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 Å ³ ) of 1 so that two equally sizeable compartments (190 Å ³ ) became joined through a conformationally flexible aromatic barrier. The compartments of such unique host could be populated with CCl ₄ (88 Å ³ ; PC=46 %), CBr ₄ (106 Å ³ ; 56 %) or their combination CCl ₄ /CBr ₄ (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.
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