Heterometallic-Organic Cages with Customized Cavities: Constructed by Bottom-Up Step-Wise Coordination-Driven Self-Assembly.

Accurately synthesizing coordination-driven metal-organic cages with customized shape and cavity remains a great challenge for chemists. In this work, a bottom-up step-wise coordination-driven self-assembly approach was put forward. Employing this strategy, three terpyridyl heterometallic-organic truncated tetrahedral cages with different sizes and cavity were precisely synthesized. Firstly, the coordination of tripodal organic ligands with Ru afforded dendritic metal-organic ligands L1-L3. Then the Ru building blocks complexed with Fe and shrunk to form the desired heterometallic-organic cages (C1-C3). These discrete heterometallic-organic supramolecular cages were fully characterized and displayed the large and open cavities varied from 7205 Å to 9384 Å. Notably, these cages could not be directly constructed by single-step assembly process using initial organic ligands or dimeric metal-organic ligands, indicative of the irreplaceability of a bottom-up step-wise assembly strategy for size-customized architectures. This work paves a new way for precisely constructing metal-organic cages with well-defined cavities.