Fractal Patterns in Nucleation and Growth of Icosahedral Core of [Au n Ag 44- n (SC 6 H 3 F 2 ) 30 ] 4- (n = 0-12) via ab Initio Synthesis: Continuously Tunable Composition Control

Abstract

An ab initio one-pot synthesis of the bimetallic clusters [Au n Ag 44-n (SC 6 H 3 F 2 ) 30 ] 4- (abbreviated (AuAg) 44 ; n ≤ 12) is reported. The mixed-metal (AuAg) 44 clusters, synthesized with different reactant Au/Ag ratios, exhibit a fractal-like distribution, suggesting that nucleation of the icosahedral core is a fractal growth process. X-ray crystallographic studies provided unambiguous evidence that the doped Au atoms occupy the icosahedral sites and the maximal doping is 12. The number of Au atoms (n) in [Au n Ag 44-n (SR) 30 ] 4- (SR = SC 6 H 3 F 2 ) can be continuously tuned from 0 to 12. A three-way correspondence between single-crystal structure, MS, and UV-vis is established, thereby facilitating future identification (finger-printing) of the alloy [Au n Ag 44-n (SR) 30 ] 4- clusters. The temperature, solvent, and temporal effects in the synthesis were also investigated.