FT-IR, FT-Raman, UV–Vis spectral and normal coordinate analysis of chlorzoxazone

The FT-IR (4000–400 cm−1) and FT-Raman spectra (3500–100 cm−1) of chlorzoxazone (CHLZ) have been recorded in the condensed state. Density functional theory calculation with B3LYP/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond length and bond angle), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of CHLZ is calculated using B3LYP/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charges is also calculated. Because of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV–Vis spectra and electronic absorption properties were explained and illustrated from the frontier molecular orbitals.