Node Flexibility Unlocks Structural Adaptability and Guest Versatility of Anionocages

Due to their exceptional nodal flexibility, anionocages are promising host molecules capable of mimicking the dynamic self-assembly and host-guest chemistry of proteins. However, their application has been limited by the challenges in constructing large internal cavities. Here, we present an effective strategy to overcome this limitation by enhancing node flexibility to improve both structural adaptability and guest encapsulation versatility. Specifically, anion coordination between a C₃-symmetric tris-urea ligand (L) and an organophosphate, PhPO₄ ^2- (A), generates highly flexible nodes that enable adaptive self-assembly and the encapsulation of guests of unprecedented size. Crystal structures revealed that the same ligand and anion can form three geometrically distinct anionocages (A₄L₄ tetrahedron 1, A₆L₆ trigonal antiprism 2, and A₆L₈ octahedron 3), with cavity sizes ranging from 0.208 to 1.320 nm³. In solution, controlled interconversions among the three anionocages can be achieved by modulating the guest template, A/L ratio, and concentration. These nanoscale cavities successfully encapsulate the luminescent metal complex, [Ru(bpy)₃]²⁺ (bpy = 2,2'-bipyridine), resulting in a ∼5-fold increase in quantum yield, and a ∼2-fold increase in lifetime. Moreover, circularly polarized luminescence of racemic [Ru(bpy)₃]²⁺ is induced via chirality transfer using a chiral-anion-directed octahedral cage (4) as the host.