Multilevel ionic co-assembly of a terpyridyl complex and polyoxometalate: Dual outcomes from frameworks to close packings

The coexistence of multiple noncovalent interactions, such as ionic interactions, hydrogen bonding, and π–π stacking, provides rich opportunities for constructing supramolecular architectures while presenting challenges in controlling assembly outcomes. Herein, we employ hydrogen bond-functionalized Anderson-type polyoxometalates and terpyridyl-based metal complexes as complementary building blocks. By varying the solvent, temperature, and assembly time, we achieve distinct supramolecular structures. Rapid assembly in water yields a kinetically trapped two-dimensional hexagonal ionic framework. By contrast, assembly in N,N-dimethylformamide–water mixtures under ambient or hydrothermal conditions leads to four thermodynamically stable ionic crystals, each characterized by unique packing arrangements governed by π–π stacking and hydrogen-bonding interactions. This study demonstrates that a single co-assembly system can generate diverse, well-defined architectures under different assembly conditions, offering a practical strategy for the controlled construction of complex supramolecular materials.