Quantum chemical studies of structural, vibrational, NBO and hyperpolarizability of ondansetron hydrochloride

• FT-IR and FT-Raman spectra were recorded and compared with the theoretical results.
• The theoretical calculations were made using HF/DFT/B3LYP/6-311++G(d,p) method.
• The absorption spectrum has been compared with the experimental UV–vis data.
• Variation of different thermodynamic properties with temperature has been given.
• The nonlinear optical properties have been calculated.

In this communication, the geometry optimization, molecular electrostatic potential surface, wavenumber and intensity of the vibrational bands of all the possible modes of dihydrated ondansetron hydrochloride have been calculated using ab initio Hartree–Fock (HF) and density functional theory (DFT) employing B3LYP functional with 6-311++G(d,p) basis set. We have compared the calculated IR and Raman wavenumbers with the observed data. Mulliken atomic charges, HOMO–LUMO gap (ΔE), ionization potential, dipole moments and total energy have also been obtained for the optimized geometry of the molecule. UV–vis spectrum has been recorded in ethanol solvent. The TD-DFT method is used to calculate the electronic absorption parameters in gas phase as well as in solvent environment using IEF-PCM model employing 6-31G basis set. The nonlinear optical properties have been calculated. Natural bond orbital (NBO) analysis, which deals about the intra- and intermolecular charge delocalization between the bonds of a molecular system, has been done. Variation of the different thermodynamic properties with temperature has also been reported.