Enantioseparation of Au-20(PP3)(4)Cl-4 Clusters with Intrinsically Chiral Cores

Au-20(PP3)(4)Cl-4 (PP3=tris(2-(diphenylphosphino)ethyl) phosphine), abbreviated as Au-20, is the only Au nanocluster with an intrinsically chiral core without a chiral environment (chiral ligands or Au-thiolate staples), making it a unique object to understand chiral evolution and explore chiral applications. Unfortunately, the synthesized Au-20 is racemic, and its enantiomers have not yet been separated. Herein, we report a supramolecular assembly strategy with -cyclodextrin (-CD) to afford enantiopure Au-20 in bulk, and an enantiomer excess (ee) value of as-separated Au-20 of 97%. As a result of its high purity, the distinctive optical activity of Au-20, which originates from electronic transitions confined in chiral cores, is fully explored. Theoretical studies reveals that the enantioseparation results from the preferential self-assembly of -CD with organic ligands on the surface of right-handed Au-20.