Chiral Inversion of Thiolate-Protected Gold Nanoclusters via Core Reconstruction without Breaking a Au–S Bond
2019
Malola, Sami | Häkkinen, Hannu
On the basis of 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 the 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 Pd-doped Au₃₈ are in the range of 1–1.5 eV, significantly lower than barriers involving the 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 (2.5−2.8 eV). Our computed barriers are in 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.
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