Photoswitchable ionophores based on 1,3-alternate calix[4]arenes bearing acridane units at the wide rim and bridged at the narrow rim by glycol chains

The complexation with alkali metal ions by calix[4]arenes with 1,3-alternate conformation bearing acridinium and acridane substituents at one rim and a glycol chain at the other rim has been studied by isothermal calorimetry. The thermodynamic parameters and the stoichiometry of the complexes are strongly influenced by the nature of the substituent (acridane or acridinium), by the solvent and by the length of the glycol chain. Both 9-methoxyacridane substituents are involved in the photoheterolysis leading to the corresponding acridinium calixcrowns. The nucleophilic attack of the methoxide leaving group reverses the reaction thermally. Therefore, the different complexation properties of acridane and acridinium calixcrowns can be switched on and off.