The Fourier transform infrared (FT-IR) and FT-Raman spectra of 4-nitro-3-(trifluoromethyl)aniline (NTFA) were recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Utilizing the observed FT-IR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compounds was carried out. Extensive studies on the vibrational, structural, thermodynamic characteristics as well as the electronic properties of NTFA were carried out using ab initio and DFT methods. In this kind of systems, the position of the substituent group in the benzene ring as well as its electron donor-acceptor capabilities play a very important role on the molecular and electronic properties. The values of the total dipole moment (μ) and the first order hyperpolarizability (β) were computed using B3LYP/6-311++G(d,p) and B3LYP/6-311G(d) calculations. The Mulliken's charges, the natural bonding orbital (NBO) analysis on 4-nitro-3-(trifluoromethyl)aniline, 4-nitro-3-(trichloromethyl)aniline and 4-nitro-3-tribromomethyl)aniline were carried out for various intramolecular interactions that are responsible for the stabilization of the molecule. Thermodynamic functions of the investigated molecule were also computed. The calculated HOMO-LUMO energies show that charge transfer occurs in the molecule. The influence of fluorine, amino and nitro group on the geometry of benzene and its normal modes of vibrations has also been discussed.
Keywords: HOMO–LUMO; MEP surface; NBO analysis and perturbation theory; Thermodynamic properties; Vibrational spectra.
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