화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.104, No.26, 6181-6185, 2000
Determination of long-range dipolar couplings using mono-deuterated liquid crystals
A new approach is presented for the determination of long-range dipolar couplings in liquid crystals. The strategy is the use of monodeuterated compounds to observe H-2-C-13 splittings in the C-13 NMR spectra. As examples, the H-C dipolar coupling constants have been obtained from the spectra of 4'-cyanobiphenyl 2-deutero- and 6-deuterohexanoate over the whole nematic range. In addition, the H-2 NMR spectra of these compounds taken with H-1-H-1 dipolar decoupling show quadrupolar splitting and H-1-H-2 dipolar coupling. Besides the information obtained from the 1D spectra, one-bond and two-bond H-1-C-13 dipolar coupling constants of 4'-cyanobiphenyl hexanoate were determined using the method of proton encoded local field (PELF) spectroscopy in combination with off-magic-angle spinning (OMAS). The order parameters were calculated from the 2D spectra, and some of the coupling constants are compared with the H-C coupling constants obtained from the 1D experiments.