Density Functional Theory Calculation and Raman Scattering of the Antihistamine Ebastine

The vibrational properties of ebastine have been investigated by density functional theory (DFT) calculations and Raman scattering experiments. The DFT calculation was performed with geometry optimization and harmonic vibration using the B3LYP function with the 6-31G(d) basis set. The DFT calculated spectrum of ebastine is in good agreement with Raman scattering experiments. A good linear correlation between calculated and experimental wavenumbers has been obtained in the spectral range of 500–3250 cm –1 . Also, the calculated bond lengths and bond angles of the ebastine molecule are consistent with reported X-ray diffraction results. The deviations of bond lengths and bond angles are smaller than 0.034 Å and 3.1°, respectively. In addition, the experimentally observed vibrational modes have been assigned and the characteristic modes of the three parts benzhydryloxy, piperidine-butanone, and tert-butylphenyl of the ebastine molecule have been discussed, which would be helpful for future degradation and activity studies of ebastine.