A comparison of proton-detected C-13 local field experiments with deuterium NMR at natural abundance for studying liquid crystals

Emsley, J.W., Lesot, P., De Luca, G., Lesage, A., Merlet, D. and Pileio, G. (2008) A comparison of proton-detected C-13 local field experiments with deuterium NMR at natural abundance for studying liquid crystals. Liquid Crystals, 35 (4), 443-464. (doi:10.1080/02678290801935887).

Abstract

A comparison is made between the information which can be derived on structure, conformation and orientational order of the molecules in a nematic liquid crystal 4-pentyl-4'-cyanobiphenyl (5CB) from the NMR spectra of the deuterium atoms at natural abundance (NAD NMR), and the two-dimensional proton-detected 13C local field experiment (PDLF). The nine residual quadrupolar splittings, ?? k , obtained experimentally have been compared with quadrupolar tensors and a geometry and conformational potentials calculated by the DFT method B3LYP/6-311G**. The PDLF experiment yielded 42 scaled 13C-1H residual dipolar couplings, kD CiHj . The scaling factor, k, is determined experimentally by comparing unscaled and scaled residual dipolar couplings in a sample of fluorobenzene dissolved in a nematic liquid crystalline solvent. The corrected residual dipolar couplings, D CiHj , are used to investigate the structure and rotational potentials about each bond in the molecule.

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Contributors

Author: G. Pileio

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