Three Cd(II) coordination polymers assembled by flexible 2,2′-azodibenzoic acid and N-donor auxiliary ligand: Structural diversities and luminescent properties

Article abstract of DOI:10.1016/j.inoche.2013.12.021

Hydrothermal reactions of Cd(OAc)₂ · 2H₂O with 2,2′-azodibenzoic acid (H₂L) and three N-donor ancillary ligands in MeOH/H₂O at 120 C gave rise to three cadmium(II) coordination polymers [CdL(bpy)]_n (1), {[Cd₄L ₄(bpe)(H₂O)₂] · 2H₂O} _n (2) and [CdL(bpp)]_n (3) [bpy = 4,4′-bipyridine, bpe = 1,2-bis(4-pyridyl)ethylene, bpp = 1,3-bis(4-pyridyl)propane]. Structural analysis reveals that compound 1 possesses a novel three-fold interpenetrating diamondoid framework constructed by linking Cd centers with L and pillared bpy ligands. Compound 2 comprises a 3D network with a rare Schla?fli symbol of (4⁴6⁵8¹)(4⁴6²), the 3D structure is built from 2D [CdL₂]_n nets and pillared bpe ligands. Compound 3 exhibits the same 6⁶ topology with that of 1. Such a 3D architecture contains 1D helical [Cd(bpp)]_n chains and [CdL]_n chains along the a axis and b axis, respectively. The structural differences among 1-3 indicate that the N-donor ancillary ligands have significant effects on the formation of the final architectures. Photoluminescent properties of 1-3 in solid state were also investigated.

Full text of DOI:10.1016/j.inoche.2013.12.021

Three Cd(II) coordination polymers assembled by flexible 2,2’-azodibenzoic
acid and N-donor auxiliary ligand: Structural diversities and luminescent
properties
Lei-Lei Liu, Cai-Xia Yu, Yan Zhou, Juan Sun, Pan-Pan Meng, Dong
Liu, Rong-Jian Sa
PII:
DOI:
Reference:
S1387-7003(13)00575-3
doi: 10.1016/j.inoche.2013.12.021
INOCHE 5408
To appear in:
Inorganic Chemistry Communications
Received date:
Accepted date:
22 November 2013
17 December 2013
Please cite this article as: Lei-Lei Liu, Cai-Xia Yu, Yan Zhou, Juan Sun, Pan-Pan Meng,
Dong Liu, Rong-Jian Sa, Three Cd(II) coordination polymers assembled by flexible 2,2’-
azodibenzoic acid and N-donor auxiliary ligand: Structural diversities and luminescent
properties, Inorganic Chemistry Communications (2013), doi: 10.1016/j.inoche.2013.12.021
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ACCEPTED MANUSCRIPT
Three Cd(II) coordination polymers assembled by flexible 2,2'-azodibenzoic acid
and N-donor auxiliary ligand: Structural diversities and luminescent properties
Lei-Lei Liua,*, Cai-Xia Yua, Yan Zhoua, Juan Suna, Pan-Pan Menga, Dong Liub,*,
Rong-Jian Sac
a
College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang 455000,
Henan, P. R. China
b College of Chemistry and Materials Science, Huaibei Normal University, Huaibei 235000, Anhui,
P. R. China
c State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China
Received xxxxx, 2013
______________
*Corresponding author. Tel: + 86 372 2900040; Fax: + 86 372 2900040.
*Correspondence to: L. L. Liu, College of Chemistry and Chemical Engineering, Anyang Normal
University, Anyang 455000, Henan, P. R. China.
E-mail address: liuleileimail@163.com (L.-L. Liu), dongliu@chnu.edu.cn (D. Liu).
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_____________________________________________________________________________
Abstract
Hydrothermal reactions of Cd(OAc)2·2H2O with 2,2'-azodibenzoic acid (H2L) and three N-donor
ancillary ligands in MeOH/H2O at 120°C gave rise to three cadmium(II) coordination polymers
[CdL(bpy)]n (1), {[Cd4L4(bpe)(H2O)2]·2H2O}n (2) and [CdL(bpp)]n (3) [bpy = 4,4'-bipyridine, bpe
= 1,2-bis(4-pyridyl)ethylene, bpp = 1,3-bis(4-pyridyl)propane]. Structural analysis reveals that
compound 1 possesses a novel three-fold interpenetrating diamondoid framework constructed by
linking Cd centers with L and pillared bpy ligands. Compound 2 comprises a 3D network with a
rare Schläfli symbol of (446581)(4462), the 3D structure is built from 2D [CdL2]n nets and pillared
bpe ligands. Compound 3 exhibis the same 66 topology with that of 1. Such a 3D architecture
contains 1D helical [Cd(bpp)]n chains and [CdL]n chains along the a axis and b axis, respectively.
The structural differences among 1−3 indicate that the N-donor ancillary ligands have significant
effects on the formation of the final architectures. Photoluminescent properties of 1−3 in solid
state were also investigated.
Keywords: N-donor ancillary ligands; 2,2'-azodibenzoic acid; Cd(II) coordination polymers;
Structural diversities; Photoluminescent properties
_______________________________________________________________________________
The synthesis and design of novel coordination polymers has attracted a considerable amount of
attention due to their intriguing architectures as well as their potential applications in
luminescence, adsorption and catalysis [1−3]. The ultimate aim of coordination chemistry is to
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control the structures of target products and investigate the relationships between structures and
properties. Although crystal engineering affords us a powerful tool for the design and construction
of expected coordination frameworks [4], the rational design and synthesis of coordination
polymers with desired structures and properties is still a long-term challenge. The structural
diversity of such materials is usually influenced by many factors, such as metal ions, metal/ligand
ratios, the nature of organic ligands, pH value and counter anion [5, 6]. Without a doubt, among
these factors, the selection of appropriate ligands is a very important one in the formation of
desired products. The length, rigidity, coordination modes, functional groups, or substituents of
organic ligands have critical effects on the final structures of coordination polymers [7]. In recent
years, the N-donor spacer ligands are extensively employed as ancillary ligands to construct
unique structures with beautiful aesthetics and various functions due to their bent backbones,
rigidity/flexibility and versatile bridging fashions [8].
On the other hand, it is well known that a mixed-ligands system [9] consisting of two or more
types of ligands provides more possibilities to construct coordination polymers with fantastic
topologies. One of the most fruitful aspects is the combination of various carboxylic acids and
neutral pyridine-containing [10] auxiliary ligands, where the carboxylic acid ligands balance the
positive charge of the metal centers and form secondary building units, while the auxiliary ligands
mediate and satisfy the coordination environments metal centers. As a result, many functional
coordination polymers with intriguing structure motifs have been reported. Recently, we have
successfully synthesized a series of 2D and 3D Cd(II) coordination polymers based on the
3,3'-azodibenzoic acid through regulating the reaction solvents or temperatures [11].
2,2'-Azodibenzoic acid is less flexible than 3,3'-azodibenzoic acid due to the steric ground. To
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further probe the influence of systematic variations of ligand structures on the overall molecular
architectures, we extend the building blocks from 3,3'-azodibenzoic acid to its isomer
2,2'-azodibenzoic acid to explore the isomeric effect on network assembly. In addition, to our
knowledge, studies engaged in the coordination chemistry of 2,2'-azodibenzoic acid has been less
explored. Taking account of these, we employed auxiliary rigid 4,4′-bipyridine (bpy), semi-rigid
1,2-bis(4-pyridyl)ethylene (bpe), and flexible 1,3-bis(4-pyridyl)propane (bpp) N-donor ligands,
the investigation on the CdII-H2L system was carried out to explore the effects of co-ligands
incorporate into coordination architectures. Herein, we reported the syntheses and
characterizations
of
three
new
coordination
polymers:
[CdL(bpy)]n
(1),
{[Cd4L4(bpe)(H2O)2]·2H2O}n (2) and [CdL(bpp)]n (3). The results indicated that the ancillary
ligands could affect the formation of these cadmium(II) coordination polymers significantly. The
crystal structures, topological analyses and fluorescence properties of these complexes are
discussed in detail.
In all hydrothermal reactions reported here, the pH value was kept at ca. 9.0. Reactions of
Cd(OAc)2·2H2O with H2L and bpy/bpe/bpp in H2O for four days at 120 °C and cooled to ambient
temperature at a rate of 5 °C h-1 produced orange crystals of 1 (52% yield), yellow crystals of 2−3
(45% and 62% yields) [12, 13]. The IR spectra of 1−3 showed peaks in the range of 1604−1615
cm-1 and 1375−1410 cm-1, which is indicative of the existence of coordinated carboxylic groups
[11]. The strong peaks at 826–865 cm-1, and middle peaks in the range of 624–662 cm-1 mean the
existence of pyridyl groups in the complexes of 1−3 [7e]. The identities of 1−3 were further
confirmed by single-crystal diffraction analysis. The PXRD patterns of 1−3 were matched with the
simulated patterns generated from their single crystals data (Fig. S1).
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Compound 1 crystallizes in the monoclinic space group C2/c, and its asymmetric unit contains
half of an independent [CdL(bpy)] molecule. As shown in Fig. 1a, each Cd atom adopts a
disordered octahedral coordination geometry, being coordinated by four O (O1, O2, O1C, O2C)
atoms of chelating carboxylate groups from two L ligands and two N (N1, N1C) atoms from two
bpy ligands. Each CdII ion is interlinked by bridging L ligands to form a 1D [CdL]n chain
extending along the ac plane (Fig. S2). Each monodentate bpy ligand coordinated with one Cd
center in the [CdL]n chain, thereby forming a rare 1D comb-like [CdL(bpy)]n chain. Each chain is
connected to its adjacent ones via bpy ligands (pink) to form a wrinkled 2D (4,4) layer with
parallelogrammic meshes (10.69 × 11.67 Å2) (Fig. 1b). Furthermore, the bpy ligands are employed
as pillars to link the 2D layer to afford a 3D network with 1D rhombic channels along the [100]
direction (Fig. 1c). These channels are filled by mutual interpenetration of three independent
equivalent frameworks, generating a 3-fold interpenetrating 3D architecture. From a topological
point of view [14], such a 3D net can be simplified as a 66 diamondoid network through treating
Cd atoms as nodes while L and bpy ligands as linkers (Fig. 1d).
(Figure 1 here)
Compound 2 crystallizes in the triclinic space group Pī, and its asymmetric unit contains one
half of [Cd4L4(bpe)(H2O)2] unit, two halves of H2O solvent molecules. The coordination
environment of Cd2+ in 2 is similar with that of in 1. Cd1 atom is coordinated by four O (O1, O4,
O5, O7) atoms of four bridging carboxylate groups from three different L ligands, one N (N5)
atom from one bpe ligand and one (O1W) atom from H2O molecule to furnish a octahedral
coordination geometry (Fig. 2a). Cd2 atom is also octahedrally coordinated by four O (O1, O2, O5,
O6) atoms of two chelating carboxylate groups from two different L ligands and two O (O3, O8)
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atoms of two bridging carboxylate groups from two L ligands (Fig. 2b). Cd2 and [Cd(H2O)]
subunit are bridged by one carboxylate group and one L ligand to generate a dinuclear
[Cd2L(CO2)(H2O)] unit. The [Cd2L(CO2)(H2O)] units are bridged by another carboxylate groups
from the second L ligands to form a 1D chain (Fig. S3). And the 1D chains are interlinked by L
ligands to produce a 1D ladder-like structure extending along the a axis (Fig. S4). Each 1D
ladder-like structure is further interconnected with neighbouring ones via the third L ligands to
form a 2D network extending along the a axis (Fig. 2c). Furthermore, similar to that of 1, the bpe
ligands are also employed as pillars to support the 2D networks to form a 3D structure (Fig. 2d).
Topologically, if the Cd(II) centres are considered as nodes, the L and bpe ligands are considered
as linkers, the structure of 2 can be specified as a (3,4)-connected framework with a Schläfli
symbol of (446581)(4462) (Fig. 2e).
(Figure 2 here)
Compound 3 crystallizes in the orthorhombic space group P212121, and its asymmetric unit
contains one half of [CdL(bpp)] unit. Each Cd atom in 3 is six-coordinated by four O (O1, O2,
O3A, O4A) atoms of chelating carboxylate groups from two L ligands, and two N (N1, N4B)
atoms from two bpp ligands. (Fig. 3a). As shown in Fig. 3b, Cd(II) ions are linked by two
carboxylate groups of L ligands, giving rise to an infinite helical [CdL]n chain (the right-handed
helix) along the b axis. Notably, Cd(II) ions are bridged by bpp ligands also generating a 1D
helical [Cd(bpp)]n chain along the c axis (Fig. 3c). The neighbouring chains exhibit two kinds of
helix (the left-handed helix and the right-handed helix, respectively) (Fig. S5). It is interesting that
such 1D helical [CdL]n and [Cd(bpp)]n chains are braided together to form a 2D network
extending along ab plane (Fig. S5). Such 2D networks are further connected by the 1D helical
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[CdL]n chains from the adjacent 2D networks to produce a 3D architecture (Fig. 3d). And the
left-handed and right-handed [Cd(bpp)]n chains are arranged in an alternative way (Fig. 3d). If the
Cd(II) ions are regarded as 4-connected nodes, and L ligands and bpp are considered as linkers,
the 3D framework can be simplified as a 66 diamondoid network (Fig. 3e).
(Figure 3 here)
The formation of different structures of 1−3 with different N-donor ligands deserves comments.
Firstly, the carboxylate groups of L ligands in 1−3 show different coordination modes. For 1 and 3,
two carboxylate groups of L ligand both adopt μ1-η1:η1 chelating mode. And the L ligands further
bridged the Cd(II) ions, leading to the formation of the 1D [CdL]n chain. For 2, there are three
distinct L ligands. The carboxylate groups of L ligands adopt μ2-η1:η1 and μ2-η2:η1 bridging modes,
respectively. The Cd atoms and L ligands resulted in the generation of the 2D [CdL2]n network.
Secondly, the 1D [CdL]n chains of 1 and 2D [CdL2]n networks of 2 are pillared by bpy (1) and bpe
(2) ligands generating the 3D structures. However, in 3, because of the employment of flexible
bpp ligand, left- and right-handed helical motifs constructed by Cd(II) ions and bpp appear, which
are further linked by L ligands to form the final 3D structure. The difference between 1, 2 and 3
indicated that N-donor ligands play important roles in the construction of polymers 1−3. Thirdly,
compound 1 possesses a three-fold interpenetrating 3D structure while 2 and 3 hold
non-interpenetrating 3D structures. From the above-mentioned comparison, it is noted that the
ancillary ligands greatly affected the coordination geometry of Cd atoms, coordination modes of
carboxylate groups as well as the whole structures of these compounds.
The photoluminescent properties of 1−3 in the solid state at room temperature were investigated
(Fig. S6). The maximal emission peaks of complexes 1−3 appear at 468 nm (λ = 353 nm) for 1,
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468 nm (λ = 353 nm) for 2, and 467 nm (λ = 353 nm) for 3. In addition, the maximal emission was
observed at 427 nm (λ = 365 nm) for the free bpy, 371 nm (λ = 345 nm) for the free bpe and 436
nm (λ = 354 nm) for the free bpp, while no clear luminescence was detected for H2L ligands, as
reported previously [11]. In comparison with that of bpy, bpe and bpp, the emission bands of 1−3
are 41, 97 and 32 nm red-shifted, respectively. Such broad emission bands may be assigned to
ligand-to-metal charge transfer (LMCT) [15], the difference for the emissions of 1−3 may be a
result of the effect of organic ligand coordination to the metal centers and interchromophore
coupling [16]. In addition, comparing with free bpp ligand, the photoluminescent intensity of 3
has an obvious enhancement, which may be ascribed to ligand chelation to the metal center, which
effectively increases the rigidity and reduces the loss of energy by radiationless decay [17].
Furthermore, in 1 and 3, the photoluminescent intensity of 1 is higher than that of 3, which may be
attributed to the existing of rigid bpy ligand in 1 while the flexible bpp ligand in 3. These results
were consistent with the previous studies [8a] and further showed compounds 1−3 may be
candidates for potential photoactive materials.
In summary, we have successfully isolated three new coordination polymers resulting from one
flexible dicarboxylate ligand and three N-donor ligands with Cd(OAc)2·2H2O. Compound 1 has an
unusual three-fold 3D interpenetrating 66 diamondoid framework constructed by the 1D [CdL]n
chains and the pillars bpy ligands. Compound 2 holds a 3D structure built from the 2D [CdL2]n
networks and the pillars bpe ligands that exhibits a rare (446581)(4462) topological structure.
Compound 3 possesses a novel 3D architecture constructed by the 1D helical [CdL]n and
[Cd(bpp)]n chains via sharing the Cd atoms and also displays a 66 topology. Compared related
complexes, the N-donor ligands have an effect on final structures.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (U1304210,
21201068 and 81001403) and Natural Science Projects of Department of Education of Henan
Province (13A150013).
Appendix A. Supplementary data
CCDC 965283-965285 contains the supplementary crystallographic data for compounds 1–3.
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. Supplementary data associated with this
article can be found, in the online version, at …..
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mixed-ligand synthetic strategy, Coord. Chem. Rev. 257 (2013) 1282–1305.
[10] H.W. Roesky, M. Andruh, The interplay of coordinative, hydrogen bonding and π–π stacking
interactions in sustaining supramolecular solid-state architectures.: A study case of
bis(4-pyridyl)- and bis(4-pyridyl-N-oxide) tectons, Coord. Chem. Rev. 236 (2003) 91–119.
[11] L.L. Liu, L. Liu, J.J. Wang, Solvent- and temperature-driven synthesis of three Cd(II)
coordination polymers based on 3,3'-azodibenzoic acid ligand: Crystal structures and
luminescent properties, Inorg. Chim. Acta 397 (2013) 75–82.
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[12] Synthesis: A mixture of Cd(OAc)2·2H2O (13 mg, 0.05 mmol), H2L ligand (7 mg, 0.025
mmol), bpy (4 mg, 0.025 mmol), 0.020 M NaOH (0.3 mL) and H2O (4 mL) was sealed in a
10 mL Pyrex glass tube and heated at 120 °C for 4 days, then cooled to room temperature at a
rate of 5 °C h-1. The orange prisms of 1 were collected and washed thoroughly with H2O and
dried in air. Yield: 7 mg (52%, based on H2L). Anal. Calcd. for C24H16N4CdO4: C, 53.70; H,
3.00; N, 10.44. Found: C, 53.50; H, 3.38; N, 10.01. IR (KBr disc): 3059 (m), 1604 (s), 1591
(s), 1549 (m), 1375 (m), 1221 (m), 1159 (w), 1070 (m), 1006 (m), 865 (m), 814 (m), 768 (m),
715 (m), 660 (m), 628 (w), 559 (w), 477 (w), 414 (w) cm-1. Compound 2 was prepared as
yellow blocks in a similar manner to that used for the preparation of 1 by using bpe (5 mg,
0.025 mmol) instead of bpy. Yield: 5 mg (45%, based on H2L). Anal. Calcd. for
C68H50N10Cd4O20: C, 45.97; H, 2.84; N, 7.88. Found: C, 45.70; H, 2.69; N, 8.07. IR (KBr
disc): 3386 (m), 3300 (m), 3059 (w), 2932 (w), 1607 (s), 1592 (s), 1381 (s), 1254 (w), 1135
(w), 1098 (m), 1014 (w), 965 (m), 826 (m), 778 (m), 770 (m), 661 (m), 586 (m), 479 (w), 416
(w) cm-1. Compound 3 was prepared as yellow blocks in a similar manner to that used for the
preparation of 1 by using bpp (5 mg, 0.025 mmol) instead of bpy. Yield: 9 mg (62%, based
on H2L). Anal. Calcd. for C27H22N4CdO4: C, 56.02; H, 3.83; N, 9.68. Found: C, 56.15; H,
3.88; N, 9.39. IR (KBr disc): 3446 (m), 3065 (w), 2941 (w), 1615 (s), 1547 (s), 1410 (m),
1401 (s), 1226 (m), 1144 (w), 1069 (w), 1018 (m), 956 (w), 857 (m), 804 (m), 781 (m), 662
(w), 611 (w), 522 (w), 443 (w) cm-1.
[13] Crystal data for 1: C24H16CdN4O4, Mr = 536.82, monoclinic, space group C2/c, a = 20.666(4)
Å, b = 7.1240(14) Å, c = 15.446(3) Å, β = 110.53(3)˚, V = 2129.6(8) Å3, Z = 4, Dc = 1.674 g
cm-3, F(000) = 1072.0 and μ = 1.066 mm-1, 10744 reflections measured, 1874 unique
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reflections (Rint = 0.0225). R1 = 0.0278, wR2 = 0.0696 and GOF = 1.064 based on 1761
observed reflections with I > 2σ(I). For 2: C34H25Cd2N5O10, Mr = 888.41, triclinic, space
group Pī, a = 7.5764(15) Å, b = 14.120(3) Å, c = 15.795(3) Å, α = 71.81(3)˚, β = 87.78(3)˚, γ
= 79.38(3)˚, V = 1577.5(6) Å3, Z = 2, Dc = 1.870 g cm-3, F(000) = 880.0 and μ = 1.419 mm-1,
10497 reflections measured, 5531 unique reflections (Rint = 0.0877). R1 = 0.0490, wR2 =
0.1304 and GOF = 0.996 based on 3099 observed reflections with I > 2σ(I). For 3:
C27H22CdN4O4, Mr = 578.90, orthorhombic, space group P212121, a = 11.624(2) Å, b =
13.338(3) Å, c = 16.603(3) Å, V = 2574.1(9) Å3, Z = 4, Dc = 1.494 g cm-3, F(000) = 1168.0
and μ = 0.888 mm-1, 27451 reflections measured, 4525 unique reflections (Rint = 0.0444). R1
= 0.0261, wR2 = 0.0482 and GOF = 1.033 based on 4102 observed reflections with I > 2σ(I).
Structural data for the three compounds were collected on a Bruker Smart Apex-II CCD area
detector by using graphite monochromated Mo K ( = 0.071073 nm) at 296(2) K. The
crystal structures of 1−3 were solved by direct method refined on F2 by full-matrix
least-squares techniques with the SHELXTL-97 program [18].
[14] A.F. Wells, Three-Dimensional Nets and Polyhedra; Wiley-Interscience: New York, 1977.
[15] X. Wang, W. Yao, Y.F. Qi, M.F. Luo, Y.H. Wang, H.W. Xie, Y. Yu, R.Y. Ma, Y.G. Li,
From ladder, net to framework: Coordination polymers based on Zn(II)/Cd(II) ions and
mixed bicarboxyl- and bipyridine-containing linear ligands, CrystEngComm 13 (2011)
2542–2549.
[16] M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.J.T. Houk, Luminescent metal–organic
frameworks, Chem. Soc. Rev. 38 (2009) 1330–1352.
[17] B. Valeur, Molecular Fluorescence: Principles and Application, Wiley-VCH, Weinheim,
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2002.
[18] G.M. Sheldrick, SHELXS-97 and SHELXL-97, Program for X-ray Crystal Structure Solution,
University of Göettingen, Germany, 1997.
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Captions for Figures
Fig. 1. (a) View of the coordination environments of Cd center in 1 with labeling schemes.
Symmetry codes: (A) − x − 1/2, − y + 1/2, − z − 1; (B) − x, − 1 − y, − z; (C) − x, y, − z − 1/2; (D) x,
− y − 1, z − 1/2; (E) x + 1/2, − y + 1/2, z + 1/2. (b) View of a 2D (4,4) layer in 1 extending along
the ac plane. (c) View of a 3D framework in 1 looking down the a axis. (d) View of the three-fold
interpenetration model in 1. Each single net represents a topology with a Schläfli symbol 66. Atom
color codes: Cd, cyan; O, red; N, blue; and C, green and pink. All H atoms are omitted for clarity.
Fig. 2. (a)−(b) View of the coordination environments of Cd1 and Cd2 centers in 2 with labeling
schemes. Symmetry codes: (A) – x + 2, − y, − z + 2; (B) – x + 3, − y, − z + 1; (C) – x + 1, − y + 1,
− z + 2; (D) – x + 1, − y, − z + 1. (c) View of a 2D network in 2 extending along the ac plane. (d)
View of a 3D structure in 2 looking down the a axis. (e) Schematic view of a (446581)(4462)
topological net of 2. Green lines represent the bpe ligands. Atom color codes: Cd, cyan; O, red; N,
blue; and C, green and pink. All H atoms are omitted for clarity.
Fig. 3. (a) View of the coordination environments of Cd center in 3 with labeling schemes.
Symmetry codes: (A) – x + 2, y − 1/2, − z + 1/2; (B) x + 1/2, − y − 1/2, − z + 1. (b) View of a 1D
helical [CdL]n chain in 3 extending along the b axis. (c) View of a 1D helical [Cd(bpp)]n chain in 3
extending along the a axis. (d) View of a 3D structure in 3 looking along the a axis. (e) Schematic
view of a 66 topological net of 3. Atom color codes: Cd, cyan; O, red; N, blue; and C, green and
pink. All H atoms are omitted for clarity.
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(a)
(b)
(c)
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(d)
Fig. 1
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(a)
(b)
(c)
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(d)
(e)
Fig. 2
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(a)
(b)
(c)
(d)
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(e)
Fig. 3
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Graphical Abstract
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Graphical Abstract
Three Cd(II) coordination polymers assembled by flexible
2,2'-azodibenzoic acid and N-donor auxiliary ligand: Structural
diversities and luminescent properties
Lei-Lei Liua,*, Cai-Xia Yua, Yan Zhoua, Juan Suna, Pan-Pan Menga, Dong Liub,*,
Rong-Jian Sac
Three new cadmium(II) coordination polymers with novel 3D structures have been successfully
synthesized by assembly of flexible 2,2'-azodibenzoic acid (H2L) with three N-donor auxiliary ligands
(bpy, bpe, bpp). The effects of auxiliary ligand have been discussed and the spectroscopic
properties of these complexes were also studied.
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Research Highlights
►Reactions of Cd(OAc)2, 2,2'-azodibenzoic acid and bpy/bpe/bpp produce coordination polymers
1-3. ►The formation of the coordination polymers depends on N-donor auxiliary ligand. ►
Compounds 1-3 have 3D novel structures with 66, (446581)(4462) and 66 topology motifs.
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