Alkynyl-Protected Chiral Bimetallic Ag 22 Cu 7 Superatom with Multiple Chirality Origins.

Understanding the origin of chirality in the nanostructured materials is essential for chiroptical and catalytic applications. Here we report a chiral AgCu superatomic cluster, [Ag 22 Cu 7 (C≡CR) 16 (PPh 3 ) 5 Cl 6 ](PPh 4 ), Ag 22 Cu 7 , protected by an achiral alkynyl ligand (HC≡CR: 3,5-bis(trifluoromethyl)phenylacetylene). Its crystal structure comprises a rare interpenetrating biicosahedral Ag 17 Cu 2 core, which is stabilized by four different types of motifs: one Cu(C≡CR) 2 , four -C≡CR, two chlorides and one helical Ag 5 Cu 4 (C≡CR) 10 (PPh 3 ) 5 Cl 4 . Structural analysis reveals that Ag 22 Cu 7 exhibits multiple chirality origins, including the metal core, the metal-ligand interface and the ligand layer. Furthermore, the circular dichroism spectra of R/S-Ag 22 Cu 7 are obtained by employing appropriate chiral molecules as optical enrichment agents. DFT calculations show that Ag 22 Cu 7 is an eight-electron superatom, confirm that the cluster is chirally active, and help to analyze the origins of the circular dichroism.