High-affinity 1:2 recognition based on naphthyl-azocalix[4]arene and its application as a cleavable noncovalent connector in constructing responsive supramolecular polymeric materials

Abstract

Macrocyclic hosts which can bind two guests simultaneously with high affinity, such as, cucurbit[8]uril, are highly useful for a wide range of application by acting as noncovalent connectors. However, the integration of stimuli-controlled release properties into such robust noncovalent connectors would be even more desirable. Here, we introduce Naph-SAC4A, a naphthyl-extended deep-cavity azocalix[4]arene with hypoxia-responsiveness, which exhibits exceptional 1:2 hosting abilities for organic dyes in aqueous solution with affinities ranging from 1014 to 1016 M–2. Furthermore, Naph-SAC4A was employed as a robust while hypoxia-cleavable noncovalent connector to construct linear supramolecular polymers and crosslinked supramolecular hydrogels. Both structures exhibit responsiveness to hypoxic stimuli. With its high-affinity 1:2 recognition, unique hypoxia-responsiveness, and easy accessibility, Naph-SAC4A holds great potential for smart supramolecular polymeric materials.