Investigation of 4′-n-alkyl-4-cyanobiphenyls structure features by IR spectroscopy methods

With the use of IR spectroscopy methods (experiment and theory), we investigated the features of structure and intermolecular interaction in the homological rows of 4′-n-alkyl-4-cyanobiphenyls (hereafter nCB, where n is the number of carbon atoms in alkyl group (AG)). We measured the IR absorbance spectra of the samples of nCB (n=2, 4, 5, 8, 9) in the 400–4000 cm−1 frequency region in the 26–100 °C temperature range for solid crystal (SC), liquid crystal (LC), and isotropic liquid (IL). We performed theoretical simulation of the IR spectra of the nCB molecules (n=1–9) with taking into account their conformational mobility. We performed the analysis of the measured spectra with taking into account available X-ray data concerning intermolecular interaction in these substances. On the basis of theoretical modeling, we presented the interpretation of the existing data. We found conformational inhomogeneity of the samples in various phase states and estimated the influence of intermolecular interaction as a structure-forming factor.