Syntheses, structures, and properties of two novel cadmium coordination polymers with 1D and 2D structures

Article abstract of DOI:10.1016/j.molstruc.2011.07.025

Two novel complexes [Cd₂(MIP)₂(BDC)₂]n (1) [MIP = 2-(3-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, BDC = terephthalic acid] and [Cd(IPM)(NDC)]n (2) [IPM = 4-(1H-imidazo[4,5-f][1,10] phenanthrolin-2-yl)-2-methoxyphenol, NDC = naphthalene-1,4-dicarboxylic acid] have been synthesized by hydrothermal reaction and characterized by elemental analysis, IR, single-crystal X-ray diffraction and thermogravimetric analysis (TGA). Complex 1 exhibits 1D zigzag chain structure and complex 2 shows 2D layer topology. The intermolecular CH?O interactions extend the complex 1 into 2D networks, and the existing H-bonds further stabilized the complexes 1-2, which can be proved by TGA experiment. Furthermore, the solid-state fluorescence spectrum of the complex 2 was studied, as well as the ligand IPM. The complex 2 exhibits intense broad emission at 540 nm at room temperature, which is red-shifted by 45 nm relative to that of free ligand IPM.

Full text of DOI:10.1016/j.molstruc.2011.07.025

Journal of Molecular Structure 1002 (2011) 172–178
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Syntheses, structures, and properties of two novel cadmium coordination
polymers with 1D and 2D structures
a
Li Yan a, Chuanbi Li b, Dongsheng Zhu a, , Lin Xu
⇑
a Department of Chemistry, Northeast Normal University, Changchun 130024, PR China
b Department of Chemistry, Jilin Normal University, Siping 136000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 May 2011
Received in revised form 12 July 2011
Accepted 12 July 2011
Available online 21 July 2011
Two novel complexes [Cd2(MIP)2(BDC)2]n (1) [MIP = 2-(3-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phe-
nanthroline, BDC = terephthalic acid] and [Cd(IPM)(NDC)]n (2) [IPM = 4-(1H-imidazo[4,5-f][1,10]phen-
anthrolin-2-yl)-2-methoxyphenol, NDC = naphthalene-1,4-dicarboxylic acid] have been synthesized by
hydrothermal reaction and characterized by elemental analysis, IR, single-crystal X-ray diffraction and
thermogravimetric analysis (TGA). Complex 1 exhibits 1D zigzag chain structure and complex 2 shows
2D layer topology. The intermolecular CAHꢀ ꢀ ꢀO interactions extend the complex 1 into 2D networks,
and the existing H-bonds further stabilized the complexes 1–2, which can be proved by TGA experiment.
Furthermore, the solid-state fluorescence spectrum of the complex 2 was studied, as well as the ligand
IPM. The complex 2 exhibits intense broad emission at 540 nm at room temperature, which is red-shifted
by 45 nm relative to that of free ligand IPM.
Keywords:
Cadmium complexes
Crystal structures
Hydrothermal synthesis
Fluorescence
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
complexes and investigate their structure–function relationships,
we synthesized two novel N-heterocyclic ligands: 2-(3-methoxy-
Recently, rational design and synthesis of novel metal–organic
coordination polymers have received more and more intense inter-
est and attentions, because of not only their intriguing structural
motifs, but also their potential for use as catalysis, porosity, sen-
sors, magnetism, luminescence, nonlinear optics, chirality, etc.
[1–6]. Selection of appropriate multidentate ligands to coordinate
metal ions is a key strategy for building metal–organic frameworks
(MOFs) [7–9]. Recently, multidentate ligands such as poly-carbox-
ylate and N-heterocyclic ligands are widely used in the rational de-
sign to obtain anticipant structures and desired properties [10–12].
Among poly-carboxylate ligands, the best studied are dicarboxyl-
phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (MIP) and 4-(1H-
imidazo[4,5-f][1,10]phenanthrolin-2-yl)-2-methoxyphenol (IPM)
in view of their following characteristics: (a) they are excellent li-
gands with two nitrogen atoms, which are similar with 2,20-bipyr-
idyl-like bidentate chelating molecules; (b) they possess rigidity of
coordination to metal atoms. The structures of the ligands MIP and
IPM are shown in Scheme 1. Following such a mixed ligand strat-
egy, in this study, we use BDC and NDC (BDC = terephthalic acid,
NDC = naphthalene-1,4-dicarboxylic acid) for the second ligands
to synthesis two new coordination polymers: [Cd2(MIP)2(BDC)2]n
(1) and [Cd(IPM)(NDC)]n (2). Compared with the similar cad-
mium(II) functional complexes, our complexes 1 and 2 display
more stable properties [22,23]. Herein, we report the syntheses,
crystal structures, thermogravimetric analysis (TGA), as well as
photoluminescence properties of coordination polymer 2 and the
ligand IPM.
ates, tricarboxylates, biphenyldicarboxylate, and oxalate (OX2ꢁ
)
[13–15]. As for the N-heterocyclic ligands, the chelate ligands
2,20-bipyridine, 4,40-bipyridine, 1,10-phenanthroline, and their
substituted derivatives have played an important role in the con-
struction of coordination polymers [16,17]. The metal ion Cd(II)
has d10 configuration and often adopts similar structure with zin-
c(II) complexes. Although Cd(II) ion has been shown to enhance
the activity in several metalloenzymes, the biological relevance
of Cd(II) is relatively unexplored [18–20]. 1D, 2D, or 3D Cd(II) coor-
dination complexes attracted intense attention for their potential
applications in catalysis, luminescent materials, NLO materials,
and others [21]. In order to obtain novel cadmium(II) functional
2. Experimental section
2.1. Materials and physical measurements
The ligands MIP and IPM were prepared according to the descrip-
tion in the literature procedures [24]. All the other chemicals from
commercial sources were commercially available, and used without
further purification. The FT-IR spectrum was measured with KBr
pellets in the range of 4000–400 cmꢁ1 on a Perkin–Elmer 240C
⇑
Corresponding author. Tel.: +86 13009010567.
E-mail address: zhuds206@nenu.edu.cn (D. Zhu).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.07.025

L. Yan et al. / Journal of Molecular Structure 1002 (2011) 172–178
173
lyzer. Fluorescence spectra were recorded on a Perkin–Elmer LS 55
luminescence spectrometer.
2.2. Syntheses
[Cd2(MIP)2(BDC)2]n (1): A mixture of MIP (0.099 g, 0.3 mmol),
Cd(NO3)2ꢀ4H2O (0.098 g, 0.3 mmol), BDC (0.100 g, 0.6 mmol) in dis-
tilled H2O (18 mL) was heated to 170 °C for 72 h in a 30-mL Teflon-
lined stainless vessel, and afterwards cooled to room temperature
at a rate of 5 °C/h. The yellow crystals of complex 1 were obtained
in 60% yield based on Cd. C56H37Cd2N8O10: calcd. C 55.74, H 3.09, N
9.29%; found: C 55.69, H 3.11, N 9.35%. IR (KBr, cmꢁ1): 3139(m),
1559(vs), 1384(vs), 1226(s), 1050(s), 843(s), 520(m), 419(m).
[Cd(IPM)(NDC)]n (2): A mixture of IPM (0.100 g, 0.3 mmol),
Cd(NO3)2ꢀ4H2O (0.098 g, 0.3 mmol), NDC (0.130 g, 0.6 mmol) in
distilled H2O (18 mL) was heated to 170 °C for 3 days in a 30-mL
Teflon-lined stainless vessel. The reaction was cooled to room tem-
perature at a rate of 5 °C/h, and then small yellow crystals of com-
plex 2 were collected in 80% yield based on Cd. C32H20CdN4O6:
calcd. C 57.46, H 3.01, N 8.38%; found: C 57.38, H 2.95, N 8.42%.
IR (KBr, cmꢁ1): 3193(s), 1563(vs), 1524(vs), 1484(s), 1403(s),
1352(vs), 1191(s), 855(s), 833(s), 784(m), 638(m), 561(m).
Scheme 1. The structures of ligands MIP and IPM.
Table 1
Crystal data and details of structure refinement parameters for 1 and 2.
Complex
1
2
Empirical formula
Formula weight
Crystal system
Space group
a (nm)
C
56H37Cd2N8O10
C32H20CdN4O6
668.92
Monoclinic
P21/n
1.2555(1)
1.4915(1)
1.3596(1)
96.231(2)
2.5313(4)
4
1206.74
Triclinic
P-1
1.1453(3)
1.3717(4)
1.5911(5)
94.572(6)
2.3892(1)
2
b (nm)
c (nm)
b (°)
2.3. X-ray crystallography
Volume (nm3)
Z
Single-crystal X-ray diffraction data for complexes 1 and 2 were
collected at 293(2) K with a Bruker SMART APEX II CCD diffractom-
eter equipped with a graphite-monochromatized Mo Ka radiation
Density (Mg/m3)
(calculated)
Absorption coefficient
1.677
1.755
0.963
1210
0.922
1344
(mmꢁ1
F(0 0 0)
)
(k = 0.71073 Å) at 293(2) K in the range of 1.55 6 h 6 25.08° for 1
and 2.03 6 h 6 26.01° for 2. Absorption corrections were applied
using multi-scan technique and all the structures were solved by
direct methods and refined by full-matrix least-squares based on
F2 using the programs SHELXS-97 [25] and SHELXTL-97 [26].
Non-hydrogen atoms were refined with anisotropic temperature
parameters and all hydrogen atoms were refined isotropically.
Experimental details for crystallographic data and structure refine-
ment parameters for complexes 1 and 2 are listed in Table 1.
Crystal size (mm3)
Theta range (°)
Reflections collected
Unique reflections [Rint
Goodness-of-fit on F2
0.430 ꢂ 0.370 ꢂ 0.300 0.250 ꢂ 0.189 ꢂ 0.183
1.55–25.08
22,702
2.03–26.01
13,505
4959 [0.0296]
0.844
]
8223 [0.0257]
1.139
Final R indices [I > 2
r
(I)]
R1 = 0.0976
wR2 = 0.1991
R1 = 0.1360
wR2 = 0.2264
R1 = 0.0328,
wR2 = 0.1024
R1 = 0.0452
wR2 = 0.1156
1160, ꢁ1123
R indices (all data)
Largest difference peak and 2087, ꢁ754
hole (e Åꢁ3
)
3. Results and discussion
3.1. Structural analysis of complex 1
The molecular structure is shown in Fig. 1. The 1D zigzag chain
structure is shown in Fig. 2. Double-chain structure linked by
NAHꢀ ꢀ ꢀO hydrogen bonds is suggested in Fig. 3, and two types of
rings in the double-chain structure is shown in Fig. 4. The 2D layer
structure is suggested in Fig. 5. Selected bond lengths and bond an-
gles are given in Table 2.
Single-crystal X-ray structural analysis reveals that the asym-
metric unit of complex 1 contains two Cd(II) atoms, two MIP li-
gands and two BDC ligands (Fig. 1). The Cd(II) atom shows a
hexa-coordinated arrangement, which arises from four carboxylic
oxygen atoms [CdAO = 2.246(8)–2.560(8) Å] from two distinct
chelating BDC ligands, and two nitrogen atoms donors [CdAN =
2.274(1)–2.297(1) Å] from one chelating MIP ligand, forming a dis-
torted octahedral geometry. The distances of CdAO/N bond lengths
are all consistent with corresponding bond lengths found in the lit-
erature [27,21,28,29]. One BDC ligand coordinate to two cadmium
ions through four carboxylic oxygen atoms in a bis-chelating fash-
ion, which give rise to a 1D zigzag chain structure. The N-heterocy-
clic ligands MIP are attached to both sides of this zigzag chain
regularly, and the ligands MIP on the same sides are parallel nearly
with the angular separation of the zigzag chain are 109.048° and
109.122°. The distances of Cdꢀ ꢀ ꢀCd are 10.9936 Å and 11.2225 Å
(Fig. 2). The asymmetric unit of complex 1 has two BDC ligands.
Fig. 1. The molecular structure of complex 1 (hydrogen atoms were omitted).
spectrometer. TGA was performed using a Perkin–Elmer TG-7 ana-
lyzer at the rate of 10 °C/min rise of temperature in nitrogen atmo-
sphere. Crystal structures were determined on a Bruker SMART
APEX II CCD X-ray diffractometer. Carbon, hydrogen and nitrogen
elemental analyses were performed with a PE-2400 elemental ana-

174
L. Yan et al. / Journal of Molecular Structure 1002 (2011) 172–178
Fig. 2. 1D zigzag chain structure of complex 1 (hydrogen atoms were omitted).
Fig. 3. Double-chain structure of complex 1 linked by NAHꢀ ꢀ ꢀO hydrogen bonds (dotted lines represent hydrogen bonds).
Fig. 4. Two types of rings in the double-chain of complex 1 linked by NAHꢀ ꢀ ꢀO hydrogen bonds (dotted lines represent hydrogen bonds).
The BDC(1) contains O3, O4, O5, O6 with the CdAO bond lengths
are from 2.249 Å to 2.334 Å, suggests that the coordination abilities
of coordinated oxygen atoms are nearly parallel. The BDC(2) con-
tains O1, O2, O7, O8 with the CdAO bond lengths are from
2.246 Å to 2.560 Å, reveals that the coordination abilities of coordi-
nated oxygen atoms are different to some extent. The differences of
coordinated ability for the oxygen atoms result in the distortion of
BDC ligands, which may be the result for the difference of the
Cdꢀ ꢀ ꢀCd distances.
There are two kinds of H-bonds interactions in complex 1:
NAHꢀ ꢀ ꢀO interactions and CAHꢀ ꢀ ꢀO interactions. The most interest-
ing aspect of the structure in 1 concerns the intermolecular
NAHꢀ ꢀ ꢀO interactions, which help in the construction of the double
chains (Fig. 3). Every pair of molecules linked by intermolecular

L. Yan et al. / Journal of Molecular Structure 1002 (2011) 172–178
175
Fig. 5. 2D layer structure of complex 1 linked by CAHꢀ ꢀ ꢀO hydrogen bonds (dotted lines represent hydrogen bonds).
NAHꢀ ꢀ ꢀO hydrogen bonding [30] [H(4A)ꢀ ꢀ ꢀO(8) = 1.986 Å,
N(4)ꢀ ꢀ ꢀO(8) = 2.844 Å and N(4)AH(4A)ꢀ ꢀ ꢀO(8) = 175.29°] with the
N atom from ligand IPM and O atom from the dicarboxylate BDC
ligand construct two types of rings: 34-membered ring and 30-
membered ring (Fig. 4). The 34-membered ring contains four Cd
atoms with the diagonal distances are 6.873 Å and 19.031 Å, and
the 30-membered ring contains two Cd atoms with the diagonal
distance is 12.432 Å. These two types of rings arrange alternately
in the double-chain structure. Moreover, as suggested in Fig. 5,
the existence of CAHꢀ ꢀ ꢀO hydrogen bonds interactions
[H(9A)ꢀ ꢀ ꢀO(5) = 2.58 Å, C(9)ꢀ ꢀ ꢀO(5) = 3.372 Å and C(9)AH(9A)
ꢀ ꢀ ꢀO(5) = 143°; H(47A)ꢀ ꢀ ꢀO(1) = 2.48 Å, C(47)ꢀ ꢀ ꢀO(1) = 3.390 Å and
C(47)AH(47A)ꢀ ꢀ ꢀO(1) = 165°] [31] lead the 1D zigzag chain to 2D
layer structure. It is noteworthy that the existence of hydrogen
bonds reinforces the structural stability of compound 1, which
has been proved by TGA.
3.2. Structural analysis of complex 2
The molecular structure is shown in Fig. 6. The 2D layer struc-
ture is suggested in Fig. 7, and the simplified 2D layer structure
is shown in Fig. 8. Selected bond lengths and bond angles are listed
in Table 3.
As shown in Fig. 6, the asymmetric unit of complex 2 consists of
one Cd(II) atom, one IPM ligand, and one NDC ligand. The Cd(II)
atom is hexa-coordinated with two nitrogen atoms (N(1), N(2))
from one chelating IPM ligand and four oxygen atoms (O(1), O(2)
from one chelating bidentate NDC, O(3A), O(4A) from two distinct
bridging monodentate NDC ligand), forming a distorted octahedral
geometry. The bond distances of CdAO in compound 2 are from
2.254(2) Å to 2.376(2) Å, and those of CdAN bond distances fall
in the 2.281(3)–2.365(3) Å range, which are similar with the values
reported [27,21,28,29].
Table 2
Selected bond lengths (Å) and bond angles (°) for complex 1.
Bond
Dist.
Bond
Dist.
Cd(1)AO(1)
Cd(1)AO(2)
Cd(2)AO(5)
Cd(2)AO(6)
Cd(1)AN(1)
Cd(1)AN(2)
2.560(8)
2.246(8)
2.318(8)
2.259(8)
2.282(10)
2.281(10)
Cd(1)AO(3)
Cd(1)AO(4)
Cd(2)AO(7)
Cd(2)AO(8)
Cd(2)AN(5)
Cd(2)AN(6)
2.334(9)
2.249(8)
2.281(9)
2.520(8)
2.297(10)
2.274(10)
The NDC ligands take bis-chelating and monodentate bridging
coordination modes [32] to link three metal Cd(II) atoms, and this
lead to the formation of 2D layer network (Fig. 7). There are two
types of rings in the 2D network: (1) 8-membered ring which con-
tains two Cd atoms with the diagonal distance is 5.0859 Å; (2) 36-
membered ring which contains four Cd atoms with the diagonal
distances are 10.3066 Å and 17.6226 Å.
In order to get better insight into the framework, we omit the
IPM ligands to obtain the simplified 2D (4, 4) network if consider-
ing these dimeric motifs as single nodes (Fig. 8). Moreover, there
Angle
(°)
Angle
(°)
O(3)ACd(1)AO(1)
O(2)ACd(1)AO(4)
O(2)ACd(1)AO(1)
O(4)ACd(1)AO(1)
O(2)ACd(1)AO(3)
O(4)ACd(1)AO(3)
O(2)ACd(1)AN(2)
O(4)ACd(1)AN(2)
O(2)ACd(1)AN(1)
O(4)ACd(1)AN(1)
N(2)ACd(1)AO(3)
N(1)ACd(1)AO(3)
N(2)ACd(1)AO(1)
N(1)ACd(1)AO(1)
N(2)ACd(1)AN(1)
106.2(3)
131.6(4)
53.2(3)
90.5(3)
99.5(4)
56.9(3)
97.2(4)
118.6(3)
88.3(3)
130.9(4)
158.9(4)
94.7(3)
94.2(3)
138.2(3)
73.0(3)
O(6)ACd(2)AO(7)
O(7)ACd(2)AO(5)
O(5)ACd(2)AO(8)
O(6)ACd(2)AO(8)
O(6)ACd(2)AO(5)
O(7)ACd(2)AO(8)
O(6)ACd(2)AN(6)
N(6)ACd(2)AO(7)
N(5)ACd(2)AO(5)
O(6)ACd(2)AN(5)
N(5)ACd(2)AO(8)
N(6)ACd(2)AO(8)
N(6)ACd(2)AO(5)
O(7)ACd(2)AN(5)
N(6)ACd(2)AN(5)
95.7(4)
115.3(3)
89.9(3)
121.4(3)
56.8(3)
53.5(3)
148.5(4)
114.0(3)
141.3(3)
96.5(3)
128.8(3)
86.3(3)
113.9(3)
93.0(3)
72.9(3)
are
p–p interactions between the aryl ring of IPM ligand and the
aryl ring of the NDC ligand in coordination polymer 2 with distance
between cg(1) ? cg(2) ring centroid is 3.488 Å [33]. Cg(1):
C8 ? C9 ? C10 ? N1 ? C7 ? C12, Cg(2): C28 ? C29 ? C30 ?

176
L. Yan et al. / Journal of Molecular Structure 1002 (2011) 172–178
Fig. 6. The molecular structure of complex 2 (hydrogen atoms were omitted).
Fig. 7. The 2D layer structure of complex 2 (hydrogen atoms were omitted).
C31 ? C22 ? C23. The existence of hydrogen bond (N3AH(3A)
interactions reinforce the struc-
tural stability of compound 2, which can be proved by TGA
tion modes [35]. The cꢁh1aracteristic absorption of IPM ligand appear
at 1484 cmꢁ1, 855 cm and 784 cmꢁ1, and the absorption peaks at
638 cmꢁ1 and 561 cmꢁ1 are ascribed to v (CdAN). The IR results are
good agreement with their solid structural features from the re-
sults of their crystal structures.
ꢀ ꢀ ꢀO4, O5AH(5A)ꢀ ꢀ ꢀO2) and
p–p
experiment.
3.3. IR spectra
The FT-IR spectra absorption peaks at 3139 cmꢁ1 for 1, and
3193 cmꢁ1 for 2 correspond to the CAH stretching mode for the
aromatic rings. In complex 1, there are two peaks at 1559 cmꢁ1
and 1384 cmꢁ1 which correspond to the antisymmetric and sym-
Table 3
Selected bond lengths (Å) and bond angles (°) for complex 2.
Bond
Dist.
Bond
Dist.
Cd(1)AO(1)
Cd(1)AO(3)
Cd(1)AN(1)
2.295(2)
2.254(2)
2.365(3)
Cd(1)AO(2)
Cd(1)AO(4)
Cd(1)AN(2)
2.376(2)
2.361(2)
2.281(3)
metric stretching of carboxyl. The
D
v (vas(COOꢁ) ꢁ vs(COOꢁ)) is
175 cmꢁ1 (smaller than 200 cmꢁ1), indicates that the carboxyls
are bidentately coordinated with Cd(II) atoms [34]. The absorption
peaks at 520 cmꢁ1 and 419 cmꢁ1 are ascribed to v (CdAN). In com-
pound 2, the strong characteristic absorption peaks at 1563 cmꢁ1
and 1524 cmꢁ1 are attributed to the antisymmetric stretching
vibration of the coordinated carboxyl groups, and the peak at
1352 cmꢁ1 corresponds to the symmetric stretching of carboxyl.
The separations are 211 cmꢁ1 and 172 cmꢁ1, which indicates that
the carboxyls groups adopt monodentate and bidentate coordina-
Angle
(°)
Angle
(°)
O(1)ACd(1)AO(2)
O(1)ACd(1)AO(4)#2
O(4)#2ACd(1)AO(2)
N(2)ACd(1)AO(2)
N(2)ACd(1)AO(4)#2
O(3)#1ACd(1)AN(2)
O(1)ACd(1)AN(1)
N(2)ACd(1)AN(1)
55.34(9)
94.21(10)
87.10(9)
92.88(9)
92.40(9)
121.14(9)
100.89(10)
71.70(9)
O(3)#1ACd(1)AO(1)
O(3)#1ACd(1)AO(4)#2
O(3)#1ACd(1)AO(2)
N(2)ACd(1)AO(1)
N(1)ACd(1)AO(2)
O(3)#1ACd(1)AN(1)
O(4)#2ACd(1)AN(1)
91.22(8)
89.29(8)
145.91(8)
147.04(10)
96.63(10)
96.17(9)
163.79(9)

L. Yan et al. / Journal of Molecular Structure 1002 (2011) 172–178
177
Fig. 8. The simplified 2D layer structure of complex 2 (hydrogen atoms and IPM ligands were omitted).
3.4. Thermal properties
3.5. Photoluminescent properties
To examine the stability of complexes 1 and 2, TGA curves have
been obtained from crystalline samples in the flowing nitrogen
atmosphere at heating rate of 10 °C/min (Fig. 9). In compound 1,
the first weight loss of 28.00% (calcd. 27.61%) between 420 °C
and 460 °C is attributable to the loss of BDC ligands. The second
weight loss of 54.10% (calcd. 54.08%) in the temperature range of
460–620 °C was ascribed to the release of MIP ligands. In com-
pound 2, the first weight loss of 31.80% from 440 to 495 °C reveals
the loss of the NDC ligands (calcd. 32.32%), and the second weight
loss of 47.20% from 495 to 670 °C corresponds to the loss of IPM li-
gands (calcd. 51.17%). The final products of compounds 1–2 maybe
metal oxide CdO [21,23]. It is concluded that the frameworks of
complexes 1–2 are very stable.
Luminescence property is very important in photochemistry
and photophysics [36,37]. So in this study, we research the lumi-
nescence of complex 2, as well as the free ligands NDC and IPM
(Fig. 10). The free ligands exhibit emissions at 490 nm for NDC
(excitation at 380 nm) and 495 nm for IPM (excitation at
249 nm). Complex 2 shows one broad emission band with the
maximum intensity at 540 nm (green region) upon excitation at
325 nm, which is red-shifted by 45 nm relative to the emission
wavelength of free ligand IPM. The red-shift suggests that the
Cd(II) ions coordinate to ligand IPM, which evokes ligand-to-metal
charge transfer (LMCT) [38]. Complex 2 shows more strong emis-
sion compared to the photoluminescent emission of similar Cd(II)
complexes [39,40], which may be attributed to the rigidity and
Fig. 10. Luminescent spectrum of complex 2 and ligand IPM in solid state at room
Fig. 9. TGA curves of complexes 1 and 2.
temperature.

178
L. Yan et al. / Journal of Molecular Structure 1002 (2011) 172–178
[4] Y. Hou, W.T. Yin, X.D. Xie, X. Chen, J.R. Zhou, H.R. Zuo, Q. Huang, L.M. Yang, C.L.
Ni, X.L. Hu, Inorg. Chim. Acta 363 (2010) 424.
[5] A.J. Blake, N.R. Champness, T.L. Easun, D.R. Allan, H. Nowell, M.W. George, J.H.
Jia, X.Z. Sun, Nat. Chem. 2 (2010) 688.
[6] R. Sun, Y.Z. Li, J.F. Bai, Y. Pan, Cryst. Growth Des. 7 (2007) 890.
[7] E. Kinoshita, M. Takahashi, H. Takeda, M. Shiro, T. Koike, Dalton Trans. (2004)
1189.
higher dimension of complex 2. The rigidity is favor of energy
transfer and reduces the loss of energy through a radiationless
pathway [41]. The coordination polymer 2 may be good candidate
for potential photoluminescence material because it is highly ther-
mally stable and insoluble in water and common organic solvents.
[8] R. Than, A.A. Feldmann, B. Krebs, Coord. Chem. Rev. 182 (1999) 211.
[9] Y.J. Shi, J.Q. Jiang, Y.H. Zhang, X.Z. You, Appl. Organometal. Chem. 18 (2004) 89.
[10] L.P. Zhang, J.F. Ma, J. Yang, Y.Y. Liu, G.H. Wei, Cryst. Growth Des. 9 (2009) 4660.
[11] F. Marandi, R. Rutvand, M. Rafiee, J.H. Goh, H.K. Fun, Inorg. Chim. Acta 363
(2010) 4000.
4. Conclusions
In summary, we have reported two new cadmium complexes
formed by poly-carboxylate and N-heterocyclic ligands. In com-
pound 1, the BDC ligands function in chelating bis-bidentate coor-
dination mode to form 1D zigzag chain structure; The NDC ligands
function in bridging bidentate-chelating bidentate coordination
modes, and this lead to the formation of a 2D layer network in
compound 2. The differences in the structures of these two Cd(II)
complexes were caused by the variations of the coordination
modes in poly-carboxylates. It is worthy to note that the intermo-
lecular hydrogen bonds of CAHꢀ ꢀ ꢀO play an important role in the
supramolecular structure. Here we studied the syntheses, struc-
tures and TG analysis of compounds 1–2, and we also investigate
the fluorescence properties of the coordination polymer 2, as well
as the ligand IPM and NDC. This material will give new impetus to
the construction of novel functional material with potentially use-
ful physical properties.
[12] C.X. Meng, D.S. Li, J. Zhao, F. Fu, X.N. Zhang, L. Tang, Y.Y. Wang, Inorg. Chem.
Commun. 12 (2009) 793.
[13] H.H. Nguyen, N. Hoang, U. Abram, Transition. Met. Chem. 35 (2010) 89.
[14] Y.Y. Liu, J.F. Ma, J. Yang, Z.M. Su, Inorg. Chem. 46 (2007) 3027.
[15] J. Yang, J.F. Ma, Y.Y. Liu, J.C. Ma, S.R. Batten, Inorg. Chem. 46 (2007) 6542.
[16] S. Swavey, R. Swavey, Coord. Chem. Rev. 253 (2009) 2627.
[17] Z.R. Meng, X. He, X.Y. WU, L.J. Chen, W.B. Yang, C.Z. Lu, Chin. J. Struct. Chem. 25
(2006) 1293.
[18] F.M. Nie, M. Li, G.X. Li, Z. Li, W. Li, Inorg. Chim. Acta 363 (2010) 3351.
[19] Y. Xu, L. Feng, P.D. Jeffrey, Y.G. Shi, F.M.M. Morel, Nature 452 (2008) 56.
[20] O. Iranzo, J.P. Richard, J.R. Morrow, Inorg. Chem. 43 (2004) 1743.
[21] R.H. Cui, Y.H. Xu, Z.H. Jiang, Z. Anorg. Allg. Chem. 636 (2010) 605.
[22] M. Hu, X.G. Yang, Q. Zhang, L.M. Zhou, S.M. Fang, C.S. Liu, Z. Anorg. Allg. Chem.
637 (2011) 482.
[23] L.P. Zhang, J.F. Ma, J. Yang, Y.Y. Pang, J.C. Ma, Inorg. Chem. 49 (2010) 1548.
[24] E.A. Steck, A.R. Day, J. Am. Chem. Soc. 65 (1943) 452.
[25] G.M. Sheldrick, SHELXS-97, Program for the Solution of Crystal Structure,
University of Göttingen, Göttingen, Germany, 1997.
[26] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structure,
University of Göttingen, Göttingen, Germany, 1997.
[27] Z. Zhang, M. Pi, T. Wang, C.M. Jin, J. Mol. Struct. 992 (2011) 111.
[28] C.S. Liu, J.J. Wang, Z. Chang, L.F. Yan, Z. Anorg. Allg. Chem. 636 (2009) 1117.
[29] C. Liu, Y.G. Yin, X.H. Shi, D. Zhang, M.H. Hu, Inorg. Chem. Commun. 10 (2007)
37.
Supplementary material
[30] F.M. Nie, M. Li, G.X. Li, Z. Li, W. Li, Inorg. Chim. Acta 363 (2010) 3357.
[31] F. Marandi, R. Rutvand, M. Rafiee, J.H. Goh, H.K. Fun, Inorg. Chim. Acta 363
(2010) 4006.
[32] B.H. Ye, M.L. Tong, X.M. Chen, Coord. Chem. Rev. 249 (2005) 545.
[33] Y.J. Huang, L. Ni, J. Inorg. Organomet. Polym. 21 (2011) 97.
[34] K. Nakamota, Infrared and Raman Spectra of Inorganic and Coordination
Compounds (D.R. Huang, R.Q. Wang, Trans.), third ed., Chemical Industry Press,
Beijing, 1896.
CCDC 814202 and 815977 contain the supplementary crystallo-
graphic data for 1 and 2, respectively. These data can be obtained
free of charge from the Cambridge Crystallographic Data Centre
via http://www.ccdc.cam.ac.uk/datarequest.cif.
Acknowledgments
[35] G.B. Deacon, R. Phillips, J. Coord. Chem. Rev. 33 (1980) 227.
[36] S. Mizukami, H. Houjou, K. Sugaya, E. Koyama, H. Tokuhisa, T. Sasaki, M.
Kanesato, Chem. Mater. 17 (2005) 50.
[37] C.W. Tang, S.A. Vanslyke, Appl. Phys. Lett. 51 (1987) 913.
[38] Y.X. Chi, S.Y. Niu, J. Jin, L.P. Sun, G.D. Yang, L. Ye, Z. Anorg. Allg. Chem. 633
(2007) 1277.
We thank the National Natural Science Foundation of China
(No. 20971019) and the Postdoctoral Science foundation of China
(No. 2005038561) for financial support.
[39] H. Chen, H. Xu, G.X. Liu, X.M. Ren, Chin. J. Inorg. Chem. 25 (2009) 1511.
[40] C.X. Meng, D.S. Li, J. Zhao, F. Fu, X.N. Zhang, L. Tang, Y.Y. Wang, Inorg. Chem.
Commun. 12 (2009) 795.
[41] X.L. Chen, J.J. Wang, H.M. Hu, F. Fu, H.M. Shu, M.L. Yang, G.L. Xue, C.Q. Du, Y.J.
Yao, Z. Anorg. Allg. Chem. 633 (2007) 2056.
References
[1] S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed. 43 (2004) 2334.
[2] C.D. Wu, A. Hu, L. Zhang, W.B. Lin, J. Am. Chem. Soc. 127 (2005) 8940.
[3] M. Kawano, M. Fujita, Coord. Chem. Rev. 251 (2007) 2592.