C-13 NMR of liquid crystals with different proton homonuclear dipolar decoupling methods

The effect of several new homonuclear dipolar decoupling methods (frequency -switching Lee-Goldburg decoupling and two sequences based on z-rotational decoupling) on the C-13 spectra of liquid crystals has been studied, and th e results are compared with those obtained by using two well-established me thods (MREV-8 and BLEW-48). For benzene dissolved in two liquid crystalline solvents, BLEW-48 gives the best spectral resolution. The BLEW-48 sequence has also been applied to the 2D method of proton-encoded local field (PELF ) spectroscopy to study a bulk liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB). The results are compared with those obtained by using MREV-8, and it is suggested that the BLEW-48 sequence may be preferable to MREV-8 for app lication in the PELF method. (C) 1999 Academic Press.