Density Functional Theory Calculations, Spectroscopic (FT-IR, FT-RAMAN), Frontier Molecular Orbital, Molecular Electrostatic Potential Analysis of 5-Fluoro-2-Methylbenzaldehyde

Abstract

Abstract The FT-IR and FT-Raman spectra of 5-fluoro-2-methylbenzaldehyde (5F2MB) have been recorded in the regions 4000–400 cm−1 and 4000–100 cm−1, respectively. Using the observed FT-IR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of vibrations of the compound were carried out. The optimum molecular geometry, vibrational frequencies and Raman scattering activities were calculated by density functional theory with B3LYP/6-311+G** basis sets. A close agreement was achieved between the calculated and observed frequencies by refinement of scale factors. Unambiguously normal modes of vibrational assignments have been made with the help of the GUASSVIEW 5.0 program and the potential energy distribution (PED) calculated by the density functional theory calculations. Natural bonding orbital (NBO) analyses were carried out to discuss the stability of the molecule. The molecular electrostatic potential (MEP) map and electron density map were drawn and analyzed. Using nuclear magnetic resonance (NMR) analysis, the chemical shifts of hydrogen atoms and carbon atoms were calculated. The charge distribution, Mullikan atomic charge values and HOMO–LUMO energy have been calculated to explore the reasons for the change in biological activity. Furthermore, the first hyperpolarizability and the dipole moment of the molecule have also been calculated.