Modeling of vibronic structure of absorption spectrum of 2-(2′-hydroxyphenyl)benzoxazole

Vibronic structure of the absorption spectrum is modeled for the first electronic transition in the isolated molecule of 2-(2'-hydroxyphenyl)benzoxazole that exhibits excited state intramolecular proton transfer. The long-range corrected density functional with empirical dispersion interaction omega B97X-D3 is found to provide good correspondence of the modeled vibronic structure to the first absorption band of the spectrum measured in solution at room temperature. At the same time energy of the absorption band is overestimated by about 0.37 eV. A number of approximations for description of the potential energy surface of the molecule in the excited state within the harmonic approximation are discussed.