Magic Size Au₆₄(S‑c‑C₆H₁₁)₃₂ Nanocluster Protected by Cyclohexanethiolate

We report a new magic-sized gold nanocluster of atomic precision formulated as Au₆₄(S-c-C₆H₁₁)₃₂. The Au₆₄ nanocluster was obtained in relatively high yield (∼15%, Au atom basis) by a two-step size-focusing methodology. Obtaining this new magic size through the previously established “size focusing” method relies on the introduction of a new synthetic “parameter”the type of protecting thiolate ligand. It was found that Au₆₄(S-c-C₆H₁₁)₃₂ was the most thermodynamically stable specie of the cyclohexanethiolate-protected gold nanoclusters in the size range from ~5k to 20k (where, k = 1000 dalton); hence, it can be selectively synthesized through a careful control of the size-focusing kinetics. The Au₆₄ nanocluster is the first gold nanocluster achieved through direct synthesis (i.e., without postsynthetic size separation) in the medium size range (i.e., ∼40 to ∼100 gold atoms). This medium-sized Au₆₄(S-c-C₆H₁₁)₃₂ exhibits a highly structured optical absorption spectrum, reflecting its discrete electronic states. The discovery of this new Au₆₄(S-c-C₆H₁₁)₃₂ nanocluster bridges the gap of the gold nanoclusters in the medium size range and will facilitate the understanding of the structure and property evolution of magic-size gold nanoclusters.