Anion‐π Interactions: What's in the Name?

Abstract

The studies of the anion‐π interactions advanced during the last two decades from the discussion of the mere existence of this counter‐intuitive bonding to its utilization for anion recognition and transport, catalysis, and other applications. Yet, there are substantial differences in the interpretation of nature and the driving forces of anion‐π bonding. Most surprisingly, there are still different opinions about the meaning of this term (i. e., which associations can be considered anion‐π complexes). After a brief overview of the studies in this area (including early examples of such complexes), we suggested that anion‐π bonding occurs when there is evidence of a net attraction between a (close‐shell) anion and the face of an electrophilic π‐system. This definition encompasses fundamentally similar supramolecular complexes comprising diverse π‐systems and anions and its general acceptance would facilitate a discussion of the nature and distinct driving forces of this fascinating interaction.

Examining the Antioxidant and Superoxide Radical Scavenging Activity of Anise, (Pimpinella anisum L. Seeds), Esculetin, and 4-Methyl-Esculetin Using X-ray Diffraction, Hydrodynamic Voltammetry and DFT Methods

“…Frequently, as in the case of the two coumarins described in our study, hydrogen bonding acts in a cooperative manner to stabilize the intermolecular interactions [ 39 ]. Description of the nature of anion– π interactions is still much discussed in the literature [ 40 , 41 , 42 ].…”