BR-79,BR-81 EFFECTS IN THE HIGH-RESOLUTION C-13 NMR-SPECTRA OF SOLID BROMOAROMATIC COMPOUNDS - DIPOLAR AND INDIRECT (BR-79,BR-81,C-13) INTERACTIONS STUDIED BY INVERSE FIRST-ORDER PERTURBATION-THEORY

Splittings in the C-13 cross-polarization magic angle spinning spectra of 1, 4-dibromobenzene and 4-bromo-3,5-dimethylpyrazole are reported. They arise from (Br-79,Br-81,C-13) interactions influenced by the quadrupolar nature of the bromine nuclei. They are analysed using both 'inverse' perturbation and exact theories to yield data on both isotropic and anisotropic coupling, including the signs. The spectra also enable the sign of the bromine quadrupole coupling constant to be confirmed as positive.