Two Pseudo-T Polyoxometalate–Organic Cages with the T_d─Keggin Template

The development of novel systems for the polyoxometalate–organic cage (POC) is an attractive research field for their fascinating topological structures and well-defined functional cavities. Here, we report the successful self-assembly of anionic POC architectures {XW9Ni6L3}4 (X = Si or P and L = p-aminobenzoic acid), comprising Ni6-substituted trivacant lacunary polyoxometalate (POM) and the organic ligand with both rigid COOH and flexible coordination NH2 groups. It is worth noting a Keggin {XW12} (X = Si or P) in the interior cavity, which is not encountered in reported POCs. More remarkably, in the cage architecture, the chiral C3 conformation was generated based on asymmetric coordination arrangement of ligands, which results in the deviation of the polyhedra and the helical arrangement of the ligands and finally constitutes the hierarchical chirality of the {POM4L12} cages. The solution stability, magnetic behavior, and dye adsorption of {SiW12}@{SiW9Ni6L3}4 have also been investigated.