КООРДИНАЦИОННАЯ ХИМИЯ, 2011, том 37, № 10, с. 728-732
УДК 541.49
SYNTHESIS, CRYSTAL STRUCTURE AND LUMINESCENCE OF A NOVEL METAL-ORGANIC POLYMER {Cd2(C4H2O4)2(C4H6N2)2(H2O)2 • 2H2O}„
© 2011 H. Chen, X. L. Wu, L. Shi, G. Huang, X. J. Lin, and D. W. Meng*
Faculty of Material Science and Chemistry Engineering, Engineering Research Center of Nano-Geo Materials of Ministry of Education, China University of Geosciences, Wuhan 430074, P.R. China
*E-mail: dwmeng@cug.edu.cn Recieved December 17, 2010
The novel 3D coordination polymer {Cd2(C4H2O4)2(C4H6N2)2(H2O)2 • 2H2O}n (I) has been synthesized and characterized by standard solid state methods including single-crystal X-ray crystallography. The compound crystallizes in triclinic space group PI with a = 8.589(4), b = 10.585(3), c = 13.094(1) A, a = 84.91(4)°, P = 79.21(0)°, у = 83.76(4)°, V = 1159.5(1) A3, Z = 2. The fumaric acid acts as a multimodal bridging ligand in the polymer unit. One of the fumaric acid ligands tridentately chelates to two Cd2+ cations in the same di-nuclear unit, while the other bidentately chelates to two Cd2+ cations in another dinuclear unit. The two metal centers possess slightly distorted pentagonal bipyramid geometry with four Cd {(p.4-fumarato)-(p.2-fuma-rato)-bis(2-methylimidazolyl)-diaqua} units joining together to form a 28-membered ring. The whole molecule exhibits a through channel along y axis and 2D layers in xz plane. With hydrogen bond and п—п interaction, the 2D layers construct a 3D microporous network.
INTRODUCTION
EXPERIMENTAL
For over two decades, the synthesis and structural analysis of metal dicarboxylic acid coordination polymer received a lot of attention owing to their unusual structure and their potential industrial applicability in luminescence, nonlinear optics, catalysis, functional porous, and magnetic properties [1—4]. Based on the study of the arrangement of the donor groups within the dicarboxylic acid, a variety of structural morphologies and supramolecular motifs has been observed in these materials. The dicarboxylic ligand could act as monodentate [5], bidentate [6], tridentate [7], and the discrete metal-oxygen polyhedra interconnected by organic linkers into polymeric chains, layers, and 3D frameworks [8—10]. However, reports about the dicar-boxylic acid that simultaneously exhibits bidentate and tridentate coordination modes to construct coordination polymers in one compound have been rarely seen [11, 12]. Here we report one Cd(II) coordination polymer self-assembly of Cd2+ cations, 2-methylimi-dazolyl, and fumaric anions in a methanolic aqueous solution under normal ambient conditions, where the Cd(II) atoms are bridged by flexible fumaric acid through both bidentate and tridentate modes to generate 2D layers with n-n interaction and hydrogen bond, the layers constructing higher dimension frameworks.
General materials and methods. All the chemicals were obtained from commercial sources and used without further purification. The IR spectra were obtained on a Nicolet Avatar 360 FT-IR spectrometer, using the KBr pellet technique (4000—400 cm-1, resolution 4 cm-1). An emission spectrum was recorded on a Hitachi F-4500 fluorescence spectrophotometer, using a slit width of 5 nm excitation at room temperature for the solid samples.
Synthesis of {Cd2(C4H2O4MC4H6N2)2№O)2 • 2H2O}„
(I). A mixted solution ofCd(CH3COO)2 • 2H2O (0.268 g, 1.0 mmol), 2-methylimidazolyl (0.082 g, 1.0 mmol), and fumaric acid (0.150 g, 1.0 mmol) in 20.0 ml of CH3OH/H2O (v/v, 1 : 1) was stirred for ~1.5 h. After the insoluble solid was filtered off, the colorless filtrate was kept at room temperature, and colorless crystals were generated by slow evaporation for two weeks.
X-ray structure determination. Diffraction data were collected at 298(2) K on a Bruker SMART 1000 CCD detector diffractometer using graphite mono-chromatized Mo^a radiation (X = 0.71073 A) in ® and 9 scan modes. The structures were solved by direct methods using the SHELXS-97 program [13, 14], and all non-hydrogen atoms were refined anisotropically on F2 by the full-matrix least-squares technique using the SHELXL-97 crystallographic software package [15] . The crystallographic data for the crystal are summarized in Table 1, and the selected bond lengths and
Table 1. Crystallographic data and experimental details for complex I
Parameter Value
Crystal size, mm 0.23 x 0.13 x 0.10
Formula weight 689.19
Crystal system Triclinic
Space group Pi
a, Â 8.589(4)
b, Â 10.585(3)
c, Â 13.094 (1)
a, deg 84.91(4)
ß, deg 79.21(0)
Y, deg 83.76(4)
Z 2
V, Â3 1159.5(1)
Pcalcd g cm-3 1.974
^(MoÄ"a), mm-1 1.902
Absorption correction Multi-scan
Tmin/Tmax 0.6688/0.8326
9 Range for data collection, deg 1.59-26.50
Data total/unique 9771/4732
Rint 0.0524
Parameters/restraints 333/8
Goodness-of-fit on F2 1.034
R1, wR2 (I> 2a(I)) 0.0367, 0.0886
R1, wR2 (all data) 0.0480, 0.0936
^Pmax/^Pmim « Â~3 0.746/-0.742
bond angles are listed in Table 2. Supplementary material for structure I has been deposited with the Cambridge Crystallographic Data Centre (no. 743827; depos-it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSIONS
The compound I possesses an asymmetric unit (Fig. 1), which consists of two crystallographically distinct cadmium atoms, two fumaric dianions, two 2-me-thylimidazolyl molecules, two coordinated water molecules, and two crystal water molecules. Each unique Cd2+ ion possesses a slightly distorted octahedral (CdO5N) coordination environment. Cd(1) is coordinated by nitrogen donor, which belongs to the 2-me-thylimidazoly ligand by oxygen atoms belonging to a chelating carboxylate terminus of two different fumaric ligands. Half of the fumaric acid ligands adopts a bridging bidentate coordinated mode, each linking two Cd2+ ion; half of the fumaric acid ligands adopts a bridging tridentate coordinated mode. The remaining one coordination site is occupied by the oxygen donor provided by one coordinated water molecule. The coordinate environment about Cd(2) is largely analogical.
Adjacent Cd(1) and Cd(2) atoms are joined into a binuclear kernel consisting of a four-membered (CdOCdO) ring by the bridging carboxylate group of two ^2-oxygen atoms (O(5)), which belong to two fumarato ligands, respectively. The Cd-Cd distance across the binuclear unit is 3.870(3) A. Connected by
Table 2. Selected bond lengths and angles for complex I
Bond d, Â Bond d, Â
Cd(1)-O(1) 2.441(3) Cd(1)-O(10) 2.263(4)
Cd(1)-O(2) 2.450(3) Cd(2)-O(5) 2.347(3)
Cd(1)-O(5) 2.414(3) Cd(2)-N(3) 2.258(4)
Cd(1)-O(6) 2.466(3) Cd(2)-O(9) 2.306(3)
Cd(1)-N(1) 2.265(4)
Angle ra, deg Angle ra, deg
O(10)Cd(1)O(1) 89.53(17) N(1)Cd(1)O(1) 92.83(12)
O(10)Cd(1)O(2) 85.46(19) N(1)Cd(1)O(2) 88.95(15)
O(10)Cd(1)O(5) 89.75(19) N(1)Cd(1)O(5) 94.07(14)
O(10)Cd(1)O(6) 88.80(15) N(1)Cd(1)O(6) 100.03(14)
O(10)Cd(1)N(1) 170.97(17) Cd(2)O(5)Cd(1) 108.77(12)
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Fig. 1. Coordination environment of Cd(II) atoms in I.
the other kinds of ^2-fumarato ligand, {Cd(fumaric)}„ (4,4) rhomboid grid coordination polymer layers, co-planar with the (010) crystal planes, are formed by the junction of binuclear kernels through both ^2-fumara-to and ^4-fumarato (Fig. 2). The 28-membered ring is formed by four Cd{(^4-fumarato)-(^2-fumarato)-6/s(2-methylimidazolyl)diaqua} units that are joined together in the layer. Contrasting with other cadmium coordination polymers, such as {Cd(fumaric)(H2O)2}„ [16] and {Cd(Bipy)(fumaric)(H2O)}„ [17], their motifs are quite similar. With the n—n interaction between different 2-methylimidazolyl ligands, as well as the hydrogen bond among free water molecules and ligands, the neighboring {Cd(fumaric)}^ layers formed a 3D {Cd2(C4H2O4)2(C4H6N2)2(H2O)2 • 2H2O}„ coordination polymer microporous network (Fig. 3).
In the IR spectrum of the compound, a strong signal is observed at around 3453 cm-1, which is assigned to the N—H vibration of the 2-methylimidazolyl
ligand and its N=C—N vibration peak is detected at 2359 cm-1. The strongest vibration of the fumaric anion for C-O and C=C is observed at about 1400 and 1637 cm-1, respectively.
The solid-state emission spectra of compound I at room temperature are depicted in Fig. 4. Compound I exhibits an intense emission maximum at 431 nm upon excitation at 349 nm. According to the previous observations [18], the N-donor ligand and the O-donor ligand show contribution to the fluorescence emission of the compound simultaneously. This emission band could be assigned to the emission of the ligand-to-metal charge transfer [19].
ACKNOWLEDGMENTS
This work was supported by the National Natural Science Foundation of China (grants nos. 40872039 and 40572114) and the Specialized Research Fund for
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Fig. 3. The 3D framework of compound I viewed along the x axis. КООРДИНАЦИОННАЯ ХИМИЯ том 37 № 10 2011
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10000 r
8000 -
6000
e
la el
Pi
4000
2000 -
300 400 500 Wavelength, nm
600 650
Fig. 4. Solid-state emission spectrum of compound I at room temperature.
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the Doctoral Program of Higher Education of China (no. 20060491504).
REFERENCES
1. Banerjee, R., Phan, A., Wang, B., et al., Science, 2008, vol. 319, p. 939.
2. Yoon, J.W., Jhung, S.H., Hwang, Y.K., et al., Adv. Mater., 2007, vol. 19, no. 14, p. 1830.
3. Kirillova, M.V., Kirillov, A.M., da Silva, M.F.C.G., et al., Eur. J. Inorg. Chem, 2008, vol. 22, p. 3423.
4. Huang, W., Wu, D.Y., Zhou, P., et al., Cryst. Growth Des, 2009, vol. 9, no. 3, p. 1361.
5. Lin, J.D., Cheng, J.W., and Du, S.W., Cryst. Growth Des., 2008, vol. 8, no. 9, p. 3345.
6. Montney, M.R., Krishnan, S.M., Patel, N.M., et al., Cryst. Growth Des., 2007, vol. 7, no. 6, p. 1145.
7. Post, M.L. and Trotter, J., Dalton. Trans., 1974, vol. 17, p. 1922.
8. Zhou, Y.Z. and Liu, J.L., Inorg. Chem. Commun., 2009, vol. 12, p. 243.
9. Wang, F.Q., Zheng, X.J., Wan, Y.H., et al., Polyhedron,
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