Encapsulation of Halocarbons in a Tetrahedral Anion Cage

Caged supramolecular systems are promising hosts for guest inclusion, separation, and stabilization. Well-studied examples are mainly metal-coordination-based or covalent architectures. An anion-coordination-based cage that is capable of encapsulating halocarbon guests is reported for the first time. This A₄L₄-type (A=anion) tetrahedral cage, [(PO₄)₄L₄]^12-, assembled from a C₃-symmetric tris(bisurea) ligand (L) and phosphate ion (PO₄^3-), readily accommodates a series of quasi-tetrahedral halocarbons, such as the Freon components CFCl₃, CF₂Cl₂, CHFCl₂, and C(CH₃)F₃, and chlorocarbons CH₂Cl₂, CHCl₃, CCl₄, C(CH₃)Cl₃, C(CH₃)₂Cl₂, and C(CH₃)₃Cl. The guest encapsulation in the solid state is confirmed by crystal structures, while the host-guest interactions in solution were demonstrated by NMR techniques.