Quadrupole Splittings of Halide Ions in Amphiphilic Mesophases

Therefore, for e.g. halide ions, the information provided is the product of quadrupole coupling constant and an order parameter and there is no unambiguous way of separating these quantities. In spite of this difficulty, the quadrupole splitting method, in providing unique qualitative binding information, is of great value. 

The counterions in amphiphile-water mesophases can reside in different binding positions which are characterized by different quadrupole splittings. It is certainly reasonable to assume that in most cases the rate of exchange of counterions between the different environments is much more rapid than the difference in quadrupolar splitting between the different sites. (The situation where exchange is slower has been treated by Persson et al, [406],) In this case the observable first-order splittings are given by 

Here p is the probability for occupation of site i characterized by the field gradient q and the order parameter S. For a powder sample the second-order quadrupole splitting is given by 

First-order static quadrupole effects give for the chlorine and bromine nuclei rise to spectra analogous to that shown in Fig. 7.4. First-order quadrupole splittings have been determined for Cl in the hexagonal mesophase of the dodecyltrimethylammonium chloride-water system [1Z6 405] and for Br in the hexagonal mesophase of the hexadecyltrimethyl-ammonium bromide-water system [Z21], (The hexagonal mesophase is built 

C denotes a n-alkyl chain containing n carbon atoms. 

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Quadrupole Splittings of Halide Ions in Amphiphilic Mesophases... 

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). 

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