POLARIZED FT-IR SPECTRA OF TRANS-STILBENE, TOLANE, PYRENE AND PHENAZINE ORIENTED IN A NEMATIC SOLVENT

FT-IR polarization spectra of trans-stilbene, tolane, pyrene and phenazine dissolved and oriented in the nematic liquid crystal ZLI-1538 (Merck) were studied with respect to their applicability for symmetry assignment of the IR bands. Obtaining knowledge on the orientation state of the solute must precede the use of the polarization spectra for this purpose since unusual orientations might sometimes take place. The pyrene molecules, for example, turn out to be oriented along an axis nearly crossing over their carbon atoms 3 and 10 while the other molecules studied are ordered along their long axes. A correction of some assignments was done.