pH-Gated Chloride Transport by a Triazine-Based Tripodal Semicage

Triazine-based preorganized tripodal receptors are reported as efficient transmembrane Cl^- carriers. These receptors were designed based on triazine core and 3,7-diazabicyclo[3.3.1]nonane arms to facilitate preorganized cavity formation. Each bicyclic arm was further functionalized to control protonation and lipophilicity, which are crucial for their efficient anion binding and effective transport through liposomal membranes. The benzyl-substituted receptor was the most effective ion transporter followed by the pentafluorobenzyl-substituted derivative. The nonsubstituted receptor was least active owing to its high polarity. Two active transporters were found to function as mobile carriers for Cl^- via an antiport exchange mechanism. Molecular dynamic simulations with the most active receptor show a strong Cl^- binding within the cavity by direct and water-mediated H-bonds with its N-H groups.