Computation and interpretation of vibrational spectra, thermodynamical and HOMO-LUMO analysis of 2-chloro-4-nitroaniline

The FT-IR (4000-400 cm) and FTRaman (4000-100 cm) spectra of 2-chloro-4-nitroaniline (2Cl4NA) have been recorded using Bruker IFS 66 V spectrometer. An ab initio HF(HF/6-311G(d,p) and DFT(B3LYP/6-311G(d,p)) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies,IR intensities and Raman activities. The study is extended to the HOMO LUMO analysis to calculate the energy gap, ionization potential, electron affinity, global hardness,chemical potential and global electrophilicity and thermodynamic properties of 2Cl4NA . A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The calculated HOMO and LUMO energies show the charge transfer occurs in the molecule. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed simulated spectrograms.