Self-assembled conjoined-cages

A self-assembled coordination cage usually possesses one well-defined three-dimensional (3D) cavity whereas infinite number of 3D-cavities are crafted in a designer metal-organic framework. Construction of a discrete coordination cage possessing multiple number of 3D-cavities is a challenging task. Here we report the peripheral decoration of a trinuclear [Pd3L6] core with one, two and three units of a [Pd2L4] entity for the preparation of multi-3D-cavity conjoined-cages of [Pd-4(La)(2)(Lb)(4)], [Pd-5(L-b)(4)(L-c)(2)] and [Pd-6(L-c)(6)] formulations, respectively. Formation of the tetranuclear and pentanuclear complexes is attributed to the favorable integrative self-sorting of the participating components. Cage-fusion reactions and ligand-displacement-induced cage-to-cage transformation reactions are carried out using appropriately chosen ligand components and cages prepared in this work. The smaller [Pd2L4] cavity selectively binds one unit of NO3-, F-, Cl- or Br- while the larger [Pd3L6] cavity accommodates up to four DMSO molecules. Designing aspects of our conjoined-cages possess enough potential to inspire construction of exotic molecular architectures.