Chiral Inversion of Thiolate-Protected Gold Nanoclusters via Core Reconstruction without Breaking an Au-S Bond

Abstract

Based on density functional theory computations of the well-known chiral Au38(SR)24 nanocluster and its Pd- and Ag-doped derivatives, we propose here a mechanism for chiral inversion that does not require breaking of a metal-sulfur bond at the metal-ligand interface, but features a collective rotation of the gold core. The calculated energy barriers for this mechanism for Au38 and Pddoped Au38 are in the range of 1 – 1.5 eV, significantly lower than barriers involving breakage of Au-S bonds (2.5 eV). For Ag-doped Au38, barriers for both mechanisms are similar (1.3 – 1.5 eV). Inversion barriers for a larger chiral Au144(SR)60 are much higher (2.8 eV). Our computed barriers are in a good agreement with racemization barriers estimated from existing experiments for bare and doped Au38. These results highlight the sensitivity of chiral inversion to the size, structure and metal composition of the metal core and sensitivity to the detailed structure of the metal-thiolate interface. Our work also predicts that enantiopure Au144(SR)60 clusters would be promising materials for applications requiring high resistance to chiral inversion.