Cation–π versus anion–π interactions: A theoretical NMR study

The influences of cation–π and anion–π interactions on NMR data have been investigated in complexes of cations and anions with 1,3,5-trifluorobenzene (TFB). Cation–π interaction increases 1JC–F, 1JC–H and the chemical shifts of hydrogen and fluorine while it decreases 1JC–C. The changes are in reverse direction in the presence of anion–π interaction. The role of geometry and electronic effects on the NMR data was considered. The distance dependence of NMR parameters has been studied in these complexes. The NMR data have been investigated in isoelectronic complexes.