D. Sandstrom et Hh. Levitt, STRUCTURE AND MOLECULAR ORDERING OF A NEMATIC LIQUID-CRYSTAL STUDIED BY NATURAL-ABUNDANCE DOUBLE-QUANTUM C-13 NMR, Journal of the American Chemical Society, 118(29), 1996, pp. 6966-6974
We have studied the mesogenic molecule 4-n-pentyl-4'-cyanobiphenyl (5C
B) in the nematic phase by double-quantum C-13 nuclear magnetic resona
nce (NMR). The experiment detects selectively the very rare isotopomer
s containing natural pairs of C-13 spins. The C-13-C-13 dipolar coupli
ngs were interpreted in terms of the structure and orientational order
of the cyanobiphenyl fragment. Different strategies were employed to
analyze the internal motion of the core moiety. This is the first inve
stigation of molecular conformation and order which exploits magnetic
C-13-C-13 dipolar couplings in a non-labeled liquid crystal.