Two distinct 2D Cd(II)/Zn(II) networks based on flexible 1,2-phenylenediacetate and N-donor co-Ligand: Synthesis, structure, and fluorescent properties

Article abstract of DOI:10.1080/15533174.2012.740710

Two novel Cd(II)/Zn(II) compounds based on flexible benzene dicarboxylate and N-donor auxiliary ligands, formulated as [Cd(phda)(dpe)]_n (1) and [Zn(phda)(acpy)(H₂O)]_n (2), have been synthesized by the hydrothermal reaction

Full text of DOI:10.1080/15533174.2012.740710

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:196–202, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.740710
Two Distinct 2D Cd(II)/Zn(II) Networks Based on Flexible
1,2-Phenylenediacetate and N-donor Co-Ligand: Synthesis,
Structure, and Fluorescent Properties
Ling-Yun Xin, Xiao-Ling Li, Guang-Zhen Liu, and Han Guo
College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang, P. R. China
fact, it is well known that flexible organic carboxylate ligands
inherently hold the potential of adopting different conforma-
tions under different conditions so as to enrich the structural
and functional diversities of MOF. In contrast to rigid carboxy-
late ligand, flexible ones have following several superiority:
First, the flexibility of ligands is more essential to forming
some coordinated polymers of particular properties and struc-
tures.[8,9] Second, the flexible ligand is more apt to display vari-
able coordination modes resulting from the geometry restric-
tions imposed by the coordination of the center metal cation.[10]
Last, larger molecular size for this primary building unit may
provide more opportunities for the formation of microporous
frameworks.[11]
Two novel Cd(II)/Zn(II) compounds based on flexible ben-
zene dicarboxylate and N-donor auxiliary ligands, formulated as
[Cd(phda)(dpe)]n (1) and [Zn(phda)(acpy)(H2O)]n (2), have been
synthesized by the hydrothermal reaction and characterized by
single-crystal X-ray diffraction, elemental analysis, IR, and fluo-
rescent spectra (phda = 1,2-phenylenediacetate, dpe = 1,2-di(4-
pyridyl)-ethylene, and acpy = 4-acetylpyridine). Complex 1 dis-
plays 2D bilayer network featuring phda-bridged binuclear cad-
mium (II) ribbon-like chain further pillared by dpe ligand, whereas
complex 2 exhibits 2D thick-layer with {4.82}-fes topology featur-
ing phda-bridging carboxylate layer constructed by the alternate
opposite helix chain. In addition, luminescent properties of the both
complexes are also investigated.
With these considerations in mind, we chose the flexible mul-
ticarboxylates with long-spanning carboxyl groups and further
investigated the effect of N-donor ligands on the framework
topology of MOFs in this synthesis system. Recently, we re-
ported some related work.[12–14] The preliminary work shows
Keywords 1, 2-phenylenediacetate, cadmium, photoluminescence,
zinc
INTRODUCTION
Design and construction of novel coordination networks that some fascinating structures including helices and interpen-
or metal-organic frameworks (MOFs) continue to receive re- etrating networks that may be attributed to the flexibility of
searchers’ attention, due to their structural diversity, intriguing carboxyl groups. Herein, we present on two new Cd(II)/Zn(II)
topology architecture,[1,2] and potential applications in the fields complexes assembled from flexible carboxylate H2phda and
of gas adsorption,[3] ion-exchange,[4] optics,[5] magnetism,[6] and N-donor ligands. One is a 2D layer featuring the carboxylate
catalysis.[7] Among them, divalent metal coordination polymers chain pillared 1,2-di(4-pyridyl)-ethylene ligand, and another is
containing tethering dicarboxylate ligands are among the most 2D carboxylate layer jointed by chiral helix-chain with dan-
commonly employed linkers in MOF chemistry, because dif- gling the 4-acetylpyridine auxiliary ligands. Furthermore, the
ferent metal coordination environments and carboxylate group fluorescence properties of both complexes are also given.
binding and bridging modes can provide a wide scope of under-
lying coordination polymer structural topologies.
To date, most of the organic ligands used in MOF chem-
istry are limited to a rigid aromatic carboxylate ligand, whereas
the study of a flexible carboxylate ligand is relatively rare. In
EXPERIMENTAL
Materials and Methods
All reagents used in these syntheses were of analytical grade
and used as purchased without further purification. Elemental
analyses (C, H, N) were performed on a German Elementar
Vario EL III elemental analyzer. Infrared spectra were recorded
on a German Bruker VECTOR-22 spectrophotometer within
400–4000 cm–1 using the samples prepared as pellets with KBr.
Luminescence spectra were performed on a Hitachi F-4500 flu-
orescence spectrophotometer (Japan) at room temperature.
Received 31 October 2011; accepted 13 October 2012.
This work was supported by the National Natural Science Founda-
tion of China (Nos. 20971064 and 21071074) and the Foundation of
Education Committee of Henan Province (no 092102210315).
Address correspondence to Guang-Zhen Liu, College of Chem-
istry and Chemical Engineering, Luoyang Normal University Luoyang,
471022, P. R. China. E-mail: gzliu@yahoo.com.cn.
196

TRANSITION METAL COMPLEX
197
Colorless crystals were obtained and crystals were filtered off,
washed with water liquid, and dried under ambient conditions.
Yield 46%. Elemental Anal. Calcd. (%) for C17H17NO6Zn: C
51.73, H 4.34, N 3.55 Found: C 51.90, H 4.42, N 3.57.
Synthesis
Synthesis of [Cd(phda)(dpe)]n (1)
The mixtures of H2phda (0.1 mmol, 19.4 mg), dpe (0.1 mmol,
19.8 mg), Cd(OAC)2·2H2O (0.1 mmol, 26.7 mg), and H2O
(8.0 mL) were placed in a 23 mL Teflon liner stainless steel re-
actor. The vessel was heated to 120◦C for 4 days, then cooled at
5◦C h–1 to room temperature. Colorless crystals were obtained
and crystals were filtered off, washed with water liquid, and
dried under ambient conditions. Yield: 52%. Elemental Anal.
Calcd. (%) for C22H18CdN2O4: C 54.28, H 3.73, N 5.75 Found:
C 54.01, H 3.81, N 5.81.
Single-Crystal X-Ray Structure Determination
Suitable single crystals of 1–2 were mounted on a Bruker
Smart APEX II CCD diffractometer (Germany) equipped with
graphite-monochromated Mo Ka radiation (λ = 0.71073 Å)
by using ꢀ/ω scan technique at room temperature. Semiempiri-
cal absorption corrections were applied using SADABS (Bruker
AXS, Germany). The structures were solved using direct method
and refined by full-matrix least-squares on F2. All non-hydrogen
Synthesis of [Zn(phda)(acpy)(H2O)]n (2)
The mixtures of H2phda (0.1 mmol, 19.4 mg), 2,3-di(4- atoms were refined anisotropically, and the hydrogen atoms
pyridyl)-2,3-butanediol (0.2 mmol, 48.9 mg), Zn(OAC)2·2H2O were placedincalculatedpositions andrefinedisotropicallywith
(0.1 mmol, 22.0 mg), and H2O (8.0 mL) were placed in a 23 mL a riding model except for those bound to water molecules, which
Teflon liner stainless steel reactor. The vessel was heated to were initially located in a difference Fourier map and included
120◦C for 4 days, then cooled at 5◦C h–1 to room temperature. in the final refinement by use of geometrical restraints with the
TABLE 1
Crystal data and structure refinement parameters for 1 and 2
1
2
Empirical formula
Formula weight
Temperature (K)
Crystal system
C22H18CdN2O4
486.78
296(2)
C17H17NO6Zn
396.69
296(2)
Triclinic
Monoclinic
P–1
9.5013(11)
10.4553(12)
10.7742(12)
82.9560(10)
89.5460(10)
63.3100(10)
947.70(19)
Space group
a (Å)
b (Å)
P2(1)/c
14.6596(16)
7.6995(8)
14.8678(16)
90.00
102.1280(10)
90.00
c (Å)
a (◦)
β (◦)
γ (◦)
Volume (Å3)
Crystal size (mm)
Z
1640.7(3)
0.39 × 0.12 × 0.11
0.48 × 0.39 × 0.30
2
4
Dcalc (g cm–3)
μ (mm–1)
F(000)
1.706
1.185
488
2.40 to 25.50
–11 ≤ h ≤ 11
–12 ≤ k ≤ 12
–13 ≤ l ≤ 13
17124
1.606
1.531
816
2.80 to 25.50
–17 ≤ h ≤ 17
–9 ≤ k ≤ 9
–18 ≤ l ≤ 18
10772
θ range (◦)
Index ranges
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit
8236 [R(int) = 0.0181]
8236 / 0 /559
1.080
3044 [R(int) = 0.0204]
3044 / 0 / 227
1.026
Final R indices [I>2σ(I)]
R indices (all data)
R1 = 0.0360, ωR2 = 0.0973
R1 = 0.0468, ωR2 = 0.1023
0.544/–0.425 830068
R1 = 0.0236, ωR2 = 0.0579
R1 = 0.0288, ωR2 = 0.0601
0.238/–0.264 850414
Final difference peaks /e.A—3 CCDC No.

198
L.-Y. XIN ET AL.
TABLE 2
Select bond lengths (Å) and angles (◦) for 1 and 2
Compound 1
Cd(1)-O(4)#1
Cd(1)-O(3)#2
Cd(1)-N(1)
2.291(2)
2.3420(16)
2.3502(17)
Cd(1)-O(2)
Cd(1)-O(1)
Cd(1)-N(2)
2.3311(17)
2.5165(18)
2.3505(17)
O(4)#1-Cd(1)-O(2)
O(2)-Cd(1)-O(3)#2
O(2)-Cd(1)-N(1)
O(4)#1-Cd(1)-N(2)
O(3)#2-Cd(1)-N(2)
O(4)#1-Cd(1)-O(1)
O(3)#2-Cd(1)-O(1
N(2)-Cd(1)-O(1)
Compound 2
139.53(7)
O(4)#1-Cd(1)-O(3)#2
O(4)#1-Cd(1)-N(1)
O(3)#2-Cd(1)-N(1)
O(2)-Cd(1)-N(2)
N(1)-Cd(1)-N(2)
O(2)-Cd(1)-O(1)
N(1)-Cd(1)-O(1)
114.70(7)
105.77(6)
89.33(6)
92.74(8)
90.63(6)
86.15(7)
159.03(6)
90.55(6)
94.32(8)
83.35(6)
87.49(6)
172.17(6)
53.39(6)
93.29(6)
Zn(1)-O(4)#1
2.0467(13)
Zn(1)-O(3)#2
2.0481(13)
Zn(1)-O(6W)
Zn(1)-N(1)
2.0731(15)
2.1662(16)
96.94(6)
96.37(7)
163.50(6)
88.31(5)
175.25(7)
158.36(5)
86.37(5)
Zn(1)-O(2)
Zn(1)-O(1)
2.1622(13)
2.2346(13)
91.07(5)
98.70(6)
88.59(6)
88.38(6)
86.85(6)
104.70(5)
59.79(5)
O(4)#1-Zn(1)-O(3)#2
O(3)#2-Zn(1)-O(6W)
O(3)#2-Zn(1)-O(2)
O(4)#1-Zn(1)-N(1)
O(6W)-Zn(1)-N(1)
O(4)#1-Zn(1)-O(1)
O(6W)-Zn(1)-O(1)
N(1)-Zn(1)-O(1)
O(4)#1-Zn(1)-O(6W)
O(4)#1-Zn(1)-O(2)
O(6W)-Zn(1)-O(2)
O(3)#2-Zn(1)-N(1)
O(2)-Zn(1)-N(1)
O(3)#2-Zn(1)-O(1)
O(2)-Zn(1)-O(1)
92.48(5)
Symmetry codes for compound 1: #1 –x + 1, –y + 1, –z + 1, #2 x + 1, y, z; symmetry codes for compound 2: #1 x, –y – 1/2, z – 1/2, #2 –x
+ 2, –y, –z + 1.
H2phda and dipyridyl-type molecule, the ideal single crystals
suitable for X-ray diffraction analysis can be isolated in the
aqueous solution, whereas complex 2 is obtained in the 1:1:2
molar ratio of metal(II) acetate, H2phda, and 2,3-di(4-pyridyl)-
2,3-butanediol. Furthermore, The structure of complex 2 shows
the 2,3-di(4-pyridyl)-2,3-butanediol molecule is unstable and
apt to transform into the 4-acetylpyridine (Scheme 1) in in situ
hydrothermal reactions.
O-H distances being fixed at 0.85 Å and Uiso(H) equivalent to
1.5 times of Ueq(O). All calculations were performed using the
SHELXTL-97 program package.[15] Crystal data and experi-
mental details for compounds 1–2 are contained in Table 1. The
selected bond lengths and angles are listed in Table 2.
RESULTS AND DISCUSSION
Synthesis and IR Characterization
The IR spectrum of 1 and 2 shows the sharp characteristic
Hydrothermal method has been extensively explored as an bands of dicarboxylate groups in the usual region at ∼1630 and
effective and powerful tool in the self-assembly of MOFs, al- ∼1500 cm–1 for the asymmetric stretching and the ∼1390 cm–1
though the mechanism is not completely clear so far. In our for the symmetric stretching. Features corresponding to pyridyl
experiment, the hydrothermal reactions of compound 1 and 2 ring puckering mechanisms were evident in the region 850 cm–1
were carried out in different molar ratio. When complex 1 is and 600 cm–1. The broad bands in the area of ∼3200 cm–1
manipulated in the equivalent molar ratio of metal(II) acetate, in compound 2 belong to the O-H stretching modes within
SCH. 1. Coordination modes of phda anion in both complexes (left) and in-situ decomposition route of ancillary ligand for complex 2 (right).

TRANSITION METAL COMPLEX
199
coordinated water molecules. None peak of compound 1–2
in ∼1680 cm–1 demonstrates complete deprotonation of the
H2phda after forming the coordination polymers.
. . . Cd separations are 4.2092(4) and 7.6442(8) Å, respectively.
Along with the [1–1-1] direction the resulted chains are inter-
linked by the dpe ligands to form a 2D bilayer structure including
two rhombic 2D grid with a side length of 14.0630\9.5013(11)
Å (Figure 1). The adjacent 2D layers stack in a slightly offset
parallel fashion with a repeating sequence of -AAA- (Figure 1).
The Structural Descriptions of [Cd(phda)(dpe)]n (1)
Complex 1 displays a 2D bilayer structure with binuclear Cd
dimer as nodes and phda and dpe as linkers. The asymmetric unit
contains one Cd(II) cation, one phda anion, and two one-half dpe
molecules in special positions as shown in Figure 1. Each Cd
center has an octahedrally coordinated geometry with the basal
plane occupied by four oxygen atoms from three phda ligands
The Structural Descriptions of [Zn(phda)(acpy)(H2O)]n
(2)
Complex 2 exhibits a unusual 2D layer with 3-connected
by mono/bidentate alternately coordinated modes (Cd-O bond {4.82}-fes topology. The asymmetric unit contains one Zn(II)
lengths are range from 2.291(2) Å to 2.5165(18) Å), while two ion, one phda dianion, one 4-acetylpyridine molecule, and one
dpe pyridyl N occupy the apical sites (Cd-N = 2.3502(17) Å and coordinated water molecule. As shown in Figure 2, the Zn(II)
2.3505(17) Å). The [CdO4N2] environment is best described as ion is six-coordinated by four oxygen atoms from three phda
slightly distorted octahedron.
ligands in the equatorial plane (Zn-O bond lengths are range
In this structure, both two carboxylates of each phda an- from 2.0467(13) Å to 2.2346(13) Å), while one 4-acetylpyridine
ion, adopting a bidentate-bridging and bidentate-chelate mode pyridyl N and one coordinated water molecule occupy the axial
(Scheme 1), respectively, link the Mn centers to generate a positions (Zn-N = 2.1662(16) Å and Zn-Ow = 2.0731(15) Å).
ribbon-like chain (Figure 1). Among them, two carboxylate
The phda anions adopting similar coordinated modes to
groups bridge two Cd(II) ions to form the 8-MRs and two phda those in 1 bridge the adjacent Zn(II) atoms to yield a undu-
ligands bridge two Cd(II) ions to form the 18-MRs with Cd lating [Zn(phda)]n layer (Figure 2). Interestingly, the 2D layer
FIG. 1. (a) ORTEP plot of the asymmetric unit showing the coordination environment of Cd cation in 1, with the symmetry related part drawn in open circles.
Thermal ellipsoids are given at 30% probability. Symmetry codes: A = 1 + x, y, z; B = 1 – x, 1 – y, 1 – z. (b) View of 1D ribbonlike chains bridged by the phda
anion. (c) The 2D bilayer featuring Cd carboxylate chains pillared by dpe molecules. (d) A space-filling view stacked by adjacent 2D layers.

200
L.-Y. XIN ET AL.
FIG. 2. (a) View of the coordination environment of Zn(II) ion in 2. Symmetry codes: A = 2 – x, –y, 1 – z; B = x, –0.5 – y, –0.5 + z. (b) A polyhedral view
of the 2D layer. (c) View of a 2D layer constructed via the left- and right-handed helical chains. (d) Side view of 2D layer including 4-acetylpyridine ligand. (e)
Schematic representation of {4.82-fes topology for 2. (f) 2D thick-layer formed by H-bonding interactions.
involves two kinds of helical chains, where the right-handed metal center as node is linked to three neighbors and each phda
and left-handed helical chains are in an alternate array by shar- ligand as bridge is joint to three metal nodes.
ing the phda bridging ligand, as shown in Figure 2. The pitch
Furthermore, the presence of coordinated water molecules
of each helical chain is equivalent as the length of the b-axis. leads to the formation of extensive H-bonding interactions (Fig-
The whole structure features 2D carboxylate layer developed by ure 2) within the layers (O(6W)-H(1W) . . . O(1)) and (O(6W)-
helical chain with 4-acetylpyridine as dangling lateral arms pro- H(2W) . . . O(3)) (Table 3). The adjacent H-bonding 2D thick-
truding out of both sides of layer (Figure 2). From a topological layers stack in a slightly off-set parallel fashion and cohered
perspective, compound 2 can be described as a three-connected together by the weak van der Waals force to form its entire 3D
net with {4.82}-fes topology (Figure 2), in which each Zn(II) supramolecular structure.

TRANSITION METAL COMPLEX
201
TABLE 3
Although more detailed theoretical and spectroscopic studies
may be necessary for better understanding of the luminescent
mechanism, the strong fluorescence emission of complexes 2
makes it potentially useful photoactive materials.
Hydrogen bond distances (Å) and bond angles (◦) for 2
D-H···A
d (D-H) d (H···A) d (D···A) ∠ (DHA)
O(6W)-H(2W) . . .
O(3)#1
0.84
1.95
2.703(2)
148.0
O(6W)-H(1W) . . .
O(1)#2
0.84
1.85 2.6775(19) 171.3
CONCLUSIONS
In summary, two novel 2D Zn(II)/Cd(II) coordination poly-
mers have been hydrothermally synthesized by using 1,2-
phenylenediacetate and two kinds of N-donor coligands.
Although the phda ligand adopts the same carboxylate coordi-
nation modes in both compounds, their structures reveal entirely
different 2D networks: the 2D bilayer of 1 features phda-bridged
binuclear Cd(II) chains pillared by flexible dpe ligands, whereas
complex 2 manifests phda-bridged [Zn(phda)]n thick-layer with
{4.82}-fes topology joined by the right-handed and left-handed
helical chains. Further studies and physical characterization of
other transition metals with the H2phda ligand are also underway
in our lab.
Symmetry transformations used to generate equivalent atoms: #1 x,
–y – 1/2, z – 1/2; #2 –x + 2, –y, –z + 1.
Fluorescent Properties of 1 and 2
Inorganic-organic hybrid coordination polymers, especially
those with d10 metal centers, have been investigated for photolu-
minescent properties and potential applications as fluorescence-
emitting materials. The solid-state photoluminescent properties
of the free H2phda ligands, complexes 1 and 2 have been inves-
tigated at room temperature, as shown in Figure 3. The emis-
sion peak of free H2phda ligand is observed at about 353 nm
and 371 nm, probably attributable to the π∗−π transitions. On
complexation of the ligand with Cd(II) atom, the emission peaks
occur at 358 nm and 371 nm for 1. Since the Zn2+ and Cd2+
ions is difficult to oxidize or to reduce due to their d10 config-
uration, the emissions of complex 1 are neither metal-to-ligand
charge transfer nor ligand-to-metal charge transfer in nature.
They can probably be assigned to the intraligand charge trans-
fer of H2phda ligand because similar emission is observed for
the free H2phda ligand and the dipyridyl-type co-ligands show
almost no contribution to the emissions of the compounds due
to their very weak fluorescent emission. However, fluorescent
spectrum of 2 appears a broad and intensity emission peak at
383 nm compared with the free phda ligand and complex 1.
REFERENCES
1. Pan, L.; Adams, K.M.; Hernandez, H.E.; Wang, X.T.; Zheng, C.; Hattori,
Y.; Kaneko, K. Porous lanthanide-organic frameworks: synthesis, charac-
terization, and unprecedented gas adsorption properties. J. Am. Chem. Soc.
2003, 125, 3062–3067.
2. Zhu, H.F.; Fan, J.; Okamura, T.; Zhang, Z.H.; Liu, G.X.; Yu, K.B.; Sun,
W.Y.; Ueyama, N. Metal–organic architectures of silver(I), cadmium(II),
and copper(II) with a flexible tricarboxylate ligand. Inorg. Chem. 2006, 45,
3941–3948.
3. Zhang, Y.B.; Zhang, W.X.; Feng, F.Y.; Zhang, J.P.; Chen, X.M. A highly
connected porous coordination polymer with unusual channel structure and
sorption properties. Angew. Chem., Int. Ed. 2009, 48, 5287–5290.
4. Yaghi, O.M.; Li, H. T-shaped molecular building units in the
porous structure of Ag(4,4’-bpy)·NO3. J. Am. Chem. Soc. 1996, 118,
295–296.
5. Allendorf, M.D.; Bauer, C.A.; Bhakta, R.K.; Houk, R.J. T. Lu-
minescent metal–organic frameworks. Chem. Soc. Rev. 2009, 38,
1330–1352.
6. Xu, H.B.; Wang, B.W.; Pan, F.; Wang, Z.M.; Gao, S. Stringing oxo-centered
trinuclear [MnIII3O] units into single-chain magnets with formate or azide
linkers. Angew. Chem., Int. Ed. 2007, 46, 7388–7392.
7. Seo, J.S.; Whang, D.; Lee, H.; Jun, S.I.; Oh, J.; Jeon, Y.J.; Kim, K.A
Homochiral metal-organic porous material for enantioselective separation
and catalysis. Nature 2000, 404, 982–986.
8. Chen, C.L.; Zhang, J.Y.; Su, C.Y. Coordination assemblies of metallacyclic,
prismatic and tubular molecular architectures based on the non-rigid lig-
ands. Eur. J. Inorg. Chem. 2007, 2997–3010.
9. Pigge, F.C. Losing control? “Design” of crystalline organic and
metal–organic networks using conformationally flexible building blocks.
CrystEngComm 2011, 13, 1733–1748.
10. Liu, T.F.; Lu¨, J.; Cao, R. Coordination polymers based on flexible di-
topic carboxylate or nitrogen-donor ligands. CrystEngComm 2010, 12,
660–670.
11. Huang, K.L.; Liu, X.; Li, J.K.; Ding, Y.W.; Chen, X.; Zhang, M.X.; Xu,
X.B.; Song, X.J. Three-dimensional metal(II)-organic coordination poly-
mers from binuclear, trinuclear, and polynuclear clusters bridged by p-
benzenediacrylates: syntheses, topologies, photosensitive properties, and
hydrogen uptake. Cryst. Growth Des. 2010, 10, 1508–1515.
FIG. 3. Solid-state emission spectra for the powdered free H2phda ligand and
complexes 1 and 2 (color figure available online).

202
L.-Y. XIN ET AL.
12. Liu, G.Z.; Xin, L.Y.; Wang, L.Y. Ancillary ligand-mediated syntheses and 14. Xin, L.Y.; Liu, G.Z.; Wang, L.Y. New coordination polymers from 1D
fluorescence properties of zinc(II) complexes based on flexible benzene
dicarboxylic acid. CrystEngComm 2011, 13, 3013–3020.
13. Liu, G.Z.; Zhang, J.; Wang, L.Y. A comparison of the coordination prefer-
ence of Cd, Zn, Cu(II) with flexible homophthalic acid and rigid bipyridine
ligands. Polyhedron 2011, 30, 1487–1493.
chain, 2D layer to 3D framework constructed from 1,2-phenylenediacetic
acid and 1,3-bis(4-pyridyl)propane flexible ligands. J. Solid State Chem.
2011, 184, 1387–1392.
15. Sheldrick, G.M. SHELXS-97, Program for the Solution of Crystal Struc-
tures. Go¨ttingen, Germany, University of Gottingen 1997.

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