self-assembly reaction of stoichiometric amounts of CuI and
L (CuI/L=4:1) in a mixture of acetonitrile and dichlorome-
thane at room temperature followed by diffusion of diethyl
ether (Figure S2a in the Supporting Information). The poly-
mer 1 was also obtained by using an excess of CuI in aceto-
nitrile instead of using dichloromethane. Without dichloro-
methane under stoichiometric conditions, polymer 1 was
contaminated by a small amount of the polymer 2 (Fig-
heat absorption owing to the loss of coordinated acetonitrile
molecules and transformation from stairstep Cu4I4 polymers
to an unknown compound (identified as the cubane Cu4I4
polymer 3, [Cu4I4L2]n) and g-CuI nanocrystals. The loss of
acetonitrile in 1 and 2 changes the ratio of CuI and L and
causes the formation of the new compound 3, and extra CuI
becomes g-CuI nanocrystals. The second endothermic
change occurs in the range of 160–1908C. This corresponds
to decomplexation to yield the free ligand and g-CuI nano-
ACHTUNGTRENNUNG
À
crystals. Since Cu S bonds in the cubane Cu4I4 polymer
assembly reaction of stoichiometric amounts of CuI and L
(CuI/L=8:3) in acetonitrile at room temperature followed
by diffusion of diethyl ether. The use of values between
these molar ratios yielded a mixture of the two polymers.
Slow diffusion of diethyl ether gave good-quality crystals for
SCXRD, while rapid mixing by ultrasonication resulted in
microcrystalline powders (Figure S2c in the Supporting In-
formation). The crystals of 1 and 2 grow as block and
needle crystals, respectively. The compounds have been
characterized by IR, elemental analysis, SCXRD, and
powder X-ray diffraction (PXRD) studies (see the Support-
ing Information).
SCXRD reveals that 1 is a 2D grid network parallel to
the crystallographic a axis (Figure S3b and Table S3 in the
Supporting Information). The network lies in the (011)
plane of the unit cell. Each square compartment of the grid
(red grid at left-hand side in Scheme 1) is composed of two
stairstep Cu4I4 tetramers, two acetonitrile molecules, and
two ligands. All copper atoms in the Cu4I4 tetramer have
distorted tetrahedral geometries. The inner copper atom
(Cu1) in the tetramer is coordinated by three iodide ions
and an S donor and the outer copper atom (Cu2) is coordi-
nated by two iodide ions, an S atom, and an acetonitrile
molecule, which gives CN stretching bands at 2299 and
2264 cmÀ1 in the IR spectrum (Figure S4 in the Supporting
Information).
become labile and the free ligand is liquid at temperatures
near 1708C, decomplexation takes place. Probably decom-
plexed Cu4I4 clusters stick to the seed crystals of g-CuI and
therefore g-CuI nanocrystals grow. We reported crystal-to-
crystal transformation from 1D loop-chain coordination
polymers [Cu2I2(C12H21NOS2)2]n and [Cu4I4(C12H21NOS2)2]n
to
2D
network
coordination
polymer
[Cu4I4(C12H21NOS2)2]n.[16] It seems that this crystal transfor-
À
mation can be possible because Cu S bonds are labile at
1808C. At 1708C, the compounds 1, 2, and 3 were complete-
ly transformed into g-CuI nanocrystals and L. The sizes of
the g-CuI nanocrystals depend on heating time. The NMR
spectrum of recovered L after heating was the same as that
of the free ligand (Figure S9 in the Supporting Information).
The second weight loss begins at about 2008C and ends at
about 3208C, which corresponds to evaporation of the
ligand.
According to the TGA and DTA results, we heated 1 and
2 in the range of 80–1708C and measured the PXRD pat-
terns (Figure 1, and Figure S10 in the Supporting Informa-
tion). The same PXRD patterns were obtained from heated
The complex 2 features a 2D supramolecular bilayer net-
work generated by linking two single-layered networks (red
and blue layers at right-hand side in Scheme 1; Figure S5b
and Table S5 in the Supporting Information) parallel to the
ac plane. The single layer is similar to that of 1 except that
half of the acetonitrile molecules are replaced by the inter-
connecting ligands (black tilted pillaring ligands in
Scheme 1). Coordinated acetonitrile molecules are also
bonded to outer copper atoms of the stairstep Cu4I4 tetram-
ers, as evidenced by weaker CN stretching bands at 2306
and 2274 cmÀ1 than those of 1 (Figure S4 in the Supporting
Information). The purity of the powders 1 and 2 was
checked by scanning electron microscopy images and
PXRD patterns (Figure S2, S6, and S7 in the Supporting In-
formation).
Thermogravimetric analysis (TGA) and differential ther-
mal analysis (DTA) curves of 1 and 2 are shown in Fig-
ure S8 in the Supporting Information. The TGA curves of 1
and 2 indicate that the weight loss begins at 808C and com-
pletes at about 1308C. The DTA curves of 1 and 2 show the
first endothermic peaks at about 1058C. This corresponds to
Figure 1. PXRD patterns of 1 before and after heating at different tem-
peratures. a) Calculated PXRD pattern of 1 with the SCXRD data.
b) PXRD pattern of 1. c) PXRD pattern after heating 1 at 1058C. Open
circles and asterisks are assigned to 3 and g-CuI nanocrystals, respective-
ly. d) PXRD pattern after heating 1 at 1708C for 3 h. Peaks are assigned
to hkl index numbers of g-CuI nanocrystals.
Chem. Asian J. 2010, 5, 252 – 255
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
253