Hydrogen bonded supra-molecular framework in inorganic-organic hybrid compounds: Syntheses, structures, and photoluminescent properties

Article abstract of DOI:10.1016/j.molstruc.2012.11.046

Two novel compounds constructed from aromatic acid and N-Heterocyclic ligands have been synthesized by hydrothermal reaction: [Cd(mip)(1,8-NDC)(H ₂O)]₂ (1) [mip = 2-(3-methoxyphenyl)-1H-imidazo[4,5-f][1, 10]phenanthroline, 1,8-NDC = naphthalene-1,8-dicarboxylic acid] and Cd(mip) ₂(NTC)₂ (2) [NTC = nicotinic acid]. Compounds 1 and 2 are characterized by elemental analysis, IR, single crystal X-ray diffraction and thermogravimetric analysis (TGA). Single-crystal X-ray investigation reveals that compounds 1-2 are 0 dimensional (0D) structures, and the existence of hydrogen bonds and π-π interactions lead the 0D to 2D novel framework. Hydrogen bonds and π-π interactions are powerful non-covalent intermolecular interactions for directing supra-molecular architectures. TG analysis shows clear courses of weight loss, which corresponds to the decomposition of different ligands. At room temperature, compound 1 exhibits emission at 449 nm upon excitation at 325 nm, and compound 2 shows a strong emission at 656 nm upon excitation at 350 nm. Fluorescent spectrum displays that compounds 1 and 2 are potential luminescent materials.

Full text of DOI:10.1016/j.molstruc.2012.11.046

Journal of Molecular Structure 1035 (2013) 240–246
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Hydrogen bonded supra-molecular framework in inorganic–organic hybrid
compounds: Syntheses, structures, and photoluminescent properties
b
a
c
a
a
Li Yan a, , Wei Liu , Chuanbi Li , Yifei Wang , Li Ma , Qinqin Dong
⇑
a College of Chemistry, Jilin Normal University, Siping 136000, PR China
b College of Computer Science, Jilin Normal University, Siping 136000, PR China
c Changchun Num. 5 Middle School, Changchun 130024, PR China
h i g h l i g h t s
"
"
"
Two cadmium complexes were prepared and characterized by IR, X-ray diffraction and TGA techniques.
The two complexes show distorted octahedral geometries.
Different intermolecular interactions lead to various crystalline aggregates in 1–2.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 August 2012
Received in revised form 20 November 2012
Accepted 20 November 2012
Available online 29 November 2012
Two novel compounds constructed from aromatic acid and N-Heterocyclic ligands have been synthesized
by hydrothermal reaction: [Cd(mip)(1,8-NDC)(H2O)]2 (1) [mip = 2-(3-methoxyphenyl)-1H-imidazo[4,5-f]
[1,10]phenanthroline, 1,8-NDC = naphthalene-1,8-dicarboxylic acid] and Cd(mip)2(NTC)2 (2) [NTC = nico-
tinic acid]. Compounds 1 and 2 are characterized by elemental analysis, IR, single crystal X-ray diffraction
and thermogravimetric analysis (TGA). Single-crystal X-ray investigation reveals that compounds 1–2 are
0 dimensional (0D) structures, and the existence of hydrogen bonds and
p–p interactions lead the 0D to
Keywords:
2D novel framework. Hydrogen bonds and interactions are powerful non-covalent intermolecular
p–p
Cadmium compounds
Crystal structures
Noncovalent interactions
Fluorescence
interactions for directing supra-molecular architectures. TG analysis shows clear courses of weight loss,
which corresponds to the decomposition of different ligands. At room temperature, compound 1 exhibits
emission at 449 nm upon excitation at 325 nm, and compound 2 shows a strong emission at 656 nm
upon excitation at 350 nm. Fluorescent spectrum displays that compounds 1 and 2 are potential lumines-
cent materials.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
factors, such as the coordination nature of metal ions, ligand
structures, pH value, the counter anion, temperature [8]. Generally,
The design and construction of metal–organic frameworks
(MOFs) has become a very attractive research field. The motive
comes not only from the interesting network topologies, but also
from the demand for potential applications as catalysis, porosity,
sensors, magnetism, luminescence, molecular recognition, nonlin-
ear optics and electrical conductivity [1–7]. In this regard, much
progress has been made on the design and synthesis of novel coor-
dination frameworks and the relationships between their struc-
tures and properties. Therefore, systematic research on this topic
is still very necessary and important. However, rational design
and controllable preparation of metal–organic coordination poly-
mers still remains a long-term challenge for the chemists. The
structures of coordination polymers are determined by several
there are two different types of interactions: covalent bonds and
non-covalent interactions, which can be used to construct varied
supramolecular architectures. To date, relatively less attention
has been given to non-covalent interactions, although, non-
covalent interactions can be one of the most powerful force for
instructing and directing the supramolecular architectures
[9–12]. Select suitable multi-dentate ligands such as poly-
carboxylate and N-heterocyclic ligands is a successful approach
to design and controlled synthesis of coordination polymers. Mul-
ti-carboxylate ligands have been demonstrated as top-rank
candidates, because of their versatile coordination modes and
strong coordination ability, for the formation of 1D, 2D or 3D
frameworks.
However,
naphthalene-1,8-dicarboxylic
acid
(1,8-NDC) and nicotinic acid (NTC) are rarely reported, which
inspirits our interest in it. NTC ligand exhibits strong coordination
ability and different kinds of coordination modes. It possesses
⇑
Corresponding author. Tel.: +86 15844440698.
E-mail address: yanli820618@163.com (L. Yan).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.11.046

L. Yan et al. / Journal of Molecular Structure 1035 (2013) 240–246
241
donor nitrogen atom and carboxylate oxygen atom simultaneously
2.3. Syntheses
in the structure of NTC, which can be used as excellent ligand to
construct intriguing structural topologies. As for the N-heterocyclic
ligands, the chelating ligands 2-(pyridin-2-yl) pyridine, 4-(pyridin-
4-yl) pyridine, 1,10-phenanthroline, and their substituted
derivatives have played an important role in the construction of
coordination polymers. In this paper, we synthesize a novel
N-heterocyclic ligand: 2-(3-methoxyphenyl)-1H-imidazo[4,5-f]
[1,10] phenanthroline (mip) in view of the following characteris-
tics: (1) it possesses extended long-conjugated unsymmetrical
aromatic system to provide supramolecular interactions; (2) it
has two nitrogen atoms, which is similar with 2,20-bipyridyl-like
bidentate chelating molecules; (3) it is a planar rigid bidentate
chelating ligand, which can provide supramolecular interactions
such as aromatic stacking to construct intriguing structures; and
(4) it possesses strong coordination ability[13]. The synthesis of
mip is shown in Scheme 1.
Ligand mip: A mixture of 3-methoxybenzaldehyde, 1,10-phe-
nanthroline-5,6-dione (0.525 g, 2.5 mmol), ammonium acetate
(3.88 g, 50 mmol) and glacial acetic acid was refluxed for 4 h, then
cooled to room temperature. Yellow precipitate was obtained
when addition of concentrated aqueous ammonia to neutralize,
which was collected and washed with water. The crude product
dissolved in ethanol was purified by filtration on silica gel. The
principal yellow band was obtained. Then evaporation of the solu-
tion gave yellow products. Yield 0.57 g, 70%. 1H NMR (CDCl3, ppm):
3.25 (s, 3H, CH3–O–Ar), 3.58 (s, 1H, NH), 6.73–7.65 (m, 4H, Ar–H),
7.90–9.10 (m, 6H, aromatic protons in the moiety of phenanthro-
line, Ar–H).
[Cd(mip)(1,8-NDC)(H2O)]2 (1):
A mixture of mip (0.100 g,
0.3 mmol), Cd(NO3)2ꢁ4H2O (0.098 g, 0.3 mmol), 1,8-NDC (0.130 g,
0.6 mmol) in distilled H2O (18 mL) was stirred at room tempera-
ture and adjusted the pH value to about 7.0 with NaOH. We put
the cloudy solution into a 30-mL Teflon-lined stainless vessel at
170 °C for 3 days and afterwards cooled to room temperature at
a rate of 5 °C/h. The yellow crystals of compound 1 were obtained
in 71% yield based on Cd. C64H44Cd2N8O12: calcd. C 57.28, H 3.30, N
8.35%; found: C 56.69, H 3.11, N 8.39%. IR (KBr, cmꢀ1): 3139(s),
1621(vs), 1559(vs), 1384(vs), 1226(s), 1050(s), 843(s), 520(m),
419(m).
For the past several years, we have worked on the synthesis of
the mip similar ligands [14–16]. However, the investigation for this
type of N-heterocyclic ligands is not enough. In this paper, we de-
sign and synthesize two novel Cd(II) coordination polymers,
namely: [Cd(mip)(1,8-NDC)(H2O)]2 1, and Cd(mip)2(NTC)2 2.
Non-covalent intermolecular interactions (coordination bonds,
hydrogen bonds and
p–p interactions) play an important role in
the architectures, which favor construction of higher dimensional
super-molecular framework and reinforce the structural stability.
The research shows that 1 and 2 are good luminescent material.
Cd(mip)2(NTC)2 (2): A mixture of mip (0.100 g, 0.3 mmol),
Cd(NO3)2ꢁ4H2O (0.098 g, 0.3 mmol), NTC (0.073 g, 0.6 mmol) in dis-
tilled H2O (18 mL) was stirred at room temperature and adjusted
the pH value to about 7.0 with NaOH. We put the cloudy solution
into a 30-mL Teflon-lined stainless vessel at 170 °C for 3 days. The
reaction was cooled to room temperature at a rate of 5 °C/h, and
then small yellow crystals of compound 2 were collected in 89%
yield based on Cd. C52H36CdN10O6: calcd. C 61.87, H 3.59, N
2. Experimental section
2.1. Materials
13.87%; found:
C 61.69, H 3.11, N
13.92%. IR (KBr, cmꢀ1):
The ligands mip was prepared according to the description in
the literature procedures [17]. The metallic salt, 1,8-NDC, NTC
and NaOH, were purchased commercially and used without further
purification.
1600(vs), 1390(vs), 1241(s), 1058(s), 706(m), 542(m).
2.4. X-ray crystallography
Single-crystal X-ray diffraction data for compounds 1 and 2
2.2. Physical measurements
were collected at 292(2) K with a Bruker SMART APEX II CCD dif-
fractometer equipped with a graphite-monochromatized Mo K
a
The FT-IR spectrum was measured with KBr pellets in the range
of 4000–400 cmꢀ1 on a Perkin–Elmer 240C spectrometer. TGA was
performed using a Perkin–Elmer TG-7 analyzer at the rate of 10 °C/
min rise of temperature in nitrogen atmosphere. Crystal structures
were determined on a Bruker SMART APEX II CCD X-ray diffrac-
tometer. Carbon, hydrogen and nitrogen Elemental analyses were
performed with a PE-2400 elemental analyzer. 1H NMR spectra
of mip ligand was carried out with Bruker AV 300 MHz spectrom-
eters and chemical shifts are referenced to internal TMS. UV–Vis
spectra were obtained on a JASCO V-570 spectrometer.
radiation (k = 0.71073 Å) at 293(2) in the range of
K
1.67 6 h 6 26.07° for 1 and 1.46 6 h 6 26.04° for 2. Absorption cor-
rections were applied using multi-scan technique and all the struc-
tures were solved by direct methods and refined by full-matrix
least-squares based on F2 using the programs SHELXS-97 [18]
and SHELXTL-97 [19]. Non-hydrogen atoms were refined with
anisotropic temperature parameters and all hydrogen atoms were
refined isotropically. Experimental details for crystallographic data
and structure refinement parameters for compounds 1 and 2 are
listed in Table 1.
Scheme 1. The synthesis of mip ligand.

242
L. Yan et al. / Journal of Molecular Structure 1035 (2013) 240–246
Table 1
Each pair of adjacent Cd(II) atoms are bridged by two 1,8-NDC
ligands to form a dinuclear structure [26,27]. The 1,8-NDC ligands
take bis-chelating and monodentate bridging coordination modes
to link two metal Cd(II) atoms, and this lead to the formation of
0D network. There is 14-membered ring in the asymmetric unit
of compound 1, and the distance of adjacent Cd atoms is
5.0859 Å. There are three kinds of H-bonds interactions in
compound 1: N–Hꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁO and O–Hꢁ ꢁ ꢁO interactions. The
most interesting aspect of the structure in 1 concerns the intermo-
lecular of N–Hꢁ ꢁ ꢁO [H(4A)ꢁ ꢁ ꢁO(4) = 1.98 Å, N(4)ꢁ ꢁ ꢁO(4) = 2.793 Å
and N(4)–H(4A)ꢁ ꢁ ꢁO(4) = 159°] interactions, which helps in the
construction of the 1 D chain structure (Fig. 2). The N-heterocyclic
mip ligands are attached to both sides of this chain regularly,
and mip ligands on the same sides are parallel nearly. Moreover,
in compound 1, adjacent dimers are linked together through
Crystal data and details of structure refinement parameters for 1 and 2.
Compound
1
2
Empirical formula
Formula weight
Crystal system
Space group
a (nm)
C
64H44Cd2N8O12
C52H36CdN10O6
1009.31
orthorhombic
pbcn
1.53142(1)
1.10794(1)
2.7814(3)
90
1341.89
triclinic
P-1
1.11999(4)
1.17767(5)
1.39283(6)
71.1350(10)
1.59567(1)
1
b (nm)
c (nm)
b (o)
Volume (nm3)
Z
4.7193(9)
4
1.421
Density (Mg/m3)
(calculated)
1.396
Absorption coefficient 0.731
0.525
(mmꢀ1
)
F(000)
676
2056
p–p
stackings (centroid-to-centroid distance of 3.661 Å and face-
to-face distance of 3.575 Å) between two 1,8-NDC ligands. Surpris-
ingly, the existence of H-bonds interactions and stackings lead
to the 2D supramolecular framework (Fig. 3). Clearly, intermolecu-
lar stacking and H-bonds interactions contribute to the
Crystal size (mm3)
Theta range (o)
0.45 ꢂ 0.30 ꢂ 0.21
1.67 to 26.07
8831
0.53 ꢂ 0.38 ꢂ 0.21
1.46 to 26.04
27912
p–p
Reflections collected
Unique reflections
6247 [0.0123]
4658 [0.0592]
(Rint
)
p–p
Goodness-of-fit on F2
1.121
R1 = 0.0771
1.034
R1 = 0.0563
stabilization of the structure of compound 1.
Final R indices (I > 2
r
(I))
3.2. Structural analysis of compound 2
wR2 = 0.2581
wR2 = 0.1472
R indices (all data)
Largest difference
peak and hole
R1 = 0.0829wR2 = 0.2672 R1 = 0.0865wR2 = 0.1678
4.223, ꢀ0.585 1.596, ꢀ0.241
The molecular structure is shown in Fig. 4, and the 1D chain
structure is shown in Fig. 5. The 2D layer structure is shown in
Fig. 6. Selected bond lengths and bond angles are listed in Table 3,
and Hydrogen bond lengths and angles for the compounds 1 and 2
are listed in Table 4.
(e Åꢀ3
)
3. Results and discussion
Single-crystal X-ray structural analysis reveals that the asymmet-
ric unit of compound 2 contains one Cd(II) atom, two mip ligands,
and two NTC ligands. The Cd(II) atom is six-coordinated by four
N-Heterocyclic nitrogen atoms from two different mip ligands
(Cd(1)–N = 2.390–2424 Å) and two oxygen atoms from two
NTC molecule (Cd(1)–O = 2.262 Å), which are similar with the
values reported [20–25]. The N(O)–Cd–O(N) angles range are
from 83.67(1) to 152.78(1)°. The angle of N(2)–Cd(1) –N(1),
3.1. Structural analysis of compound 1
The molecular structure is shown in Fig. 1. The 1 D chain struc-
ture is shown in Fig. 2, and the 2D layer structure is suggested in
Fig. 3. Selected bond lengths and bond angles are given in Table 2.
Single-crystal X-ray structural analysis reveals that the asym-
metric unit of compound 1 contains two Cd(II) atoms, two mip
ligands, two 1,8-NDC ligands and two lattice H2O molecules. The
Cd(II) atom is hexa-coordinated with two nitrogen atoms (N(1),
N(2)) from one chelating mip ligand and four oxygen atoms
((O(1W) from one lattice water molecule, O(1), O(2) from one che-
lating bidentate 1,8-NDC, O(3A) from another distinct bridging
monodentate 1,8-NDC ligand). For the coordination environment
of Cd(1), the Cd(1), O1W, O1, N1, N2 atoms define the basal plane,
and the O2, O3 atoms occupy the apical axial positions, forming a
distorted octahedral geometry. The N(O)–Cd–O(N) angles range are
from 83.18(1) to155.01(1)°. The bond distances of Cd–Ocarboxylic
= 2.193(5)–2.471(5) Å, Cd–Owater = 2.414(5) Å, and those of Cd–N
bond distances fall in the 2.326(6)–2.352(6) Å range, which are
similar with the values reported [20–25].
N(2)#1–Cd(1)–N(1), O(2)–Cd(1)–N(2)#1
,
and O(2)–Cd(1)–N(2)
(
#1 = ꢀx, y, ꢀz+1/2) is 69.24, 82.86, 122.36 and 83.67°, and the
sum is 358.13°. For the coordination environment of Cd(1), the
Cd(1), O(2), N(2), N(1) and N(2)#1 atoms define the basal plane,
and N(1)#1 and O(2)#1 atoms occupy the apical axial positions to
form a distorted octahedral environment. In compound 2, the
NTC ligand coordinates to one Cd(II) atom in bridging coordination
mode to form 0D structure. Interesting, the existence of
N4–H4Aꢁ ꢁ ꢁO1 hydrogen bonds interactions [H(4A)ꢁ ꢁ ꢁO(1) =
1.940 Å, N(4)ꢁ ꢁ ꢁO(1) = 2.785 Å and N(4)–H(4A)ꢁ ꢁ ꢁO(1) = 167°] lead
the 0D to 1D chain structure with the distances of Cdꢁ ꢁ ꢁCd are
9.4509 Å. The N-heterocyclic ligands mip are attached to both sides
of this chain regularly, see Fig. 5. Moreover, there is another type of
hydrogen bonds interactions: C(17)–H(17A)ꢁ ꢁ ꢁO(3) [H(17A)ꢁ ꢁ ꢁO(3)
= 2.430 Å, C(17)ꢁ ꢁ ꢁO(3) = 3.342 Å and C(17)–H(17A)ꢁ ꢁ ꢁO(3) = 168°],
which lead the 1D chain to 2D layer structure, see Fig. 6. Moreover,
there are
p–p interactions between the aryl ring of mip ligands
with distances between cg(1) ? cg(2) ring centroid is 3.696 Å.
Cg(1): C5 ? C6 ? N3 ? N4 ? C13, Cg(2): C14 ? C15 ? C16
? C17 ? C18 ? C19. It is noteworthy that the existence of
hydrogen bonds and
p–p interactions reinforce the structural
stability of compound 2, which can be proved by TG analysis.
The Cd(II) atom is hexa-coordinated in the compound 1 with
two nitrogen atoms from one chelating mip ligand and four oxygen
atoms ((O(1W) from one lattice water molecule). The 1,8-NDC
ligands take bis-chelating and monodentate bridging coordination
modes to link two metal Cd(II) atoms. The Cd(II) atom is hexa-
coordinated in the compound 2 with four nitrogen atoms from
two chelating mip ligands and two oxygen atoms from two
Fig. 1. The molecular structure of compound 1 (hydrogen atoms were omitted).

L. Yan et al. / Journal of Molecular Structure 1035 (2013) 240–246
243
Fig. 2. 1D chain structure by N–Hꢁ ꢁ ꢁO hydrogen bonds of compound 1 (dotted lines represent hydrogen bonds).
Fig. 3. 2D supramolecular structure by N–Hꢁ ꢁ ꢁO hydrogen bonds and
p–p interactions of compound 1 (dotted lines represent hydrogen bonds).
Table 2
Selected bond lengths (Å) and bond angles (°) for compound 1.
bond
Dist.
bond
Dist.
Cd(1)–O(3)#1
Cd(1)–O(1)
Cd(1)–N(1)
2.193(5)
2.471(5)
2.352(6)
Cd(1)–O(2)
Cd(1)–O(1W)
Cd(1)–N(2)
2.297(5)
2.414(5)
2.326(6)
Angle
(°)
Angle
(°)
O(3)#1–Cd(1)–O(2)
O(2)–Cd(1)–O(1W)
O(2)–Cd(1)–O(1)
O(3)#1–Cd(1)–N(2)
N(1)–Cd(1)–O(1W)
O(2)–Cd(1)–N(2)
141.9(2)
78.06(1)
54.64(1)
106.5(2)
155.01(1)
101.5(2)
O(3)#1–Cd(1)–O(1W)
O(3)#1–Cd(1)–O(1)
O(1W)–Cd(1)–O(1)
N(2)–Cd(1)–O(1W)
N(2)–Cd(1)–O(1)
O(3)#1–Cd(1)–N(1)
79.36(1)
109.64(1)
113.90(1)
84.80(1)
141.6(2)
113.2(2)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx, ꢀy+1, ꢀz.
different NTC, and donor nitrogen atom in the structure of NTC is
absent in the coordination. The structures of adjacent Cd(II) atoms
in 1 are symmetric, and the most interesting aspect of the structure
in 1 concerns the intermolecular of O1W–H1WBꢁ ꢁ ꢁO1 interactions,
which strengthen the stability of the dimer structure.
Fig. 4. The molecular structure of compound 2 (hydrogen atoms were omitted).
absorption at 1390 cmꢀ1 is the symmetric stretching of carboxyl.
The separation is 210 cmꢀ1 (larger than 200 cmꢀ1), which indicates
the carboxyls adopt monodentate coordination mode. The IR re-
sults are good agreement with their solid structural features from
the results of their crystal structures.
3.3. IR spectra
In compound 1, the two peaks at 1621 and 1559 cmꢀ1 corre-
spond to the antisymmetric stretching of carboxyl, the peak at
1384 cmꢀ1 corresponds to the stretching of carboxyl. The
Dv
(vas(COOꢀ)–vs(COO–)) are 237 and 175 cmꢀ1, indicating that the
carboxyls adopt bidentate and monodentately coordinated with
Cd(II) atoms. In compound 2, the strong absorption peaks at
1600 cmꢀ1 is the antisymmetric stretching of carboxyl, and the
3.4. UV–Vis absorption spectra
The UV–Vis absorption spectra of mip ligand and compounds 1
and 2 are determined in the solid state at room temperature

244
L. Yan et al. / Journal of Molecular Structure 1035 (2013) 240–246
Fig. 5. The 1D chain structure by N–Hꢁ ꢁ ꢁO hydrogen bonds of compound 2 (dotted lines represent hydrogen bonds).
Fig. 6. The 2D layer structure by N–Hꢁ ꢁ ꢁO and C–Hꢁ ꢁ ꢁO hydrogen bonds of compound 2 (dotted lines represent hydrogen bonds).
Table 3
compounds 1 and 2 are between 404 nm and 410 nm, which are
Selected bond lengths (Å) and bond angles (°) for compound 2.
red-shifted by 129–177 nm relative to that of free ligand. After
coordination, the formation of the more large conjugated system
may be the reason for the strong red-shift. The above analyses
for UV–Vis spectral are in agreement with the determined crystal
structure of 1 and 2.
Bond
Dist.
Bond
Dist.
Cd(1)–O(2)
Cd(1)–N(1)
Cd(1)–N(2)
2.262(3)
2.424(4)
2.390(3)
Cd(1)–O(2)#1
Cd(1)–N(1)#1
Cd(1)–N(2)#1
2.262(3)
2.424(4)
2.390(3)
Angle
(°)
Angle
(°)
O(2)–Cd(1)–O(2)#1
O(2)#1–Cd(1)–N(2)#1
O(2)#1–Cd(1)–N(2)
O(2)#1–Cd(1)–N(1)#1
O(2)#1–Cd(1)–N(1)
N(2)#1–Cd(1)–N(1)#1
N(2)#1–Cd(1)–N(1)
98.88(1)
83.67(1)
122.36(1)
152.78(1)
93.64(1)
69.24(1)
82.86(1)
O(2)–Cd(1)–N(2)#1
O(2)–Cd(1)–N(2)
O(2)–Cd(1)–N(1)#1
O(2)–Cd(1)–N(1)
N(2)#1–Cd(1)–N(2)
N(2)–Cd(1)–N(1)#1
N(2)–Cd(1)–N(1)
122.36(1)
83.67(1)
93.64(1)
152.78(1)
141.85(1)
82.86(1)
69.24(1)
3.5. Thermal properties
To examine the stability of compounds 1 and 2, we examined
the TGA curves of crystalline samples in the flowing nitrogen
atmosphere at a heating rate of 10 °C/min (Fig. 8). As expected,
in compound 1, the first weight loss corresponding to the removal
of lattice H2O is 2.90% (calcd. 2.68%) from 107 to 145 °C. The sec-
ond weight loss of 31.80% from 145 to 438 °C corresponds to the
loss of 1,8-NDC ligands (calcd. 32.22%). The last weight loss of
47.20% in the temperature range of 438–564 °C can be ascribed
to the release of mip ligands (calcd. 48.60%). In compound 2,
the first weight loss of 24.00% from 312 to 363 °C corresponds to
the loss of NTC ligands (calcd. 24.38%). The second weight loss
in the temperature range of 380–620 °C can be ascribed to the
release of mip ligands (obsd 62.50%, calcd 64.64%). The final
formation may be the metal oxide CdO. The analysis results indi-
cate that the frameworks of compounds 1–2 are very stable.
Symmetry transformations used to generate equivalent atoms: #1 ꢀx, y, ꢀz+1/2.
Table 4
Hydrogen bond lengths (nm) and angles (°) for the compounds 1 and 2.
D–Hꢁ ꢁ ꢁA
D–H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D–Hꢁ ꢁ ꢁA
1
O1W–H1WBꢁ ꢁ ꢁO1
N4–H4Aꢁ ꢁ ꢁO4
C8–H8Aꢁ ꢁ ꢁO2
C19–H19Aꢁ ꢁ ꢁO4
0.0960
0.0860
0.0930
0.0930
0.1890
0.1980
0.2510
0.2440
0.2676
0.2793
0.3121
0.3327
138
159
123
159
2
N(4)–H(4A) ꢁ ꢁ ꢁO(1)
C(8)–H(8A) ꢁ ꢁ ꢁO(1)
C(17)–H(17A)ꢁ ꢁ ꢁO(3)
0.0860
0.0930
0.0930
0.1940
0.2540
0.2430
0.2785
0.3413
0.3342
167
155
168
3.6. Photoluminescent properties
Luminescence property is very important in photochemistry
and photophysics [28,29]. So in this study, we research the lumi-
nescence of compounds 1 and 2, as well as the free ligand mip
(Figs. 9 and 10). The free ligand exhibits emission at 539 nm (exci-
tation at 347 nm) for mip. Compound 1 exhibits one broad
(Fig. 7). The result suggests that the ligand mip shows two
absorption bands at 275 nm and 233 nm. Absorption bands for

L. Yan et al. / Journal of Molecular Structure 1035 (2013) 240–246
245
Fig. 7. UV–Vis spectrum of compound 1 and 2 in solid state at room temperature.
Fig. 10. Luminescent spectrum of ligand mip and compound 2 in solid state at room
temperature.
emission wavelength of free ligand mip. While compound 2 shows
one broad emission band with the maximum intensity at 656 nm
upon excitation at 350 nm, which is red-shifted by 117 nm relative
to the emission wavelength of free ligand mip. It is worth to men-
tion that the heavy atom effect is quenching to some extent, so the
luminescent of compound 1 is weaker than mip ligand. Com-
pounds 1–2 exhibit strong emissions, which may be attributed to
the ligand rigidity. The rigidity is favor of energy transfer and re-
duces the loss of energy through a radiationless pathway. How-
ever, the effect of the microenvironment between ligands and
compounds on the luminescence properties still needs further
investigations. 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.
4. Conclusions
Fig. 8. TGA curves of compounds 1 and 2.
In conclusion, two unique compounds have been synthesized
by using plane multifunctional ligands mip, 1,8-NDC and NTC. It
is noteworthy that non-covalent interactions (
p p interactions,
ꢁ ꢁ ꢁ
H-bond and coordination bonds) can be one of the most powerful
force for instructing and directing the supra-molecular architec-
tures, as well as reinforcing the structural stability of the title com-
pounds. TG analysis reveals that the title compounds are very
stable and worthy of further study as candidate of potential photo-
luminescence material.
Supplementary material
CCDC 859084 and 859139 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 www.ccdc.cam.ac.uk/ data request. cif.
Acknowledgments
We thank the National Natural Science Foundation of China
(No. 20971019) and the Postdoctoral Science foundation of China
(No. 2005038561) for financial support.
Fig. 9. Luminescent spectrum of ligand mip and compound 1 in solid state at room
temperature.
References
emission band with the maximum intensity at 449 nm upon exci-
tation at 325 nm, which is blue-shifted by 90 nm relative to the
[1] S.R. Batten, R. Robson, Angew. Chem. Int. Ed. 37 (1998) 1460.
[2] C.D. Wu, A. Hu, L. Zhang, W.B. Lin, J. Am. Chem. Soc. 127 (2005) 8940.

246
L. Yan et al. / Journal of Molecular Structure 1035 (2013) 240–246
[3] J.L.C. Rowsell, O.M. Yaghi, J. Am. Chem. Soc. 128 (2006) 1304.
[4] O.R. Evans, W. Lin, Acc. Chem. Res. 35 (2002) 511.
[18] G.M. Sheldrick, SHELXS 97, Program for the Solution of Crystal Structure,
University of Göttingen, Germany, 1997.
[5] J.P. Zhang, Y.Y. Lin, X.C. Huang, X.M. Chen, J. Am. Chem. Soc. 127 (2005) 5495.
[6] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629.
[7] S.L. Zheng, J.P. Zhang, W.T. Wong, X.M. Chen, J. Am. Chem. Soc. 125 (2003)
6882.
[19] G.M. Sheldrick, SHELXS 97, Program for the Refinement of Crystal Structure,
University of Göttingen, Germany, 1997.
[20] W.Q. Geng, X.L. Li, J.H. Yin, H.P. Zhou, J.Y. Wu, Y.P. Tian, Inorg. Chem. Commun.
13 (2010) 1285.
[8] J. Yang, B. Wu, F. Zhuge, J.J. Liang, C.D. Jia, Y. Y Wang, N. Tang, X.J. Yang, Q.Z. Shi,
Cryst. Growth Des. 10 (2010) 2331.
[9] Q.X. Liu, X.J. Zhao, X.M. Wu, L.N. Yin, J.H. Guo, X.G. Wang, J.C. Feng, Inorg. Chim.
Acta 361 (2008) 2616.
[10] G.N. Li, J. Xiong, Y. Liao, L. Sun, Y.Z. Li, J.L. Zuo, Polyhedron 30 (2011) 2473.
[11] F. Hu, X. Yin, Y. Mi, S. Zhang, W. Luo, Y. Zhuang, Inorg. Chem. Comm. 13 (2010)
33.
[12] S. Zhang, Q. Wei, G. Xie, Q. Yang, S. Chen, Inorg. Chim. Acta 387 (2012) 52.
[13] Y.J. Huang, L. Ni, J. Inorg. Organomet. Polym. 21 (2011) 97.
[14] L. Yan, C.B. Li, D.S. Zhu, L. Xu, J. Inorg. Organomet. Polym. 22 (2012) 236.
[15] L. Yan, C.B. Li, D.S. Zhu, L. Xu, J. Inorg. Organomet. Polym. 22 (2012) 395.
[16] L. Yan, C.B. Li, D.S. Zhu, L. Xu, J. Mol. Struct. 1002 (2012) 172.
[17] E.A. Steck, A.R. Day, J. Am. Chem. Soc. 65 (1943) 452.
[21] F. Yang, Y. Ren, D. Li, F. Fu, G. Qi, Y. Wang, J. Mol. Struct. 892 (2008) 283.
[22] J. Zhang, B. Li, X. Wu, H. Yang, W. Zhou, X. Meng, H. Hou, J. Mol. Struct. 984
(2010) 276.
[23] Z. Zhang, M. Pi, T. Wang, C.M. Jin, J. Mol. Struct. 992 (2011) 111.
[24] M. Hu, X.G. Yang, Q. Zhang, L.M. Zhou, S.M. Fang, C.S. Liu, Z. Anorg, Allg. Chem.
637 (2011) 480.
[25] S.L. Li, Y.Q. Lan, J.F. Ma, J. Yang, G.H. Wei, L.P. Zhang, Z.M. Su, Cryst. Growth Des.
8 (2008) 680.
[26] F.M. Nie, M. Li, G.X. Li, J. Mol. Struct. 977 (2010) 45.
[27] F. Yang, Y.X. Ren, D.S. Li, F. Fu, G.C. Qi, Y.Y. Wang, J. Mol. Struct. 892 (2008) 283.
[28] C.H. Chen, J.M. Shi, Coord. Chem. Rev. 171 (1998) 165.
[29] S. Mizukami, H. Houjou, K. Sugaya, E. Koyama, H. Tokuhisa, T. Sasaki, M.
Kanesato, Chem. Mater. 17 (2005) 51.