2017. 58, 1 UDC 548.737 SOLVENT EFFECTS ON THE NH STRETCHING OF 1-(4-PYRIDYL)PIPERAZINE C. Parlak Department of Physics, Science Faculty, Ege University, Izmir, Turkey E-mail: cparlak20@gmail.com Received November, 18, 2015 The solvent effects on the NH stretching of 1-(4-pyridyl)piperazine (1-4pypp, C9H13N3) are investigated by density functional theory (DFT). <...> The B3LYP hybrid density functional is used with the 6-311+G(3df,p) basis set in the polarizable continuum model (PCM). <...> The calculated frequencies of the solvent-induced NH stretching vibrations are correlated with some solvent parameters such as the Kirkwood—Bauer—Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters, and the linear solvation energy relationships (LSER). <...> The findings of this research can be useful for piperazines. <...> Piperazines exhibit a wide range of pharmacological activities such as antibacterial, antifungal, antitubercular, anticancer, antiviral, and antioxidant [ 1 ]. <...> Solvent effects on vibrational frequencies and intensities have been well known [ 5—8]. <...> The characteristic infrared stretching vibrations of solute structures have been extensively studied. <...> There are numerous works on the solvent effect on frequencies of some groups [ 7—13]. <...> Moreover, several empirical approaches attempt to characterize the solvent effects on vibrational frequencies, such as KBM [14, 15 ], AN [ 16 ], Swain [ 17 ], and LSER [18 ] equations. <...> We also reported the solvent effects on the vibrational frequencies of some organic compounds [ 19—21 ]. <...> In 2010, Alver and enyel examined the vibrational spectra and conformations for the powder form of 1-4pypp [ 22 ]. <...> DFT data showed that the equatorial-equatorial (e-e) conformer is the most stable form of the compound. <...> In another study conducted by Mary and coworkers in 2014 [ 23 ], the acid-base properties, vibrational spectra, NBO analysis for the single crystal form of the compound were also studied both experimentally and theoretically. <...> The conformational preference (e-e) is in agreement with the results obtained from the XRD data [ 23 ]. <...> Further, the frequencies of NH stretching vibrations were correlated with the KBM, AN, Swain, and LSER solvent scales. <...> Optimized structure for the e-e conformer of 1-4pypp illustrations were made with the GaussView 5.0.8 program [ 26 ]. <...> For all the computations, the e-e conformer of 1-4pypp in various solvents <...>