(AuAg)44(SPhtBu)26 versus (AuAg)44(SPhF2)30: Tailoring the Geometric Structures and Optical Properties of Nanocluster Analogues

Abstract

Monolayer-protected nanoclusters are ideal models for understanding the correlations between structures and properties of inorganic nanoparticles, especially for those molecules with identical sizes but comparable structures. Here, we controllably prepared and structurally determined a valence-neutral Au24+xAg20‑x(SPhtBu)26 (0 < x < 4) nanocluster with comparable structure features to a well-known Au12Ag32(SPhF2)30 cluster. The Au24+xAg20‑x(SPhtBu)26 cluster contained a hollow Au12@M20 metallic kernel (M = Au/Ag), 12 Au1(SR)2 staples, and two bridging SR molecules, and its average molecular formula was determined to be Au26.3Ag17.7(SPhtBu)26, as evidenced by X-ray crystallography and electrospray ionization mass spectrometry. Because of the ligand effect and the asymmetrical arrangement of the Au dopants in the dodecahedral cage, the Au24+xAg20‑x(SPhtBu)26 nanocluster exhibited lower molecular symmetry relative to Au12Ag32(SPhF2)30 in terms of the dodecahedral kernel and motif shell structures. Besides, the strong π–π interaction in Au24+xAg20‑x(SPhtBu)26 contributed to its enhanced photoluminescence intensity compared with Au12Ag32(SPhF2)30. The study, herein, extends the 44-metal-atom cluster family, thereby enabling us to better understand the correlations between their structures and properties at the atomic level.