Observations of 4-cyano-4'-alkylbiphenyls with Various Conformations by IR Spectroscopy and Density Functional Theory Calculations

Abstract

IR absorption spectra of 4-cyano-4'-alkylbiphenyl with various alkyl chain conformations were calculated with Density Functional Theory of B3LYP/6-31G(d) level. Calculated spectral patterns of phenvl ring C-H out-of-plane (CHOOP) deformation modes, which are strongly coupled with alkyl chain vibrations, show marked differences with conformational change of alkyl chain. The observed spectral patterns of CHOOP bands are well explained by the existence of 5CB conformers. Peak shifts and intensity changes of the spectra in this region with temperature are also well explained by the population changes of 5CB conformers.