Order Parameters and Carbon Shielding Tensors of Some Anthracene Derivatives from 13 C NMR Experiments

The orientational order parameters and approximate 13 C shielding tensors of anthracene and of six of its 9,10-derivatives, 9,10-dihydroanthracene, 9,10-dimethylanthracene, 9,10-dibromoanthracene, anthraquinone, 9,10-diphenylanthracene, and 9,10- bis (phenylethynyl)anthracene, dissolved in the nematic liquid crystal ZLI-1167 have been determined using a recently proposed 13 C NMR method. The biaxial order parameters obtained are compared with some current theoretical models of ordering. We find that none of these mean field approaches have fully satisfactory predictive capabilities.