Construction of a unique 3D coordination polymer from assembly of Cd(NO3)2 with a new tetrakis(m-carboxyphenyl)azo calix[4]arene ligand

Article abstract of DOI:10.1016/j.inoche.2011.03.077

Reactions of 25,26,27,28-tetrahydroxy-calix[4]arene (1) with 4 equiv. of m-carboxybenzenediazonium chloride in the presence of NaOAc·3H ₂O in DMF produced a new azo calix[4]arene [H₄L] (2) (H₄L = 5,11,17,23-tetrakis[(m-car

Full text of DOI:10.1016/j.inoche.2011.03.077

Inorganic Chemistry Communications 14 (2011) 1069–1072
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Construction of a unique 3D coordination polymer from assembly of Cd(NO3)2 with a
new tetrakis(m-carboxyphenyl)azo calix[4]arene ligand
Lei-Lei Liu a, Li-Min Wan a, Zhi-Gang Ren a, Jian-Ping Lang a,b,
⁎
a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, PR China
b
State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 25,26,27,28-tetrahydroxy-calix[4]arene (1) with 4 equiv. of m-carboxybenzenediazonium
chloride in the presence of NaOAc∙3H2O in DMF produced a new azo calix[4]arene [H4L] (2) (H4L=5,11,17,23-
tetrakis[(m-carboxyphenyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene) in 96% yield. Hydrothermal reac-
tions of Cd(NO3)2·4H2O with H4L at 90 °C under pH=5.0–6.0 gave rise to a coordination polymer {[H3O]2
[Cd7L4(DMF)4(EtOH)2(H2O)2]·5DMF·11.5EtOH·H2O}n (3). Compound 3 was characterized by elemental
analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. Compound 3 consists of a 3D
framework with an unprecedented (3346526371)(364135861) topology. The thermal properties of 2 and 3 were
also investigated.
Received 21 February 2011
Accepted 31 March 2011
Available online 12 April 2011
Keywords:
Cadmium
Solvothermal synthesis
Tetrakis(m-carboxyphenyl)azo calix[4]arene
Thermal properties
© 2011 Elsevier B.V. All rights reserved.
Coordination polymer
The fascinating area of self-assembly presently attracts the
attention of many scientists [1]. Starting with a number of selected
building blocks, it offers almost unlimited possibilities for the
construction of various intriguing architectures [1,2]. In recent
years, water-soluble calix[4]arenes as the building blocks in self-
assembly processes have been investigated as the presence of native
cavity-like structures showing interesting inclusion properties and a
wide range of metal coordination complexes both in solution and in
the solid state [3]. Some calix[4]arene complexes could be arranged
into so-called molecular capsules, “Ferris wheels” and “Russian dolls”,
etc. through coordination bond and/or weak interactions such as
hydrogen bonding, π···π stacking, electrostatic and van der Waals
interactions and so on [3a,b,e,h,4]. In addition, a number of supra-
molecular compounds via self-assembly of main group, transition
metal or lanthanide species, and additional organic molecules with
water-soluble p-sulfonatocalix[4]arenes (C4AS) have been reported
[3b,d,4d,e,5]. To our knowledge, studies engaged in coordination
polymers via self-assembly of azo calix[4]arenes with transition
metals have not been reported yet. In this work, we used 25,26,27,28-
tetrahydroxy-calix[4]arene (1) [6] as a starting material to success-
fully prepare a new water-soluble azo calix[4]arene with four
carboxylic groups, 5,11,17,23-tetrakis[(m-carboxyphenyl)azo]-
25,26,27,28-tetrahydroxycalix[4]arene (2, H4L). This compound is
anticipated to have the following two interesting features. One is that
it contains four carboxylic groups, which may adopt a lot of bridging
modes when it binds to metal centers. The other is that it is four long
and flexible carboxylic groups, which may have more chances to
create various coordination environments for metals, thereby forming
various intriguing supramolecular architectures. With these ideas in
mind, we carried out the solvothermal reactions of Cd(NO3)2·4H2O
with H4L and isolated a unique 3D coordination polymer {[H3O]2
[Cd7L4(DMF)4(EtOH)2(H2O)2]·5DMF·11.5EtOH·H2O}n (3). Herein we
report its synthesis, crystal structure, and thermal property.
Compound 1 was employed to react with 4 equiv. of m-
carboxybenzenediazonium chloride and NaOAc∙3H2O in DMF afford-
ing an azo calix[4]arene product 2 in 96% yield (Scheme 1) [7].
Treatment of 2 with 2 equiv. of Cd(NO3)2·4H2O in DMF/EtOH at
pH=5.0–6.0 followed by a hydrothermal treatment at 90 °C for one
day produced orange block crystals of 3 in 62% yield [8]. It was worth
noting that when the reaction temperature was raised up to 140 °C
with the variable pH values from 2.0 to 6.0, only 3 was generated with
a lower yield. In all of the cases, if the pH values and reaction
temperatures were fixed, changes of Cd(NO3)2∙4H2O/H4L molar ratios
from 1:1 to 1:2 to 2:1 always generated the same product 3.
Compounds 2 and 3 were stable towards oxygen and moisture, and
2 was soluble in DMF and DMSO, but 3 was almost insoluble in
common organic solvents. We investigated the exchange properties of
3 to other solvents. When the crystals of 3 were immersed into the
normal solvents such as CH2Cl2, CHCl3, MeCN, and MeOH, its powder
X-ray diffraction patterns showed that solvent exchange did not take
place. We also attempted the so-called single-crystal-to-single-crystal
⁎
Corresponding author at: Key Laboratory of Organic Synthesis of Jiangsu Province,
College of Chemistry, Chemical Engineering and Materials Science, Soochow University,
Suzhou 215123, Jiangsu, PR China. Tel.: +86 512 65882865; fax: +86 512 65880089.
E-mail address: jplang@suda.edu.cn (J.-P. Lang).
1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2011.03.077

1070
L.-L. Liu et al. / Inorganic Chemistry Communications 14 (2011) 1069–1072
Scheme 1. Synthetic route of new azo calix[4]arene ligand 2.
conversion of 3 by placing its single crystal in the atmosphere of
MeOH, MeCN or pyridine vapor but all failed. The elemental analyses
of 2 and 3 were consistent with their chemical formula. The 1H NMR
spectrum of 2 in DMSO-d6 exhibited two singlets, one doublet–
doublet and one triplet for the phenyl groups at 8.27 ppm, 7.85 ppm,
7.96–8.03 ppm, 7.59–7.63 ppm, and the bridging methylene groups at
4.17–4.56 ppm. And the signal for the bridging methylene groups
appear at δ=31.44 ppm in its 13C NMR spectrum, suggesting
existence of a cone conformation of the tetra-substituted calix[4]
arene in solution at room temperature [9]. The IR spectra of 2 showed
an C=O and C–O stretching vibrations at 1715 and 1470 cm−1, which
downshifted to 1658 and 1385 cm−1 of 3, indicating existence of
Fig. 1. (a)−(d) View of the coordination environments of Cd centers in 3 with labeling schemes. Symmetry codes: (A) −x+2, −y, z; (B) −x+2, – y−1, −z; (C) −x+2, −y, −z;
(D) x+1, y, z; (E) −x+2, −y, −z−1. All hydrogen atoms are omitted for clarity.

L.-L. Liu et al. / Inorganic Chemistry Communications 14 (2011) 1069–1072
1071
coordinated carboxylic groups [10]. The middle peaks at in the range
of 1593–1596 cm−1 were assigned to the asymmetric N=N vibration
of complexes 2 and 3 [9]. Compound 3 was finally confirmed by X-ray
crystallography [11]. The X-ray powder pattern of 3 was matched
with the simulated patterns generated from their single crystals data
(Fig. S1).
Compound 3 crystallizes in the triclinic space group Pī, and its
asymmetric unit contains half a [Cd7L4(DMF)4(EtOH)2(H2O)2]2−
dianion, a protonated H3O+ cation, one quarter of EtOH, five halves
of EtOH, three EtOH, one DMF, three halves of DMF, and half a H2O
solvent molecules. As shown in Fig. 1, the Cd atoms in 3 adopt two
different coordination geometries. Cd1 is seven-coordinated by six O
atoms of three chelating carboxylate groups from three different H4L
ligands and one O atom from one EtOH molecule (Fig. 1a). Cd2 is
octahedrally coordinated by four O atoms of four carboxylate groups
from four different H4L ligands, two O atoms from one DMF and one
H2O molecule (Fig. 1b). Cd3 adopts the same coordination geometry
as Cd1, coordinated by four O atoms of four carboxylic groups from
four different H4L ligands, two O atoms of one chelating carboxylate
groups from H4L ligand and O atom from one DMF molecule (Fig. 1c).
Cd4 is also octahedrally coordinated by four O atoms of two chelating
carboxylate groups from two different H4L ligands, two O atoms of
two carboxylate groups from two different H4L ligands (Fig. 1d).
Besides, it is noted that there existed two weak interactions (2.878 Å)
between Cd4 and O21 and between Cd4 and O21A. The carboxylate
groups in 3 also show three different coordination modes: chelating,
bridging, chelating–bridging. For the seven-coordinated Cd, the mean
Cd–O bond length (2.437(5) Å) of 3 (Table S1) is longer than that of
the corresponding one in [Cd2(BTC)2(H2O)2]·2HCHA·2EtOH·2H2O
(2.380(2) Å, BTC=1,3,5-benzenetricarboxylate, CHA=cyclohexyla-
mine) [13a]. For the six-coordinated Cd, the mean Cd–O bond length
(2.138(6) Å) of 3 is shorter than that of the corresponding one in [Cd
(PDC)(4-nitrobenzoate)2(H2O)] (2.312(5) Å, HPDC=4-piperidine-
carboxylic acid) [13b].
Interestingly, Cd3, Cd3A, Cd3B, Cd3C, Cd4 and Cd4A are linked by
two L ligands to form a hexanuclear [Cd6L2] cage-like unit with an
approximate dimension of 2.98 Å (between O13 and O14)×8.07 Å
(between C65 and C109)×17.43 Å (between C84 and C112 ) Å
(Fig. 2a). Each Cd atom in such a unit interconnects its equivalent ones
via L ligands to form a 1D chain extending along the a axis (Fig. S2).
Besides, Cd1, Cd1A, Cd1B, Cd1C, Cd2 and Cd2A atoms and two other L
ligands to produce another [Cd6L2] cage-like unit with a rough size of
2.50 Å (between O1 and O4)×9.02 Å (between C39 and C51)×18.94 Å
(between C14 and C42) Å. Such a unit also creates a 1D chain extending
along the c axis. These two 1D chains are interconnected together by
two chelating and/or bridging carboxylates, affording a 2D network
extending with ac plane (Fig. S3). Each 2D network is further
connected by Cd2 atoms to form an unprecedented 3D framework
(Fig. 2b), which is calculated by the Platon program [14] showing that
the effective solvent accessible volume of 3396.8 Å3 per unit cell
(41.7% of the total cell volume) is filled with DMF, EtOH and H2O
solvent molecules. The calix[4]arene parts between two layers in the
3D structure not only exhibited a vertical up-down fashion but also a
slipped up-down fashion (Fig. S4). Topologically, compound 3 consists
of a 3D (6,8)-connected framework with one L ligand as a 6-connecting
node and one L as a 8-connecting node (Fig. 2c). According to Wells
[15], such a net can be further specified by an new Schläfli symbol of
(3346526371)(364135861).
Fig. 2. (a) View of one hexanuclear [Cd6L2] cage-like unit of 3. Symmetry codes:
A: −x+1, −y, −z–1; B: −x+2, −y, −z–1; C: x–1, y, z. (b) View of a 3D framework
in 3 looking along the b axis. The yellow and purple spheres represent the two kinds of
cavities in 3. (c) Schematic view of a (3346526371)(364135861) topological net of 3. The sky
blue and yellow balls represent 6- and 8-connected nodes, respectively. Atom color codes:
Cd, green; O, red; N, blue; and C, gray. All hydrogen atoms are omitted for clarity.
Thermogravimetric (TGA) and differential thermal analysis (DTA)
experiments were carried out to study the thermal stability of azo
groups in 2 and 3. The DTA curves (Fig. S5) exhibited the onset at
283 °C (2) and 285 °C (3) and the maximum at 290 °C (2) and 295 °C
(3) with the exothermic energy of 324 J/g for 2 and 373 J/g for 3,
respectively, which were ascribed to the decomposition of azo groups
[16]. As shown in the TGA curve of 3 (Fig. S6), the weight loss
(observed 21.27%) in the range of 20–231 °C corresponded to the
removal of all the coordinated and uncoordinated EtOH, H2O and DMF
molecules (calculated 21.47%). As shown in the TGA curve of 2
(Fig. S6), the weight loss (observed 10.57%) in the range of 235–
364 °C was ascribed to the removal of four azo groups (calculated
11.02%). For 3, the removal of four azo groups started at 248 °C for 3,
which is consistent with that of 2.

1072
L.-L. Liu et al. / Inorganic Chemistry Communications 14 (2011) 1069–1072
(c) C. Tedesco, L. Erra, I. Immediata, C. Gaeta, M. Brunelli, M. Merlini, C.
Acknowledgements
Meneghini, P. Pattison, P. Neri, Cryst. Growth Des. 10 (2010) 1527;
(d) S.J. Dalgarno, C.L. Raston, Dalton Trans. (2003) 287;
This work was financially supported by the National Natural Science
Foundation of China (20871088 and 90922018), the Nature Science Key
Basic Research of Jiangsu Province for Higher Education (09KJA150002),
the Specialized Research Fund for the Doctoral Program of higher
Education of Ministry of Education (20093201110017), the State Key
Laboratory of Coordination Chemistry of Nanjing University, the Priority
Academic Program Development of Jiangsu Higher Education Institu-
tions, the Qin-Lan and the “333” Projects of Jiangsu Province, and the
“Soochow Scholar” Program and the Program for Innovative Research
Team of Suzhou University. We highly appreciated the useful
suggestions of the reviewers and the editor.
(e) S.J. Dalgarno, M.J. Hardie, C.L. Raston, Cryst. Growth Des. 4 (2004) 227;
(f) R.G. Lin, L.S. Long, R.B. Huang, L.S. Zheng, Cryst. Growth Des. 8 (2008) 791;
(g) S.J. Dalgarno, J.L. Atwood, C.L. Raston, Cryst. Growth Des. 7 (2007) 174.
[5] (a) W.P. Liao, Y.F. Bi, S. Gao, D.Q. Li, H.J. Zhang, R. Dronskowski, Eur. J. Inorg.
Chem. (2008) 2959;
(b) M. Makha, A.N. Sobolev, C.L. Raston, Chem. Commun. (2006) 57;
(c) M. Makha, A.N. Sobolev, Cryst. Growth Des. 7 (2007) 1441.
[6] (a) C.D. Gutsche, J.A. Levine, P.K. Sujeeth, J. Org. Chem. 50 (1985) 5802;
(b) Y. Morita, T. Agawa, E. Nomura, H. Taniguchi, J. Org. Chem. 57 (1992) 3658.
[7] A solution of m-carboxybenzenediazonium chloride prepared from m-amino-
benzoic acid (2.74 g, 20 mmol), sodium nitrite (1.38 g, 20 mmol) and concd. HCl
(7.5 mL) in 35 mL of water was slowly added into a cold (0–5 °C) solution
containing 1 (2.0 g, 4.72 mmol) and sodium acetate trihydrate (8.16 g, 60 mmol)
in 50 mL of DMF. After being stirred for 4 h, the red suspension was adjusted to be
acidic with 300 mL of aqueous HCl (0.25%). The mixture was warmed at 60 °C for
30 min to produce 2 as a reddish solid, which was filtered and thoroughly washed
with water and MeOH, and dried in vacuo. Yield: 4.61 g (96%). Anal. Calcd. for
Appendix A. Supplementary data
C
56H40N8O12: C, 66.14; H, 3.96; N, 11.02. Found: C, 66.02; H, 3.83; N, 11.33. IR (KBr
disc): 3407 (m), 2948 (w), 1715 (s), 1699 (m), 1593 (m), 1532 (w), 1470 (m),
1450 (m), 1332 (w), 1268 (s), 1189 (w), 1119 (w), 899 (w), 810 (w), 761 (m),
CCDC no. 810114 contains the supplementary crystallographic
data for 3. These data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystal-
lographic data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Sup-
plementary data associated with this article can be found, in the
online version, at doi:10.1016/j.inoche.2011.03.077.
684 (w), 502 (w)cm-1 1H NMR (400 MHz, DMSO-d6): δ 8.27 (s, 4 H, ArH), 7.96-
.
8.03 (dd, 8 H, J=8 Hz, ArH), 7.85 (s, 8 H, ArH), 7.59-7.63 (t, 4 H, J=8 Hz, ArH),
4.17 and 4.56 (br, d, 8 H, ArCH2Ar). 13C NMR (400 MHz, DMSO-d6): δ 167.00,
158.24, 151.82, 145.00, 132.06, 130.67, 130.20, 129.81, 126.96, 124.74, 121.88,
31.44.
[8] To a 10 mL Pyrex glass tube was loaded Cd(NO3)2·4H2O (8 mg, 0.025 mmol), H4L
(13 mg, 0.0125 mmol), 1.5 mL of DMF and 1.5 mL of EtOH, forming a red clear
solution. After the pH value was adjusted to 5.0–6.0 by addition of 0.5 M HClO4,
the tube was sealed and heated in an oven to 90 °C for one day, and then cooled to
ambient temperature at the rate of 5 °C h-1 to form red blocks of 3, which were
collected and washed with EtOH and dried in air. Yield: 14 mg (62%, based on Cd).
Anal. Calcd. for C278H231Cd7N41O75.5: C, 53.75; H, 4.90; N, 9.24. Found: C, 53.99; H,
4.63; N, 9.65. IR (KBr disc): 3428 (m), 2927 (w), 1659 (s), 1596 (m), 1548 (s),
1470 (s), 1385 (s), 1267 (m), 1116 (m), 1020 (w), 913 (w), 771 (w), 688 (m),
References
[1] (a) K. Nakabayashi, Y. Ozaki, M. Kawano, M. Fujita, Angew. Chem. Int. Ed. 47
(2008) 2046;
(b) I.M. Müller, D. Möller, C.A. Schalley, Angew. Chem. Int. Ed. 44 (2005) 480;
(c) K. Ghosh, H.B. Yang, B.H. Northrop, M.M. Lyndon, Y.R. Zheng, D.C. Muddiman,
P.J. Stang, J. Am. Chem. Soc. 130 (2008) 5320;
(d) F. Huang, D.S. Nagvekar, C. Slebodnick, H.W. Gibson, J. Am. Chem. Soc. 127
(2005) 484;
666 (w), 505 (w)cm-1
.
[9] I.T. Ho, G.H. Lee, W.S. Chung, J. Org. Chem. 72 (2007) 2434.
[10] D. Liu, Z.G. Ren, H.X. Li, Y. Chen, J. Wang, Y. Zhang, J.P. Lang, CrystEngComm 12 (2010)
1912.
(e) B.H. Northrop, Y.R. Zheng, K.W. Chi, P.J. Stang, Acc. Chem. Res. 42 (2009)
1554.
[2] (a) S. Sato, J. Iida, K. Suzuki, M. Kawano, T. Ozeki, M. Fujita, Science 313 (2006)
1273;
[11] Crystal data for 3: C278H231Cd7N41O75.5, Mr =6140.92, triclinic, space group Pī,
a=18.7929(5), b=19.0242(4), c=26.2547(11) Å, α=74.825(6)˚, β=78.090
(6)˚, γ=64.843(5)˚, V=8151.2(6) Å3, Z=1, Dc =1.251 g cm-3, μ=0.526 mm-1
,
64479 reflections measured, 28444 unique reflections (Rint =0.0495), 21941
observed reflections (IN2σ(I)), 1808 parameters, R1 =0.0843, wR2 =0.2277,
S=1.106. X-ray single-crystal diffraction data for 3 was collected on a Rigaku
Mercury CCD diffractometer by using graphite monochromated Mo-Kα
(λ=0.71073 Å). Cell parameters were refined by using the program CrystalClear
(Rigaku and MSC, version 1.3, 2001). The crystal structures of 3 was solved by
direct methods and refined on F2 by full-matrix least-squares methods with the
SHELXL-97 program [12]. In 3, two EtOH solvent molecules were found to be
disordered over two positions with an occupancy factor of 0.737/0.263 for O30,
C128-C129/O30A, C128A-C129A, and 0.462/0.538 for O35, C139-C140/O35A,
C139A-C140A. All non-hydrogen atoms except for those of DMF (O27-O29, N19-
N21, C119-C127 and O32, N22, C132-C134), EtOH (O31, C130-C131 and O35-O40,
C139-C150) and H2O (O2W and O3W) solvent molecules were refined
anisotropically. The H atom of the protonated water molecule (O2W) was located
from Fourier maps. Except those of CO2H groups and the water solvent molecules
of 3, all other H atoms were introduced at the calculated positions and included in
the structure-factor calculations.
(b) J.P. Lang, Q.F. Xu, R.X. Yuan, B.F. Abrahams, Angew. Chem. Int. Ed. 43 (2004)
4741;
(c) Z.H. Wei, H.X. Li, M.L. Cheng, X.Y. Tang, Y. Chen, Y. Zhang, J.P. Lang, Inorg.
Chem. 48 (2009) 2808;
(d) W.H. Zhang, Y.L. Song, Z.H. Wei, L.L. Li, Y.J. Huang, Y. Zhang, J.P. Lang, Inorg.
Chem. 47 (2008) 5332.
[3] (a) K.C. Xiong, M.Y. Wu, Q.F. Zhang, W. Wei, M. Yang, F.L. Jiang, M.C. Hong, Chem.
Commun. (2009) 1840;
(b) C. Liu, F. Luo, W.P. Liao, D.Q. Li, X.F. Wang, R. Dronskowski, Cryst. Growth Des.
7 (2007) 2282;
(c) Y.F. Bi, W.P. Liao, H.J. Zhang, Cryst. Growth Des. 8 (2008) 3630;
(d) Y.B. Liu, W.P. Liao, Y.F. Bi, X.F. Wang, H.J. Zhang, Cryst. Growth Des. 9 (2009)
5311;
(e) J.L. Atwood, T. Ness, P.J. Nichols, C.L. Raston, Cryst. Growth Des. 2 (2002) 171;
(f) Y. Liu, K. Chen, D.S. Guo, Q. Li, H.B. Song, Cryst. Growth Des. 7 (2007) 2601;
(g) D.S. Guo, X. Su, Y. Liu, Cryst. Growth Des. 8 (2008) 3514;
(h) A. Lazar, E. Da Silva, A. Navaza, C. Barbeyb, A.W. Coleman, Chem. Commun.
(2004) 2162;
[12] G.M. Sheldrick, SHELXS-97 and SHELXL-97, Program for X-ray Crystal Structure
Solution, University of Göettingen, Germany, 1997.
(i) O. Danylyuk, B. Leśniewska, K. Suwinska, N. Matoussi, A.W. Coleman, Cryst.
Growth Des. 10 (2010) 4542;
[13] (a) Q.R. Fang, G.S. Zhu, M. Xue, Z.P. Wang, J.Y. Sun, S.L. Qiu, Cryst. Growth Des.
8 (2008) 319;
(j) H. Bakirci, A.L. Koner, M.H. Dickman, U. Kortz, W.M. Nau, Angew. Chem. Int.
Ed. 45 (2006) 7400;
(b) R.W. Zhang, L.L. Wang, X.J. Zhao, Acta Crystallogr, Sect. E: Struct. Rep. Online
65 (2009) m664.
(k) F. Perret, A.N. Lazar, A.W. Coleman, Chem. Commun. (2006) 2425.
[4] (a) M. Bolte, I. Thondorf, V. Böhmer, V. Rudzevich, Y. Rudzevich, CrystEngComm
10 (2008) 270;
[14] A.L. Spek, J. Appl. Crystallogr. 36 (2003) 7.
[15] A.F. Wells, Three-Dimensional Nets and Polyhedra, Wiley-Interscience, New York,
1977.
(b) J.M. Matheny, E. Bosch, C.L. Barnes, Cryst. Growth Des. 7 (2007) 984;
[16] B. Kiskan, F. Dogan, Y. Yuksel Durmaz, Y. Yagci, Des. Monomers Polym. 11 (2008) 473.