Covalent halogen compounds crystals

Introductory Aspects. Relaxation in Molecules or Ions with Covalently Bonded Halogens. Shielding Effects in Covalent Halogen Compounds. Scalar Spin Couplings. Relaxation of Chloride, Bromide and Iodide Ions. Shielding of Halide Ions. Quadru-pole Splittings in Liquid Crystals. Halide Ions in Biological Systems. Studies of the Perchlorate Ion. 

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). 

At this point we are essentially left with two families of compounds binary charge-transfer complexes and hydrogen-bonded or halogen-bonded co-crystals. This section will focus almost exclusively upon representatives from the latter categories [67]. The terms binary/ternary supermolecule indicates a discrete species with predictable and desirable connectivity, constructed from two /three different molecular species and assembled via directional non-covalent forces [68-78]. 

The relatively small radius of F", 1.19 A, is almost identical with that of the oxide, O2-, ion (1.25 A) consequently, many fluorides and oxides are ionic with similar formulae and crystal structures, for example, CaO and NaF. The compounds of the other halogens with the same formula usually form quite different lattices and may even give molecular lattices. Thus chlorides and other halides often resemble sulfides, just as the fluorides often resemble oxides. In several cases the fluorides are completely ionic, whereas the other halides are covalent for example, CdF2 and SrF2 have the CaF2 lattice (nearly all difluorides have the fluorite or rutile structure), but CdCl2 and MgCl2 have layer lattices with the metal atoms octahedrally surrounded - by chlorine atoms.-----------------------------... 

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

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