Synthesis and structure of three novel complexes based on 4-chlorophenyloxyacetic acid

Article abstract of DOI:10.1080/15421406.2013.821917

Three new metal-organic complexes, [CoL₂(H₂O) ₄] 1, [CdL₂(H₂O)₂] 2, and [CuL ₂(H₂O)₂] 3 [HL = 4-chlorophenyloxyacetic acid], have been synthesized and chara

Full text of DOI:10.1080/15421406.2013.821917

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Synthesis and Structure of Three
Novel Complexes Based on 4-
Chlorophenyloxyacetic Acid
Long Li a , Kaisheng Diao a b , Yuqiu Ding a & Xianhong Yin a
a College of Chemistry and Chemical Engineering , Guangxi
University for Nationalities , Nanning , China
b Guangxi Key Laboratory of Chemistry and Engineering of Forest
Products , Guangxi University for Nationalities , Nanning , China
Published online: 30 Dec 2013.
To cite this article: Long Li , Kaisheng Diao , Yuqiu Ding & Xianhong Yin (2014) Synthesis and Structure
of Three Novel Complexes Based on 4-Chlorophenyloxyacetic Acid, Molecular Crystals and Liquid
Crystals, 588:1, 63-73, DOI: 10.1080/15421406.2013.821917
To link to this article: http://dx.doi.org/10.1080/15421406.2013.821917
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Mol. Cryst. Liq. Cryst., Vol. 588: pp. 63–73, 2014
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2013.821917
Synthesis and Structure of Three Novel Complexes
Based on 4-Chlorophenyloxyacetic Acid
LONG LI,1 KAISHENG DIAO,1,2,∗ YUQIU DING,1
AND XIANHONG YIN1
1College of Chemistry and Chemical Engineering, Guangxi University for
Nationalities, Nanning, China
2Guangxi Key Laboratory of Chemistry and Engineering of Forest Products,
Guangxi University for Nationalities, Nanning, China
Three new metal–organic complexes, [CoL2(H2O)4] 1, [CdL2(H2O)2] 2, and
[CuL2(H2O)2] 3 [HL = 4-chlorophenyloxyacetic acid], have been synthesized and
characterized by IR spectra, elemental analysis, fluorescence spectra, and single-crystal
X-ray diffraction. Compounds 1, 2, and 3 are all zero-dimensional dimers. The carboxy-
late ligand exhibits different coordination modes in all compounds. These compounds
exhibit interesting supramolecular architecture according to O–H···O and C–H···Cl
interactions. Compounds 1, 2, and 3 develop to different framework though they all are
from same ligands, which will be helpful to design of different materials.
[Supplemental materials are available for this article. Go to the publisher’s online
edition of Molecular Crystals and Liquid Crystals to view the free supplemental file:
CCDC 902676, 902674, 902675 contains the supplementary crystallographic data for
this article. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB2 1EZ, UK; Fax: C44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk).]
Keywords 4-Chlorophenyloxyacetic acid; complex; dimer
Introduction
Halogen phenoxyl carboxylates have been widely used as excellent pesticides and as a plant
auxin in agriculture in recent decades [1–4]. However, it can also pollute our environment
and hurt the health of animals and humans [5]. In order to decrease these bad effects, many
researches focused on the degradation of the pesticide. Coordinating halogen phenoxyl
carboxylates with metal ion is a good way. In addition, the self-assembly of metal ions
and halogen phenoxyl carboxylate ligands have made progress by detailed studies of their
structural characteristics, such as diverse coordination modes and conformations, and their
potential applications as catalysts, luminescent, sorption, magnetic materials, and biological
reagents [6–10]. As bridging ligands, halogen phenoxyl carboxylates are of huge interest
in the construction of polymeric coordination architectures, not only because of the fact
that these polymers have a wide range of structural diversities and potential applications
∗Address correspondence to Kaisheng Diao, College of Chemistry and Chemical Engineering,
Guangxi University for Nationalities, Nanning, 530006, China. E-mail: llgxmd@163.com
63

64
L. Li et al.
as porous materials and magnetic materials, but also because these ligands exhibit rich
coordination chemistry. It is well known that many of the most interesting metal–organic
polymers with one-, two-, and three-dimensional networks have been engineered using an-
ionic and carboxylate ligands. The title ligand, (4-chlorophenyloxy)acetic acid, is a typical
carboxylate ligand because it possesses one flexible acetate. In supermolecular construc-
tion, hydrogen bonding and the π–π stacking interactions are usually very important, which
make the structure more stable.
However, no literatures related to the titled complexes have been published. Herein, we
report the synthesis and structure of three new complexes: [CoL2(H2O)4] 1, [CdL2(H2O)2]
2, and [CuL2(H2O)2] 3 [HL = 4-chlorophenyloxyacetic acid]. In addition, the function of
water cluster existing in these complexes was also investigated. The work will contribute
to the supermolecular construction of different framework with the same ligands.
Experimental Section
Materials and Instrumentation
All reagents and solvents were used directly as supplied commercially without further
purification. Elemental analysis for C and H was carried out on a Perkin–Elmer 2400
II elemental analyzer. The FT-IR spectrum was obtained on a PE spectrum one FT-IR
spectrometer Fourier transform infrared spectroscopy in the 4000–400 cm−1 regions, using
KBr pellets. Excitation and emission spectra were acquired on a Perkin–Elmer instruments
LS55 spectrofluorometer.
Synthesis of Complex 1
To a solution of HL (93 mg, 0.5 mmol) in 5 mL methanol and 15 mL H2O, the solution
of sodium hydroxide was added dropwise with stirring to adjust its pH to 6. And 10 mL
aqueous solution of CoCl2·6H2O (118.5 mg, 0.5 mmol) was subsequently added. The
mixture in autoclave was reacted for three days at 130◦C, then cooled to room temperature.
A week later, X-ray quality red block-shaped single crystals were obtained. The crystals
were isolated, washed with carbinol, and dried at room temperature (Yield: 65% based on
Co). Calcd. For C16H20Cl2CoO10: C 38.24, H 3.98%. Found: C 38.18, H 3.91%. IR (KBr,
cm−1): 3454 (s), 1659 (w), 1610 (s), 1492 (s), 1426 (s), 1217 (m), 821 (w), 725 (m).
Synthesis of Complex 2
The synthesis of 2 was similar to that of 1 except that metallic moiety is CdCl2 (91.5 mg,
0.5 mmol). A week later, colorless block-shaped single crystals were obtained. The crystals
were isolated, washed with ethanol, and dried at room temperature (Yield: 70% based on
Cd). Calcd.For C16H16CdCl2O8: C 36.99, H 3.82%. Found: C 36.93, H 3.74%. IR (KBr,
cm−1): 3557 (m), 1625(w), 1595(w), 1490 (s), 1428 (s), 1235 (s), 819 (s), 706 (m).
Synthesis of Complex 3
The synthesis of 3 was similar to that of 1 except that metallic moiety is CuSO4·5H2O
(125 mg, 0.5 mmol). A week later, blue block-shaped single crystals were obtained. The
crystals were isolated, washed with ethanol, and dried at room temperature (Yield: 72%
based on Cu). Calcd.For C16H16Cl2CuO8: C 40.85, H 3.40%. Found: C 40.78, H 3.36%.

Complexes Based on 4-Chlorophenyloxyacetic Acid
65
IR (KBr, cm−1): 3428 (s), 1658(w), 1594 (w), 1492 (m), 1426 (w), 1237 (m), 821 (w), 704
(m).
X-ray Data Collection and Structure Refinement
Crystallographic data of complexes were collected on a Bruker SMART CCD diffrac-
tometer with graphite monochromated Mo-Ka radiation (λ = 0.71073 Å) at T = 296 K.
Absorption corrections were applied by using the multi-scan program [11]. The structure
was solved by direct methods and successive Fourier difference syntheses (SHELXS-97),
Table 1. Experimental data for Complexes 1, 2, and 3
Compounds
1
2
3
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C16H20Cl2CoO10
502.15
C16H16CdCl2O8
519.59
Monoclinic
C2
C16H16Cl2CuO8
470.74
Triclinic
P-1
Triclinic
P-1
4.923(2)
5.789(2)
18.276(7)
96.997(5)
90.252(5)
97.047(5)
513.0(3)
1
11.805(5)
5.485(2)
14.948(6)
90
101.211(5)
90
949.4(7)
2
1.817
5.1160(19)
7.060(3)
13.253(5)
81.801(4)
86.325(5)
76.315(4)
460.1(3)
1
b (Å)
c (Å)
α (◦)
β (◦)
γ (◦)
V (Å3)
Z
Dc (Mg/m3)
1.626
1.148
257
1.699
1.519
239
μ (mm−1
F(000)
)
1.472
516
Crystal size (mm)
θ range
Reflections collected
Independent reflections
0.36 × 0.34 × 0.33 0.38 × 0.35 × 0.32 0.36 × 0.33 × 0.32
1.12–28.32
3315
1.39–28.28
3116
1.55–28.61
3053
2279 [R(int) =
1952 [R(int) =
2070 [R(int) =
0.0267]
0.0309]
0.0199]
Completeness to θ =
25.00
0.984
0.995
0.985
Absorption correction
Max. and min.
Multi-scan
Multi-scan
Multi-scan
0.7032 and 0.6827 0.6501 and 0.6046 0.6421 and 0.6108
transmission
Data/restraints/parameters
Goodness of fit on F
R indices [I > 2σ(I)]
2279/0/133
1.054
1952/1/123
1.058
2070/0/124
1.139
R1 = 0.0413,
wR2 = 0.1222
R1 = 0.0502,
wR2 = 0.1358
0.437 and –0.737
R1 = 0.0350,
wR2 = 0.0913
R1 = 0.0355,
wR2 = 0.0916
0.869 and –0.420
R1 = 0.0392,
wR2 = 0.1037
R1 = 0.0510,
wR2 = 0.1358
0.426 and –0.438
R indices (all data)
Largest diff. features
(eÅ−3
)

66
L. Li et al.
Table 2. Hydrogen-bond geometry (Å)
D H···A
D H
H···A
D···A
D H···A
Symmetry codes
Complex 1
2.679
2.884
2.724
2.872
O4 H4A···O2
O4 H4B···O5
O5 H5A···O2
O5 H5B···O3
0.850
0.850
0.849
0.850
1.888
2.090
1.896
2.042
154.22
155.25
164.51
164.95
−x, −y + 1, −z + 2
x + 1, y, z
x, y + 1, z
x – 1, y, z
Complex 2
2.697
2.704
O4 H4C···O2
O4 H4D···O3
0.850
0.850
1.849
1.855
176.13
176.27
x, y – 1, z
x + 1/2, y – 1/2, z
Complex 3
2.722
2.663
O7 H7E···O3
O7 H7F···O2
0.850
0.850
1.877
1.818
172.83
172.79
x – 1, y, z
−x + 2, −y + 1, −z + 1
and anisotropic thermal parameters for all nonhydrogen atoms were refined by full-matrix
least-squares procedure against F2 (SHELXL-97) [12]. All nonhydrogen atoms were re-
fined anisotropically. Hydrogen atoms were set in calculated positions and refined by a
riding mode, with a common thermal parameter. H atoms for H2O molecules were located
in different synthesis and refined isotropically. The crystallographic data and experimental
details for the structure analysis are summarized in Table 1, the hydrogen-bonds of the
three complexes are listed in Table 2, and the selected bond lengths (Å) and bond angles
(a˚) for the three complexes are shown in Table 3.
Results and Discussion
Crystal Structure Descriptions
Single crystal X-ray analysis reveals that 1 and 3 crystallize in the triclinic P-1 space group,
while 2 belongs to the monoclinic system with space group C2. The structure of 1 can
be assigned as a dimer; the Co1 coordinate with two carboxyl oxygen atoms from two L
ligands and four oxygen atoms from water molecules (Fig. 1). The two L ligands nearly
locate on a same plane in which Co1, O3, and O4 lay, and Co1 O5 in its vertical plane.
In the asymmetric unit of 1, there are a half of Co(II) ion, one L ligand, and two water
molecules. The Co1 O3, Co1 O4, and Co1 O5 bond lengths are 2.084(5), 2.073(7),
and 2.105(5)Å, respectively. Two H2O are created by symmetry operation of the other
two. These four water molecules develop the dimer in two direction and make it a 2D
layer through the typical hydrogen bonds O H···O (Fig. 2). Since any kinds of π–π
stacking interactions can not occur in this structure, what makes the complex to be a 3D
supermolecule? It is the C H···Cl interactions that link the 2D layers together to be a 3D
structure (Fig. 3): in these interactions the distance of C H···Cl is only 3.037(2)Å.
X-ray diffraction analysis for Complex 2 confirms that the asymmetric unit contains
one L ligand, a half of cadmium ion, and one water molecule. Each cadmium (II) center
adopts a distorted octahedral coordination, and its six hybrid orbits are coordinated by two
oxygen atoms from two water molecules and four oxygen atoms from two carboxyl of two
L ligands (Fig. 4). Contrary to Complex 1, the carboxyl of Complex 2 shows bidentate

Complexes Based on 4-Chlorophenyloxyacetic Acid
67
Figure 1. The coordination environment of 1. Thermal ellipsoids are shown at 30% probability. All
H atoms are omitted for clarity.
Figure 2. The 2D layer of Complex 1 via H-bonding. Unnecessary atoms are omitted for clarity.

68
L. Li et al.
Figure 3. A part of 3D structure of Complex 1 constructed by O H···O and C H···Cl interactions.
Unnecessary atoms are omitted for clarity.
Figure 4. The coordination environment of 2. Thermal ellipsoids are shown at 30% probability. All
H atoms are omitted for clarity.

Complexes Based on 4-Chlorophenyloxyacetic Acid
69
Table 3. The selected bond lengths (Å) and bond angles (a˚) for Complexes 1, 2, and 3
Complex 1
Co(1)-O(4)#1
Co(1)-O(4)
Co(1)-O(3)#1
O(4)#1-Co(1)-O(4)
O(4)#1-Co(1)-O(3)#1
O(4)-Co(1)-O(3)#1
O(3)#1-Co(1)-O(3)
O(4)#1-Co(1)-O(5)#1
2.0727(19)
2.0727(19)
2.084(2)
180.0(2)
88.39(8)
91.61(8)
180.00(7)
89.42(8)
Co(1)-O(3)
Co(1)-O(5)#1
Co(1)-O(5)
O(4)-Co(1)-O(5)#1
O(3)#1-Co(1)-O(5)#1
O(3)-Co(1)-O(5)#1
O(3)#1-Co(1)-O(5)
O(3)-Co(1)-O(5)
2.084(2)
2.105(2)
2.105(2)
90.58(8)
91.87(8)
88.13(8)
88.13(8)
91.87(8)
Complex 2
Cd(1)-O(4)#1
2.197(4)
Cd(1)-O(2)#1
2.349(4)
Cd(1)-O(4)
2.197(4)
Cd(1)-O(3)
2.370(4)
Cd(1)-O(2)
2.349(4)
Cd(1)-O(3)#1
2.370(4)
O(4)#1-Cd(1)-O(4)
O(4)#1-Cd(1)-O(2)
O(4)-Cd(1)-O(2)
O(2)-Cd(1)-O(2)#1
O(4)#1-Cd(1)-O(3)
O(4)-Cd(1)-O(3(CLR))
92.8(2)
O(2)-Cd(1)-O(3)
O(2)#1-Cd(1)-O(3)
O(4)#1-Cd(1)-O(3)#1
O(2)#1-Cd(1)-O(3)#1
O(3)-Cd(1)-O(3)#1
55.82(11)
90.52(13)
124.42(14)
55.82(11)
134.81(19)
142.94(13)
101.21(16)
87.99(18)
87.99(13)
124.42(14)
Complex 3
Cu(1)-O(7)
Cu(1)-O(7)#1
Cu(1)-O(3)#1
O(7)-Cu(1)-O(7)#1
O(7)-Cu(1)-O(3)#1
O(7)#1-Cu(1)-O(3)#1
O(3)#1-Cu(1)-O(3)
O(7)-Cu(1)-O(1)#1
1.947(2)
1.947(2)
1.952(2)
180.00(17)
90.20(11)
89.80(11)
180.00(7)
91.76(11)
Cu(1)-O(3)
Cu(1)-O(1)#1
Cu(1)-O(1)
O(7)#1-Cu(1)-O(1)#1
O(3)#1-Cu(1)-O(1)#1
O(3)-Cu(1)-O(1)#1
O(3)#1-Co(1)-O(5)
O(3)#1-Cu(1)-O(1)
1.952(2)
2.401(3)
2.401(3)
88.24(11)
74.52(9)
105.48(9)
88.13(8)
105.48(9)
Note. Symmetry transformations used to generate equivalent atoms: #1 for Complex 1: –x, –y + 1,
–z + 2; #1 for Complex 2: –x + 1, y, –z; #1 for Complex 3: –x + 2, –y, –z + 1.
coordination, in which two L ligands that link the Cd1 ion make the complex a V shape.
The dihedral angle about the two benzene rings is 84.65(4)◦ and the Cd1 O2 and Cd1 O3
bond lengths are 2.349(4) and 2.371(4), respectively. Fig. 5 shows the mode that hydrogen
bonds O4 H4C···O2 and O4 H4D···O3 connect adjacent dimer to form a 2D layer. Here,
an interesting phenomenon is that the the distance of C H···Cl in 2 is 3.037(2)Å, absolutely
the same with 1. This interaction builds these 2D layers to be a 3D network.
As shown in Fig. 6 for Complex 3, the coordination mode is different from that of
1 and 2. One O atom of the carboxyl and one O atom from the phenoxy work together
to be a bidentate coordination. This kind of coordination constructs the Complex 3 to
be a zigzag dimer. Two water molecules coordinate with the center Cu(II) ion of the
zigzag dimer, which link the other dimer to be a 2D layer according to O7 H7E···O3 and
O7–H7F···O2 hydrogen bonds. In this new 2D layer, all Cl atoms arrange on the surface of
layer. So, the C H···Cl interactions can be created during the adjacent layers, and help the

70
L. Li et al.
Figure 5. The 2D layer of Complex 2 linked by hydrogen bonding.
Figure 6. The coordination environment of 3. Thermal ellipsoids are shown at 30% probability. All
H atoms are omitted for clarity.

Complexes Based on 4-Chlorophenyloxyacetic Acid
71
Figure 7. The 3D supermolecule network of Complex 3 via O H···O and C H···Cl interactions.
Unnecessary atoms are omitted for clarity.
structure become a stable 3D supermolecule network (Fig. 7). This new network offers the
supermolecule more stable 2D and 3D structures.
IR Spectroscopy
The IR spectrum of Complexes 1, 2, and 3, respectively, exhibit two peaks at 1659 and
1426 cm−1, 1625 and 1428 cm−1, and 1658 and 1426 cm−1, which are assigned to the νCOO
stretching vibration and indicate that in complexes these carboxylate groups undoubtedly
coordinate with center metal because of their large red-shift comparing with that of the free
L ligand. The skeleton vibration bands of the phenyl ring appear at 1610 and 1492 in 1,
1595 and 1490 in 2, and 1594 and 1492 in 3. Furthermore, the band at around 821 cm−1 in
all these complexes are attributable to the γ ( = C H) of 1, 4-substituted phenyl ring, and
the peak at around 706 cm−1 can be attributed to the γ ( CH 2 ) of the ligand.
Fluorescence Emission Properties
The photoluminescence behavior of the free L ligand and its corresponding cobalt(II),
cadmium(II), and copper(II) compounds was studied in the solution of methanol at room
temperature. The excitation and emission spectra of L, 1, 2, and 3 are in Fig. 8. Upon
photoexcitation at 288 nm, the free L exhibits fluorescence emission at 310 nm. Upon
excitation at 260 nm, the Compound 1 shows a similar emission peak at 314 nm. Compound
2 exhibits emission around 313 nm upon excitation at 262 nm. Upon photoexcitation at

72
L. Li et al.
Figure 8. Photoluminescent spectrum of Complexes 1, 2, and 3 in the solution of methanol at room
temperature.
286 nm, Compound 3 shows a similar but broad emission peak at 312 nm. The emission
band for Compounds 1, 2, and 3 are similar to that found for the free L ligand in terms
of position and band shape. Therefore, the luminescence behaviors in 1, 2, and 3 may be
attributed to the intraligand (π-π∗) transition; the expected metal-to-ligand charge transfer
(MLCT) or ligand-to-metal transfer (LMCT) is not observed.
Conclusion
Complexes of [CoL2(H2O)4] 1, [CdL2(H2O)2] 2, and [CuL2(H2O)2] 3 were synthesized, and
they were characterized by elemental analysis, single-crystal X-ray diffraction techniques,
X-ray powder diffraction, and photoluminescent spectrum. The results show that the water
cluster in these complexes play an important role in developing the structure to be a
stable 2D layer by their hydrogen bonds. The successful preparation of these complexes
confirmed that the hydrogen bonds of water cluster are important factors in influencing the
architecture of metal-L complexes. In addition, all the three complexes exhibit fluorescence
property.
Acknowledgments
This work is supported by the Innovation Project of Guangxi University for Nationalities
(gxun-chx2012089), Guangxi Natural Science Foundation (No. 2013GXNSFAA019091),
the Scientific Research Program of Education Department of Guangxi Zhuang Autonomous
Region (Project No. 201010LX081), and the Scientific Research Program of Guangxi
University for Nationalities (Project No. 2010QD019).

Complexes Based on 4-Chlorophenyloxyacetic Acid
73
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