Improvement of Anion Transport Systems by Modulation of Chalcogen Interactions: The influence of solvent

A series of potential anion transporters, dithieno[3,2-b;2′,3′-d]thiophenes (DTT), involving anion-chalcogen interactions have been studied by analyzing the interaction energy, geometry, and charge transfer. It was found that gas phase calculations show very negative interaction energies with short anion-chalcogen distances, but when solvent effects are considered, the interaction energy values decreased drastically concomitantly with an elongation on the interatomic distances. To enhance the chalcogen interaction between the DTT derivatives and the anion, increasing the anion transporter capacity, bisisothioazole moiety was considered; i.e., the σ-hole of the chalcogen atom was modulated by substitution of the adjacent carbon by a nitrogen atom in the S-C axis, increasing the depth of the σ-hole and therefore the interaction between the chalcogen and anion. Finally, different anions were analyzed within the complexes, finding that F^- and NO₃^- would be the best candidates to form complexes and possibly displace other anions such as Cl^- or Br^-.