The Influence of Flexibility of Alkynyl Ligands on the Formation of an Fcc Au110 Nanocluster

Isomerization of nanoclusters is helpful for understanding the relationships between structures and properties. Surface-protecting ligands play a crucial role in controlling the atomic packing mode of the inner core. The synthesis and total structural determination of the all alkynyl-protected gold nanocluster (NEt₃CH₂Cl)₂[Au₁₁₀(C≡CC₃H₆Ph)₄₈] (Au₁₁₀-1) are reported. Au₁₁₀-1 and the previously reported [Au₁₁₀(C≡CC₆H₄-4-CF₃)]^2- (Au₁₁₀-2) constitute the largest alkynyl-protected nanocluster quasi-isomers (> 100 metal atoms). Both Au₁₁₀ consist of an fcc Au₈₆ kernel and a shell of 24 RC≡C─Au─C≡CR staples, but the specific arrangements are different. The application of the flexible alkynyl ligands creates a significant difference in the face-centered cubic (fcc) kernel structure in Au₁₁₀-1, showing a different electronic structure, thermal- and photo-stability. Transient absorption spectra reveal that Au₁₁₀-1 still does not show any metallic characteristics, even though it has a smaller energy gap (Eg) than Au₁₁₀-2.