Fluorine chemical shielding tensors and crystal structure of potassium tetrafluorophthalate

Abstract

The 19F shielding tensors of the two aromatic fluorines of potassium tetrafluorophthalate (KTFP) are reported. The results indicate that the most shielded elements of the tensors lie perpendicular to the carbon ring in agreement with previous powder studies and, of the two in-plane components, the more shielded is along the CF bond. The results also show that the ``ortho effect'' of Karplus and Das is not simply additive in the case of KTFP. Such additivity has been assumed by Nehring and Saupe in their liquid crystal study of fluorine shielding tensors in multifluorobenzenes.