Vibrational spectroscopic, UV–Vis, molecular structure and NBO analysis of Rabeprazole

Abstract The molecular structural parameters, thermodynamic properties and vibrational frequencies of the fundamental modes of Rabeprazole have been obtained using density functional theory (DFT) technique in the B3LYP approximation and 6-31G(d,p) basis set. Detailed vibrational assignments of the observed FT-IR and FT-Raman bands have been proposed on the basis of potential energy distribution (PED). Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis (NBO). Absorption wavelengths and their assignments in UV–Vis region have been predicted, based on time-dependent density functional theory (TD-DFT) calculations. Besides, molecular electrostatic potential (MEP), HOMO and LUMO analysis, Mulliken population analysis and several other thermodynamic properties were performed by DFT method.