One-pot formation of hydrazide macrocycles with modified cavities: An example of pH-sensitive unimolecular cation channels

A series of pH-sensitive, cation-selective hydrazide macrocyclic channels have been synthesized. The macrocyclic channels bear multiple carboxyls in the inner cavity, which have a significant impact on their membrane-incorporation ability and NH₄⁺ transport activity. Moreover, the K⁺/Cl^- selectivities of the macrocyclic channels can be tuned by the pH value of the electrolyte.