Two Giant Calixarene-Like Polyoxoniobate Nanocups {Cu 12 Nb 120 } and {Cd 16 Nb 128 } 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 {Cu 12 Nb 120 } and {Cd 16 Nb 128 }. The former integrates three tricyclic Nb 24 clusters and a hexacyclic Nb 48 cluster into a cup-shaped molecule via a Cu 12 metallacalixarene, while the latter unifies two tricyclic Nb 24 clusters and a brand-new pentacyclic Nb 40 cluster into another cup-shaped molecule via a hybrid Cd 16 unit. With 132 and 144 metal centers, {Cu 12 Nb 120 } and {Cd 16 Nb 128 } show the largest two inorganic-organic hybrid PONbs known to date.