Controlled Self-Assembly and Multistimuli-Responsive Interconversions of Three Conjoined Twin-Cages

Stimuli-responsive structural transformations
between discrete
coordination supramolecular architectures not only are essential to
construct smart functional materials but also provide a versatile
molecular-level platform to mimic the biological transformation process.
We report here the controlled self-assembly of three topologically
unprecedented conjoined twin-cages, i.e., one stapled interlocked
Pd12L6 cage (2) and two helically
isomeric Pd6L3 cages (3 and 4) made from the same cis-blocked palladium corners and a
new bis-bidentate ligand (1). While cage 2 features three mechanically coupled cavities, cages 3 and 4 are topologically isomeric helicate-based twin-cages
based on the same metal/ligand stoichiometry. Sole formation of cage 2 or a dynamic mixture of cages 3 and 4 can be controlled by changing the solvents employed during the self-assembly.
Structural conversions between cages 3 and 4 can be triggered by changes in both temperature/solvent and induced-fit
guest encapsulations. Well-controlled interconversion between such
topologically complex superstructures may lay a solid foundation for
achieving a variety of functions within a switchable system.