A novel μ-(H2O)-bridged double-chain coordination polymer [Cd(pc)(phen)(H2O)]n with rhombic grids (H2pc = pamoic acid, phen = 1,10-phenanthroline)

Article abstract of DOI:10.1002/zaac.200801384

A novel coordination polymer [Cd(pc)(phen)(H₂O)]_n (H₂pc = pamoic acid, phen = 1,10-phenanthroline) has been synthesized under hydrothermal conditions. Single crystal X-ray diffraction analysis reveals that the compound cry

Full text of DOI:10.1002/zaac.200801384

ARTICLE
DOI: 10.1002/zaac.200801384
A Novel µ2ꢀ(H2O)ꢀBridged DoubleꢀChain Coordination Polymer
[Cd(pc)(phen)(H2O)]n with Rhombic Grids (H2pc = pamoic acid, phen =
1,10ꢀphenanthroline)
GuangꢀXi Han,[a] YongꢀJuan Song,[a] PengꢀCheng Zhao,[b] Xia Chen,[a] and
ZhengꢀBo Han*[a]
Keywords: Coordination chemistry; Polymerizations; Cadmium; Pamoic acid
Abstract. A novel coordination polymer [Cd(pc)(phen)(H2O)]n Furthermore, two adjacent zigzag chains are connected by the µ2ꢀ
(H2pc = pamoic acid, phen = 1,10ꢀphenanthroline) has been syntheꢀ (H2O) molecules to form a doubleꢀchain with rhombic grids. There
sized under hydrothermal conditions. Single crystal Xꢀray diffraction exist intermolecular C–H···π contacts, π–π stacking and hydrogenꢀ
analysis reveals that the compound crystallizes in triclinic space group bonding interactions. Compound 1 displays strong fluorescent emisꢀ
P1. All the CdII atoms in the compound are hexacoordinate and are sion in the solid state at room temperature.
linked by pamoicate ligands to form a oneꢀdimensional zigzag chain.
many common solvents such as water, ethanol, ether or benꢀ
Introduction
zene, so that the coordination polymers formed by pamoic acid
In the past few years, low dimensional coordination polyꢀ
are less reported [15]. In this paper, we report the synthesis,
mers, generally including chain and layer structures, have reꢀ
crystal structure, and photoluminescence of a novel CdIIꢀpamoꢀ
ceived much attention owing to their interesting structural feaꢀ
ate [Cd(pc)(phen)(H2O)]n (1),that features an interesting douꢀ
tures and unique electroꢀconductivity, nonꢀlinear optical and
ble chain structure with rhombic grids.
photoluminescent properties, which are different from those of
threeꢀdimensional (3D) coordination polymers [1–7]. Particuꢀ
larly some possess photoluminescent properties, a feature that
has contributed to d10 mental coordination polymers being inꢀ
vestigated in the search for new materials. Many CdII coordinaꢀ
Results and Discussion
tion polymers assembled from different ligands and with difꢀ
ferent structures have been reported by us [8] and others [9–
13], those complexes feature interesting supramolecular strucꢀ
tures and most of them possess photoluminescent properties.
The hydrothermal method has been a promising technique in
synthesizing novel coordination polymers [14]. On the other
hand, the strategy for designing coordination polymers generꢀ
ally relies on the using of the multidentate Nꢀ and/or Oꢀdonor
ligands that can act as bridges between metal atoms and form
polymeric structures. In order to synthesize novel CdII comꢀ
plexes, different bridging ligand systems such as benzene diꢀ
carboxylic acid, pyrazinedicarboxylic acid, pyridinedicarboxꢀ
ylic acid and oxalic acid have successfully been used.
Compared with other acids, pamoic acid is more difficult to
form coordination polymers mainly because it is insoluble in
Crystal Structure
Xꢀray analysis reveals that compound 1 features a novel µ2ꢀ
(H2O)ꢀbridged doubleꢀchain structure with repeated rhombic
grids constructed by pamoate linkers, CdII atoms and phen liꢀ
gands. Figure 1 shows the coordination environment of the
CdII atom. Each CdII atom is hexacoordinate and surrounded
by two nitrogen atoms of one phen ligand [Cd(1)–N(1)
2.341(3), Cd(1)–N(2) 2.320(3) Å], two carboxyl oxygen atoms
of two different pc ligands [Cd(1)–O(2) 2.296(3), Cd(1)–
O6(A) 2.240(3) Å] and two aqua ligands [Cd(1)–O(1W)
2.488(3), Cd(1)–O(1WA) 2.316(3) Å]. Thus, the CdII atom disꢀ
plays a distorted octahedral [CdO4N2] coordination arrangeꢀ
ment with a Cd–O1W–Cd bond angle of 108.3(1)°. The pc
ligand adopts a bis(monodentate) bridging coordination mode
(Scheme 1) to connect two Cd (II) atoms into a zigzag chain.
One intriguing structural feature is that a pair of CdII atoms
from two adjacent zigzag chains are linked together by two µ2ꢀ
H2O molecules to form a double chain with the rhombic
[Cd2(µ2ꢀH2O)2] core. As we know, such bridging mode, in
which two water molecules bridging two CdII atoms into a
* Dr. Z.ꢀB. Han
Fax: +86ꢀ24ꢀ62202380
EꢀMail: ceshzb@lnu.edu.cn
[a] College of Chemistry
Liaoning University
Shenyang 110036, P. R. China
[b] Department of Forensic Chemistry
China Criminal Police University
Shenyang 110015, P. R. China
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A Novel µ2ꢀ(H2O)ꢀBridged DoubleꢀChain Coordination Polymer [Cd(pc)(phen)(H2O)]n with Rhombic Grids
dinuclear CdII subunit have been observed in CdII complexes lengths of 14.449(2) and 12.023(3) Å. The pc ligands and diꢀ
[16].
nuclear cadmium atoms occupy the corners of the rhombic grid
and two phen ligands fill in the void space of it (Figure 2).
Calculation using PLATON [17] revealed that there exist interꢀ
molecular π–π, C–H···π and hydrogenꢀbonding interactions
(Table 1). The intermolecular π–π stacking interactions link the
doubleꢀchains to form a twoꢀdimensional layer along the bc
plane (Figure 3). These intermolecular interactions enhance
the stability of the compound. Although the formula of 1 is
similar to that {[Cd(pc)(phen)](DMF)}n [15a] its architecture
is different from the latter, in which pamoate connectors interꢀ
link the CdII ions to form an undulating layered coordination
framework along the ac plane. These layers are decorated with
perpendicular phen terminals, being outward in the same orienꢀ
tation. Furthermore, pairs of the neighboring layers are arꢀ
ranged in a headꢀtoꢀhead fashion to form a zipperꢀlike interdigꢀ
itated stacking. The difference of the structure between
compound 1 and {[Cd(pc)(phen)](DMF)}n mainly because of
the different synthesizing conditions. Compound 1 was syntheꢀ
Figure 1. OPTEP view of coordination environment (30 % probability
level).
sized
under
hydrothermal
conditions,
whereas
{[Cd(pc)(phen)](DMF)}n was prepared with the presence of
DMF through solution evaporation.
Figure 2. View of the 1D doubleꢀchain structure of 1 viewed along
the aꢀaxis.
Scheme 1. Coordination mode of the pc ligand.
XRPD patterns and TGA
Comparing with the previously reported doubleꢀchain strucꢀ
ture that results from two µ2ꢀH2O molecules as bridges,
[Cd(C4O4)(dpa)(H2O)] (dpa = 2,2ꢀdipyridylamine) [16a], in
which the CdII atom is hexacoordinated and adopts a slightly
distorted octahedral coordination environment bonded to two
nitrogen atoms from dpa ligands and two oxygen atoms from
two squarate ligands and two water molecules. Two cadmium
ions are linked through two bridging water molecules to form
a [Cd(dpa)(H2O)]2 dimeric fragment in the equatorial plane
with bond lengths of Cd(1)–O(1W) 2.330(2), Cd(1)–O(1WA)
2.384(2) Å, Cd(1)–N(1) 2.296(2) and Cd(1)–N(3) 2.276(2) Å.
The squarate ligand adopts a µ1,2ꢀbinding mode to connect the
neighboring [Cd(dpa)(µ2ꢀOH2)]2 fragments at the axial sites
The simulated and experimental XRPD patterns of 1 are
shown in Figure 4. Their peak positions are in good agreement
with each other, indicating the phase purity of the products.
The differences in intensity may be due to the preferred orienꢀ
tation of the powder samples [18]. The thermal stability of 1
was examined by TGA in a dry nitrogen atmosphere from 40
to 900 °C. Complex 1 was stable up to ca. 300 °C and then
began to decompose upon further heating (Figure 5).
Photoluminescent Properties
Photoluminescence properties of 1 are shown in Figure 6. In
with bond lengths of Cd(1)–O(1) 2.240(2), Cd(1)–O(2) the solid state, strong photoluminescent emission bands at 460
2.269(2) Å, constructing a linear, ladderlike MOF along the a and 530 nm (λex = 380 nm) are observed. There is no obvious
axis. In this work, Cd–O1W bond lengths, 2.488(3) and emission observed for free H2pc under the same experimental
2.316(3) Å, fall in the normal range.
conditions. Therefore, the fluorescent emissions of 1 may be
Interestingly, two pc ligands and two CdII atoms as well as attributed to the charge transition of pc2– to CdII atoms
two phen ligands form a rhombic grid unit with the diagonal (LMCT) [19].
Z. Anorg. Allg. Chem. 2009, 1664–1668
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Z.ꢀB. Han et al.
ARTICLE
Table 1. Significant intermolecular interactions found in the Xꢀray structure of 1.
D–H···A
D–H
H···A
D···A
D–H···A
132.69
Symmetry operations for A
O(1W)–H(1B···O(5)
O(3)–H(3B)···O(2)
C(3)–H(3A)···Cg(1)
C(5)–H(5A)···Cg(2)
C(6)–H(6A)···Cg(4)
Cg(1)···Cg(2)
0.85
0.82
0.93
0.93
0.93
–
1.949
1.862
2.637
2.939
3.183
–
2.602(2)
2.598(3)
3.537(4)
3.804(5)
3.422(3)
3.732(4)
3.708(6)
1+x, –1+y, z
x, y, z
–x, –y,1–z
–x, –y,1–z
1–x, –y, 1–z
–x, –y, –z
1–x, –y, 1–z
148.70
163.02
155.20
96.93
–
Cg(3)···Cg(3)
–
–
–
Cg(1): C(25), C(26), C(31)–C(34); Cg(2): C(26)–C(31); Cg(3): C(4)–C7, C11, C12; Cg(4): C16–C21.
Figure 5. TGA curve of 1.
Figure 3. Two dimensional layer structure showing the π–π stacking
interactions.
Figure 6. . The photoluminescence spectra of 1 in the solid state at
room temperature.
Figure 4. Simulated (i) and experimental (ii) Xꢀray powder diffraction
patterns for 1.
400 cm–1 range with a Nicolet 5DX spectrometer. The emission spectra
were recorded with a Perkin–Elmer LS50B fluorescence spectrophoꢀ
tometer.
Experimental Section
Materials and Methods
All reagents and solvents employed were commercially available and
used as received without further purification. The C, H, and N microaꢀ
Hydrothermal Synthesis
nalyses were carried out with a Perkin–Elmer 240 elemental analyzer. [Cd(pc)(phen)(H2O)]n: A mixture of Cd(CH3COO)2·2H2O (0.133g,
The FTꢀIR spectra were recorded from KBr pellets in the 4000– 0.5 mmol), pamoic acid (0.194 g, 0.5 mmol), phen (0.09g, 0.5 mmol),
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Z. Anorg. Allg. Chem. 2009, 1664–1668

A Novel µ2ꢀ(H2O)ꢀBridged DoubleꢀChain Coordination Polymer [Cd(pc)(phen)(H2O)]n with Rhombic Grids
Table 2. Crystallographic data for 1.
in Table 3. CCDCꢀ670654 contains the supplementary crystallographic
data for this paper. Copy of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax:
int code +44ꢀ1223ꢀ336ꢀ033; EꢀMail: deposit@ccdc.cam.ac.uk].
Empirical formula
C35H24CdN2O7
696.96
Formula weight
Wavelength /Å
0.71073
triclinic
P1
Crystal system
Space group
Unit cell dimensions:
Conclusions
a /Å
9.900(3)
In conclusion,
a
novel CdII coordination polymer
b /Å
11.316(2)
c /Å
14.205(3)
[Cd(pc)(phen)(H2O)]n (1) has been successfully synthesized, in
which CdII atoms are hexacoordinate with nitrogen and oxygen
atoms from pc groups and phen ligands. The pc ligand adopts
a bis(monodentate) coordination mode to connect two CdII atꢀ
oms to form a zigzag singleꢀchain. Then the adjacent singleꢀ
chains are linked by the µ2ꢀH2O molecules to form a doubleꢀ
chain with repeated rhombic grids. In addition, the compound
is stabilized by intermolecular π–π, C–H···π stacking and hyꢀ
drogenꢀbonding interactions. Compound 1 displays strong fluꢀ
orescent emission in the solid state at room temperature.
α /°
67.78(1)
β /°
79.95(2)
γ /°
69.53(2)
V /Å3
1378.5(6)
Z
2
Dc /g·cm–3
1.679
µ /mm–1
0.851
F(000)
704
Crystal size /mm
θ Range for data collection /°
Reflections collected
Independent reflections(Rint)
Max. and min. transmission
T /K
0.37 × 0.32 × 0.27
1.55 to 27.50
7286
6203 (0.0412)
0.8059,0.7448
293(2)
Goodnessꢀofꢀfit on F2
Data/restraints/parameters
Final R indices [I > 2σ(I)]
R indices (all data)
Largest diff. peak and hole /e·Å–3
1.092
Acknowledgement
This work was granted financial support from National Natural Sci
ence Fundation of China (Grant 20871063) and the Program for Lia
oning Excellent Talents in University (RCꢀ05ꢀ11).
6203 / 0 / 406
R1 = 0.0400, wR2 = 0.0999
R1 = 0.0557, wR2 = 0.1132
0.546, –0.920
2
2 2
2 2 1/2
R1 = ∑||Fo|–|FC||/∑|Fo|; wR2 = ∑[w(Fo –Fc ) ]/∑[w(Fo ) ]
References
NaOH (0.04 g, 1 mmol), Et3N (0.05 mL) and H2O (10 mL) was put
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and final pH value of the reaction mixture is 8.5 and 7.0, respectively.
C35H24CdN2O7: calcd.: C 60.31; H 3.47; N 4.02; found: C 60.25; H
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1
Cd(1)–O(6)#1
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Cd(1)–N(1)
2.240(3)
2.316(3)
2.341(3)
Cd(1)–O(2)
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Symmetry transformations used to generate equivalent atoms: #1 x–1, y+1, z; #2 –x+1, –y+1, –z+1.
Z. Anorg. Allg. Chem. 2009, 1664–1668
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Published Online: June 2, 2009
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Z. Anorg. Allg. Chem. 2009, 1664–1668