K Ermolaev | PubMed Health

PubMed2000

An improved broadband decoupling sequence for liquid crystals and solids.

Recently we developed an efficient broadband decoupling sequence called SPARC-16 for liquid crystals ¿J. Magn. Reson. 130, 317 (1998). The sequence is based upon a 16-step phase cycling of the 2-step TPPM decoupling method for solids ¿J. Chem. Phys. 103, 6951 (1995). Since then, we have found that a stepwise variation of the phase angle in the TPPM sequence offers even better results. The application of this new method to a liquid crystalline compound, 4-n-pentyl-4'-cyanobiphenyl, and a solid, L-tyrosine hydrochloride, is reported. The reason for the improvement is explained by an analysis of the problem in the rotating frame.

Crystallization↗

PubMed1999

13C 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 13C spectra of liquid crystals has been studied, and the results are compared with those obtained by using two well-established methods (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 application in the PELF method. Copyright 1999 Academic Press.

Journal Article↗