Exploring the structure evolution and core/ligand structure patterns of a series of large sized thiolate-protected...

The atomic structures of many atomically precise nanosized ligand protected gold clusters have been resolved recently. However, the determination of the atomic structures of large sized ligand protected gold clusters containing metal atoms over ∼100 is still a grand challenge. The lack of structural information of these larger sized clusters has greatly hindered the understanding of the structure evolution and structure-property relations of ligand protected gold nanoclusters. In this work, we theoretically studied the structure evolution of a series of large sized Au_145-3N(SR)_60-2N (N = 1-8) clusters based on an "[Au₂@Au(SR)₂] fragmentation" pathway starting from a model Au₁₄₅(SR)₆₀ cluster. Through comprehensively searching the atomic structure of various clusters and evaluating their stabilities by means of first principles calculations, the stabilization mechanism of experimentally reported Au₁₃₀(SR)₅₀ and Au₁₃₃(SR)₅₂ clusters is first rationalized. Our studies indicated that Au₁₃₀(SR)₅₀ and Au₁₃₃(SR)₅₂ are two critical sized clusters on which the gold cores underwent configuration transitions between decahedral and icosahedral cores. The energy comparisons of various cluster isomer structures indicated that the Au₁₃₀(SR)₅₀, Au₁₂₇(SR)₄₈, Au₁₂₄(SR)₄₆ and Au₁₂₁(SR)₄₄ clusters favored a decahedral core, while the Au₁₃₃(SR)₅₂, Au₁₃₆(SR)₅₄, Au₁₃₉(SR)₅₆, and Au₁₄₂(SR)₅₈ clusters preferred icosahedral gold cores. Furthermore, we also find that the cuboctahedral gold core is less stable in the cluster size region between ∼120 and ∼140 gold atoms. The optical absorption properties and relative thermodynamic stabilities of the Au_145-3N(SR)_60-2N (N = 1-8) clusters are also surveyed by density functional theory (DFT) and time-dependent DFT calculations.