NMR investigations with liquid crystals are being used to study weak molecular interactions and to provide information on the degree of ordering or molecules dissolved in a liquid crystal solvent. A sample of chloroform enriched with both carbon-13 and deuterium has been studied in a nematic solvent while being spun at the """"""""magic angel."""""""" The relative intensities of the spinning sidebands have been shown to provide information on the sign of the order parameter. We are continuing to explore the mechanism and potential applications of the effect of isotopic substitution on NMR chemical shifts of nuclei that are several bonds away from the site of substitution. Studies of a number of differently substituted binuclear aromatic molecules (including cis- and trans-stilbenes, trans-azobenzene, diphenyl-acetylene and diphenylethane) were previously reported to show isotope-induced changes in carbon-13 chemical shifts through as many as 10 chemical bonds and as small as 0.64 parts per billion. The relation of the observations to detail of molecular structure is being evaluated.
