Cation-Coordinating Properties of Perfluoro-15-Crown-5.

The coordinative properties of perfluoro-15-crown-5 with monocations were investigated using (19)F NMR spectroscopy and ion-selective electrodes with perfluoro-15-crown-5 as the matrix of their sensor membranes and the fluorophilic tetrakis[3,5-bis(perfluorohexyl)phenyl]borate as ion exchanger site. The results show that perfluoro-15-crown-5 interacts weakly but significantly with Na(+) and K(+). Assuming 1:1 stoichiometry, the formal complexation constants were determined to be 5.5 and 1.7 M(-1), respectively. This weak binding is consistent with the strong electron withdrawing nature of the many fluorine atoms in the perfluorocrown ether. While perfluorinated crown ethers have been known to form host-guest complexes with the anions O(2) (-) and F(-) in the gas phase, this is the first study that quantitatively confirms cation binding to a perfluorocrown ether.