Chlorine, Bromine, and Iodine Solid-State NMR Spectroscopy

We review the solid-state NMR literature for the Cl-35/37, Br-79/81, and I-127 nuclides, with coverage up to August 2008. The theory related to NMR spectroscopy of half-integer quadrupolar nuclei in powdered samples is briefly summarized, as are the experimental methods for recording such spectra. The most recent experimental results demonstrate the increasing feasibility and utility of observing solid-state NMR spectra for these nuclei, particularly chlorine-35/37. Several chlorine chemical shift tensors have been measured recently, along with their orientation relative to the electric field gradient tensor. The increased availability of ultrahigh-field solid-state NMR spectrometers (B-0 >= 18.8 T) is the dominant factor responsible for the increased number of studies and increased amount of available information. For example, insights have been gained into the hydrogen bonding environment at the chlorine atoms in various organic hydrochloride salts by interpreting trends in the chlorine quadrupolar coupling and chemical shift tensors. The sensitivity of the Cl-35/37 NMR parameters to polymorphism and pseudo-polymorphism has also been demonstrated. Important advances in quantum chemistry which are having an impact on the computation of quadrupolar and magnetic shielding tensors for these nuclei are also briefly discussed. Data available from gas-phase molecular beam and microwave spectroscopy experiments are presented. Finally, prospects for future studies of Cl-35/37, Br-79/81, and I-127 by solid-state NMR spectroscopy are presented.