Interaction of cesium ions with calix[2]furan[4]pyrrole and its fluoride complex

► Calix[2]furan[4]pyrrole (1) weakly binds cesium cations in acetonitrile. ► Complexing 1 with fluoride ions increases the equilibrium constant by one order of magnitude. ► Exchange of bound and free Cs ions is about five times slower in the fluoride complex.