Chemistry Reference
In-Depth Information
Fig. 12 Total structure of Au
38
(SC
2
H
4
Ph)
24
. The carbon tails (-SC
2
H
2
Ph) are omitted for clarity.
(a)Au
23
biicosahedral kernel. (b) Position of dimeric staples [Au
2
(SR)
3
] and monomeric staple
[Au(SR)
2
]. (c)
Side view
and
top view
of the Au
38
(SR)
24
total structure. Color labels:
yellow
¼
sulfur,
other colors
¼
gold
top of the first one via sharing a triangular face, we obtain a rod-like biicosahedron
structure
(Fig.
12a
). When counting the number of
atoms,
there
are
13 + 13
23 in this face-sharing biicosahedral structure; of note, face-
sharing consumes 3 atoms. This Au
23
kernel has a
D
3h
symmetry. Among the
23 atoms, 2 atoms are in the icosahedral centers, 3 atoms are used for face-sharing;
hence, only 18 atoms are exposed and need protection by thiolate groups.
The 18 surface gold atoms on the biicosahedral kernel are protected by 9 staple
motifs, with 3 of them being monomeric staples (-SR-Au-SR-), and the remaining
6 motifs being dimeric staples (-SR-Au-SR-Au-SR-). If viewed from the
C
3
axis of
the biicosahedral kernel, the 18 surface atoms can be divided into 6 layers (1-3 and
mirror imaged 1
0
-3
0
, Fig.
12a
). Three dimeric staples are located on the top
icosahedron, with one end of each dimeric staple pinning down to the atom on
layer 1, while the other end pining down on layer 3 (Fig.
12b
). The rotary
arrangement of the three dimeric staples along the
C
3
axis resembles the
tri-blades of a fan or propeller [
10
] (Fig.
12c
). The remaining three dimeric staples
are located on the bottom icosahedron with the same rotation direction. The three
monomeric staples are located on the waist of the biicosahedral kernel, connecting
the atoms on the layer 2 and 2
0
together, reinforcing the connection between the two
icosahedra. The protecting staples reduce the
D
3h
symmetry of the Au
23
biicosahedral kernel to the
D
3
symmetry of the overall Au
38
S
24
. Similar to the
3
¼
