Assembly of an A₆L₆ Anion Trigonal Antiprism and Binding of Glucopyranosides and Polyethylene Glycols (PEGs)

Anion-coordination-driven assembly (ACDA) has proven to be a very effective strategy for the construction of polyhedral structures. Here we demonstrate that variation of the “angle” of the backbone of C₃-symmetric tris-bis(urea) ligands, from triphenylamine to triphenylphosphine oxide, results in the change of the final construct from an A₄L₄ tetrahedron to a higher-nuclearity, A₆L₆ trigonal antiprism (A=anion, herein PO₄³⁻; L=ligand). Most interestingly, this assembly features a huge hollow internal space that is divided into three compartments: one central cavity and two large outer pockets. This multi-cavity character enables the binding of different guests, namely monosaccharides or polyethylene glycol molecules (PEG600, PEG1000 and PEG2000), respectively. The results prove that anion coordination by multiple hydrogen bonds may provide both sufficient strength and flexibility, thus making possible the formation of complicated structures with adaptive guest binding ability.