Dynamic selection in metallo-organic cube Cd conformations induced by perfluorooctanoate encapsulation

Metallo-organic cages possess flexibility comparable to that of biological receptors and can alter their conformations to better accommodate guest species due to the dynamic reversibility of the coordination bond. Induced fit is widely accepted involving conformation change of the host, while few definitive examples are related to conformation selection. Herein, we report the generation of metallo-organic cube Cd II 8 L 4 with two coexisting conformations, which have been fully confirmed by NMR, ESI-MS and single-crystal X-ray diffraction analysis. The specific guest perfluorooctanoate PFOA selectively binds to the active conformer C 2h - 1 to form the PFOA⊂ C 2h - 1 complex. Furthermore, conformer D 2 - 2 isomerizes to conformer C 2h - 1 in the presence of PFOA, for maximizing the guest binding affinity. This study provides an effective working paradigm for conformation selection, facilitating the understanding of the fundamental mechanism of molecular recognition. Self-assembly of ligand L and Cd II ions affords two metallo-organic cage Cd II 8 L 4 conformers: meta-stable C 2h - 1 and thermodynamically favored D 2 - 2 . The inclusion of guest perfluorooctanoate shifts the equilibrium distribution to meta-stable conformer C 2h - 1 .