Bottom-Up Construction and Reversible Structural Transformation of Supramolecular Isomers based on Large Truncated Tetrahedra.

A rational synthetic strategy to construct two supramolecular isomers based on polyoxovanadate organic polyhedra with tetrahedral symmetries is presented. VMOP-α, a low-temperature product, has an extremely large cell volume (470 842 Å3 ), which is one of the top three for well-defined MOPs. The corner-to-corner packing of tetrahedra leads to a quite low density of 0.174 g cm-3 with 1D channels (ca. 5.4 nm). The effective pore volume is up to 93.6 % of cell volume, nearly the largest found in MOPs. For the high-temperature outcome, VMOP-β, the cell volume is only 15 513 Å3 . The packing mode of tetrahedra is corner-to-face, giving rise to a high-density architecture (1.324 g cm-3 ; channel 0.8 nm). Supramolecular structural transformation between VMOP-α and VMOP-β can be reversibly achieved by temperature-induced solvent-mediated transformation. These findings give a good opportunity for understanding 3D supramolecular aggregation and crystal growth based on large molecular tectonics.