The pivotal alkyne group in the mutual size-conversion of Au9 with Au10 nanoclusters

Abstract

Herein, density functional theory (DFT) calculations were performed to elucidate the mechanism of the reversible single atom size conversion between [Au₁₀(DMPP)₄(C₆H₁₁CC)]³⁺ and [Au₉(DMPP)₄]³⁺ (DMPP is 2,2′-bis-(dimethylphosphino)-1,1′-biphenyl, the simplified, theoretical model of the experimentally used 2,2′-bis-(diphenylphosphino)-1,1′-binaphthyl). The presence of a unique alkyne group is pivotal to the nucleophilic attack of the phosphine ligand on the electron-deficient Au₁₀ core. After that, a formal ligand exchange and facile 1,2-P (of the diphosphine ligand) transfer occur to generate the Au₉ cluster product. By contrast, the absence of the alkyne group results in a relatively electron-rich Au₉ core, and thus an electrophilic attack of the Au(alkyne) complex on the most electron-rich metal sites occurs first. After that, the Au(alkyne) migration on the cluster surface, 1,2-P transfer and core-reconstruction occur successively to generate the thermodynamically highly stable Au₁₀ cluster product.