Second-order quadrupolar effects for directly bonded and remote13C–79/81Br spin pairs in high-resolution13C NMR spectra of solids

Abstract

High-resolution solid-state 13C NMR spectra of 1,4-dibromobenzene, 1,3,5-tribomobenzene, 1,2,4,5-tetrabromobenzene and hexabromobenzene (recorded at several different magnetic field strengths from 4.7–14.1 T) are reported. The bandshapes for 13C nuclei directly bonded to 79/81Br nuclei are characteristic multiplets arising from the effects of second-order quadrupolar interactions and both direct and indirect dipole–dipole interactions between 13C and 79/81Br. Numerical simulations have been used to obtain data on dipolar coupling constants and/or anisotropies in indirect coupling. In these simulations, effects arising from interaction with the directly bonded 79/81Br nucleus, intramolecular interactions with 79/81Br nuclei in the ortho, meta and para positions relative to the 13C nucleus, and intermolecular interactions with 79/81Br nuclei in neighbouring molecules were considered. Spectra are also presented for a range of other organic solids containing bromine.