Spectroscopic and molecular structure (monomeric and dimeric structure) investigation of 2-[(2-hydroxyphenyl) carbonyloxy] benzoic acid by DFT method: A combined experimental and theoretical study

The experimental and theoretical study on the structures and vibrations of 2-[(2-hydroxyphenyl) carbonyloxy] benzoic acid (abbreviated as HPCBA) are presented. The FT-IR and FT-Raman spectra of the title compound have been recorded in the region 4000–400 cm−1 and 4000–100 cm−1 respectively. The molecular structures, vibrational wavenumbers, infrared intensities, Raman activities were calculated using DFT (B3LYP) method with 6-31G(d,p) basis set. The most stable conformer of HPCBA is identified from the computational results. 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. Intermolecular hydrogen bonds are discussed in dimer structure of the molecule. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of HPCBA are calculated. The stability and charge delocalization of the molecule was studied by natural bond orbital (NBO) analysis. The molecule orbital contributions are studied by density of energy states (DOSs). UV–Visible spectrum of the compound was recorded in the region 200–400 nm and the electronic properties such as HOMO and LUMO energies were determined by time-dependent TD-DFT approach. Fukui functions, local softness and electrophilicity indices for selected atomic sites of the title compound are determined. Mulliken population analysis on atomic charges is also calculated. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures are calculated.

► FT-IR and FT-Raman spectra of 2-[(2-hydroxyphenyl) carbonyloxy] benzoic acid in the solid phase are recorded and analyzed. ► The optimized geometry and vibrational wavenumbers are computed using DFT method for monomer and dimer. ► The complete vibrational assignment and spectroscopic analysis have been carried out. ► The first order hyperpolarizability and HOMO, LUMO energy gap are theoretically predicted. ► The NBO analysis explained the intramolecular hydrogen bonding.