Temperature-controlled structural diversity of two Cd(II) coordination polymers based on a flexible tripodal multicarboxylate ligand

Inorganic Chemistry Communications 45 (2014) 84–88

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Temperature-controlled structural diversity of two Cd(II) coordination polymers based on a flexible tripodal multicarboxylate ligand Min Chen, Zhuo-Wei Wang, Hui Zhao, Chun-Sen Liu ⁎ Zhengzhou University of Light Industry, Henan Provincial Key Lab of Surface & Interface Science, Zhengzhou, Henan 450002, China

a r t i c l e

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Article history: Received 29 January 2014 Received in revised form 1 April 2014 Accepted 10 April 2014 Available online 24 April 2014 Keywords: Cadmium(II) MOFs Reaction temperature Crystal structures Luminescence

a b s t r a c t Two new 3-D Cd(II) coordination polymers (CPs) with 3,5-bi(4-carboxyphenoxy)-benzoic acid (H3L), namely [Cd3(L)2(H2O)4]·4H2O (1) and [Cd3(L)2(H2O)3]·2H2O (2), were successfully synthesized under hydrothermal condition at 140 °C and 180 °C, respectively. Complex 1 is constructed from 1-D (–Cd–O–)∞ rod-shaped SBUs (secondary building units) and ‘Y’-shaped L ligands. In complex 2, the 3-D network is mediated by 2-D [Cd(COO)2]n layered motifs and ‘T’ and ‘Y’-shaped L ligands. The results show that the reaction temperature plays a key role on the final structures of the complexes. The luminescent properties of the complexes have also been investigated. © 2014 Elsevier B.V. All rights reserved.

Coordination polymers (CPs) have attracted intense attention in recent years because of their intriguing structures and potential applications as functional materials [1,2]. Up to now, it is well known that large number of CPs have been successfully obtained by using tripodal carboxylate ligands, such as 4,4′,4″-benzene-1,3,5-triyl-tribenzoate (BTB) [3], 4,4′,4″-s-trizaine-2,4,6-triyltribenzoate (TATB) [4], 4,4′,4″[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)]tribenzoate (BTE) [3a,5], 4,4′,4″-(benzene-1,3,5-triyl-tris (benzene-4,1-diyl))tribenzoate (BBC) [6], 4,4′,4″-(triazine-2,4,6-triyl-tris(benzene-4,1-diyl))tribenzoate (TAPB) [6b], 4,4′,4″-s-triazine-1,3,5-triyltri-p-aminobenzoate (TATAB) [7], 4,4′,4″-(benzene-1,3,5-triyltris(azanediyl)) tribenzoate (BTATB) [7b]. Compared with the rigid tripodal carboxylate ligands, far less interest has been focused on the investigation of the flexible ones [8]. However, the diverse conformations of the flexible ligands inspired by the various experimental conditions, such as the solvents, reaction temperature, pH value of the solution, reaction time, solvent system, and counterion, would influence the final structures [9]. Apart from these factors, higher reaction temperature may lead to complicated structures due to the increase in connected number of ligands, the appearance of entanglement, hydroxo metal clusters and so on [10]. Inspired by the aforementioned considerations, herein we employed a tripodal carboxylate ligand with one rigid and two flexible carboxylate groups, 3,5bis(4-carboxy-phenoxy)benzoic acid (H3L), as an excellent candidate for the construction of CPs. On the basis of this ligand, two new 3–D Cd(II) CPs, [Cd3(L)2(H2O)4]·4H2O (1) and [Cd3(L)2(H2O)3]·2H2O (2), were obtained under hydrothermal condition at different temperatures [11], which were characterized by elemental analysis, IR spectra, ⁎ Corresponding author. E-mail address: [email protected] (C.-S. Liu).

http://dx.doi.org/10.1016/j.inoche.2014.04.007 1387-7003/© 2014 Elsevier B.V. All rights reserved.

thermogravimetric analysis (TGA), and variable temperature PXRD (VT-PXRD) technique. Single-crystal X-ray diffraction reveals that complex 1 has a 3–D polymeric structure [12]. The asymmetric unit consists of one and a half crystallographically unique Cd(II) atoms, one L ligand, two water ligands, and two lattice water molecules. As shown in Fig. 1a, two Cd(II) atoms are six-coordinated and exhibit the distorted octahedral geometries. For Cd1, the equatorial plane comprises three oxygen atoms (O2A, O8B, and O8C) from three distinct L ligands and one bridging aqua oxygen atom (O9) while one terminal aqua oxygen atom (O10) and one carboxylate atom (O6) occupy the apical coordination sites. For Cd2, four carboxylate atoms (O5, O5E, O7C, and O7D) from four distinct L ligands and two bridging aqua atoms (O9 and O9E) are in the equatorial plane and the axial positions, respectively. The bond angles around Cd(II) centers lie in the range of 74.55(17)°–168.31(16)° and the Cd\O bond lengths range from 2.260(4) to 2.357(4) Å (see Table S1 in the Supplementary material). The full deprotonated L ligand in 1 links six Cd(II) atoms (see Scheme 1a) and exhibits the ‘Y’-shaped conformation with the angle γ of 34.7° (γ is the angle between the two adjacent lines linked by the rigid carboxylate carbon atom and the two flexible carboxylate carbon atoms, γ b 90° defines the ‘Y’-shaped conformation, see Scheme 1a). The rigid carboxylate group is in the μ1-η1:η0 coordination mode while the two flexible ones display μ2-η1:η1 and μ3-η2:η1 coordination modes, respectively. The three carboxylate groups of L ligands and bridging aqua ligands link Cd(II) atoms to result in an infinite 1-D rodshaped inorganic SBUs that are running along [001] direction (see Fig. 1b, left). Each rod consists of corner-sharing (Cd1 and Cd2) and edge-sharing (Cd1 and Cd1) CdO6 polyhedra (see Fig. 1b, middle). The Cd⋯Cd distances within the rod-shaped SBUs are 3.64 Å for Cd1⋯ Cd2

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Fig. 1. (a) Local coordination environment of Cd(II) atoms in 1 [The symmetry-related atoms labeled with the suffixes A, B, C, D, and E are generated by the symmetry operations (x + 1, −y + 3/ 2, z + 1/2), (x + 1, y, z), (−x + 1, −y + 2, −z + 1), (x + 1, y, z + 1), and (−x + 2, –y + 2, −z + 2)]. (b) View of the 1D rod-shaped SBU (left and middle) and the 3–D framework (right) viewed along the c axis in 1.

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Scheme 1. View of the coordination modes of L ligands appeared in 1 and 2, showing the different values of the γ angle between the two adjacent lines linked by the rigid carboxylate carbon atom and the two flexible carboxylate carbon atoms.

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and 3.67 Å for Cd1⋯Cd1, respectively. Such 1-D rod-shaped SBUs are connected by ‘Y’-shaped L ligands to produce the final 3-D network of 1 (see Fig. 1b, right). When increasing the reaction temperature from 140 °C to 180 °C, complex 2 was successfully isolated. The asymmetric unit of 2 consists of one and a half crystallographically unique Cd(II) atoms, one L ligand, one and a half water ligands, and one lattice water molecule. As shown in Fig. 2a, Cd1, Cd2 and Cd3 exhibit octahedral geometries. Cd1 is coordinated by two carboxylate oxygen atoms (O1 and O1A) from two different L ligands and four aqua oxygen atoms (O17, O17A, O18, and O18A). Cd2 is surrounded by five carboxylate oxygen atoms (O2, O3B, O4C, O11, and O12) from four distinct L ligands and one aqua oxygen atom (O19) while six carboxylate oxygen atoms (O5, O5D, O9H, O9G, O13E, and O13F) from six different L ligands complete the coordination sphere of Cd3. The six-coordinated Cd4 atom displays distorted triangular prism with the two triangular bases furnished by six carboxylate atoms from five different L ligands (O6, O10G and O12F; O2F, O13E, and O14E). The Cd\O bond lengths are in the ranges of 2.142(6)–2.666(6) and the O\Cd\O bond angles vary from 54.2(2) to 166.82(19)° (see Table S1 in the Supplementary material). In 2, the L ligand exhibits ‘T’ and ‘Y’-shaped conformations, namely L1 (γ = 94.0°, γ N 90° defines the ‘T’-shaped conformation) and L2 (γ = 50.6°), respectively (see Scheme 1b,c). The ‘T’-shaped L1 link seven Cd(II) atoms through one rigid carboxylate group in μ3-η1:η2 coordination mode and two flexible ones in μ2-η1:η1 and μ2-η1:η2 coordination modes (see Scheme 1b). For the ‘Y’-shaped L2, the rigid carboxylate group in the μ2-η1:η1 coordination

mode and the two flexible ones in μ2-η1:η2 coordination modes link six Cd(II) atoms (see Scheme 1c). It is evident that the highly connected ligands are obtained by increasing the reaction temperature. Based on the connectivity pattern, L1 ligands link Cd(II) atoms forming a 3-D network with fusiform channels (see Fig. S1 in the Supplementary material). Then, the L2 ligands fill the interior of the cavities to furnish the final 3-D framework (see Fig. 2b, left). More specifically, the Cd\O\C rods built from pairs of edge-linked (Cd2) and corner-linked (Cd3 and Cd4) CdO6 polyhedra are further linked by isolated CdO6 polyhedra (Cd1) to generate the 2-D [Cd(COO)2]n layered motifs parallel to the ac plane (see Fig. 2b, right). To investigate the thermal stability of the complexes, their thermal behaviors were studied by TGA (see Fig. 3). For 1 and 2, the first weight losses of 11.45% and 7.49% were observed in the temperature range of ca. R. T.−140 °C, which correspond to the liberation of the free and coordinated water molecules (calculated: 11.41% for 1 and 7.45% for 2), and further weight losses were observed at about 325 °C and 385 °C, owing to the collapse of the whole frameworks of 1 and 2, respectively. The variable temperature PXRD (VT-PXRD) experiments are consistent with the TGA measurements and further indicate that the framework structures of 1 and 2 are retained over 300 and 360 °C, respectively (see Fig. 4). The solid-state photoluminescent properties of 1 and 2 were investigated at room temperature, due to the various potential applications of polymeric Cd(II) complexes as luminescent materials [13]. The free H3L ligand shows the maximal emission peak at 362 nm (see Fig. 5),

(a)

(b) Fig. 2. (a) Local coordination environment of Cd(II) atoms in 2 [The symmetry-related atoms labeled with the suffixes A, B, C, D, E, F, G, and H are generated by the symmetry operations (−x + 1, −y, −z + 1), (−x + 2, −y − 1, −z + 1), (x, y + 1, z), (−x + 3, −y, −z), (x + 1, y, z), (−x + 2, −y, −z), (x + 1, y − 1, z), and (−x + 2, −y + 1, −z)]. (b) View of the 3–D framework viewed along the a axis (left) and 2–D [Cd(COO)2]n layered motifs parallel to the ac plane (right) in 2.

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Complex 1 Complex 2

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Fig. 3. TGA curves of 1 and 2.

Fig. 5. Solid-state emission spectra of free H3L, 1, and 2 at room temperature.

which should be attributable to the π → π* and/or n → π* transitions. The similar fluorescent behaviors of 1 and 2 are observed with the maximum peaks of 361 nm for 1 and 364 nm for 2 (see Fig. 5), which should be assigned to the ligand-centered transitions. In summary, two new 3-D Cd(II) coordination polymers have been prepared under hydrothermal conditions by employing 3,5-bi(4carboxyphenoxy)-benzoic acid (H3L) ligand. In 1, the 1-D (–Cd–O–)∞ rod-shaped SBUs are linked by the ‘Y’-shaped L ligands, while, in 2, the 2-D [Cd(COO)2]∞ layered motifs and ‘T’ and ‘Y’-shaped L ligands are found. Remarkably, the changes in coordination numbers of metal

atoms, coordination modes, and conformations of ligands stimulated by reaction temperatures result in the distinct frameworks of 1 and 2, which promote us to make a further research on related functional crystalline solids through such a reliable synthetic procedure. Acknowledgments This work was supported by the National Natural Science Foundation of China (grant nos. 21171151 and 21201154) and the Startup Fund for PhDs of the Natural Scientific Research of Zhengzhou University of Light Industry (to C.M.). Appendix A. Supplementary material

310 oC 300 oC 200 oC

CCDC 983935 and 983936 contain the crystallographic data for 1 and 2. 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: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.inoche.2014.04.007.

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370 oC 360 oC 350 oC 300 oC As-synthesized Simulated from cif

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(b) Fig. 4. The VT-PXRD patterns of 1 (a) and 2 (b).

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References [1] (a) M. Li, D. Li, M. O'Keeffe, O.M. Yaghi, Topological analysis of metal–organic frameworks with polytopic linkers and/or multiple building units and the minimal transitivity principle, Chem. Rev. 114 (2014) 1343–1370; (b) M. O'Keeffe, O.M. Yaghi, Deconstructing the crystal structures of metal–organic frameworks and related materials into their underlying nets, Chem. Rev. 112 (2012) 675–702; (c) E.V. Alexandrov, V.A. Blatov, A.V. Kochetkova, D.M. Proserpio, Underlying nets in three-periodic coordination polymers: topology, taxonomy and prediction from a computer-aided analysis of the Cambridge Structural Database, Cryst. Eng. Commun. 13 (2011) 3947–3958; (d) M. Du, C.-P. Li, C.-S. Liu, S.-M. Fang, Design and construction of coordination polymers with mixed-ligand synthetic strategy, Coord. Chem. Rev. 257 (2013) 1282–1305. [2] (a) K. Sumida, D.L. Rogow, J.A. Mason, T.M. McDonald, E.D. Bloch, Z.R. Herm, T.-H. Bae, J.R. Long, Carbon dioxide capture in metal–organic frameworks, Chem. Rev. 112 (2012) 724–781; (b) L.E. Kreno, K. Leong, O.K. Farha, M. Allendorf, R.P.V. Duyne, J.T. Hupp, Metal–organic framework materials as chemical sensors, Chem. Rev. 112 (2012) 1105–1125; (c) P. Horcajada, R. Gref, T. Baati, P.K. Allan, G. Maurin, P. Couvreur, G. Férey, R.E. Morris, C. Serre, Metal–organic frameworks in biomedicine, Chem. Rev. 112 (2012) 1232–1268. [3] (a) H. Furukawa, N. Ko, Y.-B. Go, N. Aratani, S.B. Choi, E. Choi, A.Ö. Yazaydin, R.Q. Snurr, M. O'Keeffe, J. Kim, O.M. Yaghi, Ultrahigh porosity in metal–organic frameworks, Science 329 (2010) 424–428; (b) K. Koh, A.G. Wong-Foy, A.J. Matzger, A crystalline mesoporous coordination copolymer with high microporosity, Angew. Chem. Int. Ed. 47 (2008) 677–680; (c) D.F. Sava, L.E.S. Rohwer, M.A. Rodriguez, T.M. Nenoff, Intrinsic broad-band white-light emission by a tuned, corrugated metal–organic framework, J. Am. Chem. Soc. 134 (2012) 3983–3986. [4] (a) D.-F. Sun, S.-Q. Ma, Y.-X. Ke, T.M. Petersen, H.-C. Zhou, Synthesis, characterization, and photoluminescence of isostructural Mn, Co, and Zn MOFs having a

88

M. Chen et al. / Inorganic Chemistry Communications 45 (2014) 84–88

(b) [5] (a)

(b) [6] (a)

(b)

[7] (a)

(b) [8] (a)

(b)

(c) [9] (a)

(b)

[10] (a)

(b)

diamondoid structure with large tetrahedral cages and high thermal stability, Chem. Commun. (2005) 2663–2665; D.-F. Sun, S.-Q. Ma, Y.-X. Ke, D.J. Collins, H.-C. Zhou, An interweaving MOF with high hydrogen uptake, J. Am. Chem. Soc. 128 (2006) 3896–3897. M.P. Suh, H.J. Choi, S.M. So, B.M. Kim, A new metal–organic open framework consisting of threefold parallel interwoven (6,3) nets, Inorg. Chem. 42 (2003) 676–678; S.-C. Du, C.-H. Hu, J.-C. Xiao, H.-Q. Tan, W.-P. Liao, A giant coordination cage based on sulfonylcalix[4]arenas, Chem. Commun. 48 (2012) 9177–9179. D.-F. Sun, Y.-X. Ke, T.M. Mattox, S. Parkin, H.-C. Zhou, Stability and porosity enhancement through concurrent ligand extension and secondary building unit stabilization, Inorg. Chem. 45 (2006) 7566–7568; H. Furukawa, Y.B. Go, N. Ko, Y.K. Park, F.J. Uribe-Romo, J. Kim, M. O'Keeffe, O.M. Yaghi, Isoreticular expansion of metal–organic frameworks with triangular and square building units and the lowest calculated density for porous crystals, Inorg. Chem. 50 (2011) 9147–9152. Q.-R. Fang, D.-Q. Yuan, J. Sculley, J.-R. Li, Z.-B. Han, H.-C. Zhou, Functional mesoporous metal–organic frameworks for the capture of heavy metal ions and sizeselective catalysis, Inorg. Chem. 49 (2010) 11637–11642; X.-S. Wang, S.-Q. Ma, D.-F. Sun, S. Parkin, H.-C. Zhou, A mesoporous metal–organic framework with permanent porosity, J. Am. Chem. Soc. 128 (2006) 16474–16475. L.-Q. Han, Y. Yan, F.-X. Sun, K. Cai, T. Borjigin, X.-Q. Zhao, F.-Y. Qu, G.-S. Zhu, Single- and double-layer structures and sorption properties of two microporous metal–organic frameworks with flexible tritopic ligand, Cryst. Growth Des. 13 (2013) 1458–1463; X.-M. Lin, T.-T. Li, Y.-W. Wang, L. Zhang, C.-Y. Su, Two ZnII metal–organic frameworks with coordinatively unsaturated metal sites: structures, adsorption, and catalysis, Chem. Asian. J. 7 (2012) 2796–2804; J.-H. Cui, Y.-Z. Li, Z.-J. Guo, H.-G. Zheng, Six new co-coordination polymers based on a tripodal carboxylate ligand, Cryst. Growth Des. 12 (2012) 3610–3618. H.-Y. Liu, H. Wu, J. Yang, Y.-Y. Liu, B. Liu, Y.-Y. Liu, J.-F. Ma, pH-dependent assembly of 1D to 3D octamolybdate hybrid materials based on a new flexible bis[(pyridyl)-benzimidazole] ligand, Cryst. Growth Des. 11 (2011) 2920–2927; X.-G. Guo, W.-B. Yang, X.-Y. Wu, K. Zhang, L. Lin, R.-M. Yu, C.-Z. Lu, Stoichiometry, temperature, solvent, metal-directed syntheses of metal–organic frameworks based on flexible V-shaped methylenebis(3,5-dimethylpyrazole) and various aromatic dicarboxylate acids, Cryst. Eng. Commun. 15 (2013) 3654–3663. M. Chen, Y. Lu, J. Fan, G.-C. Lv, Y. Zhao, Y. Zhang, W.-Y. Sun, High structural diversity controlled by temperature and induction agent, Cryst. Eng. Commun. 14 (2012) 2015–2023; G.-P. Yang, L. Hou, L.-F. Ma, Y.-Y. Wang, Investigation on the prime factors influencing the formation of entangled metal–organic frameworks, Cryst. Eng. Commun. 15 (2013) 2561–2578.

[11] Synthesis of 1. A mixture of Cd(NO3)3·4H2O (0.1 mmol, 30.8 mg), H3L (0.05 mmol, 19.7 mg), NaOH (0.15 mmol, 6 mg), and water (10 mL) was heated to 140 °C for 3 days, and then cooled to room temperature. Colorless prism crystals of 1 were obtained in yield ca. 40%. Anal. calcd for C42H38O24Cd3: C, 39.91; H, 3.03%. Found: C, 39. 87; H, 2.98%. IR (KBr pellet, cm−1): 3417 (m), 1691 (s), 1593 (vs), 1553 (m), 1505 (m), 1396 (s), 1370 (s), 1305 (m), 1231 (vs), 1165 (s), 1125 (w), 1007 (w), 859 (w), 792 (w), 701 (w), 607 (w). Complex 2 was obtained by the similar procedure as used for 1 except the reaction temperature was changed to 180 °C. After cooling to room temperature, colorless block crystals of 2 were obtained in yield 60%. Anal. calcd for C42H32O21Cd3: C, 41.69; H, 2.67%. Found: C, 41.63; H, 2.62%. IR (KBr pellet, cm−1): 3259 (w), 1595 (m), 1529 (m), 1500 (s), 1379 (vs), 1315 (m), 1220 (s), 1163 (s), 1123 (m), 1001 (m), 962 (w), 857 (w), 800 (w), 740 (w), 704 (w), 640 (w), 569 (w). [12] Diffraction intensities for complexes 1 and 2 were collected on Oxford Xcalibur Eos diffractometer with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) at 294(2) K. Multi-scan absorption corrections were performed with the CrysAlisPro program (Oxford Diffraction Ltd., Version 1.171.35.15). Empirical absorption corrections were carried out using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. The structures were solved by direct methods, and all nonhydrogen atoms were refined anisotropically by full-matrix least-squares method with the SHELXTL crystallographic software package. Hydrogen atoms were generated theoretically and refined with isotropic thermal parameters riding on the parent atoms. Crystal data for 1: C42H38O24Cd3, M = 1263.92, Monoclinic, space group P21/c, a = 8.5614(11) Å, b = 30.757(2) Å, c = 9.1898(11) Å, α = 90.00º, β = 116. 346(16)º, γ = 90.00º, V = 2168.5(4) Å3, Z = 2, Dc = 1.936 Mg m−3, μ (Mo–Ka) = 1.552 mm−3, F(000) = 1252, T = 294(2) K, Rint = 0.0522, final R1 = 0.0438, wR2 = 0.1070 [for selected data with I N 2σ(I)], GOF = 1.065 for all data. Crystal data for 2, C42H32O21Cd3, M = 1209.88, Triclinic, space group P-1, a = 10.6470(8) Å, b = 13. 9628(8) Å, c = 14.6808(11) Å, α = 81.190(5)º, β = 87.549(6)º, γ = 80. 972(5)º, V = 2129.6(3) Å3, Z = 2, Dc = 1.887 Mg m−3, μ (Mo–Ka) = 1. 571 mm − 1 , F(000) = 1192, T = 294(2) K, R int = 0.0473, final R 1 = 0.0580, wR2 = 0.1251 [for selected data with I N 2σ(I)], GOF = 1.037 for all data. [13] C.-P. Li, J. Chen, P.-W. Liu, M. Du, Structural diversity and fluorescent properties of CdII coordination polymers with 5-halonicotinates regulated by solvent and ligand halogen-substituting effect, Cryst. Eng. Commun. 15 (2013) 9713–9721; (b) Y.-X. Qiu, W.-B. Chen, X.-M. Lin, M. Yang, H. Yan, F.-X. Gao, X.-J. Ruan, Z.-J. Ou Yang, W. Dong, Synthesis, structure, photochromic and fluorescent imaging properties of a 3D cadmium(II) complex [Cd2(AT)2(H2O)4]·H2O (AT = 5,5′azotetrazolate), Inorg. Chem. Commun. 29 (2013) 201–204; (c) F.-Y. Yi, W.T. Yang, Z.-M. Sun, Highly selective acetone fluorescent sensors based on microporous Cd(II) metal–organic frameworks, J. Mater. Chem. 22 (2012) 23201–23209.