Crown Ether Functionalized Potassium-Responsive Anionocages for Cascaded Guest Delivery.

In many critical biological processes, host-guest chemistry of protein receptors is regulated by effector molecules to realize cascaded delivery of messenger molecules between different targets. Mimicking these natural processes with artificial receptors remains a challenge. Herein, we report a cascaded guest delivery between two anionocages (anion-coordination-driven cages), in a reversible manner, wherein binding of K ⁺ ions by a crown ether functionalized, heteroleptic A ₂ L ₃ (A=anion, L=ligand) anionocage triggers the release and delivery of a TEA ⁺ (tetraethylammonium) guest to another A ₂ L ₃ anionocage that is a weaker and less K ⁺ -sensitive receptor. Elimination of the K ⁺ with [2,2,2]-cryptand enables recapture of the TEA ⁺ by the crown ether functionalized anionocage and thus realizes a reversed guest delivery. Moreover, integrative self-sorting of anionocages is firstly reported, leading to heteroleptic cages with enhanced guest binding affinities.
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