VIBRATIONAL-SPECTRA AND STRUCTURE OF 4-CYANO-4'-PENTALKOXYBIPHENYL INDIFFERENT PHYSICAL STATES

The polymorphism, conformation mobility, and structure of 4-cyano-4'-p entalkaxybiphenyl (5OCB) in different physical states are studied by I R spectroscopy. The spectra were measured in the frequency range 400-4 000 cm(-1) at temperatures front 300 to 350 K. The IR spectra of 5OCB are modeled using the concept of conformational mobility of these mole cules. An analysis of the experimental and theoretical spectra reveals absorption bands whose spectroscopic parameters are sensitive to vari ations of temperature (experiment) and conformation (theory); a relati onship between these changes is established. It is concluded that the polymorphism of 5OCB is of conformation type. In the solid crystalline state, 5OCB molecules have conformations with a planar biphenyl fragm ent; the angle of orientation of the plane of the carbon framework of the alkyl radical relative to the biphenyl fragment decreases as the t emperature increases from 35 degrees in the solid crystalline state to 10% in the liquid crystalline and isotropic liquid states. In both of these states the biphenyl fragment becomes nonplanar. the angle betwe en the phenyl rings is up to 30 degrees.