Theoretical anharmonic Raman and infrared spectra with vibrational assignments and NBO analysis for 2,3,4,5,6-pentafluoroaniline

2,3,4,5,6-Pentafluoroaniline (PFA) is a very attractive object to theoretical study of fluorine interaction with an aromatic ring. Two major opposite effects are observed in PFA: interaction of the σ–π electron donating amino group, promoting electrophilic substitution at the ortho/para position by increasing the electron density at the ortho/para carbons versus fluorine substituents. This very strongly withdraws electron density from the aromatic system through the σ bond (inductive effect) and donates electron density through the π system (resonance effect). The stability of PFA arising from hyper conjugative interaction is investigated with natural bond orbital (NBO) analysis. The influences of the fluorine atoms on the geometrical and electronic properties as well as the detailed interpretation of vibrational spectra and potential energy distribution (PED) are also reported. The assignment of fundamental frequencies is confirmed by the qualitative agreement between the observed and calculated wavenumbers.