An interdigitated 3D framework with 5-connected BN topology

Article abstract of DOI:10.1016/j.inoche.2011.04.019

A flexible coordination polymer 1 with interdigitated structure has been synthesized from 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) ligand and Cd²⁺ salt, whose 3D interdigitated framework displays novel 5-connected BN topology involving both covalent and strong hydrogen bonds. The luminescent properties of 1 are discussed.

Full text of DOI:10.1016/j.inoche.2011.04.019

Inorganic Chemistry Communications 14 (2011) 1174–1177
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Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
An interdigitated 3D framework with 5-connected BN topology
Cun-Kuan Wang a, Yan Zhou b, Lan-Ping Xu b, Lei Han b,
⁎
a
Faculty of Yang-Ming, Ningbo University, Ningbo, Zhejiang 315211, China
b
Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang 315211, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A flexible coordination polymer 1 with interdigitated structure has been synthesized from 4,4′-(hexafluor-
oisopropylidene)bis(benzoic acid) ligand and Cd2+ salt, whose 3D interdigitated framework displays novel
5-connected BN topology involving both covalent and strong hydrogen bonds. The luminescent properties of 1
are discussed.
Received 2 March 2011
Accepted 15 April 2011
Available online 23 April 2011
© 2011 Elsevier B.V. All rights reserved.
Keywords:
Coordination polymer
Interdigitated framework
BN topology
4,4′-(hexafluoroisopropylidene)bis
(benzoic acid)
Considerable effort has been devoted to the synthesis and
characterization of metal-organic coordination polymers as functional
materials because of their potential applications and fascinating
topologies [1,2]. Currently, the topological analysis of coordination
polymers has been a topical research area not only for the importance
of simplifying complicated structures but also for the instructive role
in the rational design of predicted functional materials [3,4]. To date, a
large number of coordination polymers with topologies related to
classical inorganic structures, such as SrSi2, diamond, quartz, NbO,
CdSO4, α-Po, CsCl, C3N4, Pt3O4, PtS, CaF2 and zeolite-like nets [4,5],
have been obtained via the use of crystal engineering concepts of
node, net and vertex symbols. However, the rational design and
controlled syntheses of novel coordination frameworks with unusual
topologies are still challenging topics. For example, the 5-connected
coordination networks, especially 5-connected BN net, are relatively
rare [6–12]. The 5-connected BN (or bnn) net may be described as
cross-linked (6,3) honeycomb network based on the trigonal
bipyramidal node with the Schläfli symbol 46⋅64.
On the other hand, the construction of flexible and dynamic porous
coordination polymers has attracted growing research interest
because of their potential applications in separation, sensor and
switching materials [13]. The flexible frameworks can reversibly
change their structures and properties in response to external stimuli,
such as guest adsorption, pressure, and temperature. As known, the
interdigitated porous frameworks constructed from two-dimensional
(2D) layers display tunable flexibility associated with layer-layer
weak interactions, including H-bonds, π-electron stacking and van der
Waals interactions [14–22]. Recently, Kitagawa's group reported a
series of interdigitated structures with selective guest sorption and
gas separation, and their pore size and shape can be tuned by varying
the V-shaped dicarboxylate ligands [18–22]. Herein we report a new
flexible coordination polymer with interdigitated motif of 2D layer by
exploring the V-shaped ligand, 4,4′-(hexafluoroisopropylidene)-bis-
(benzoic acid) (H2hfipbb) [23–25]. The compound, [Cd(hfipbb)(H2O)
(H2hfipbb)]n (1), displays an interesting 5-connected BN topology
involving both covalent and strong hydrogen bonds.
The colorless crystals of 1 were hydrothermally synthesized in 64%
yield by reacting CdCl2⋅2.5H2O with H2hfipbb ligand at 170 °C for 3 days
[26]. The structure of 1 was identified by satisfactory elemental analysis,
IR and single crystal X-ray diffraction [27]. The phase purity of the
crystalline sample of 1 was characterized by powder X-ray diffraction
(Fig. S1). The asymmetric unit of 1 contains one Cd2+ cations, one H2O
molecule, one deprotonated hfipbb ligand and one protonated H2hfipbb
ligand. As shown in Fig. 1, each Cd2+ cation exhibits distorted
pentangular–bipyramidal configuration and is seven-coordinated by
five oxygen atoms from deprotonated hfipbb ligands, one oxygen atom
from protonated H2hfipbb ligand, and one oxygen atom from water
molecule. The Cd―O bond distances present a broad region in range
from 2.226 Å to 2.676 Å, in which the longest bond length is axial Cd
(1)―O(5) from protonated H2hfipbb ligand. Two carboxylate groups
of deprotonated hfipbb adopt chelate and chelate-bridging coordina-
tion modes, respectively, and the dihedral angle between two benzene
rings is 116.3°. The protonated H2hfipbb ligand adopts weak
coordination bond by only use of one oxygen atom, and others act as
donor or acceptor of hydrogen bonds. The dihedral angle between two
benzene rings of protonated H2hfipbb is 75.1°. The extended structure
of 1 exhibits 2D framework constructed by Cd2+ cations and
deprotonated hfipbb ligands with coordination bonds. The protonated
⁎
Corresponding author.
E-mail address: hanlei@nbu.edu.cn (L. Han).
1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2011.04.019

C.-K. Wang et al. / Inorganic Chemistry Communications 14 (2011) 1174–1177
1175
Fig. 1. View of the coordination sphere in 1 with 50% ellipsoid probability. The hydrogen bonds are indicated with dashed line. (symmetry codes. a: x−1, y, z; b: x−1, 1/2−y, z−1/2; m: 1+
x, y, z; n: 1+x, 1/2−y, 1/2+z; i: x, 1/2−y, z−1/2; j: 1−x, −y, 2−z).
H2hfipbb ligands act as up-and-down arms of 2D layer through both
weak coordination bond (Cd(1)―O(5) of 2.676 Å) and strong intra-
layer hydrogen bonds (O(6)―H(1)⋅O(1) with 2.596 Å and 170°).
To clearly analyze the whole 3D topology structure of 1, the 2D
coordination framework is shown in Fig. 2a. This 2D framework without
H2hfipbb arms can be simplified as a (4,4) grid topology considering Cd
atom as 4-connected node, hfipbb ligand and Cd–O–Cd chain as linear
linkers, respectively. The strong intra-layer hydrogen bond is present
between coordinated H2O molecule and carboxylate oxygen atom with
O(9)―H(3)⋅O(2i) of 2.699 Å (symmetry code: i x, 1/2−y, z−1/2).
Furthermore, the (4,4) grids are mutually interdigitated to create a
stable 3D assembled framework by strong inter-layer hydrogen bonds,
as shown in Fig. 3a. Interestingly, there are two kinds of inter-layer
hydrogen bonds (Figs. 2b and 1), one is O(7)―H(2)⋅O(5j) of 2.717 Å
(symmetry code: j 1−x, −y, 2−z) between protonated H2hfipbb and
deprotonated hfipbb ligand, the other is O(9)―H(4)⋅O(8j) of 2.785 Å
between coordinated H2O molecule and protonated H2hfipbb ligand.
This interdigitated motif with inter-layer hydrogen bonds results in a
dimmer ring of two protonated H2hfipbb from two layers, which can
serve as a linear linker in layer-to-layer (Fig. 2b). Therefore, the whole
3D interdigitated framework can be simplified as a novel 5-connected
46⋅64 net with BN topology (Fig. 3b). In contrast to the extensive
investigations on 3-, 4-, 6-, 8-connected 3D coordination networks [4],
there have been only a few on 5-connected BN topology [6–12]. To the
best of our knowledge, the compound 1 is the first example of 3D
interdigitated coordination network with interesting 5-connected BN
topology involving both covalent and strong hydrogen bonds. More-
over, it should be pointed out that the structure of 1 may be flexible and
candidate as dynamic framework for separation application due to its
interdigitated architecture. The total potential solvent accessible
volume is 124.0 Å3, as calculated by PLATON[28], which indicates the
microporous feature of 1.
Fig. 2. (a) 2D (4,4) grid network and schematic representation of 1; (b) view of H-bonds modes of layer-to-layer, which act as linear linkers.

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C.-K. Wang et al. / Inorganic Chemistry Communications 14 (2011) 1174–1177
Fig. 3. (a) 3D interdigitated framework of 1 assembled with H-bonds; (b) schematic representation of 5-connected BN topology.
Taking into account the excellent luminescent properties of d10
metal complexes, the preliminary photoluminescent property of 1 has
been investigated in the solid state at room temperature. It gave
strong emission peak maximum at 500 nm under 352 nm light
excitation (Fig. S2). It has been reported that the organic H2hfipbb
ligand has emission band centered at 383 nm (λex =342 nm) [29].
Therefore, the emission bands for 1 are tentatively attributed to the
ligand-to-metal charge transfer (LMCT) and metal-to-ligand charge
transfer (MLCT) [29–32]. These observations indicate that 1 may
be candidate as potential photoactive materials. On the other hand,
thermogravimetric analysis (TGA) of 1 was performed at a heating
rate of 10 °C min−1 in N2 atmosphere. The result shows that the weight
loss in the range of 150–180 °C corresponds to the loss of coordinated
water molecules, and the removal of the organic components occurs
at 270 °C (Fig. S3).
In conclusion, a novel Cd(II)-organic coordination polymer has been
synthesized from the V-shaped ligand 4,4′-(hexafluoroisopropylidene)-
bis-(benzoic acid). Compound 1 is a 3D interdigitated coordination
network from 2D layerand exhibits interesting5-connected BN topology
involving both covalent and strong hydrogen bonds. The successful
isolation of this solid material not only affords new coordination polymer
with interesting topology structure but also helps us to further under-
stand the flexible interdigitated motif.
[3] M. O'keeffe, M.A. Peskov, S.J. Ramsden, O.M. Yaghi, The reticular chemistry
structure resource (RCSR) database of, and symbols for, crystal nets, Acc. Chem.
Res. 41 (2008) 1782–1789.
[4] S. Natarajan, P. Mahata, Metal-organic framework structures—how closely are
they related to classical inorganic structures? Chem. Soc. Rev. 38 (2009)
2304–2318.
[5] F. Nouar, J. Eckert, J.F. Eubank, P. Forster, M. Eddaoudi, Zeolite-like metal-organic
frameworks (ZMOFs) as hydrogen storage platform: lithium and magnesium ion-
exchange and H2-(rho-ZMOF) interaction studies, J. Am. Chem. Soc. 131 (2009)
2864–2870.
[6] L. Pan, N. Ching, X.Y. Huang, J. Li, An unprecedented two-fold interpenetrated
heterometallic 4664 network constructed by five-connected copper metal nodes,
Chem. Commun. (2001) 1064–1065.
[7] F. Millange, C. Serre, J. Marrot, N. Gardant, F. Pellé, G. Férey, Synthesis, structure
and properties of a three-dimensional porous rare-earth carboxylate MIL-83(Eu):
Eu2(O2C–C10H14–CO2)3, J. Mater. Chem. 14 (2004) 642–645.
[8] H.L. Sun, B.Q. Ma, S. Gao, S.R. Batten,
A novel three-dimensional network
containing Mn(II) ions and tricyanomethanide with rare 46⋅64 Topology, Cryst.
Growth Des. 5 (2005) 1331–1333.
[9] X.-W. Wang, Y.-R. Dong, Y.-Q. Zheng, J.-Z. Chen, A novel five-connected BN
topological network metal-organic framework Mn(II) cluster complex, Cryst.
Growth Des. 7 (2007) 613–615.
[10] L.-F. Ma, Y.-Y. Wang, L.-Y. Wang, D.-H. Lu, S.R. Batten, J.-G. Wang, Two
coordination polymers involving triangular and linear trinuclear Co(II) clusters
created via in situ ligand synthesis, Cryst. Growth Des. 9 (2009) 2036–2038.
[11] R.Z. Tong, X.Y. Ren, Z.X. Li, B. Liu, H.M. Hua, G.L. Xue, F. Fu, J.W. Wang, A novel
extended architecture with 46⋅64 topology based on mixed-valence Wells–
Dawson arsenotungstate and mixed-ligand Cu(I) units, J. Solid State Chem. 183
(2010) 2027–2031.
[12] F. Li, Y. Kang, Y.-M. Dai, J. Zhang, Rare 5-connected BN topology in homochiral
Cd(II) camphorate with 2-(4-pyridyl)benzimidazole, Inorg. Chem. Commun. 14
(2011) 228–230.
[13] S. Horike, S. Shimomura, S. Kitagawa, Soft porous crystals, Nat. Chem. 1 (2009)
695–704.
Acknowledgments
[14] X.-L. Wang, C. Qin, E.-B. Wang, L. Xu, An unusual 3D interdigitated architecture
We are thankful for the financial support from the National Science
Foundation of China (No. 21071087), the Ningbo Municipal Natural
Science Foundation (No. 2009A610129), and the K. C. Wong MagnaFund
in Ningbo University.
self-assembled from sidearm-containing 2D bilayer motifs with
a cuboidal
framework, Eur. J. Inorg. Chem. (2005) 3418–3421.
[15] Y. Zou, S.H. Hong, M. Park, H. Chun, M.S. Lah, Selective gas sorption property of an
interdigitated 3-D metal-organic framework with 1-D channels, Chem. Commun.
(2007) 5182–5184.
[16] E.-Y. Choi, L.D. DeVries, R.W. Novotny, C.H. Hu, W.Y. Choe, An interdigitated
metalloporphyrin framework: two-dimensional tessellation, framework flexibil-
ity, and selective guest accommodation, Cryst. Growth Des. 10 (2010) 171–176.
[17] S. Lipstman, I. Goldberg, Supramolecular crystal chemistry of tetra(3-pyridyl)
porphyrin. 2. two- and three-dimensional coordination networks with cobalt and
cadmium ions, Cryst. Growth Des. 10 (2010) 5001–5006.
[18] S. Horike, D. Tanaka, K. Nakagawa, S. Kitagawa, Selective guest sorption in an
interdigitated porous framework with hydrophobic pore surfaces, Chem.
Commun. (2007) 3395–3397.
Appendix A. Supplementary material
X-ray crystallographic file in CIF format and powder X-ray diffraction
for complex 1. Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.inoche.2011.04.019.
[19] D. Tanaka, K. Nakagawa, M. Higuchi, S. Horike, Y. Kubota, T.C. Kobayashi, M.
Takata, S. Kitagawa, Kinetic gate-opening process in a flexible porous coordination
polymer, Angew. Chem. Int. Ed. 47 (2008) 3914–3918.
[20] T. Fukushima, S. Horike, Y. Inubushi, K. Nakagawa, Y. Kubota, M. Takata, S.
Kitagawa, Solid solutions of soft porous coordination polymers: fine-tuning of gas
adsorption properties, Angew. Chem. Int. Ed. 49 (2010) 4820–4824.
References
[1] J.R. Long, O.M. Yaghi, The pervasive chemistry of metal-organic frameworks,
Chem. Soc. Rev. 38 (2009) 1213–1214.
[2] A. Corma, H. García, F.X. Liabrés i Xamena, Engineering metal organic frameworks
for heterogeneous catalysis, Chem. Rev. 110 (2010) 4606–4655.

C.-K. Wang et al. / Inorganic Chemistry Communications 14 (2011) 1174–1177
1177
[21] K. Nakagawa, D. Tanaka, S. Horike, S. Shimomura, M. Higuchia, S. Kitagawa,
Enhanced selectivity of CO2 from a ternary gas mixture in an interdigitated porous
framework, Chem. Commun. 46 (2010) 4258–4260.
[22] Y. Inubushi, S. Horike, T. Fukushima, G. Akiyama, R. Matsudacd, S. Kitagawa,
Modification of flexible part in Cu2+ interdigitated framework for CH4/CO2
separation, Chem. Commun. 46 (2010) 9229–9231.
[23] L. Han, Y. Zhou, W.-N. Zhao, X. Li, Y.-X. Liang, Assembly of metal-organic
frameworks with helical layer: from 2D parallel interpenetrated layer to 3D self-
penetrating network, Cryst. Growth Des. 9 (2009) 660–662.
1601(m), 1529(s), 1398(s), 1248(s), 1210(w), 1167(s), 1027(m), 982(s), 938(s),
859(m), 772(s), 726(s), 667(s), 540(w).
[27] Crystal data for 1: C34H20CdF12O9, M=912.9, monoclinic, space group P21/c
(No. 14), a = 13.752(3), b = 31.654(6), c = 7.9464(16) Å, β = 93.44(3)°
V=3452.9(12) Å3, Z=4, Dc=1.756 g/cm3, F000=1808, Mo Kα radiation,
λ=0.71073 Å, T=298(2)K, 2θmax=55.0º, 30316 reflections collected, 7607
unique (Rint =0.0484), μ =0.752 mm−1
. Final GooF=1.016, R1 =0.037,
wR2=0.0723.
[28] A.L. Spek, Single-crystal structure validation with the program PLATON, J. Appl.
Crystallogr. 36 (2003) 7–13.
[24] L. Han, Y. Zhou, X.-T. Wang, X. Li, M.-L. Tong, High thermal stability and
antiferromagnetic properties of
carboxylate chains, J. Mol. Struct. 923 (2009) 24–27.
[25] Y. Zhou, L. Han, J.G. Pan, X. Li, Y.Q. Zheng, A novel 2D (4,4) cobalt(II)-organic
framework based on tetranuclear cluster nodes and double stranded organic
linkers, Inorg. Chem. Commun. 11 (2008) 1107–1109.
a
3D Mn(II)-organic framework with metal
[29] X.-J. Kong, K. Zhu, T.-H. Kai, G.-X. Liu, X.-M. Ren, Synthesis, crystal structure and
luminescent property of one-dimensional chain complex Cd(FA)(pyim)(H2O),
Chinese J. Inorg. Chem. 25 (2009) 2193–2196.
[30] C.C. Ji, L.F. Huang, J. Li, H.G. Zheng, Y.Z. Li, Z.J. Guo, Solvothermal syntheses,
structures, and physical properties of four new coordination compounds
[26] Preparation of 1: The mixture of CdCl2⋅2.5H2O (31.1 mg, 0.14 mmol), H2hfipbb
(50.5 mg, 0.13 mmol) and deionized water (8 mL) was homogenized at room
temperature for 30 min, then the final solution was sealed in a 20 mL Teflon-lined
steel autoclave, heated at 170 °C for 3 days. After the vessel was cooled naturally
to room temperature, the resulting product was recovered by filtration, washed
with distilled water and then a quantity of colorless single crystals of 1 was
obtained. The yield of 1 is ca. 64% based on CdCl2⋅2.5H2O. Anal. Calcd. For
C34H20CdF12O9 (%): C, 44.73; H, 2.21; O 15.77. Found (%): C, 44.22; H, 2.55; O,
15.96. IR (KBr, cm−1): 3410(br), 3088(m), 2650(w), 2535(w), 2360(m), 1707(s),
constructed from a bent dicarboxylate ligand, Dalton Trans. 39 (2010)
8240–8247.
[31] H.-L. Jiang, B. Liu, Q. Xu, Rational assembly of d10 metal-organic frameworks with
helical nanochannels based on flexible V-shaped ligand, Cryst. Growth Des. 10
(2010) 806–811.
[32] P.S. Wagenknecht, P.C. Ford, Metal centered ligand field excited states: their roles
in the design and performance of transition metal based photochemical molecular
devices, Coord. Chem. Rev. 255 (2011) 591–616.