Theoretical model for a tetrad of hydrogen bonds and its application to interpretation of infrared spectra of salicylic acid

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Abstract
Theoreticalmodel of vibrational interactions in hydrogen-bonded salicylic acid dimer is presented which takes into account the adiabatic couplings between high- and low-frequency O–H and O ⋯ O stretching vibrations, resonanceinteractions between both intermolecular hydrogen bonds and between inter- and intramolecular hydrogen bonds, and Fermi resonance between the O–H stretching fundamental and the first overtone of the O–H in-plane bending vibrations. The model is used for theoretical simulation of the ν s stretching bands of salicylic acid and its OD derivative at 300 K. The effect of deuteration is successfully reproduced by our model. Infrared, far infarared, Raman, and low-frequency Raman spectra of the polycrystalline salicylic acid and its deuterated derivative have been measured. The geometry and experimental frequencies are compared with the results of density-functional theory calculations performed at the B 3 LYP ∕ 6 - 31 + + G * * , B3LYP/cc-pVTZ, B 3 PW 91 ∕ 6 - 31 + + G * * , and B3PW91/cc-pVTZ levels. O–H, O–D, and O ⋯ O stretching frequencies are used in theoretical simulation of the ν s stretching bands.