Binding of fluoro-containing anions to hexaazamacrocyclic ligand: Competitive interactions of fluoride and tetrafluoroborate anions with hexaprotonated [18]aneN6

Reaction of hexaazamacrocycle, 1,4,7,10,13,16-hexaazacyclooctadecane (L = [18]aneN6) with boron trifluoride etherate in an aqueous solution of hydrofluoric acid yields the proton-transfer complex of the composition [H6L(F) (BF4)5] · 3H2O (1). X-ray crystallographic analysis shows that the macrocyclic cation adopts an unusual conformation to accommodate the fluoride anion and to keep the tetrafluoroborate anions in a close proximity. The tetrafluoroborate anions and water molecules participate in NH⋯F, NH⋯O and OH⋯F hydrogen bonding responsible for the 3D supramolecular architecture.