Anion Recognition by Neutral and Cationic Iodotriazole Halogen Bonding Scaffolds

A computational study of the iodide discrimination by different neutral and cationic iodotriazole halogen bonding hosts was carried out by means of Density Functional Theory. The importance of the size of the scaffold was highlighted and its impact observed in the binding energies and intermolecular X⋯I distances. Larger scaffolds were found to reduce the electronic repulsion and increase the overlap between the halide electron lone pair and the corresponding I-C antibonding orbital, increasing the halogen bonding interactions. Additionally, the planarity plays an important role within the interaction, and can be tuned using hydroxyl to perform intramolecular hydrogen bonds (IMHB) between the scaffold and the halogen atoms. Structures with IMHB exhibit stronger halogen bond interactions, as evidenced by the shorter intramolecular distances, larger electron density values at the bond critical point and more negative binding energies.