On the synthesis and characterization of two different titanium-based supramolecular structures of identical stoichiometry

Self-assembled supramolecular coordination complexes can take on a wide range of three-dimensional architectures with varying ratios of metal-to-ligand. Control over which architecture will be adopted can be difficult to maintain, as many may form from the starting materials and conditions present. Characterizing the resulting architectures formed can be challenging, in particular when discerning between lower or higher ordered structures of identical stoichiometry. Here we report the synthesis and characterization of a Ti2L3 football-like or pill-shaped capsule, unexpectedly formed from attempts to synthesize variations on a Ti4L6 tetrahedron. The two anionic cores are formed from identical stoichiometric ratios of organic linkers and metal nodes. The high symmetry of the structures, and identical m/z ratios, posed characterization challenges. Crystallization was the only method that allowed for precise structural determination. In the presence of appropriate counter ion guests, the Ti2L3 capsule converts into the Ti4L6 tetrahedron at elevated temperatures over several days.