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Wpływ częściowego uporządkowania orientacji cząsteczek na ich widma NMR dużej zdolności rozdzielczej

Ejchart A., Gryff-Keller A.

Wiadomości Chemiczne

2000

[Z] 54, 11-12

949-969

Molecules of solute in the liquid phase can display partial orientation owing to the interaction of an anisotropic magnetic susceptibility tensor with an external magnetic field or/and to the interaction with anisotropic liquid crystal solvent. In the latter case orientation of the solvent molecules is caused by the magnetic field as well. Formal, statistic description of the solute molecular orientation is identical in both cases and it has been demonstrated without recalling to the Wigner rotation matrices. Since the orientation of solute molecules is not averaged out due to the rotational diffusion completely, several interactions, additional to the isotropic liquid phase, manifest in the NMR spectra, namely, dipolar nad quadrupolar interactions as well as anisotropic parts of chemical shifts (screening) and spin-spin couplings. Therefore, a number of structural molecular parameters, which depend on those interactions, become accessible. Determination of very accurate geometries of small organic molecules and the accuracy improvement of the NMR-derived structures of biomolecules are the most frequent applications of the NMR studies in anisotropic phases. Analysis of the NMR spectra of 3,5-dichlorphenylacethylene in the nematic solvent ZLI1169 has been presented as an example of the liquid crystal solvent application.