Angewandte
Chemie
Gold Nanoclusters
A Near-Infrared-Emissive Alkynyl-Protected Au Nanocluster**
24
Xian-Kai Wan, Wen Wu Xu, Shang-Fu Yuan, Yi Gao,* Xiao-Cheng Zeng, and Quan-
Ming Wang*
Abstract: An alkynyl-protected gold nanocluster [Au (CꢀC-
phosphanyl)propane) through the dialkynylation of pre-
2
4
2+ [23]
Ph) (PPh ) ](SbF ) has been prepared by a direct reduction
formed [Au (dppp) ] .
More recently, we have shown
1
4
3
4
6
2
8
4
method. Single-crystal X-ray diffraction reveals that the
molecular structure contains a Au22 core that is made of two
Au -centered cuboctahedra that share a square face. Two
that the direct reduction of gold alkynyl precursors with
sodium borohydride led to the isolation of [Au (CꢀCPh) -
19
9
(Hdppa) ](SbF )
6 2
(Hdppa = N,N-bis-(diphenylphosphino)-
1
3
3
[24,25]
staple-like PhCꢀCÀAuÀCꢀCPh motifs are located around the
amine) and [Au (CꢀCPh) (PPh ) ](SbF ) .
Similar to
23
9
3
11]
6
6 2
[
center of the rod-like Au22 core. This Au nanocluster is highly
the gold–thiolate staple motif,
V-shaped PhCꢀCÀAuÀ
24
emissive in the near-infrared region with lmax = 925 nm and the
nature of the HOMO–LUMO transition is investigated by
time-dependent DFT calculations.
C (Ph)ÀAuÀCꢀCPh motifs were found in both Au and
2
19
[24,25]
Au clusters.
With these results in mind we set out to
23
investigate if other types of gold–alkynyl staple moieties exist
in gold nanoclusters.
G
old nanoclusters attract increasing attention because of
Herein, we report the synthesis and structure determi-
nation of [Au (CꢀCPh) (PPh ) ](SbF ) (1). The species has
their importance in fundamental research and their potential
2
4
14
3
4
6 2
[
1–5]
[6–16]
applications.
protected gold nanoclusters,
protected have been reported.
In contrast to thiolate-
or phosphine-
a unique Au22 core structure composed of two centered
cuboctahedral Au13 units which share a square face. Two
extending Au atoms are attached to the core through new
gold–alkynyl binding motifs PhCꢀCÀAuÀCꢀCPh. Interest-
[17–21]
few examples of alkynyl-
An alkynyl ligand con-
[22–25]
tains a CꢀC group that, upon coordination to metal centers,
can function as both a s and p donor. This dual functionality
could give rise to interesting features in the resulting products.
First, a new gold nanocluster core may be formed as a result of
ligand control. Second, the interfacial structure between the
gold core and the alkynyl ligand may be different from that of
thiolate-protected gold nanoclusters. Finally, the unsaturated
nature of the triple bond in alkynyl ligands can bring new
properties to the clusters. The synthesis of alkynyl-protected
gold nanoclusters has been achieved only recently. Tsukuda
ingly, this Au24 cluster is highly emissive in the near-infrared
region in solution at room temperature.
Cluster 1 was prepared from the reduction of PhCꢀCAu
and Ph PAuSbF by NaBH in CHCl . The composition of
3
6
4
3
1 was determined by Fourier transform ion-cyclotron-
resonance MS (FT-ICR-MS; Figure 1), which showed
a single signal at m/z 3595.56 corresponding to the molecular
2
+
ion [Au (CꢀCPh) (PPh ) ] . The detected isotopic pattern
2
4
14
3 4
2
+
of [Au (CꢀCPh) (PPh ) ] is in good agreement with the
2
4
14
3 4
[26]
et al. found that Brust method was not applicable in the
preparation of alkynyl-protected gold nanoclusters so they
synthesized Au (PhCꢀC) by direct ligation of phenylacetyl-
simulated pattern (Figure 1, inset).
The structure of 1 was determined by single-crystal X-ray
[27]
diffraction.
The centrosymmetric structure contains
n
m
ene to preformed Au clusters (Au:PVP; PVP = poly(vinyl-
a Au22 core and two PhCꢀCÀAuÀCꢀCPh motifs and the
[
22]
pyrrolidone)).
Konishi et al. prepared a mixed-ligand-
core is further protected by 14 CꢀCPh and 4 PPh ligands
3
2+
protected [Au (dppp) (CꢀCR) ] (dppp = l,3-bis(diphenyl-
(Figure 2a). Four surface gold atoms are each terminally
coordinated by a PPh ligand. The PPh ligands are in very
8
4
2
3
3
31
similar environments, as confirmed by the P NMR spectrum
[
*] X.-K. Wan, S.-F. Yuan, Prof. Dr. Q.-M. Wang
State Key Lab of Physical Chemistry of Solid Surfaces
Department of Chemistry, College of Chemistry and Chemical
Engineering, Xiamen University
Xiamen, 361005 (P.R. China)
E-mail: qmwang@xmu.edu.cn
Dr. W. W. Xu, Prof. Y. Gao
Shanghai Institute of Applied Physics
Chinese Academy of Sciences, Shanghai, 201800 (China)
E-mail: gaoyi@sinap.ac.cn
Prof. X. C. Zeng
Department of Chemistry, University of Nebraska-Lincoln
Lincoln, NE 68588 (USA)
[
**] This work was supported by the 973 program (2014CB845603), the
Natural Science Foundation of China (21125102, 21390390,
2
1473139, and 21273268), China Postdoctoral Science Foundation
Figure 1. Mass spectrum of the Au24 cluster. Inset: Enlarged portion of
the spectrum showing the measured (black, solid trace) and simulated
(gray, dotted trace) isotopic distribution patterns of the species
(
Y419022011).
2+
[Au (CꢀCPh) (PPh ) ]
.
2
4
14
3 4
Angew. Chem. Int. Ed. 2015, 54, 9683 –9686
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
9683