Quadrupole splittings in liquid crystals

Similar to the situation for quadrupole-induced relaxation, the quadrupole splitting in liquid crystals is zero if the molecular symmetry is tetrahedral or higher. Electric field gradients are zero for such symmetries so there can be no quadrupolar interaction. However, one expects to see small splittings from tetrahedral or octahedral derivatives because of structural distortions. These predominately arise from specific interactions with extraneous materials such as lipophilic headgroups in surfactant systems, as seen, for instance, in both cationic and anionic octahedral cobalt(III) species [23], Much larger splittings will be expected from other structure... 

Halogen Quadrupole Splittings of Covalent Compounds in Liquid Crystals... 

The first system for which quadrupole splittings of ions in liquid crystals were observed was the octylammonium chloride-decanol-water system. Here the lamellar phase, built up of alternating amphi-... 

A review [525] on the NMR-quadrupole splitting method for studying ion binding in liquid crystals has recently been prepared, surveying the underlying theory and, inter alia, halide ion splitting results and their interpretation. 

Quadrupole splittings of a covalent halogen compound in liquid crystals were first observed in Cl NMR spectra of CH2CI2 in polybenzyl-L-glutamate by Gill, Klein, and Kotowycs (14). Quadrupole splittings of halide ions in amphiphilic mesophases were first observed in 1971 by Lindblom, Winnerstrom, and Lindman (15). 

Lithium behaves differently from sodium or cesium also in the monooctanoin Li/H2 0 system. Quadrupole splittings for all the alkali metal cations are reported in decylammonium mesophases. A recent report finds Na quadrupole splittings in a nonaqueous liquid crystal in which the sodium is complexed by the cryptand C222, and this is believed to indicate that the splittings arise because of ordering effects rather than electrostatic interactions. ... 

From quadrupole splittings in nematic liquid crystals. 

The order and mobility of a labeled flexible alkyl spacer in the linear thermotropic polymeric nematic liquid crystal poly(2,2 -dimethyl-4,4 -dioxyazoxybenzenedodecanedioyl-dj0) (poly[oxy(3-methyl-1,4-phenylene)azoxy 2-methyl-1,4-phenylene)oxy(1,12-dioxo-1,12-dodecanediyl-d2oll) is explored with deuterium NMR. The quadrupol splittings of the spacer methylene segments in the nematic melt of the polymer are reported as a function of the temperature and are contrasted with observations on model compounds solubilized in a nematic solvent. 

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