Structural, spectroscopic (FT-IR, FT-Raman and UV) studies, HOMO–LUMO, NBO, NLO analysis and reactivity descriptors of 2,3 Difluoroaniline and 2,4-Difluoroaniline

• Comparative Spectroscopic analysis of 2,3-DFA and 2,4-DFA were performed by FT-IR, FT-Raman and UV–Vis. techniques.
• DOS, PDOS and OPDOS plots show the make-up as well as bonding/anti-bonding interactions of the orbitals.
• NLO properties and NBO analysis were investigated and compared.
• Global and local reactivity descriptors along with thermo-dynamical properties were determined.

Complete vibrational analysis of the fundamental modes of 2,3-Difluoroaniline and 2,4-Difluoroaniline has been carried out using theoretical and experimental FTIR as well as FT-Raman spectral data and compared to reveal the effect of substituted F atoms on aromatic ring. Comprehensive investigation of geometrical and electronic structure in ground as well as the first excited state of both molecules has been performed. UV–Vis spectra of the title compounds were also recorded and the electronic properties, such as frontier orbitals and band gap energies were calculated by TD-DFT approach. DOS, OPDOS, natural atomic charges, molecular electrostatic potential surface and thermo-dynamical properties have been calculated to get a better insight of the properties of the title compounds. Non-linear optical properties such as dipole moment, polarizability, first static hyperpolarizability were also calculated to predict their NLO behavior. Stability of the compounds arising from hyper-conjugative interaction and charge delocalization has been analyzed using Natural bond orbital (NBO) analysis. Global and local reactivity descriptors have been computed to predict reactivity and reactive sites on the molecules.

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