Chiral Inversion and Conservation of Clusters: A Case Study of Racemic Ag32Cu12 Nanocluster.

Chiral metal nanoclusters have been widely reported, but their separation and optical stabilization remain challenging. We used a deracemization strategy to accomplish the enantioseparation of a racemic mixture of [Ag32Cu12(CH3COO)12(SAdm)12(P(CH3OPh)3)4] (M44) in a yield exceeding 50%, forming two optically active [Ag32Cu12(R/S-Cl(CH3)CHCOO)12(SAdm)12(P(CH3OPh)3)4] (R/S-M44') enantiomers. The optical activity of these products was conserved after exchange of the chiral carboxyl ligands with achiral ligand (Br-), to give two additional optically active nanoclusters R/S-[Ag28Cu16Br12(SAdm)12(P(CH3OPh)3)4] (R/S(Br)-M44). The crystal structures of the above nanoclusters were determined by single-crystal X-ray crystallography. Based on these structures, the chiral transformation and conservation are mapped out.