Single Crystal Study of the 19F Shielding Tensors of a Trifluoromethyl Group

Abstract

Coherent averaging techniques are used to examine the 19F shielding tensors of the trifluoromethyl group in single crystals of silver trifluoroacetate. At room temperature, where the CF3 groups are rotating rapidly, the spectrum consists of a single line whose orientation dependence allows a determination of the orientation of the CF3 groups in the unit cell. The rigid lattice (40°K) spectra exhibit the six lines expected on the basis of the x-ray crystal structure, also determined in this work, and allow a determination of all six independent elements of each of the three incongruent chemical shift tensors.