A Molecular Capsule with Revolving Doors Partitioning Its Inner Space

Covalent capsule 1 was designed to include two molecular baskets linked with three mobile pyridines tucked into its inner space. On the basis of both theory (DFT) and experiments (NMR and X-ray crystallography), we found that the pyridine "doors" split the chamber (380 ų ) of 1 so that two equally sizeable compartments (190 ų ) became joined through a conformationally flexible aromatic barrier. The compartments of such unique host could be populated with CCl₄ (88 ų ; PC=46 %), CBr₄ (106 ų ; 56 %) or their combination CCl₄ /CBr₄ (PC=51 %), with thermodynamic stabilities ΔG° tracking the values of packing coefficients (PC). Halogen (C-X⋅⋅⋅π) and hydrogen bonding (C-H⋅⋅⋅X) contacts held the haloalkane guests in the cavities of 1. The consecutive complexations were found to occur in a negative allosteric manner, which we propose to result from the induced-fit mode of complexation. Newly designed 1 opens a way for probing the effects of inner conformational dynamics on noncovalent interactions, reactivity and intramolecular translation in confined spaces of hollow molecules.