"Visualizing" the partially reversible conversion of gold nanoclusters via the Au 23 (S- c -C 6 H 11 ) 17 intermediate.

Transformation chemistry of atomically precise metal nanoclusters has emerged as a novel strategy for fundamental research on the structure-property correlations of nanomaterials. However, a thorough understanding of the transformation mechanism is indeed necessary to understand the structural growth patterns and corresponding property evolutions in nanoclusters. Herein, we present the ligand-exchange-induced transformation of the [Au 23 (SR) 16 ] - (8e - ) nanocluster to the [Au 25 (SR') 18 ] - (8e - ) nanocluster, through the Au 23 (SR) 17 (6e - ) intermediate species. Identification of this key intermediate through a partially reversible transformation helped in a detailed investigation into the transformation mechanism with atomic precision. Moreover, photophysical studies carried out on this Au 23 (SR) 17 species, which only differs by a single ligand from that of the [Au 23 (SR) 16 ] - nanocluster reveal the property evolutions at the slightest change in the nanocluster structure.