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.