Intramolecular hydrogen bonding in N-salicylideneaniline: FT-IR spectrum and quantum chemical calculations

Abstract

FT-IR and FT-Raman spectra of N-salicylideneaniline (SAn) and its deuterated analogue (D-SAn) are recorded, and the theoretical calculations are performed on their molecular structures and vibrational frequencies. The same calculations are performed for SAn in different solutions using the polarizable conductor continuum model (CPCM) method. Comparisons between the spectra obtained and the corresponding theoretical calculations are used to assign the vibrational frequencies for these compounds. The spectral behavior of SAn upon deuteration is also used to distinguish the positions of OH vibrational frequencies. The hydrogen bond strength of SAn is investigated by applying the atoms-in-molecules (AIM) theory, natural bond orbital (NBO) analysis, and geometry calculations. The harmonic vibrational frequencies of SAn are calculated at B3LYP and X3LYP levels of theory using 6–31G*, 6–311G**, and 6–311++G** basis sets.The AIM results support a medium hydrogen bonding in SAn. The observed νOH/νOD and γOH/γOD for SAn appear at 2940/2122 and 830/589 cm−1, respectively.