Abstract
Metalloligands with multiple preorganized binding sites provide unique advantages for modulating structural patterns and enhancing the surface stability of metal nanoclusters. However, the precise structure-directing effect of metalloligands in nanocluster transformation remains a missing puzzle piece. Herein, three nested concentric bitetrahedral Cd(8)X nanoclusters were synthesized through a stepwise evolutionary pathway. These nano-sized architectures comprise tetrahedrally arranged tripodal Cd(II) macrocyclic metalloligands encapsulating a halide-supported Cd(4) tetrahedron, and the template effect of halide ions on the stabilization of Cd(8)X was dependent on their ionic size. Initiated by Ag(I), the released metalloligands from Cd(8)Cl precisely direct the light-activated fabrication of a yellow-emissive 8e(-) superatomic Cd(7)Ag(21) nanocluster. Evidently, different carboxylate O-donor triads and tetrads from the metalloligands geometrically adaptively cap the surface Ag(3) triangles of the convex polyhedral kernel in Cd(7)Ag(21), thus shaping and protecting the multi-silver kernel in the post-transformed nanocluster. Due to the labile coordination between the carboxylate-rich metalloligand and surface atoms of the Ag(20) kernel, the selective fluorescence quenching response of Cd(7)Ag(21) towards cysteine (Cys) can be rationalized by a ligand replacement-cluster aggregation process. This study demonstrates the distinctive utility of the preformed tripodal metalloligand as a passivating agent, facilitating shape- and size-matching with the surface motifs of metal nanoclusters to induce structural transformation, thereby enabling the synthesis of novel nanocluster architectures.