Herein, we describe
the synthesis of a toroidal Au
10
cluster stabilized by
N
-heterocyclic carbene and
halide ligands
via
reduction of the corresponding
NHC–Au–X complexes (X = Cl, Br, I). The significant
effect of the halide ligands on the formation, stability, and further
conversions of these clusters is presented. While solutions of the
chloride derivatives of Au
10
show no change even upon heating,
the bromide derivative readily undergoes conversion to form a biicosahedral
Au
25
cluster at room temperature. For the iodide derivative,
the formation of a significant amount of Au
25
was observed
even upon the reduction of NHC–Au–I. The isolated bromide
derivative of the Au
25
cluster displays a relatively high
(
ca
. 15%) photoluminescence quantum yield, attributed
to the high rigidity of the cluster, which is enforced by multiple
CH−π interactions within the molecular structure. Density
functional theory computations are used to characterize the electronic
structure and optical absorption of the Au
10
cluster.
13
C-Labeling is employed to assist with characterization of
the products and to observe their conversions by NMR spectroscopy.