Modeling of absorption spectrum of 2,5-bis(2-benzoxazolyl)hydroquinone

Abstract

Vibronic structure of the absorption band of 2,5-bis(2-benzoxazolyl)hydroquinone is calculated for the transitions to the first excited state using the Franck-Condon approximation and harmonic model for vibrations. 2,5-bis(2-benzoxazolyl)hydroquinone is an organic compound that undergoes the excited state intramolecular proton transfer. It is found that the use of normal modes and values of energy of the electronic states calculated with the ωB97X-D3 density functional provides good agreement with the experimental spectrum, overestimating energy of the 0-0 transition by 0.13 eV. The largest intensity of vibronic transitions is demonstrated by deformation vibrations changing the distance between the oxygen and nitrogen atoms of the hydrogen bonds, a deformation vibration of the oxazole rings, deformation and stretching vibrations of the hydroquinone moiety.