Structure and topology of liquid crystalline molecules by Separated Local Field NMR

Liquid crystals are small organic molecules, commercially used for display purposes and yet important, instantly orient uniaxially when placed in a strong magnetic field. Moleculat structure and optical image of a cylindrical shape molecule is sown in left. Separated local field (SLF) solid state NMR technique is widely used to correlate anisotropic chemical shifts with heteronuclear dipole-dipole moments and yield a two-dimensional spectrum such as the one shown to the right. Azomethane, aromatic, methylene, and methyl carbon shifts are marked for demonstration. At the very buttom a new class of radio frequency pulse sequence is shown to record the SLF-2D. This sequence is designed to improve sensitivity, resolution, and measurement accuracy even at low power radio frequency pulses thus reducing the sample heating by many folds.