Fourier transform infrared spectra and normal mode analysis of 1-(3-methyl phenyl piperazin-1-yl)-2-(quinolin-2-yl)ethane (Centhaquin): a potent centrally acting anti-hypertensive agent

Abstract 1-(3-methyl phenyl piperazin-1-yl)-2-(quinolin-2-yl) ethane (Centhaquin) and its analogs showed potent hypotensive activity. As the interaction of a drug with its receptor is the rate-limiting step in eliciting its biological response, the knowledge of its conformation is of key importance. The conformation of Centhaquin was determined by X-ray diffraction, but this determination is very hard for its analogs because of the difficulty in preparing their single crystals. A novel and easy approach is envisaged to determine the conformation in such cases by the application of molecular modeling, Fourier transform infrared (FTIR) spectroscopy and normal mode analysis. As a first step in this direction, the FTIR spectrum of the title compound was recorded and its normal mode analysis carried out. The assignments of the frequencies are based on the concept of group frequencies and band intensities. The theoretically calculated frequencies were tabulated along with the spectrally observed ones. Good agreement was obtained between them and a set of 45 force field constants was established.