Pentafluorophenyl salicylamine receptors in anion–π interaction studies

Abstract

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.

Keywords:

• anion–π interaction
• pentafluoro salicylamine
• crystal structure
• NMR titration

Acknowledgement

The Academy of Finland is gratefully acknowledged for funding (grant nos 130629, 122350 and 140718 to KR).