Ligand Effects on Luminescence of Atomically Precise Gold Nanoclusters

Great efforts have been made to establish the structure-property relationships of ligand-protected metal nanoclusters. An alkynyl-protected gold nanocluster Au₂₈(BuC₆H₄C≡C)₂₀ (Au-C) was synthesized and structurally characterized. It has an isostructural metal kernel and a quite similar ligand shell to its counterpart Au₂₈(BuC₆H₄S)₂₀ (Au-S), which provides a valuable platform for studying ligand effects on the luminescence of clusters. The emission intensity of Au-C in solution is ∼10-fold that of Au-S. The only structural difference between these two clusters is the donor atom or group, i.e., C≡C for Au-C versus S for Au-S. Temperature-dependent experiments indicate that the two Au₂₈ clusters have different thermodynamic behaviors and radiative processes. The study on the excited-state dynamics by transient absorption spectroscopy indicates that Au-C has a larger triplet-state population than Au-S. This work shows important ligand effects on the emission properties of metal nanoclusters, which provide new perspectives for the designed synthesis of functional metal nanoclusters.