Vibrational and theoretical studies of the non-steroidal anti-inflamatory drugs Niflumic [2-3((3-trifluoromethyl)phenylamino)-3-pyridinecarboxylic acid]; Diclofenac [[2-(2,6-dichlorophenyl)amino]-benzeneacetic acid] and Indometacin acids [1-(4-chlorobenzo

Mid and far-infrared vibrational spectra of Indometacin [1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid], Diclofenac [[2-(2,6-dichlorophenyl)amino]-benzeneacetic acid] and Niflumic acid [2-3((3-trifluoromethyl)phenylamino)-3-pyridinecarboxylic acid] have been measured at room and low temperatures and analyzed by means of ab initio calculations. The conformational space of these compounds has been scanned using molecular dynamics and complemented with functional density calculations that optimize the geometry of the lowest-energy conformers of each species as obtained in the simulations. The vibrational frequencies were assigned using functional density calculations. The molecular electrostatic potential maps (MEPs) were obtained and analyzed and the corresponding topological study was performed in the frame of the Bader's theory (atoms in molecules).