Vibrational structure of absorption spectrum of 2,5-bis(2-benzoxazolyl)hydroquinon

2,5-bis(2-benzoxazolyl)hydroquinone is an organic compound that undergoes intramolecular proton transfer in the excited state. The vibrational structure of the UV-Vis absorption bands of 2,5-bis(2-benzoxazolyl)hydroquinone is calculated for the first and second excited state transitions using the Franck–Condon approximation and the harmonic model for vibrations. It is found that the use of normal modes obtained with the ωB97X-D3 density functional gives good agreement with the vibronic pattern of the experimental spectrum, while the calculations overestimate the energy of the electronic transitions. The normal vibrations of the molecule, which show a large intensity of the vibronic transition, are determined.