Spectroscopic and quantum chemical electronic structure investigations of 2-(trifluoromethyl)aniline and 3-(trifluoromethyl)aniline V. Arjunan a,⇑ , T. Rani b , S. Mohan c a Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Puducherry 605 008, India b Centre for Research and Development, PRIST University, Thanjavur 613 403, India c Department of Mathematical and Physical Sciences, Hawasa University, Hawasa, Ethiopia article info Article history: Received 7 February 2011 Received in revised form 6 March 2011 Accepted 7 March 2011 Available online 12 March 2011 Keywords: 2-(Trifluoromethyl)aniline 3-(Trifluoromethyl)aniline DFT FTIR FT-Raman UV–visible abstract 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 À1 , respectively. The experimental vibrational frequencies were assigned and interpreted satisfactorily. The interpretation relies on the the- oretical calculations at B3LYP and B3PW91 gradient methods using the standard 6-31G ÃÃ and higher 6-311++G ÃÃ basis sets. The frequency calculations were done in ab initio HF method with only 6- 311++G ÃÃ 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 prop- erties. 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 1 H and 13 C FTNMR spectra have been recorded and 1 H and 13 C 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 ener- gies, were performed by time-dependent DFT (TD-DFT) approach. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction 3-(Trifluoromethyl)aniline is used as an intermediate in the production of the herbicides fluometuron and norflurazon. It is also used as an intermediate for pharmaceuticals [1]. Fluorinated com- pounds are the most significant chemicals due to their biological activities [2–5]. The administration of 4-(trifluoromethyl)aniline (4TFMA) initially suppressed the utilisation of labelled thymidine for splenic DNA synthesis. 4TFMA caused a significant increase of incorporation of labelled thymidine into DNA thymine also in the thymus. It appears that enhanced incorporation of labelled thymi- dine into splenic and thymic DNA is a phenomenon specific for compounds bearing the ACF 3 group on the 4-position of the phenyl ring, such as 4TFMA. Increased incorporation of labelled thymidine into spleen and thymus DNA apparently represents an increased DNA synthesis and cellular proliferation in lymphatic organs. The proliferative response was possibly evoked by the preceding hemo- lysis or by other toxic effects caused by the drug [6]. The presence of trifluoromethyl group in bioactive compound induces great changes in molecular properties like hydrophobicity, solubility, special biometric effect and electronegativity [7]. The combination of vibrational spectroscopy coupled with quantum mechanical calculations can be a powerful method for understanding the structural, conformational, vibrational and elec- tronic behaviour of molecules. Electronic correlation to the calcula- tions is necessary to get more reliable results on the structural parameters, physio-chemical properties and vibrational properties [8,9]. The DFT calculations with the hybrid exchange–correlation functional B3LYP and B3PW91 have been proved to be very effec- tive [10–13] for vibrational studies of fluorinated compounds [14], and show better agreement with the experimental values of struc- tural characteristics. Thus, in the present investigation, owing to the industrial and biological importance of 2TFMA and 3TFMA, the FTIR and FT-Raman vibrational frequencies are determined and by using quantum chemical calculations the wavenumbers were theoretically calcu- lated. Detailed vibrational analyses were carried out, in an effort to provide possible explanations for the experimentally observed vibrational fundamentals and to understand the effect of trifluoro- methyl group on the characteristic frequencies of aniline moiety. The potential energy distributions (PED) which where aided by ab initio calculations, has also been carried out using Wilson’s FG 0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2011.03.015 ⇑ Corresponding author. Tel.: +91 413 2211111, mobile: 9442992223; fax: +91 413 2251613. E-mail address: varjunftir@yahoo.com (V. Arjunan). Journal of Molecular Structure 994 (2011) 179–193 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc