Robust, Highly Luminescent Au13 Superatoms Protected by N-Heterocyclic Carbenes

Abstract

Gold superatom nanoclusters stabilized entirely by N-heterocyclic carbenes (NHCs) are reported. The reduction of well-defined NHC–Au–Cl complexes produces clusters com-prised of an icosahedral Au13 core surrounded by a symmetrical arrangement of 9 NHCs and 3 chlorides. X-ray crystallography shows that the clusters are characterized by multiple CH–π and π–π interactions, which rigidify the ligand and likely con-tribute to the exceptionally high photoluminescent quantum yields observed, up to 16.0 %, which is significantly greater than the most luminescent ligand-protected Au13 superatom cluster. Density functional theory analysis suggests that clus-ters are 8-electron superatoms with a wide HOMO-LUMO energy gap of 2 eV. Consistent with this, the clusters have high stability relative to all-phosphine clusters.