Exploring the Capability of Mechanically Interlocked Molecules in Anion Recognition: A Computational Insight

The present study elucidated the role of both hydrogen and halogen bonds, from an electronic structure perspective, in the anion recognition process by the [2]catenane (<b>1</b>) containing a moiety with hydrogen bond donors entangled with another macrocyclic halogen bond donor. Spherical and nonspherical anions have been employed. The roles of different σ-hole donors have also been considered. The structure of <b>1</b> was modified by incorporating other σ-hole donors, namely bromine, chlorine, fluorine, as well as -Te-CH₃ as a chalcogen bond donor, leading to the modified [2]catenanes <b>2</b>-<b>5</b>. Insights into anion recognition were gained by quantifying the contributions of not only the mechanical but also hydrogen and halogen/chalcogen bonds to anion recognition using the GKS-EDA energy partition scheme and homodesmostic reactions scheme. GKS-EDA reveals that the anions Cl^- and TS^- exhibit the most stabilizing interactions with the <b>1</b> binding pocket. The EDA results confirm that by changing from a stronger σ-hole donor (I) to a weaker σ-hole donor (F) will have a considerable impact on anion interaction, thereby demonstrating that the halogen bonds formed between the [2]catenane and the anion play a pivotal role.