Achiral-Core-Metal Change in Isomorphic Enantiomeric Ag12Ag32 and Au12Ag32 Clusters Triggers Circularly Polarized Phosphorescence

Abstract

Understanding how the chiral or achiral section in chiral nanostructures contributes to circularly polarized light emission (CPLE) at the atomic level is of fundamental importance. Here, we report two pairs of atomically precise enantiomers of homosilver (R/S-Ag₁₂Ag₃₂) and heterometal (R/S-Au₁₂Ag₃₂) clusters. The geometrical chirality of R/S-Ag₁₂Ag₃₂ arises from the chiral ligand and interface consisting of positive moieties of Ag₃₂(R/S-PS)₂₄. The circular dichroism of R/S-Ag₁₂Ag₃₂ is active, but CPLE-silent. A complete metal change from Ag₁₂ to Au₁₂ in the achiral core section of S^2-@M₁₂@S₈ engenders isomorphous heterometal R/S-Au₁₂Ag₃₂, which activates CPLE. We further quantify the contributions of achiral and chiral sections and for the first time unveil that heterometal bonding (Au₁₂-Ag₃₂) at the linkage varies the delocalization of orbitals and proportion of achiral and chiral section in electron transition-involved orbitals, thus activating CPLE. Based on these unique atomically precise homochiral metal clusters, our work provides a new insight into the contributions of achiral and chiral sections to the origin of chiroptical response of chiral metal clusters, paving the way to advance the development of CPLE nanoparticles.