Hydrothermal syntheses, structures, and properties of four metal-organic coordination polymers assembled from V-shaped tetracarboxylate ligands and N-donor ancillary ligands

Article abstract of DOI:10.1016/j.poly.2010.07.013

A series of four metal-organic frameworks, namely, [Cu(sdpa) _0.5(2,2′-bpy)]·H₂O (1), [Zn ₂(sdpa)(2,2′-bpy)₂(H₂O) ₂]·3H₂O (2), [Zn₂(sdpa)(4,4′-bpy)] ·3H₂O (3

Full text of DOI:10.1016/j.poly.2010.07.013

Polyhedron 29 (2010) 2907–2915
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Hydrothermal syntheses, structures, and properties of four metal–organic
coordination polymers assembled from V-shaped tetracarboxylate ligands
and N-donor ancillary ligands
Shuang-Quan Zang a, , Jia-Bin Li a,b, Qi-Yao Li a, Hong-Wei Hou a, Thomas C.W. Mak a,b
*
a Department of Chemistry, Zhengzhou University, Zhengzhou 450001, PR China
b Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, PR China
a r t i c l e i n f o
a b s t r a c t
A series of four metal–organic frameworks, namely, [Cu(sdpa)0.5(2,20-bpy)]ꢀH2O (1), [Zn2(sdpa)(2,20-
bpy)2(H2O)2]ꢀ3H2O (2), [Zn2(sdpa)(4,40-bpy)]ꢀ3H2O (3), [Cd2(sdpa)(4,40-bpy)1.5(H2O)2] (4), have been
hydro(solvo)thermally synthesized through the reaction of 2,3,20,30-sulfonyldiphthalic acid (H4sdpa) with
divalent copper, zinc and cadmium salts in the presence of ancillary nitrogen ligands (4,40-bpy = 4,40-
bipyridine, 2,20-bpy = 2,20-bipyridine) and structurally characterized by elemental analysis, IR and
X-ray diffraction. Both complex 1 and 2 show metal–organic chain structure, and the adjacent chains
Article history:
Received 10 June 2010
Accepted 14 July 2010
Available online 21 July 2010
Keywords:
Coordination polymer
Cluster
Crystal structure
Weak interaction
Multicarboxylate ligands
are further linked by
p
ꢀ ꢀ ꢀ
p
and C–Hꢀ ꢀ ꢀ
p
interactions for 1 and hydrogen bonds and
pꢀ ꢀ ꢀp interactions
for 2 to form 3D supramolecular structure. In complex 3, two Zn1 and two Zn2 atoms appear alternately
and are bridged by sdpa4ꢁ anion ligands to form an infinite Zn-sdpa chain. Such chains are further linked
together through 4,40-bpy ligands in four orientations to form a robust 3D metal–organic network. In
compound 4, a 3D Cd-sdpa metal–organic network is accomplished through sdpa4ꢁ anion ligands, and
further stabilized by 4,40-bpy in six orientations. Their luminescence and thermal analysis have also been
investigated.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
constructed [19–32]. According to previous reports, owing to the
nonlinear flexibility around etheric oxygen or sulfur atom and
The design and construction of metal–organic frameworks
(MOFs) based on various secondary building units (SBUs) which
are connected through coordination bonds, supramolecular con-
twisted conformation of carboxylate groups, it is easy for V-shaped
multicarboxylate ligands 2,3,20,30-oxydiphthalic acid (H4odpa)
[30,31] and 2,3,20,30-thiaphthalic acid (H4tdpa) [32,33] ligands to
construct helical coordination polymers. The tdpa ligand show dra-
matic distinction against the odpa ligands: five of the six tdpa com-
plexes are achiral, whereas five odpa complexes are chiral. Results
indicate that the small adjustment for the ligand may result large
difference for the assembly of metal-organic networks. Considering
this, we want to further reinforce rigidity of the ligand by introduc-
ing O@S@O group and get more interesting polymeric structures.
In particular, the relatively rigid ligands are more useful to produce
coordination polymers with active photoluminescent properties
when reacting with d10 metals such as Zn(II) or Cd(II). On the other
hand, the use of auxiliary ligands is also an effective method for the
framework formation of coordination polymers owing to the fact
that they can satisfy and even mediate the coordination needs of
the metal center and consequently generate more meaningful
architectures [33–36].
tacts (hydrogen bonding,
pꢀ ꢀ ꢀp stacking, etc.), or their combination,
has been an increasingly active research area [1–8]. The self-assem-
bly of multidentate organic ligands and metal ions has resulted in
many coordination polymeric frameworks, whose structures are
influenced by the subtle interplay of many factors such as the geo-
metric preference of metal ions, the sizes and shapes of the organic
building blocks, templates, and solvent systems [9–18]. Hence, the
selection or design of suitable ligands containing certain features
like flexibility and versatile binding modes is crucial to the
construction of metal–organic coordination polymers.
It is known that multicarboxylate ligands are good candidates
for the construction of coordination frameworks with specific
structure due to their multicarboxylate groups and various coordi-
nation modes, from which a rich variety of one-, two- and three-
dimensional metal–organic polymeric architectures have been
In this study, we investigated four metal coordination polymers
assembled from 2,3,20,30-sulfonyldiphthalic acid (H4sdpa) ligand
in the presence of the ‘‘second” ligand 2,20-bpy or 4,40-bpy:
[Cu(sdpa)0.5(2,20-bpy)]ꢀH2O (1), [Zn2(sdpa)(2,20-bpy)2(H2O)2]ꢀ3H2O
Corresponding author. Tel./fax: +86 371 67780136.
E-mail address: zangsqzg@zzu.edu.cn (S.-Q. Zang).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.07.013

2908
S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
(2), [Zn2(sdpa)(4,40-bpy)]ꢀ3H2O (3), and [Cd2(sdpa)(4,40-bpy)1.5
-
(H2O)2] (4). The photoluminescent properties of 2, 3 and 4 com-
pounds were studied as well. To the best of our knowledge, this
is the first time to report the metal–organic frameworks con-
structed from 2,3,20,30-sulfonyldiphthalic acid.
2. Experiments
2.1. Materials and general methods
All commercially available chemicals are of pure grade and used
as received without further purification. Solvents were purified
according to the standard methods. Elemental analyses for C, H,
and N were performed on a Perkin–Elmer 240 elemental analyzer.
The FT–IR spectra were recorded from KBr pellets in the range from
4000 to 400 cmꢁ1 on a Bruker VECTOR 22 spectrometer. Thermal
analyses were performed on a simultaneous SDT 2960 thermal
analyzer from room temperature to 800 °C with a heating rate of
20 °C/min under nitrogen flow. Luminescence spectra for the
solid samples were recorded on
a Hitachi 850 fluorescence
spectrophotometer.
2.2. Synthesis of H4sdpa
2,3,20,30-tdpa (H4tdpa) was prepared according to the literature
[28–32]. 2,3,20,30-sdpa (H4sdpa) was synthesized using an adapta-
tion of a literature [37] procedure. As shown in Charts 1 and 2,
3,20,30-tdpa (0.6524 g, 2 mmol) and MoO3 (0.014 g, 0.1 mmol) were
dissolved in 10 ml ethanol, and this mixture was added to H2O2
(1.2 ml, 10.68 mmol). After 4 h heated at reflux the reaction mix-
ture was clear yellow solution. On cooling of the reaction mixture,
the MoO3 was filtered. The ethanol solution of the H4sdpa was
collected in volume via rotary evaporation. Other reagents and sol-
vents employed were commercially available and used as received
without further purification.
Chart 2. Coordination modes of the sdpa4ꢁ a in 1; b in 2; c in 3; d in 4.
cmꢁ1): 3457(m), 1640(s), 1556(s), 1473(m), 1450(s), 1372(s),
1313(m), 1282(m), 1160(m), 1093(m), 1068(w), 891(m), 847(m),
770(s), 729(m), 633(m), 572(m), 443(w).
2.3.2. Synthesis of [Zn2(sdpa)(2,20-bpy)2(H2O)2]ꢀ3H2O (2)
Complex 2 can be obtained following the same synthetic proce-
dures as that of 1 except using 0.1 mmol (29.7 mg) Zn(NO3)2ꢀ6H2O
instead of 0.1 mmol Cu(NO3)2ꢀ3H2O as the starting material, and
the colorless block single crystals were obtained (yield: 80% based
on Zn). Anal. Calc. for C36H32N4O15SZn2 (923.46): C, 46.82; H, 3.49;
N, 6.06. Found: C, 46.79; H, 3.41; N, 6.02%. IR (KBr pellet, cmꢁ1):
3404(m), 1656(s), 1597(s), 1578(s), 1445(m), 1376(s), 1314(s),
1160(m), 1147(m), 1095(m), 1061(w), 1027(w), 886(m), 767(s),
743(m), 696(m), 593(w), 463(w).
2.3. Synthesis of complexes 1–4
2.3.1. Synthesis of [Cu(sdpa)0.5(2,20-bpy)]ꢀH2O (1)
Complex 1 was synthesized hydrothermally in a 23 mL Teflon-
lined autoclave by heating a mixture of Cu(NO3)2ꢀ3H2O (0.1 mmol,
24.2 mg), 2,3,20,30-sdpa (0.05 mmol, 19.7 mg), 2,20-bipyridine
(0.1 mmol, 15.6 mg), and one drop of Et3N in 10 mL of water at
110 °C for 3 days under autogenous pressure. Then the reaction
system was cooled to room temperature with a cooling rate of
5 °C/h. Blue block single crystals were collected (yield: 78% based
on Cu). Anal. Calc. for C36H26N4O12SCu2 (865.75): C, 49.94; H,
3.03; N, 6.47. Found: C, 49.90; H, 2.98; N, 6.41%. IR (KBr pellet,
2.3.3. Synthesis of [Zn2(sdpa)(4,40-bpy)]ꢀ3H2O (3)
Similar to the preparation of 2 except using 4,40-bipyridine
(0.1 mmol, 15.6 mg) instead of 2,20-bipyridine. The resulting color-
less block single crystals were collected (yield: 71% based on Zn).
Anal. Calc. for C52H34N4O23S2Zn4 (1408.43): C, 44.34; H, 2.44; N,
3.98. Found: C, 44.31; H, 2.41; N, 3.96%. IR (KBr pellet, cmꢁ1):
3447(m), 1580(s), 1556(m), 1457(m), 1400(s), 1383(m), 1330(m),
1219(s), 1169(m), 1126(w), 1070(m), 896(m), 817(m), 773(m),
702(m), 646(M), 598(m), 461(w).
2.3.4. Synthesis of [Cd2(sdpa)(4,40-bpy)1.5(H2O)2] (4)
Complex 4 can also be obtained following the same synthetic
procedure as that of
3 except using 0.1 mmol (30.8 mg)
Cd(NO3)2ꢀ6H2O instead of 0.1 mmol Zn(NO3)2ꢀ6H2O, and the color-
less block single crystals were obtained (yield: 65% based on Cd).
Anal. Calc. for C62H50N6O27S2Cd4 (1824.80): C, 40.81; H, 2.76; N,
4.60. Found: C, 40.79; H, 2.74; N, 4.55%. IR (KBr pellet, cmꢁ1):
3386(m), 1578(s), 1490(m), 1383(s), 1314(m), 1217(m), 1153(m),
1091(m), 1066(m), 811(m), 780(m), 755(w), 740(w), 686(m),
632(m), 502(w).
Chart 1. Synthesis of H4sdpa.

S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
2909
2.4. X-ray crystallography
Crystallographic data collections for complexes 1–4 were car-
ried out on a Bruker Smart Apex II CCD with graphite-monochro-
mated Mo K
a radiation (k = 0.71073 Å) at 296(2) K using the
x
-scan technique. The structures were obtained by the direct
methods using the program SHELXS-97 and all non-hydrogen atoms
were refined anisotropically on F2 by the full-matrix least-squares
technique which used the SHELXL-97 crystallographic software
package [38,39]. The hydrogen atoms of the water molecules ex-
cept for those of the uncoordinated water molecules were located
in a difference Fourier map, and the other hydrogen atoms were
generated geometrically. Crystal data as well as details of data
collection and refinements for 1–4 are summarized in Table 1.
Selected bond distances and bond angles for 1–4 are listed in Table
S1.
Fig. 1. Metal coordination and atom labeling in complex 1 (thermal ellipsoids at
50% probability level). All hydrogen atoms are omitted for clarity. Symmetry codes:
#1 1.5 ꢁ x, 1.5 ꢁ y, 2 ꢁ z.
3. Results and discussion
3.1. Crystal structures
These units are further interlinked by the symmetrically-related
sdpa4ꢁ ligands to form an infinite zigzag chain (Fig. 2a).
At the same time, owing to the nonlinear flexibility of sdpa4ꢁ li-
gand around O@S@O and twisted carboxylate groups, the inter-
3.1.1. [Cu(sdpa)0.5(2,20-bpy)]ꢀH2O (1)
Single-crystal X-ray diffraction analysis reveals that the struc-
ture of 1 features a 1D zigzag polymeric coordination chain. As
shown in Fig. 1, the sdpa4ꢁ anion located at an inversion center
chain
pꢀ ꢀ ꢀp (3.83 Å) stacking interactions of pyridine rings from
two neighboring chains are apparent in four orientations to lead
and the Cu ion is in
a distorted square-pyramid geometry
a 3D supramolecular structure (Fig. 2b). In addition, the inter-chain
(
s
= 0.0983 [40]) coordinated by two nitrogen atoms from the che-
C–H@
p
interactions (C–Hꢀ ꢀ ꢀcenter 2.91 Å) between the pyridine
molecules and phenyl rings of sdpa4ꢁ ligands from neighboring
chains (Fig. S2) make the 3D framework more stable.
lating 2,20-bipyridine ligand and three oxygen atoms from three
monodentate carboxylate groups of two sdpa4ꢁ anions. Four atoms
O3, O5, N1 and N2 comprise the equatorial plane; while another
atom O3#1 occupies the axial position.
The sdpa4ꢁ anion with trans-conformation is centrosymmetric
and the dihedral angle between two phenyl rings is 69.9°. The
dihedral angles between the carboxylate groups of sdpa4ꢁ and
their corresponding phenyl ring are 87.2° (2,20-COOꢁ groups) and
67.8°(3,30-COOꢁ groups), respectively. The 2- and 3-COOꢁ groups
of the same sdpa4ꢁ anion are first connected with one Cu ion in
a monodentate coordination mode, and then two O3 atoms of 2-
COOꢁ groups from two adjacent sdpa4ꢁ ligands bridge two Cu ions
into a four membered ring to form a binuclear basic building unit.
3.1.2. [Zn2(sdpa)(2,20-bpy)2(H2O)2]ꢀ3H2O (2)
Single-crystal X-ray diffraction analysis reveals that compound
2 presents a double zipper chain. The asymmetric unit of 2 con-
tains two crystallographically nonequivalent ZnII ions, one sdpa4ꢁ
anion, one 2,20-bipyridine molecule, two coordinated water mole-
cules and three solvent water molecules (Fig. 3). The Zn1 ion is in a
distorted square-pyramid geometry (s = 0.1115 [40]) coordinated
by two nitrogen atoms from one chelating 2,20-bipyridine ligand,
two oxygen atoms from monodentate 2- and 20-COOꢁ groups of
Table 1
Crystallographic data for compounds 1–4.
1
2
3
4
Empirical formula
Formula weight
Crystal system
space group
a (Å)
C
36H26N4O12Cu2S
C36H32N4O15Zn2S
923.46
C52H34N4O23Zn4S2
1408.43
monoclinic
P21/c
11.098(2)
21.441(4)
11.773(2)
90
94.43(3)
90
2793.1(1)
2
C62H50N6O27Cd4S2
1824.80
monoclinic
P21/c
10.232(2)
13.410(3)
22.890(5)
90
100.39(3)
90
3089.4(1)
2
865.75
monoclinic
C2/c
15.282(5)
11.841(4)
21.799(9)
90
113.728(1)
90
3611(2)
4
triclinic
ꢀ
P1
10.626(2)
13.991(3)
14.941(3)
109.22(3)
101.95(3)
109.76(3)
1842.9(1)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
T (K)
296(2)
1.592
1760
2.25–25.00
10035
296(2)
1.664
944
2.10–25.00
21107
296(2)
1.675
1420
1.84–25.00
31575
296(2)
1.962
1808
2.02–25.00
34423
Dcalc (g cmꢁ3
F(0 0 0)
h range (°)
)
Reflections collected
Independent reflections
Independent reflections (Rint
3538
0.0358
1.036
0.0327
0.0930
0.814 and ꢁ0.353
6331
0.0423
1.056
0.0370
0.0833
0.469 and ꢁ0.387
4881
0.0741
1.186
0.0649
0.1477
0.954 and ꢁ0.381
5362
0.0402
1.1013
0.0363
0.0977
0.585 and ꢁ0.698
)
Goodness-of-fit (GOF) on F2
a
R1 (I > 2
r
(I))
(I))
Largest difference in peak and hole (e Åꢁ3
b
wR2 (I > 2
r
)
a
R1
=
R
||Fo| ꢁ |Fc||/
R|Fo|.
P
P
2
1=2
wR2 ¼ ½ ½wðFo2 ꢁ F2c Þ ꢂ= wðFo2Þ2ꢂ
:
b

2910
S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
Fig. 2. (a) Cu-sdpa Chain in 1. 2,20-bpy ligands are partial omitted for clarity. (b) 3D supramolecular structure for 1. Cu atoms are marked as blue.
Fig. 3. Metal coordination and atom labeling in complex 2 (thermal ellipsoids at 50% probability level). All hydrogen atoms are omitted for clarity. Symmetry codes: #1 x,
ꢁ1 + y, z.
sdpa4ꢁ ligand, another oxygen atom from the coordinated water.
The Zn2 ion is in distorted trigonal bipyramid geometry
adjacent sdpa4ꢁ ligands from neighboring double chains with a
edge-to-centroid distance of 4.022 Å, as shown in Fig. 4b.
a
(s
= 0.4723 [40]) coordinated by O10 from 30-COOꢁ group of sdpa4ꢁ
What interests us is that the channels of adjacent layers are
occupied by the remaining water molecules, which are associated
by strong O–Hꢀ ꢀ ꢀO hydrogen bonds into cyclic centrosymmetric
hexamers to result in a (H2O)6 cluster that adopts a plane confor-
mation (Fig. 4c) different from the aforetime report [41]. The
hydrogen bond lengths (Å) and angles (°) are listed in Table S2.
The average Oꢀ ꢀ ꢀO distance is 2.731 Å. There is a variation in the
anion, O6#1 from 3-COOꢁ group of neighboring sdpa4ꢁ ligand,
O2W from the coordinated water, N3 and N4 from another chelat-
ing 2,20-bipyridine molecule.
As to sdpa4ꢁ anion ligand, the dihedral angle between two phe-
nyl rings is 74.1°, the bond angle \C1SC7 is 107.3° and the four
COOꢁ groups (2-, 3-, 20-, 30-carboxylate groups) make dihedral an-
gles of 54.9°, 76.9°, 83.8°, and 79.4° with the corresponding linked
benzene rings, respectively. The four carboxylate groups of sdpa4ꢁ
are all monocoordinated, in which the 2- and 20-COOꢁ groups from
the same sdpa4ꢁ ligand bind Zn1 atom into a 10-membered ring,
While the 3- and 30-COOꢁ groups from two neighboring sdpa4ꢁ li-
gands connect Zn2 atoms to form an infinite chain running along
the b axis, and two adjacent chains are face-to-face packed into a
double slide fastener chain (Fig. 4a) connected by two kinds of
Oꢀ ꢀ ꢀOꢀ ꢀ ꢀO angles, with an average of 119.9° (\O4WO3WO5W#1
=
130.6°, \O4WO5WO3W#1 = 112.3°, \O5WO4WO3W = 116.8°), which
deviates considerably from the corresponding value of 109.3° in
hexagonal ice [42]. The solvent (H2O)6 cluster from two asymmet-
ric unit of neighboring chains fills in the interspace of adjacent
chains to form rich hydrogen-bonds of inter- and intra-chains
(Fig. 4c). In addition, the hydrogen-bonds exist not only among
the solvent (H2O)6 cluster but also between (H2O)6 cluster and
coordinated water O2W, O6, O8 from the carboxylate groups of
sdpa4ꢁ ligand, and O2 from sulphone (Fig. 4c). Adjacent layers
are interconnected by hydrogen bonds to form a 3D supramolecu-
lar structure as shaded in purple, as shown in Fig. 4d. This supra-
molecular association of water molecules in tapes is presumably
p p
stacking interactions between the 2,20-bipyridine, as show
ꢀ ꢀ ꢀ
in Fig. 4a. The centroid-to-centroid distances are 3.615 Å for type
A and 3.559 Å for type B, respectively. The double chains are fur-
ther linked into 2D undulating layers through another kind of weak
pꢀ ꢀ ꢀp stacking interaction along the c axis happening between

S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
2911
Fig. 4. (a) The slide fastener structure in 2. (b) Slide fastener structures are further linked together through another kind of
structure. (c) Representation of the cyclic water hexamers found in the channels of 2 and self-assembly of the water hexamers into extended structure. (d) 3D supramolecular
network in 2.
p
ꢀ ꢀ ꢀ
p
interactions to form a 2D supramolecular
enforced by the shape of the host’s channels, whose relatively nar-
row openings result in the formation of more stable clusters. In
conclusion, the packing structure of 2 shows a three-dimensional
supramolecular network via rich hydrogen bonds and
ing interactions.
pꢀ ꢀ ꢀp stack-
3.1.3. [Zn2(sdpa)(4,40-bpy)]ꢀ3H2O (3)
When a space extending 4,40-bpy ligand was used as an bridg-
ing auxiliary linkage, compound 3 displays a 3D coordination net-
work consisting of tetranuclear zinc SBU chains and 4,40-bpy
bridge ligands. As illustrated in Fig. 5, the asymmetric unit of 3
contains two independent ZnII ions, one sdpa4ꢁ anion, one 4,40-
bipyridine (bpy) molecule, and three solvent water molecules.
The Zn1 ion is in a distorted octahedral geometry coordinated by
N1 from the bridging 4,40-bipyridine ligand, O3, O5 from 2- to 3-
COOꢁ groups of sdpa4ꢁ ligand, O3#1, O4#1 and O7#1 from 2- to
20-COOꢁ groups of another sdpa4ꢁ ligand. The Zn2 ion is in a tetra-
hedral geometry coordinating to O6, O9#1, and O8#2 from 2- , 30-,
to 20-COOꢁ groups of three different sdpa4ꢁ ligands, N2#3 from an-
other bridging 4,40-bipyridine ligand.
Fig. 5. Metal coordination and atom labeling in complex 3 (thermal ellipsoids at
50% probability level). Hydrogen atoms and the solvent water molecules are
omitted for clarity. Symmetry codes: #1 1 ꢁ x, ꢁ0.5 + y, 1.5 ꢁ z; #2 1 + x, y, z; #3
2 ꢁ x, ꢁ0.5 + y, 1.5 ꢁ z.
The 2,3,20,30-sdpa employs a twisted conformation with the
bond angle around S1 is 105.2°, and the dihedral angle between
the two phenyl rings is 89°. The dihedral angles between the 2-,

2912
S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
3-, 20- and 30-carboxylate groups and their corresponding phenyl
rings are 84.3°, 10.8°, 82.6° and 20.5°, respectively. It is worth not-
ing that the sdpa4ꢁ ligand adopts a octadentate coordination
3.1.4. [Cd2(sdpa)(4,40-bpy)1.5(H2O)2]ꢀ2H2O (4)
Single-crystal X-ray diffraction analysis reveals that compound
4 exhibits a 3D coordination network consisting of tetranuclear
cadmium unit chains interlinked through sdpa4ꢁ and 4,40-bpy li-
gands. The asymmetric unit of 4 contains one sdpa4ꢁ anion ligand,
two independent CdII ions, one and a half bpy molecules, as well as
two coordinated water molecules (Fig. 7). Cd1 is in an octahedron
geometry coordinating to O4, O5 from 2- and 3-COOꢁ groups of
sdpa4ꢁ ligand, O8#1 ,O9#1 from 20- to 30-COOꢁ groups of the
neighboring sdpa4ꢁ anion ligand, and N1, N2#4 from two different
bicoordinated bpy molecules. Four O atoms comprise the equato-
rial plane, while N1 and N2 occupy the axial positions. Cd2 is in
a distorted octahedron geometry coordinating to O3 from 2-COOꢁ
group of sdpa4ꢁ ligand, O6#2 from 3-COOꢁ group of the neighbor-
ing sdpa4ꢁ ligand, O10#3 from 30-COOꢁ group of another neighbor-
ing sdpa4ꢁ ligand, N3 from the third bicoordinated bpy molecule,
O1W and O2W from two coordinated water molecules. Four atoms
O3, N3, O1W and O2W comprise the equatorial plane, while O6#2
and O10#3 occupy the axial positions. As to sdpa4ꢁ anion ligand,
the dihedral angle between the two phenyl rings is 87.7° and the
bond angle \C1S1C7 is 104.9°. The dihedral angles between the
2-, 3-, 20- and 30-carboxylate groups and their corresponding phe-
nyl rings are 20.2°, 7.9°, 89.1° and 45.7°, respectively. The 2-, 3- and
30-COOꢁ groups of sdpa4ꢁ adopt bridge bidentate coordination
modes connecting Cd1 and Cd2 ions, whereas the 20-COOꢁ group
is monocoordinated to Cd1.
mode: the 2-COOꢁ group adopts
a
chelate/bridge tridentatꢁe
coordination mode connecting two Zn1 ions, the 20- and 3-COO
groups adopt bridge bidentate coordination modes connecting
Zn1 and Zn2 ions, whereas the 30-COOꢁ group is monocoordinated
to Zn2.
Based on these connection modes, each pair of Zn1 ions are
bridged by O3, O3#1 atoms of 2-COOꢁ groups from two face-to-
face sdpa4ꢁ ligands to form a four membered ring {Zn12O2} unit,
such rings are further associated together through Zn2 ions to form
an infinite Zn-sdpa chain (Fig. 6a and b), in which Zn1 and Zn2
atom pairs appear alternately. Each Zn-sdpa chain is further con-
nected to the other four Zn-sdpa chains through 4,40-bipyridine
ligands along four orientations to form a 3D network structure
(Fig. 6c and Fig. S3). A better understanding of this complicated
structure can be achieved via topological considerations [43–45].
If the sdpa4ꢁ ligand is considered as a three-connected node
(connecting to two bimetallic units [Zn22(CO2)2] and one bimetal-
lic unit [Zn12(CO2)2])?the bimetallic unit [Zn12(CO2)2] as a six-
connected node (connectiong four 4,40-bipyridine and two sdpa4ꢁ),
the bimetallic unit [Zn22(CO2)2] as an eight-connected node
(connecting four sdpa4ꢁ and four 4,40-bipyridine), the structure of
3 can be described as a (3,6,8)-connected network with a Schläfli
symbol of (43)2(45ꢀ610)(46ꢀ618ꢀ84) topology.
Fig. 6. (a) Zn-Sdpa chain in 3. Hydrogen atoms and water molecules are omitted for clarity. (b) Chain structure with Zn shown as polyhedra. Irrespective atoms are omitted
for clarity. (c) Zn-Sdpa chains are linked together through 4,40-bpy ligands (marked as blue rods) to form a 3D metal-organic network. (d) Schematic presentations of a (3,6,8)-
connected network with a Schläfli symbol of (43)2(45ꢀ610)(46ꢀ618ꢀ84) topology: pink, purple and blue represent bimetallic unit [Zn12(CO2)2], bimetallic units [Zn22(CO2)2] and
sdpa4ꢁ ligand, respectively.

S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
2913
mium Unit{Cd12Cd22C4O8} (Fig. 8b). The Units are interlinked
through sdpa4ꢁ ligands to form an infinite tetranuclear basic Cd-
sdpa chain, and such Cd-sdpa chains are interlinked through
sdpa4ꢁ anion ligands in four orientations to form a 3D network
structure which are further strengthened by 4,40-bpy ligands in
six orientations (Fig. S4 and Fig. 8c). If the sdpa4ꢁ are considered
as five-connected node (connecting to two Cd1 cations and three
Cd2 cations), and Cd1 cations as four-connected node (connecting
two sdpa4ꢁ and two 4,40-bpy), Cd2 also as four-connected node
(connecting three sdpa4ꢁ and one 4,40-bpy), the structure of 4
can be described as a (4,4,5)-connected network with a Schläfli
symbol of (4ꢀ53ꢀ72)(4ꢀ55ꢀ6ꢀ82)(52ꢀ62ꢀ7ꢀ8) topology.
3.2. Discussions
According to the above structural description of the four coordi-
nation polymers, there are four different coordination modes of the
2,3,20,30-sdpa4ꢁ ligand. In 1, the sdpa4ꢁ anion with trans-conforma-
tion is centrosymmetric and adopts
carboxylate group to coordinate four Cu atoms with l4
g1g1g2g2 coordination modes (Chart 2a), while in the case of 2,
sdpa4ꢁ adopts a
4-bridging mode with each of the four carboxylate
groups in a same monodentate mode (l4
g1g1g1g1) as show in
Chart 2b. The sdpa4ꢁ ligand in 3 also adopts a
4-bridging fashion
with four carboxylate groups to coordinate to four Zn atoms with
g1g1g2g2 coordination mode (Chart 2c), whereas in 4, each
sdpa4ꢁ ligand adopts
5-bridging fashion with four carboxylate
group to coordinate five Cd atoms with l5
g1g2g2g2 coordination
l4-bridging mode with four
:
Fig. 7. Molecular structures of 4 showing the geometry of the Cd2+ ions and the
coordination modes of the carboxylate groups. Hydrogen atoms and the solvent
water molecules are omitted for clarity. Symmetry codes: #1 2 ꢁ x, 0.5 + y, 0.5 ꢁ z;
#2 2 ꢁ x, ꢁy, 1 ꢁ z; #3 1 ꢁ x, 0.5 + y, 0.5 ꢁ z; #4 x, 0.5 ꢁ y, 0.5 + z.
l
:
l
Based on these connection modes, each Cd1 and Cd2 ion appear
alternately and connected through 2-, 3- and 30-COOꢁ groups from
three different sdpa4ꢁ ligands (Fig. 8a) to form a tetranuclear cad-
l4:
l
:
Fig. 8. (a) The unit in 4. Cd is shown as polyhedron. (b) Units linked together via sdpa4ꢁ anion ligands to form a chain structure. (c) A view of Cd-sdpa 3D metal–organic
network. (d) (4,4,5)-connected network with a Schläfli symbol of (4ꢀ53ꢀ72)(4ꢀ55ꢀ6ꢀ82)(52ꢀ62ꢀ7ꢀ8) topology: sdpa (blue), Cd1 (green),Cd2 (bottle green). (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)

2914
S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
mode (Chart 2d). Furthermore, the steric hindrance of the 2,20-bpy
molecule may contribute to the simple bridging fashion of the
sdpa4ꢁ ligand, whereas rigid rod-like 4,40-bpy acts as a pillar con-
nector to make sdpa4- adopt relatively complicated coordination
modes.
As V-shaped multicarboxylate ligands, the rigidity of the ligand
is known to be essential for the polymeric structure, which is sim-
ilar to H4tdpa and H4odpa ligands. The tdpa ligand behave much
like the odpa ligand since the nonlinear flexibility around etheric
oxygen or sulfur atom and twisted conformation of carboxylate
groups which make it easy to form helical structure, whereas sdpa
ligand lost its flexibility owing to the O@S@O which make it not
suitable for the construction of helixes. The sdpa ligands show dra-
matic distinction against the tdpa and odpa ligands: six of the se-
ven tdpa complexes and five of the six odpa complexes contain
helical structures, whereas all four sdpa complexes have no helix,
which proved that the flexibility is the crucial factor in the forma-
tion of the helical architecture. These interesting results suggest
that there exist some fundamental differences between sdpa and
tdpa, odpa that are covered up by their seeming analogy and thus
need further exploration.
Fig. 9. Fluorescence emission spectrum of the complexes 2, 3, 4.
Results also revealed that the secondary ligands play an impor-
tant role in determining the structural diversity in MOFs: 2,20-
bipyridine ligands chelate metal cations which makes it difficult
to form three-dimensional structure, such as in 1 and 2, whereas
in 3 and 4, the rigid rod-like 4,40-bpy makes it easy to form
three-dimensional architecture.
emission is observed at 396 nm for the free 2,3,20,30-sdpa ligand
[46–48]. By comparing the emission spectra of 2–4 and ligand,
we can conclude that the enhancement of luminescence in 2–4
may be attributed to the ligation of ligand to the metal center,
which effectively increases the rigidity and reduces the loss of en-
ergy by radiationless decay [49–51]. Comparably, the complexes
from 2,3,20,30-tdpa exhibit intense blue fluorescence emission
bands at ca. 429ꢃ492 nm [32]. The shifts of emission spectrum
are due to the differences of ligand. The ligand 2,3,20,30-sdpa is
more rigid than 2,3,20,30-tdpa, and this phenomena reduces the loss
of energy by radiationless decay so as to make the Anti-Stoke’s
shift.
3.3. IR spectral analyses
In the IR spectrum of complexes 1 and 2, the characteristic
bands observed at around 1650 cmꢁ1 are attributed to the proton-
ated carboxylic groups, indicating the incomplete deprotonation
H4sdpa. Strong absorption bands between 1350 and 1600 cmꢁ1
in the IR spectra of complexes 1–4 can be assigned to the coordi-
nated carboxylate groups. The sulfones characteristic bands are
measured at around 1310, 1160, 1080 cmꢁ1 [37]. All this agrees
well with the result of X-ray single-crystal analyse.
4. Conclusion
In this paper, a series of four MOFs constructed from 2,3,20,30-
sdpa have been hydrothermally synthesized and structurally char-
acterized. Different structures of compounds 1–4 indicate that the
new aromatic tetracarboxylic acid anion ligand sdpa4ꢁ has the
ability of adjusting its coordination configuration and mode in dif-
ferent reaction systems. The results also revealed that the second-
ary ligands play an important role in determining the structural
diversity in MOFs: 2,20-bipyridine ligands chelate metal cations li-
gand which make it difficult to form three-dimensional structure,
such as in 1 and 2, whereas in 3 and 4, the rigid rod-like 4,40-bpy
behave good space extending and make it easy to form three-
dimensional architecture.
3.4. Thermal properties and photoluminescence properties
Thermal analyses for 1–4 were carried out from room tempera-
ture to 800 °C under a nitrogen atmosphere (see Fig. S1 for TGA
curves). The TGA curve of 1 shows that the first weight loss of
2.41% appeared between 80 and 150 °C corresponds to the loss of
the coordinated water molecule (calculated, 2.07%), and then the
network was decomposed quickly at 209 °C, resulting in the resi-
due. Comparably, compound 2 is dehydrated, with the weight loss
of 9.52% between 42.5 to 170 °C also corresponding to the loss of
three lattice water molecules per formula unit (calculated,
9.76%), and the framework collapsed in the temperature range of
250ꢁ530 °C resulting in the residue. For 3, the first weight loss of
4.10% indicates that the water molecules (calculated, 3.83%) lost
in the range of 34ꢁ229 °C. A gradual weight loss from 395 °C indi-
cates the structure was decomposed. The TGA curve of 4 shows
that the weight loss of 3.72% appeared between 40 and 200 °C cor-
responds to the loss of two coordinated water molecules per for-
mula unit (calculated, 3.94%), and the framework collapsed in the
temperature range of 200ꢁ500 °C.
In conclusion, the 2,3,20,30-sdpa ligand could be used as a versa-
tile ligand to construct novel MOFs by appropriate choice of coli-
gands and metal-centers. Subsequent works will be focused on
the construction of new interesting coordination polymers by
reacting 2,3,20,30-sdpa and other assistant N-donor ligands with
more metal ions.
5. Supplementary data
Taking into account the excellent luminescent properties of d10
metal–organic polymers, the luminescent properties of compound
2–4 were investigated in the solid-state at room temperature. As
shown in Fig. 9, complexes 2–4 exhibit photoluminescence with
an emission maximum at ca. 395, 395, and 397 nm upon excitation
CCDC 777761–777764 contain the supplementary crystallo-
graphic data for complexes 1–4. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
at 362 nm, respectively. These emissions can probably be assigned
*
to the intraligand (p–p ) fluorescent emission because similar

S.-Q. Zang et al. / Polyhedron 29 (2010) 2907–2915
2915
[22] L. Pan, M.B. Sander, X.-Y. Huang, J. Li, M. Smith, E. Bittner, B. Bockrath, J.K.
Johnson, J. Am. Chem. Soc. 126 (2004) 1308.
Acknowledgment
[23] X.-L. Wang, C. Qin, E.-B. Wang, Y.-G. Li, Z.-M. Su, Chem. Commun. (2005) 5450.
[24] X.-L. Wang, C. Qin, E.-B. Wang, Y.-G. Li, Z.M. Su, L. Xu, L. Carlucci, Angew.
Chem., Int. Ed. 44 (2005) 5824.
[25] X.-L. Wang, C. Qin, E.-B. Wang, Z.-M. Su, Chem. Eur. J. 12 (2006) 2680.
[26] J. Tao, J.-X. Shi, M.-L. Tong, X.-X. Zhang, X.-M. Chen, Inorg. Chem. 40 (2001)
6328.
We are grateful to the financial support by the National Natural
Science Foundation of China (No. 20901070).
Appendix A. Supplementary data
[27] X.-M. Chen, G.-F. Liu, Chem. Eur. J. 8 (2002) 4811.
[28] S.-Q. Zang, Y. Su, Y.-Z. Li, Z.-P. Ni, Q.-J. Meng, Inorg. Chem. 45 (2006) 3855.
[29] S.-Q. Zang, Y. Su, Y.-Z. Li, Z.-P. Ni, Q.-J. Meng, Inorg. Chem. 45 (2006) 174.
[30] S.-Q. Zang, Y.Su, Y.-Z. Li, H.-Z. Zhu, Q.-J. Meng, Inorg. Chem. 45 (2006) 2972.
[31] Y. Su, S.-Q. Zang, Y.-Z. Li, Q.-J. Meng, Cryst. Growth Des. 7 (2007) 1277.
[32] S.-Q. Zang, Y. Su, Y. Song, Y.-Z. Li, Z.-P. Ni, H.-Z. Zhu, Q.-J. Meng, Cryst. Growth
Des. 6 (2006) 2369.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.poly.2010.07.013.
References
[33] B.-H. Ye, B.-B. Ding, Y.-Q. Weng, X.-M. Chen, Cryst. Growth Des. 5 (2005) 801.
[34] L. Cheng, W.-X. Zhang, B.-H. Ye, J.-B. Lin, X.-M. Chen, Inorg. Chem. 46 (2007)
1135.
[35] E.C. Carson, S.J. Lippard, Inorg. Chem. 45 (2006) 837.
[36] S.-N. Wang, J.-F. Bai, Y.-Z. Li, Y. Pan, M. Scheer, X.-Z. You, Cryst. Eng. Commun. 9
(2007) 1084.
[37] M.M. Khodaei, K. Bahrami, M. Khedri, Can. J. Chem. 85 (2007) 11.
[38] G.M. Sheldrick, SHELXS-97, Program for Crystal Structure Solution, University of
Göttingen, Göttingen, Germany., 1997.
[39] G.M. Sheldrick, SHELXL-97, Program for Crystal Structure Refinement, University
of Göttingen, Göttingen, Germany., 1997.
[40] A.W. Addison, T.N. Rao, J. Reedijk, J.V. Rijn, G.C. Verschoor, J. Chem. Soc., Dalton
Trans. (1984) 1349.
[41] R. Custelcean, C. Afloroaei, M. Vlassa, M. Polverejan, Angew. Chem., Int. Ed. 39
(2000) 3094.
[42] J. Wang, Z.-J. Lin, Y.-C. Ou, N.-L. Yang, Y.-H. Zhang, M.-L. Tong, Inorg. Chem. 47
(2008) 190.
[43] S.R. Batten, R. Robson, Angew. Chem., Int. Ed. 37 (1998) 1460.
[44] R. Robson, J. Chem. Soc., Dalton Trans. (2000) 3735.
[45] A.F. Wells, Three-Dimensional Nets and Polyhedra, Wiley Interscience, New
York, 1977.
[46] J. Zhang, Z.-J. Li, Y. Kang, J.-K. Cheng, Y.-G. Yao, Inorg. Chem. 43 (2004) 8085.
[47] D.-R. Xiao, Y.-G. Li, E.-B. Wang, L.-L. Fan, H.-Y. An, Z.-M. Su, L. Xu, Inorg. Chem.
46 (2007) 4158.
[48] A. Vogler, H. Kunkely, Coord. Chem. Rev. 250 (2006) 1622.
[49] B. Valeur, Molecular Fluorescence Principles and Applications, Wiley-VCH,
Weinheim, 2002. pp. 137–387.
[50] L.-Y. Zhang, G.-F. Liu, S.-L. Zheng, B.-H. Ye, X.-M. Zhang, X.-M. Chen, Eur. J.
Inorg. Chem. (2003) 2965.
[51] X.-L. Wang, C. Qin, E.-B. Wang, L. Xu, Z.-M. Su, C.-W. Hu, Angew. Chem., Int. Ed.
43 (2004) 5036.
[1] J.M Lehn, Supramolecular Chemistry: Concepts and Perspectives, VCH,
Weinheim, Germany, 1995. Chapter 9, pp. 139–197.
[2] J.W. Steed, J.L. Atwood, Supramolecular Chemistry, Wiley and Sons, New York,
2000. pp. 116–216.
[3] P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem., Int. Ed. 38 (1999) 2638.
[4] S. Leininger, B. Olenyuk, P.J. Stang, Chem. Rev. 100 (2000) 853.
[5] A. Erxleben, Coord. Chem. Rev. 246 (2003) 203.
[6] K. Biradha, Y. Hongo, M. Fujita, Angew. Chem., Int. Ed. 39 (2000) 3843.
[7] P.D. Harey, H.B. Gray, J. Am. Chem. Soc. 110 (1988) 2145.
[8] D. Cave, J.M. Gascon, A.D. Bond, S.J. Teat, P.T. Wood, Chem. Commun. (2002)
1050.
[9] V.S.S. Kumar, F.C. Pigge, N.P. Rath, New J. Chem. 28 (2004) 1192.
[10] A.J. Blake, N.R. Brooks, N.R. Champness, M. Crew, A. Deveson, D. Fenske, D.H.
Gregory, L.R. Hanton, P. Hubberstey, M. Schröder, Chem. Commun. (2001)
1432.
[11] Y.-J. Qi, Y.-H. Wang, C.-W. Hu, M.-H. Cao, L. Mao, E.-B. Wang, Inorg. Chem. 42
(2003) 8519.
[12] Z.-H. Zhou, J.-M. Yang, H.-L. Wan, Cryst. Growth Des. 5 (2005) 1825.
[13] S.L. Childs, L.J. Chyall, J.T. Dunlap, V.N. Smolenskaya, B.C. Stahly, G.P. Stahly, J.
Am. Chem. Soc. 126 (2004) 13335.
[14] P. Vishweshwar, A. Nangia, V.M. Lynch, Cryst. Growth Des. 3 (2003) 783.
´
[15] C. Livage, C. Egger, G. Ferey, Chem. Mater. 11 (1999) 1546.
[16] A. Dimos, D. Tsaousis, A. Michaelides, S. Skoulika, S. Golhen, L. Ouahab, C.
Didierjean, A. Aubry, Chem. Mater. 14 (2002) 2616.
[17] D.T. de Lill, N.S. Gunning, C.L. Cahill, Inorg. Chem. 44 (2005) 258.
[18] L.A. Borkowski, C.L. Cahill, Inorg. Chem. 42 (2003) 7041.
[19] R.-Q. Zou, R.-Q. Zhong, M. Du, T. Kiyobayashi, Q. Xu, Chem. Commun. (2007)
2467.
[20] R.-Q. Zhong, R. -Q. Zou, M. Du, T. Yamada, G. Maruta, S. Takeda, Q. Xu, Dalton
Trans. (2008) 2346.
[21] M.L. Tong, X.M. Chen, B.H. Ye, S.W. Ng, Inorg. Chem. 37 (1998) 5278.