Perfluoroalkylated Calix[4]pyrroles: fluoride ion extraction from an aqueous medium

Abstract

Octaalkenyl calix[4]pyrrole ((CH2= CH(CH2 )2 )8C4P) is highly useful for the postfunctionalization of different calix[4]pyrroles with desired functionalities. Functionalization with perfluoroalkyl chains [CF3 (CF2 )n ; Rfn ] gave perfluoroalkyl calix[4]pyrroles (Rfn (CH2 )4 )8C4P; n=6, 8), having >60% fluorine content, which created a hydrophobic environment inside the calix[4]pyrrole cavity and recognized fluoride and chloride ions in solution as well as in the solid state. The fluoride ion is extracted efficiently from aqueous CsF and TBAF solutions by using (Rf6(CH2 )4 )8C4P, as droplets. The fluorinated chain generated a hydrophobic environment which broke the hydration shell associated with the anion and separated out fluoride ions as droplets from aqueous medium. Furthermore, the fluoride ions competitively replaced chloride ions from the (Rf6(CH2 )4 )8C4P cavity