A conformationally adaptable tetrahedral cage with different guest encapsulation models

Abstract

Through imine condensation, a tetrahedral cage-shaped molecule was obtained in a one-pot manner, which comprises four trisamino vertices and four trisformyl faces each containing three meta-methyl-pyridyl units. Within the cage framework, each of the twelve pyridines undergoes pivoting around the corresponding imine-pyridine-phenyl axle, endowing the cage with adaptable conformations. By modulating the number of pyridyl nitrogen atoms that point inwards, the cage can switch the effective volume of its cavity where a wide range of guest molecules including quaternary ammoniums, or different amounts of alkali cations, are encapsulated, by utilizing dipole–cation forces and/or hydrogen bonding. This behavior is reminiscent of biological enzymes that can adjust their conformations to optimize binding affinity.