Transformable quadruply interpenetrated cage with multiple states of different reactivities

Abstract

Molecular self-assemblies with multiple tunable pockets are potentially functional molecules that generate multiple states. Pd₄L₈ interpenetrated cages (ICs), in which two Pd₂L₄ cages are quadruply interpenetrated, have three correlating, tunable pockets for anions. Here, we report six ICs that bind halide ions (F⁻ and Cl⁻), which we rationally designed on the basis of the anion matching index (AMI). They have different numbers and positions of F⁻ and Cl⁻ in their pockets. Three ICs are stable, and the other three are metastable. The outer anions in the stable ICs are selectively exchanged under kinetic control. The three thermodynamically stable ICs, whose suitability of anions was different only within 2 Å, showed totally different reactivities with BF₃ and Ag⁺, and the IC with three Cl⁻ was transformable into [2]-catenane by unusual ligand exchanges. A total of seven states were generated, affording a complicated network in response to halide ions, Lewis acids, Lewis bases, and Ag⁺.