The coordinative properties of perfluoro-15-crown-5 with monocations were investigated using 19F 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 O2- and F- in the gas-phase, this is the first study that quantitatively confirms cation binding to a perfluorocrown ether.
Bibliographical noteFunding Information:
This project was supported by the National Science Foundation (grant CTS-0428046 ) and the National Institute of Health (grant 1R01 EB005225-01 ). We also thank the University of Minnesota for sponsoring this work through a Louise T. Dosdall fellowship to C.-Z. L.
- Ion-selective electrodes
- Perfluorocrown ether