© 2015 IEEE. Vibrational spectrum of molecules is an important characteristic of the material, which allows to identify different molecular structures. Determination of vibrational frequencies complete set is needed for the calculation of the thermodynamic functions of simple substance formation. We found complexes of 4-n-pentyl-4′-cyanobiphenyl (CB5) molecules with the most advantageous energy structure in a vacuum. Also frequencies of the normal vibrations of the studied systems were calculated. CB5 molecule is widely used as a liquid crystal, the properties of which were studied using various computational and experimental methods [1]-[6]. Cyanobiphenyl liquid crystal phase CB5 was observed by infrared spectroscopy with the frequency of 2252 cm-1. In this regard, we can assume that vibration band consists of several points corresponding to different values of oscillation frequencies.