Spectroscopic and quantum chemical electronic structure investigations of 2-(trifluoromethyl)aniline and 3-(trifluoromethyl)aniline

The FTIR and FT-Raman spectra of 2-(trifluoromethyl)aniline (2TFMA) and 3-(trifluoromethyl)aniline (3TFMA) have been recorded in the range 4000–400 and 4000–100 cm−1, respectively. The experimental vibrational frequencies were assigned and interpreted satisfactorily. The interpretation relies on the theoretical calculations at B3LYP and B3PW91 gradient methods using the standard 6-31G** and higher 6-311++G** basis sets. The frequency calculations were done in ab initio HF method with only 6-311++G** basis set. An extensive study on the vibrational, structural, thermodynamic characteristics as well as the electronic properties of 2TFMA and 3TFMA 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 structural and electronic properties. The influences of the substituents on the structural and electronic properties have been analysed. The intramolecular hydrogen bonds responsible for many features of 2TFMA were analysed. The 1H and 13C FTNMR spectra have been recorded and 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method. UV–visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach.