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 [Pd(3)L(6)] core with one, two and three units of a [Pd(2)L(4)] entity for the preparation of multi-3D-cavity conjoined-cages of [Pd(4)(L(a))(2)(L(b))(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 [Pd(2)L(4)] cavity selectively binds one unit of NO(3)(−), F(−), Cl(−) or Br(−) while the larger [Pd(3)L(6)] cavity accommodates up to four DMSO molecules. Designing aspects of our conjoined-cages possess enough potential to inspire construction of exotic molecular architectures.