Synthesis and Characterization of a Monodentate N-Heterocyclic Carbene-Protected Au11-Nanocluster via Reduction with KC8

Abstract

Atomically precise gold nanoclusters are an exciting and growing class of nanomaterials. While normally protected with ligands such as thiols or phosphines, gold nanoclusters protected with N-heterocyclic carbenes (NHCs) have recently garnered attention due to potential improvements in stability and optical properties of the resulting clusters. However, as this field is in its infancy, little work has been done with reducing agents beyond sodium borohydride (NaBH4), a reagent that dominated synthetic efforts in other clusters as well. Herein, we report the use of potassium intercalated graphite (KC8) in the synthesis of nanoclusters, and the novel Au11-nanocluster protected with monodentate NHC ligands it produces, [Au11(NHC)8Br2]Br. The cluster is characterized by ESI-MS, UV–vis spectroscopy, 1H and 13C{1H} NMR. Starting from a partially resolved X-ray crystal structure showing the heavy atoms, DFT calculations enable us to propose a total structure.