Crystal Structure and Optical Properties of a Chiral Mixed Thiolate/Stibine-Protected Au 18 Cluster.

We report the first example of a chiral mixed thiolate/stibine-protected gold cluster, formulated as Au 18 (S-Adm) 8 (SbPh 3 ) 4 Br 2 (where S-Adm = 1-adamantanethiolate). Single crystal X-ray crystallography reveals the origin of chirality in the cluster to be the introduction of the rotating arrangement of Au 2 (S-Adm) 3 and Au(S-Adm) 2 staple motifs on an achiral Au 13 core and the subsequent capping of the remaining gold atoms by SbPh 3 and Br - ligands. Interestingly, the structure and properties of this new Au 18 cluster are found to be different from other reported achiral Au 18 clusters and the only other stibine-protected [Au 13 (SbPh 3 ) 8 Cl 4 ] + cluster. Detailed analyses on the geometric and electronic structures of the new cluster are carried out to gain insights into its optical properties as well as reactivity and stability of such mixed monolayer-protected clusters.