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(tBuC6H4C≡C)20 (Au28-C2) was synthesized and structurally characterized. It has an isostructural metal kernel and a quite similar ligand shell to its counterpart Au28(tBuC6H4S)20 (Au28-S), which provides a valuable platform for studying ligand effects on the luminescence of clusters. The emission intensity of Au28-C2 in solution is ∼10-fold that of Au28-S. The only structural difference between these two clusters is the donor atom or group, i.e., C≡C for Au28-C2 versus S for Au28-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 Au28-C2 has a larger triplet-state population than Au28-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.