Tetrabenzylcyclen as a receptor for fluoride

Abstract

A tetraazacyclic ligand, tetrabenzylcyclen (L), was synthesized using an improved method with a higher yield by treatment of cyclen with benzylchloride in the presence of potassium carbonate. The reaction of L with an aqueous solution of fluorosilicic acid yielded a mixed-anionic salt with the composition [H₃L][F][SiF₆]·4H₂O (1). The single crystal X-ray study revealed that the macrocyclic tri-cation essentially changes the conformation compared to the free ligand in order to tightly accommodate the fluoride inside and to keep the hexafluorosilicate anions and water molecules outside in the solid state complex.