Determination of the average orientation of 4-phenylpyridine in nematic solvent by means of infrared linear dichroism: Study of its conformational dependence on the dihedral angle between aromatic rings

A method using IR linear dichroic measurements for determination of the average orientation of the twisted 4-phenylpyridine in a nematic solvent is proposed. By means of this approach the relationship between orientational characteristics of solute molecule and its conformational state in nematic phase has been studied. This method combines an interactive subtraction procedure of IR polarized spectra of 4-phenylpyridine for determination of its vibrational transition moment orientation and DFT quantum chemical calculations as additional source of information of mutual orientation of aromatic subunits of the guest molecule.