Quantum chemical studies, vibrational analysis, molecular structure, first order hyper polarizability, NBO and HOMO-LUMO analysis of 3-hydroxybenzaldehyde and its cation

FT-IR spectroscopy has been applied to investigate the potential nonlinear optical (NLO) material 3-hydroxybenzaldehyde (3HBA). The equilibrium geometry, Fukui function, harmonic vibrational frequencies, infrared intensities, and thermodynamic properties of 3HBA and its cation were calculated by HF/6-31G(d,p) and density functional theory B3LYP/6-31G(d,p), B3LYP/6-311++G(d,p) methods. The first order hyperpolarizability (βtotal) of this molecular system and related properties (β, μ, and Δα) are calculated based on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond-like weak interaction has been analyzed using natural bond orbital (NBO) analysis by using B3LYP/6-311++G(d,p) method. The results show that electron density (ED) in the σ(*) and π(*)anti-bonding orbitals and second-order delocalization energies E((2)) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The thermal stability of 3HBA and its cation is studied by the thermogravimetric analysis (TGA). The harmonic-vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR spectrum. The observed and the calculated frequencies are found to be in good agreement. The experimental spectrum also coincides satisfactorily with those of theoretically constructed spectrograms.

FT-IR; Hyperpolarizablity; NBO; TGA; Thermodynamic properties.