The effect of fluorine substituents on the parameters of intra- and intermolecular interaction of 1,4-distirylbenzene molecules

We have compared and analyzed the parameters of the Franck–Condon (FC) and Herzberg–Teller (HT) interactions, which form the fine-structure spectra of stilbene, 1,4-distyrylbenzene, and tetrafluorodistyrylbenzene–compounds that are similar in their chemical structures but differ in the length of $\pi$-conjugation and in the presence of substituents in their benzene rings. The numerical values of the FC intramolecular interaction constants have been obtained, and, simultaneously, the values of the HT parameter have been found as quantitative values of the projections of the electronic transition vector of the dipole moment onto the normal vibrational coordinates. We have solved the question of transferability of these parameters in the homologous series of stilbene molecules containing the same sets of structural elements, which has made it possible to extend the use of the fragmentary approach to describe the fundamental bands of organic molecules of different homological series and to solve the problem of studying the structure of the spectra of large molecules.