies of normal vibrations in the S 0 and S 1 * states have been refined. It has been found that the energy of the purely electronic transition in the molecule of the fluorine-substituted derivative is higher by 950 cm−1 compared to the unsubstituted DSB. The parameters of the Franck-Condon and Herzberg-Teller interactions have been determined. The observed violation of the mirror symmetry between the conjugated spectra is explained by the interference of intramolecular interactions.