The intramolecular β-fluorine⋯ammonium interaction in 4- and 8-membered rings.

The structures of 3-fluoroazetidinium hydrochloride and 3-fluoro-1,5-diazacyclooctane hydrobromide are explored both by X-ray diffraction analysis and DFT calculations, and the conformations of these molecules are shown to be significantly influenced by the through space C–F⋯N+ interaction