Chemistry Reference
In-Depth Information
Fig. 11 Total structure of the left-handed Au
38
(SC
2
H
4
Ph)
18
nanocluster (
L
-isomer, color labels:
magenta
, Au;
yellow
,S;
gray
: C, H atoms are omitted). Reprinted from [
49
] with permission by the
American Chemical Society
Despite the successes in the synthesis of atomic monodispersed Au
38
nanoclusters, the products are often in low yield and small quantities. In this
context, recently, Qian et al. [
97
] reported a facile, large-scale synthesis of truly
monodispersed Au
38
(SC
12
H
25
)
24
nanoclusters in high purity and yield of ~10%.
The synthesis was realized through a two-phase ligand exchange process with
glutathione-capped Au
n
clusters as the starting material. The aqueous Au:SG
clusters were then subject to ligand exchange using neat 1-dodecanethiol in a
two-phase system. The authors found that the pre-synthesized gold cluster can be
etched with the presence of neat dodecanethiols and secondary growth of clusters
subsequently occurred, and eventually exclusively monodispersed Au
38
nanoclusters were produced. The SEC confirmed the purity of the as-synthesized
Au
38
nanoclusters. To further improve the product yield, the authors developed a
size-focusing method for synthesizing Au
38
(SCH
2
CH
2
Ph)
24
nanoclusters in a yield
of 25% [
94
]. The synthesis mainly includes two steps. Polydispersed Au
n
nanoclusters stabilized by SG were first synthesized by reducing Au(I)-SG in
acetone. The core size-mixed Au
n
nanoclusters subsequently react with excess
phenylethylthiol, during which Au
38
(SC
2
H
4
Ph)
24
clusters were gradually converted
from larger clusters in the thiol-etching-induced growth process. These studies
demonstrated that size-focusing process is an effective route to synthesize stable
Au
n
(SR)
m
nanoclusters. Qian et al. [
49
] then determined the crystal structure of the
Au
38
(SC
2
H
4
Ph)
24
cluster by X-ray crystallography. It was
fo
und that the Au
38
nanocluster has crystal structure with a triclinic space group P 1. The total structure
of the left-handed Au
38
(SC
2
H
4
Ph)
24
nanocluster shown in Fig.
11
can be viewed as
a core-shell structure with face-fused biicosahedral Au
23
core capped by other
15-atom shell or a Au
23
core plus three monomeric staples (RS-Au-SR) and six
dimeric staples (RS-Au-S(R)-Au-SR). This result is in good agreement with the
structure previously reported by Pei et al. in DFT calculations [
98
].
