Same Magic Number but Different Arrangement: Alkynyl-Protected Au25 with D3 Symmetry

Article abstract of DOI:10.1002/anie.201811859

Two homoleptic alkynyl-protected gold clusters with compositions of Na[Au₂₅(C≡CAr)₁₈] and (Ph₄P)[Au₂₅(C≡CAr)₁₈] (Na?1 and Ph₄P?1, Ar=3,5-bis(trifluoromethyl)phenyl) were synthesized via a direct reduction method. 1 is a magic cluster analogous to [Au₂₅(SR)₁₈]^? in terms of electron counts and metal-to-ligand ratio. Single-crystal structure analysis reveals that 1 has an identical Au₁₃ kernel to [Au₂₅(SR)₁₈]^?, but adopts a distinctly different arrangement of the six peripheral dimer staple motifs. The steric hindrance of alkynyl ligands is responsible for the D₃ arrangement of Au₂₅. The introduction of alkynyl also significantly changes the optical absorption features of the nanocluster as supported by DFT calculations. This magic cluster confirms that there is a similar but quite different parallel alkynyl-protected metal cluster universe in comparison to the thiolated one.