Solvent- and Concentration-Induced Topological Transformation of a Ruthenium(II)-Based Trigonal Prism to a Triply Interlocked [2] Catenane.

Synthesis of interlocked supramolecular cages has been a growing field of interest due to their structural diversity. Herein, we report the template-free synthesis of a Ru(II) triply interlocked [2] catenane using coordination-driven self-assembly. The self-assembly of a triazine-based tripyridyl donor (2,4,6-tris(5-(pyridin-4-yl)thiophen-3-yl)-1,3,5-triazine) with a dinuclear Ru(II) acceptor (Ru(dhnq)(η--cymene))(CFSO)) yielded two distinct structures depending on the solvent and concentration. In methanol, a triply interlocked metalla [2] catenane () was formed, whereas in nitromethane, a non-interlocked cage () was obtained. The non-interlocked cage was gradually converted to in nitromethane by the increase in the concentration of cage from 0.5 to 9 mM. The interlocked cage () was stable after formation and was unaffected by the change in concentration. Notably, the free cage () exhibited host-guest interactions with polycyclic aromatic aldehydes, stabilizing the non-interlocked structure even at higher concentrations. In contrast, the triply interlocked [2] catenane () remains stable due to self-penetration and does not encapsulate guest molecules. This work showcases the stimuli-induced irreversible structural transformation of a triangular prismatic cage to its triply interlocked [2] catenane by employing metal-ligand coordination chemistry.