A Carbon-13 Study of Conformation and Order in 50.7 and 50.7-d1

Abstract

Abstract In principle, liquid crystal spectra should provide information on conformation and orientation as well as on ordering. The quadrupolar spectra of 4-n-pentyloxybenzylidene-4′-n-heptylaniline (50.7) and of three of its homologues have been studied previously. The homologue MBBA-d 1, where a deuteron replaces the proton on the methine carbon of the linkage group has also been studied. The crystal structure of the homologue 40.8 also exists. The aromatic carbon-13 chemical shifts of the 50.7 and the carbon-deuterium dipole-dipole splittings of 50.7-d 1 have been obtained over the entire mesogenic range. The data suggest: (1) that only the order parameter S zz is important in determining the chemical shifts and dipole-dipole splittings of the protonated carbons in the nematic and smectic A and C phases; (2) that the chemical shifts of the unprotonated carbons are, in addition to S zz, influenced either by (S xx – S yy) or by deviations from symmetry in the chemical shift tensor; and (3) that the smec...