Nematic phase nuclear magnetic resonance studies of the structure and orientation of 1,5- and 2,6-naphthyridines

The proton magnetic resonance spectra of 1,5- and 2,6-naphthyridine dissolved in the nematic liquid crystal MBBA have been analysed. The proton geometries do not give good fits to the ring skeleton structure but it appears that the carbon–hydrogen bond lengths are not all of equal length and the bond angles indicate some bending of the C—H bonds toward the adjacent nitrogen atom. The probability functions for orientation of diazanaphthalenes in nematic solvents show that nitrogen atoms in the ring framework affect the direction of principal orientation, which does not follow either the maximum molecular dimension or the inertial axis.