Two Giant Calixarene-Like Polyoxoniobate Nanocups {Cu12 Nb120 } and {Cd16 Nb128 } Built from Mixed Macrocyclic Cluster Motifs.

Cup-shaped molecules are of great interest due to their appealing architectures and properties. Compared with widely studied calixarenes, polyoxometalate-based cup-shaped molecules currently remain a virgin land waiting for exploration. In this work, we report the first discovery of two giant cup-shaped inorganic-organic hybrid polyoxoniobates (PONbs) of {Cu12 Nb120 } and {Cd16 Nb128 }. The former integrates three tricyclic Nb24 clusters and a hexacyclic Nb48 cluster into a cup-shaped molecule via a Cu12 metallacalixarene, while the latter unifies two tricyclic Nb24 clusters and a brand-new pentacyclic Nb40 cluster into another cup-shaped molecule via a hybrid Cd16 unit. With 132 and 144 metal centers, {Cu12 Nb120 } and {Cd16 Nb128 } show the largest two inorganic-organic hybrid PONbs known to date.