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

1-(3-methyl phenyl piperazin-1-yl)-2-(quinolin-2-yl) ethane (Centhaquin) an d its analogs showed potent hypotensive activity. As the interaction of a d rug with its receptor is the rate-limiting step in eliciting its biological response, the knowledge of its conformation is of key importance. The conf ormation of Centhaquin was determined by X-ray diffraction, but this determ ination 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, F ourier 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 intensit ies. The theoretically calculated frequencies were tabulated along with the spectrally observed ones. Good agreement was obtained between them and a s et of 45 force field constants was established. (C) 2000 Elsevier Science B .V. All rights reserved.