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.