Isomerization in Alkynyl-Protected Gold Nanoclusters
Zong‐Jie Guan, Feng Hu, Jiao‐Jiao Li, Zhaorui Wen, Yu‐Mei Lin, Quan‐Ming Wang
Abstract
We report the controlled synthesis and structures of two isomeric gold nanoclusters, whose compositions are determined to be Au23(C≡CBut)15 (denoted as Au23-1 and Au23-2) by single-crystal X-ray diffraction and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. This is the first time isomerism is discovered in alkynyl-protected gold nanoclusters. The metal-to-ligand ratios in these two clusters are different from known Aun(SR)m systems and have not been observed in the Aux(C≡CPh)y family. This pair of isomers exhibits different optical properties, although they have similar structures and identical components. For both Au23 clusters, time-dependent density functional theory calculations revealed the frontier orbitals highest occupied molecular orbital (HOMO)–1, HOMO, and lowest unoccupied molecular orbital (LUMO) are mainly constructed from the Au15 kernel and V-shaped alkynyl–gold motifs. The HOMO → LUMO transition of Au23-1 is optically forbidden, whereas it is allowed in Au23-2. It is also found that Au23-2 cluster can be transformed to Au23-1 spontaneously under ambient conditions. This work offers further insight into the synthesis and isomerism of all-alkynyl-protected gold nanoclusters and will stimulate more investigation of isomeric metal nanoclusters.