Chiral footprint of the ligand layer in the all-alkynyl-protected gold nanocluster Au144(CCPhF)60

Abstract

The electronic structure and chiroptical properties of the recently isolated and structurally characterized all-alkynyl-protected gold nanocluster Au₁₄₄(CCPhF)₆₀ were analyzed via density functional theory (DFT) computations and compared to those of the structurally similar all-thiolate-protected Au₁₄₄(SCH₂Ph)₆₀. While DFT predicts very strong CD signals of similar strength for both clusters, the origins of chiroptical activity are markedly different. The chiral response of Au₁₄₄(CCPhF)₆₀ originates only from the footprint of the outermost gold-ligand layer of 30 FPhCC-Au-CCPhF units covering an achiral I_h-symmetric Au₁₁₄ core whereas the Au₁₁₄ core of the Au₁₄₄(SCH₂Ph)₆₀ cluster has a chiral I symmetry and it alone produces CD signals that are comparable to those of the well-studied chiral Au₃₈(SR)₂₄. These signals are then amplified by a chiral arrangement of the protecting 30 PhH₂CS-Au-SCH₂Ph units. These results shed light on the origins of chiroptical activity of ligand-protected gold clusters that form an important class of atom-precise nanomaterials with potential applications in chiral sensing and enantioselective catalysis.