Anion-Coordination-Driven Assembly of Anionic Hexagonal and Square Architectures and the Structural Interconversion

A biphenyl-bridged bis-tris(urea) ligand L was rationally designed with a favorable angle to construct a hexagon-shaped A₆L₆ (A = anion) complex upon assembly with phosphate anions (PO₄³⁻) via anion-coordination-driven assembly (ACDA). Due to the moderate flexibility of L, another well-defined discrete architecture, a square-like A₄L₄ complex, has also been obtained from ligand L and PO₄³⁻. Interconversion between these two self-assemblies can be readily realized by solvent regulation. In addition, the two anionic architectures display different binding abilities for selected cationic guest molecules, enabling the uptake of a desired guest from a mixture of guests.