Ionic Recognition Controlled by Conformational Change: A DFT Investigation.

Ions play a crucial role in the production of important materials and are associated with various health and environmental issues. Noncovalent interactions serve as fundamental tools for controlling the availability of cations and/or anions. Herein, we investigate the ability of two conformations of the 2,6-bis(1,2,3-triazol-4-yl)pyridine molecule to recognize cations (), such as Li, Na, or K, and anions (), including F, Cl, or Br. EDA-NOCV analysis demonstrates that the conformers preferentially recognize ions based on the size of the cations (K → Na → Li) and anions (Br → Cl → F). The preferential interaction with smaller cations (and anions) arises from the more attractive electrostatic and orbital interactions (Ncation and C-Hanion bonds). The presence of electron-donor groups (-NH) in the first conformer () enhances cation recognition through stronger electrostatic Ncation interactions. Conversely, the presence of electron-acceptor groups (-NO) in the second conformer () facilitates anion recognition via more favorable electrostatic, orbital, and dispersion C-Hanion interactions. Cation recognition is found to be more favorable in the first conformer than anion recognition in the second due to more attractive electrostatic energy and/or less Pauli repulsive energy associated with (O or primarily N)cation interactions in cations compared to (N or mainly C)-Hanion bonds in anions. These findings provide significant insights into the mechanisms of cation and/or anion recognition through different conformations using the same base structure and can inform the design of molecules with enhanced functionalities.