X-ray and vibrational analysis of amino and chloro bibenzyl 4,4′-derivatives supported by quantum chemical calculations

Abstract

Two derivatives of bibenzyl, 4,4′-diaminobibenzyl and 4,4′-dichlorobibenzyl, were studied for the first time by X-ray diffraction and vibrational spectroscopy in this work. The vibrational assignment was made in detail using Raman and IR measurements accompanied by DFT simulations performed in hybrid B3LYP version employing 6-31G (d,p) basis set. The normal modes interpretation was carried out on the basis of a potential energy distribution obtained by VEDA program. The structural diversity, consisting in the existence of eight crystallographically independent structures, is observed for DCBB while only one structure was revealed in crystal of DABB. This difference is attributed to the stabilization effect provided by intermolecular interactions between the amino groups and water molecules included in the crystalline structure of DABB. Trustworthy shortening of C (sp3)-C (sp3) bond length in ethane fragment was established in the crystal structures of both compounds and is explained by torsional vibration of C—Ph bonds. The characteristic vibrational modes of ethane fragment were assigned in the experimental Raman and IR spectra. The vibrations with participation of functional groups were also distinguished in the measured spectra. The obtained new data about bibenzyl derivatives could contribute in a better understanding of physical chemistry of compounds with freedom of rotation around the central C–C bond that is significant for targeted development of nanomachines and other prospective molecular systems.