Reversible Structural Transformation Between a Hopf Link and a Solomon Link

By utilizing the chemical reactivity of Ag(I) ions under mild conditions, we successfully demonstrated the reversible topological transformation between a Hopf link and a Solomon link. A macrocycle and a Hopf link were synthesized through the template-free self-assembly of a semirigid ligand through the adjustment of the length of the binuclear building blocks. The introduction of Ag(I) ions facilitated the topological transformation of the macrocycle and the Hopf link into Solomon link assemblies. In contrast, the Solomon links reverted to the macrocycle and the Hopf link when Ag(I) ions were reduced under sunlight irradiation or when Ag(I) ions were reacted with chloride ions, which was accompanied by a conformational change in the semirigid ligand. In addition, the diverse coordination geometry of the Ag(I) ion led to the metal-ion-templated assembly of the bipyridyl chelating ligand with the binuclear Cp*Rh acceptor B3, resulting in two assemblies: A Solomon link and a Hopf link, with the Solomon link eventually transforming into the Hopf link over time. This work not only highlights the construction of a Solomon link using Ag(I) ions as templates, but also presents, for the first time, a process of topological transformation between a Hopf link and a Solomon link.