PHASE-TRANSITIONS, CONFORMATIONAL LABILITY, AND INTERMOLECULAR INTERACTIONS IN ALKOXYCYANOBIPHENYLS

Vibrational spectroscopy methods (IR absorption, Raman scattering, cal culations) were used to study changes in molecular structures of alkox ycyanobiphenyls during phase transitions. The spectra were measured in the 33-3500 cm(-1) region at temperatures of 100-450 K. The temperatu re dependences of the IR bands that correspond to the noncharacteristi c vibrations of molecular fragments between the phenyl rings and the a lkyl radicals point to the conformational polymorphism of these molecu les. An analysis of the Raman bands corresponding to the characteristi c vibrations of the C-H bonds of alkyl radicals [q(CH)], the C-H and C -C bands of phenyl rings [q(CH) and Q(CC)], and the CN bonds of the cy ano groups [Q(CN)] suggests significant intermolecular interactions. T he conformational lability and intermolecular interactions are associa ted with differences in molecular packing in the substances of this ho mologous series.