Horizontal expansion of biicosahedral M 13 -based nanoclusters: resolving decades-long questions.

For metal nanoclusters with the "cluster of clusters" intramolecular evolution pattern, most efforts have been made towards the vertical superposition of icosahedral nanobuilding blocks ( e.g. , from mono-icosahedral Au 13 to bi-icosahedral Au 25 and tri-icosahedral Au 37 ), while the horizontal expansion of these rod-shaped multi-icosahedral aggregates was largely neglected. We herein report the horizontal expansion of the biicosahedral M 25 cluster framework, yielding an [Au 19 Ag 12 (S-Adm) 6 (DPPM) 6 Cl 7 ] 2+ nanocluster that contains an Au 13 Ag 12 kernel and six Au 1 (DPPM) 1 (S-Adm) 1 peripheral wings. The structural determination of [Au 19 Ag 12 (S-Adm) 6 (DPPM) 6 Cl 7 ] 2+ resolved a decades-long question towards rod-shaped multi-icosahedral aggregates: how to load bidentate phosphine and bulky thiol ligands onto the nanocluster framework? The structural comparison between [Au 19 Ag 12 (S-Adm) 6 (DPPM) 6 Cl 7 ] 2+ and previously reported [Au 13 Ag 12 (PPh 3 ) 10 Cl 8 ] 2+ or [Au 13 Ag 12 (SR) 5 (PPh 3 ) 10 Cl 2 ] 2+ rationalized the unique packing of Au 1 (DPPM) 1 (S-Adm) 1 motif structures on the surface of the former nanocluster. Overall, this work presents the horizontal expansion of rod-shaped multi-icosahedral nanoclusters, which provides new insights into the preparation of novel icosahedron-based aggregates with both vertically and horizontally growing extensions.