Reversible Cu–S Motif Transformation and Au₄ Distortion via Thiol Ligand Exchange Engineering

The thiol ligand-induced structural change is a good strategy to construct new metal nanoclusters. In this paper, ligand engineering was exploited to render reversible Cu–S motif transformation between [Au 4 Cu 4 (SAdm) 5 (Dppm) 2 ]Br and [Au 4 Cu 5 (C 6 H 11 S) 6 (Dppm) 2 ](BPh 4 ) (SAdmH = 1-adamantane mercaptan, C 10 H 15 SH; C 6 H 11 SH = cyclohexyl mercaptan; Dppm = bis-(diphenylphosphino)methane, Ph 2 PCH 2 PPh 2 ), which was well characterized by single-crystal X-ray crystallography (SCXC) and monitored by time-dependent UV–vis absorption spectroscopy. Surprisingly, by etching with cyclohexyl mercaptan (C 6 H 12 S), [Au 4 Cu 4 (SAdm) 5 (Dppm) 2 ] + was converted to [Au 4 Cu 5 (C 6 H 11 S) 6 (Dppm) 2 ] +, accompanied by the transformation of Cu 4 (SAdm) 5 to Cu 5 (C 6 H 11 S) 6 . Besides, a reversible transformation reaction can be achieved via HSAdm etching with [Au 4 Cu 5 (C 6 H 11 S) 6 (Dppm) 2 ] + . These reversible Cu–S motif transformations via thiol ligand engineering between [Au 4 Cu 4 (SAdm) 5 (Dppm) 2 ] + and [Au 4 Cu 5 (C 6 H 11 S) 6 (Dppm) 2 ] + present a new desirable model to tailor the structure of Au–Cu alloy nanoclusters capped with Dppm and thiol ligands at the atomic level.