Calculations of Infrared Spectra of Benzoxazoles Exhibiting Excited-State Proton Transfer by a Composite Method

Infrared spectra of 2-(2'-hydroxyphenyl)benzoxazole, 2,5-di-(2-benzoxazolyl)phenol and 2,5-bis(2-benzoxazolyl)hydroquinone are calculated by the composite method B3LYP-3c.The calculated frequencies and intensities are in good agreement with the experimental values, including the region of torsional vibrations of the bonds OH, which is not reproduced well by common density functional theory methods.The bands in the region are assigned to OH torsion modes, CH out-of-plane bending vibrations, and torsions of the aromatic and oxazole rings.