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

Abstract

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.

Graphical Abstract

Keywords:

• Cage
• capsule
• nano-container
• titanium
• M₂L₃
• M₄L₆
• interconversion

Acknowledgements

The authors thank Dr. Thomas Weldeghiorghis from the LSU Chemistry NMR Facility for help with DOSY experiments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge support from the National Science Foundation under award number 2046445 and from Louisiana State University startup funds. RJB thanks the Louisiana Board of Regents for partial fellowship support under award number LEQSF(17-22)-GF-03.