Pentafluorophenyl Salicylamine Receptors In Anion-Pi Interaction Studies

A crystal structure analysis confirms the appropriateness of pentafluorophenyl salicylamine (1a) as a pi-acceptor for anion-pi interactions. Crystals of 1a.HCl show that the OH-group fixes the anion in a eta(2)-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-pi interactions. Due to the hydrogen bonding, the non-fluorinated receptor exhibits the highest binding constants within this series.