Structure of molecules by NMR spectroscopy using liquid crystal solvents

Abstract

Nuclear magnetic resonance spectroscopy of molecules aligned in nematic liquid crystalline media provides information on the molecular structure and order parameters. The partial alignment of the molecules in the liquid crystalline phases gives rise to residual intramolecular dipolar couplings which are dependent on internuclear distances, and therefore yield information on the structure of molecules. The dipolar couplings are in general large compared to chemical shifts, and the spectra become rapidly complex with the increase in the number of interacting spins and decrease of symmetry of molecules. In this article, the procedure for the analyses of such spectra is outlined in a pedagogical manner. The concept of the order parameter is illustrated in a phenomenological way. The utility of the technique and obtainable information is demonstrated using practical examples. ©1998 John Wiley & Sons, Inc. Concepts Magn Reson 10: 167–192, 1998