Pentafluorophenyl salicylamine receptors in anion–π interaction studies

A crystal structure analysis confirms the appropriateness of pentafluorophenyl salicylamine (1a) as a π-acceptor for anion–π interactions. Crystals of 1a·HCl show that the OH-group fixes the anion in a η2-type binding motif above the electron-deficient arene. Attempts to find some relevance for this weak intermolecular force in solution failed. Stronger CH–, NH– and OH–anion interactions are dominant over the weak anion–π interactions. Due to the hydrogen bonding, the non-fluorinated receptor exhibits the highest binding constants within this series.