DOI: 10.1021/cg100074g
Novel 2D f 2D Entanglement Pattern in the Coordination Network with Both Polyrotaxane and Polycatenane Features
2010, Vol. 10 2832–2834
Yu Ma,† Ai-Ling Cheng,† and En-Qing Gao*,† †
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062, China Received January 19, 2010; Revised Manuscript Received May 8, 2010
ABSTRACT: The combination of R,R0 -dihydroxybibenzyl-4,40 -dicarboxylate and 4,40 -bipyridine as bridging ligands to bind Zn(II)
leads to an unprecedented 2D f 2D entanglement pattern having both polyrotaxane and polycatenane features. Metal-organic coordination polymers are currently of great interest, not only for their potential applications but also for their intriguing topological variety.1-3 Despite some successes achieved in the design of materials with interesting structures and/or properties,4,5 a true engineering of polymeric networks, both from a structural and a functional point of view, still remains a quite difficult and long-term challenge, needing more elaborate and systematic studies. Supramolecular entanglements of polymeric coordination motifs are among the most difficult phenomena to predict, to control, or to avoid, but their occurrence contributes much to the structural diversity and intrigue of coordination polymers. In addition, the entanglements can lead to materials with enhanced properties or functions, such as superhard materials,6 magnetic materials,7 and even porous materials with high stability or enhanced adsorption capacity.8 Among the entangled systems, interpenetrating nets have attracted particular interest for chemists, many fascinating coordination networks with different polycatenane or polyrotaxane topologies have been constructed and well elucidated in recent years,9-12 and some excellent reviews on related subjects have been published.1c,13 However, the polyrotaxane frameworks, especially those having both polyrotaxane and polycatenane characters, are still quite rare.9b,c,12 Recently we have focused on the construction of coordination polymers using flexible or semirigid dicarboxylate ligands including bibenzyl-4,40 -dicarboxylate ligand and trans-stilbene-4,40 -dicarboxylate ligand,14 some of the materials exhibiting interesting entanglements with the aid of hydrogen bonding and π-π stacking. We herein report two coordination polymers derived from a new dicarboxylate ligand bearing hydroxyl groups, rac-R,R0 dihydroxybibenzyl-4,40 -dicarboxylic acid (H2DHBBDC, Chart 1). Compound 1, [Zn(DHBBDC)(H2O)4] 3 2H2O, contains simple 1D polymeric chains assembled into a 3D network through hydrogen bonding, while compound 2, [Zn3(OH)2(DHBBDC)2(bpy)(H2O)2] 3 H2O (bpy=4,40 -bipyridine), consists of 2D coordination networks with a novel entanglement topology having both polyrotaxane and polycatenane features, which are the focus of this paper. Compound 1 was obtained by slow evaporation of the aqueous solution of Zn(OAc)2 3 H2O, H2DHBBDC, and sodium hydroxide.15a According to single crystal X-ray analyses,16 the unique metal ion is six-coordinated by two carboxylate oxygen atoms from two different DHBBDC ligands and four water molecules, with a trans-octahedral geometry (Figure 1, top). The DHBBDC ligand adopts a zigzag conformation, with the two benzoate groups being transoid with respect to the central C-C bond, and serves as a bridge linking neighboring metal ions with the carboxylate groups in the monodentate mode. Consequently, an infinite quasi-linear *To whom correspondence should be addressed. E-mail: eqgao@chem. ecnu.edu.cn. pubs.acs.org/crystal
Published on Web 05/18/2010
Chart 1. R,R0 -Dihydroxybibenzyl-4,40 -dicarboxylic acid (H2DHBBDC)
coordination chain is formed along the (203) direction. The chains are assembled into a 3D network through extensive hydrogen bonds involving coordinated water molecules, hydroxyl groups of the ligand, and carboxylate oxygens (for details, see Figure S1 of the Supporting Information). In order to extend the dimensionality, bpy was introduced. Compound 2 was obtained by simply layering a methanol solution of bpy on the reaction mixture for the synthesis of 1.15b Rather surprisingly, the structure of compound 2 bears little resemblance to that of 1, with a novel 2-fold parallel interpenetrating network. As shown in Figure 1 (bottom), a linear trinuclear motif is formed in 2. The terminal Zn1 ion of the linear trinuclear motif is tetrahedrally coordinated by two carboxylate oxygen atoms (O1 and O2A) from different DHBBDC ligands, a hydroxo group (O7) and a pyridyl nitrogen atom (N1) from bpy. The central Zn2 atom resides on a 2-fold axis with the octahedral coordination geometry completed by two carboxylate oxygen atoms (O2 and O2B) from different DHBBDC ligands, two water molecules (O8 and O8B), and two hydroxo groups (O7 and O7B). The terminal and central metal ions are linked by a μ2-O bridge and a μ2-COO bridge in the syn-syn mode, with a Zn 3 3 3 Zn distance of 3.30 A˚. The trinuclear unit is reinforced by the hydrogen bond between the water molecule binding Zn2 and the uncoordinated oxygen atom of the carboxylate group binding Zn1, which constitutes the third bridge between Zn1 and Zn2. The [Zn3(μ2-OH)2(μ2-COO)2] motifs are linked into a 2D network through the DHBBDC and bpy ligands. The DHBBDC ligand has a monodentate carboxylate and a μ2-syn-syn carboxylate. The two benzoate groups in the ligand are in the cisoid positions with respect to the central C-C bond to generate a C-shaped conformation, which is in contrast with the zigzag conformation observed in 1. The C-shaped ligands in 2 appear in pairs and serve as the double bridges linking neighboring trinuclear motifs into large parallelogram loops, with the diagonal distances of 8.96 and 14.73 A˚ (for nearest Zn 3 3 3 Zn and C 3 3 3 C, respectively). The loops share the Zn3 motifs to generate a 1D necklace-like coordination chain along the (101) direction (Figure 2a). Viewing down the (101h) direction, the chain has a wavelike shape with the trinuclear motifs at the peak and valley positions. The chains are interlinked into a 2D network along the (101h) plane through the linear bpy coligands. Each Zn3 motif from one chain is connected to two identical motifs from another chain through two bpy ligands of different orientations. These r 2010 American Chemical Society
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Figure 1. Chain structure of 1 (top) and the trinuclear substructure in 2 (bottom). Hydrogen bonds are shown as dashed lines. Some hydrogen atoms are omitted for clarity. Symmetry codes: (A) -1 þ x, 0.5 - y, -1.5 þ z; (B) 1 þ x, 0.5 - y, 1.5 þ z for 1; (A) 0.5 - x, 2.5 y, 1 - z; (B) -x, y, 0.5 - z; (C) -0.5 þ x, 2.5 - y, -0.5 þ z for 2.
Figure 3. (a) View of the parallel 2-fold interpenetrating nets in 2; (b) schematic view of the unusual parallel 2D f 2D interpenetration in 2; (c) the two previous unusual parallel 2D f 2D interpenetration patterns with both polyrotaxane and polycatenane features.
Figure 2. (a) The necklace-like chain in 2; (b) a single sheet; (c) schematic presentation of the sheet.
interchain linear connections combined with the wavelike chain shape lead to unique and large sector-shaped windows in the resulting 2D layer, with a side edge of 11.16 A˚ (the Zn 3 3 3 Zn distance spanned by bpy) (Figure 2b). Taking the trinuclear motifs as 6-connecting nodes and the DHBBDC and bpy as arclike linkers and straight rods, respectively, the layer can be simplified as the intuitionistic net illustrated in Figure 2c. To fill the large void space in a single layer, two layers sharing the common plane defined by metal ions are interpenetrated with each other in a parallel fashion to give an unusual entangled doublelayer network. As can be seen from Figure 3a, the parallelogram loops in one layer are threaded by the linear bpy ligands from the other layer, and the sector-shaped windows from one layer are
occupied by the trinuclear motifs from the other layer. A schematic illustration of the entanglement is shown in Figure 3b. The entanglement represents an unprecedented 2D f 2D topology of interpenetration with coexistent polyrotaxane and polycatenane features. It is worthwhile to make a comparison with the previous networks with similar features. The unusual coexistence of polyrotaxane and polycatenane features has been observed in a few previous coordination networks.9b,c,12 Two different types of 2D f 2D parallel interpenetration of the layers through polyrotaxane and polycatenane structures have been previously described (Figure 3c): in the layer of type I (Figure 3c, left), each loop is connected to four loops through four linear rods, while the loops in type II (Figure 3c, right) are connected directly into necklace chains by sharing nodes (single metal ions or binuclear units).9b,c,12 The layer in 2 is similar to that in type II in that it also contains necklace chains. However, they are quite different in the chain shape and the interchain connection. The necklace chains in type II are linear, the rod linkers attached to the same node are on the opposite sides of the chains, and hence, the chains are connected by parallel rods. By contrast, the necklace chains in 2 assume the wavelike (or zigzag) shape, and the rod linkers attached to the same node are on the same sides of the chains. As a result, the neighboring necklace chains in 2 are connected by a zigzag chain of rod linkers. Apparently, the formation of this peculiar pattern of polyrotaxane and polycatenane units requires a more strict match between the bent and linear linkers. For example, the length of the linear or bent linkers in type II can be changed independently while the topology and local coordination geometry remain unchanged, but this cannot be achieved for the new topology without changes in the local coordination geometry or the overall topology. The success in obtaining the new topology in 2 benefits from the unique combination of the flexible DHBBDC ligand and the rodlike bpy ligand with well-matched lengths. This
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illustrates the great difficulty and challenges faced by chemists in predicting and designing coordination networks, especially those with interpenetration. The two interpenetrated layers in 2 are simply related by translation along the b direction, and viewing from this direction, the double layer has highly undulated surfaces (Figure S2 of the Supporting Information): Zn(II) and bpy are in plane while DHBBDC is bumped up and down. Neighboring double layers are packed in an offset and interdigitating fashion (Figure S3 of the Supporting Information). While there are no evident indications of hydrogen bonding and π-π stacking between the two interpenetrated layers, there are strong O-H 3 3 3 O hydrogen bonds between the interdigitated layers, which involve the hydroxyl groups of the DHBBDC ligand from one layer and the carboxylate groups from another layer (Figure S3 of the Supporting Information). This suggests that the hydroxyl groups incorporated into the ligand play an important role in sustaining the interdigitation and stabilizing the whole structure. To summarize, from the new DHBBDC ligand, we have succeeded in obtaining a simple 1D chain (1) and a novel 2D network (2) in the absence and presence of bpy, respectively. The unique combination of the flexible bent DHBBDC ligand and the rigid linear bpy ligand in 2 leads to an unprecedented 2D f 2D entanglement having both polyrotaxane and polycatenane features. This, on the one hand, illustrates the great challenge in “designing” entangled networks and, on the other hand, demonstrates the great potential of finding novel and intriguing entanglement patterns. Acknowledgment. The authors thank NSFC (20771038) and the Shanghai Leading Academic Discipline Project (B409) for financial support. Supporting Information Available: Crystallographic data in CIF format and supplementary structural graphics in PDF format. This material is available free of charge via the Internet at http://pubs. acs.org.
References (1) (a) Gimeno, N.; Vilar, R. Coord. Chem. Rev. 2006, 250, 3161. (b) Robin, A. Y.; Fromm, K. M. Coord. Chem. Rev. 2006, 250, 2127. (c) Carlucci, L.; Ciani, G.; Proserpio, D. M. Coord. Chem. Rev. 2003, 246, 247. (d) Ockwig, N. W.; Delgado-Friedrichs, O.; O'Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2005, 38, 176. (2) (a) Fujita, Y. M.; Kwon, Y. J.; Washizu, S.; Ogura, K. J. Am. Chem. Soc. 1994, 116, 1151. (b) Kepert, C. J. Chem. Commun. 2006, 695. (c) Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem., Int. Ed. 2004, 43, 2334. (3) (a) Janiak, C. Dalton Trans. 2003, 2781. (b) Mueller, U.; Schubert, M.; Teich, F.; Puetter, H.; Schierle-Arndt, K.; Pastre, J. J. Mater. Chem. 2006, 16, 626. (c) Champness, N. R. Dalton Trans. 2006, 877. (4) (a) Biradha, K.; Sarkar, M.; Rajput, L. Chem. Commun. 2006, 4169. (b) Pan, L.; Sander, M. B.; Huang, X. Y.; Li, J.; Smith, M.; Bittner, E.; Bochrath, B.; Johnson, J. K. J. Am. Chem. Soc. 2004, 126, 1308. (c) Noro, S.; Kitagawa, S.; Kondo, M.; Seki, K. Angew. Chem., Int. Ed. 2000, 39, 2081. (5) (a) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003, 423, 705. (b) Moulton, B.; Zaworotko, M. Chem. Rev. 2001, 101, 1629. (c) Eddaoudi, M.; Kim, J.; Rosi, N. L.; Vodak, D. T.; Wachter, J.; O'Keeffe, M.; Yaghi, O. M. Science 2002, 295, 469. (6) Proserpio, D. M.; Hoffman, R.; Preuss, P. J. Am. Chem. Soc. 1994, 116, 9634.
Ma et al. (7) Miller, J. S. Adv. Mater. 2001, 13, 525. (8) Rowsell, J. L. C.; Yaghi, O. M. Angew. Chem., Int. Ed. 2005, 44, 4670. (9) (a) Hoskins, B. F.; Robson, R.; Slizys, D. A. J. Am. Chem. Soc. 1997, 119, 2952. (b) Hoskins, B. F.; Robson, R.; Slizys, D. A. Angew. Chem., Int. Ed. Engl. 1997, 36, 2336. (c) Goodgame, D. M. L.; Menzer, S.; Smith, A. M.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1995, 34, 574. (10) (a) Fraser, C. S. A.; Jennings, M. C.; Puddephatt, R. J. Chem. Commun. 2001, 1310. (b) Wang, Z.; Cheng, Y.; Liao, C.; Yan, C. CrystEngComm 2001, 3, 237. (c) Zhu, H.-F.; Zhao, W.; Okamura, T.; Fan, J.; Sun, W.-Y.; Ueyama, N. New J. Chem. 2004, 28, 1010. (d) Fan, J.; Sun, W.-Y.; Okamura, T.; Zheng, Y.-Q.; Sui, B.; Tang, W.-X.; Ueyama, N. Cryst. Growth Des. 2004, 4, 579. (e) Arora, K. K.; Pedireddi, V. R. Cryst. Growth Des. 2005, 5, 1309. (11) (a) Carlucci, L.; Ciani, G.; Proserpio, D. M. Cryst. Growth Des. 2005, 5, 37. (b) Zhu, H. F.; Fan, J.; Okamura, T.; Sun, W.-Y.; Ueyama, N. Cryst. Growth Des. 2005, 5, 289. (12) (a) Yang, J.; Ma, J.-F.; Batten, S. R.; Su, Z.-M. Chem. Commun. 2008, 2233. (b) Wang, G.-H.; Li, Z.-G.; Jia, H.-Q.; Hu, N.-H.; Xu, J.-W. Cryst. Growth Des. 2008, 8, 1932. (c) Luo, F.; Yang, Y.-T.; Che, Y.-X.; Zheng, J.-M. CrystEngComm 2008, 10, 981. (d) Lan, Y.-Q.; Li, S.-L.; Qin, J.-S.; Du, D.-Y.; Wang, X.-L.; Su, Z.-M.; Fu, Q. Inorg. Chem. 2008, 47, 10600. (e) Liu, J.-Q.; Wang, Y.-Y.; Zhang, Y.-N.; Liu, P.; Shi, Q.-Z.; Batten, S. R. Eur. J. Inorg. Chem. 2009, 147. (f) Cao, X.-Y.; Yao, Y.-G.; Batten, S. R.; Ma, E.; Qin, Y.-Y.; Zhang, J.; Zhanga, R.-B.; Cheng, J.-K. CrystEngComm 2009, 11, 1030. (13) (a) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460. (b) Batten, S. R. CrystEngComm 2001, 3, 67. (c) Batten, S. R. In Encyclopedia of Supramolecular Chemistry; Atwood, J. L., Steed, J. W., Eds.;Marcel Dekker: New York, 2004; pp 735-741. (14) (a) Cheng, A.-L.; Liu, N.; Yue, Y.-F.; Jiang, Y.-W.; Gao, E.-Q.; Yan, C.-H.; He, M.-Y. Chem. Commun. 2007, 407. (b) Cheng, A.-L.; Ma, Y.; Zhang, J.-Y.; Gao, E.-Q. Dalton Trans. 2008, 1993. (c) Ma, Y.; Cheng, A.-L.; Zhang, J.-Y.; Yue, Q.; Gao, E.-Q. Cryst. Growth Des. 2009, 9, 867. (d) Yue, Q.; Qian, X.-B.; Yan, L.; Gao, E.-Q. Inorg. Chem. Commun. 2008, 11, 1067. (15) (a) Synthesis of 1: A mixture of Zn(OAc)2 3 H2O (0.20 mmol, 0.040 g), H2DHBBDC15c (0.20 mmol, 0.060 g), and sodium hydroxide (0.25 mmol, 0.010 g) in water (5 mL) was stirred for 10 min at room temperature. Slow evaporation of the solution at room temperature yielded colorless crystals of 1 within one week. Yield: 45% based on Zn. Anal. Found: C, 40.79; H, 5.17. Calcd for C16H24O12Zn: C, 41.13; H, 5.18. IR (KBr, cm-1): 3510(m), 3347(br), 1647(m), 1598(s), 1539(s), 1389(vs), 1238(w), 1178(w), 1082(w), 1043(w), 1011(w), 843(w), 746(m), 645(w). (b) Synthesis of 2: A solution of bpy (0.10 mmol, 0.016 g) in 6 mL of methanol was layered on a mixture of Zn(OAc)2 3 H2O (0.20 mmol, 0.040 g), H2DHBBDC (0.20 mmol, 0.060 g), and sodium hydroxide (0.25 mmol, 0.010 g) in water (6 mL) at room temperature. After 30 days, colorless crystals of 2 were obtained. Yield: 35% based on Zn. Anal. Found: C, 48.25; H, 4.21; N, 2.55. Calcd for C42H42N2O17Zn3: C, 48.37; H, 4.06; N, 2.69. IR (KBr, cm-1): 3396(br), 1606(s), 1558(s), 1404(s), 1394(w), 1219(w), 1173(w), 1052(m), 1012(w), 868(w), 820(w), 785(m), 715(w), 642(w), 559(w). (c) Tsuritani, T.; Ito, S.; Shinokubo, H.; Oshima, K. J. Org. Chem. 2000, 65, 5066. (16) Crystal data for 1: C16H24O12Zn, monoclinic, space group P21/c; a = 13.7934(4) A˚, b = 14.2293(4) A˚, c = 10.3064(3) A˚, β = 109.2810(10)°, V = 1909.38(10) A3, Z = 4; Dc = 1.648 g cm-3, 23463 reflections measured, 3755 unique with Rint =0.0285, 1.56< θ 2σ(I)], R1 = 0.0304, and wR2 = 0.0704 (for all data). Crystal data for 2: C42H42N2O17Zn3, monoclinic, space group C2/c; a = 29.780(4) A˚, b = 7.2495(9) A˚, c = 24.163(3) A˚, β = 123.628(3)°, V = 4343.7(9) A3, Z = 4; Dc = 1.595 g cm-3, 26808 reflections measured, 4468 unique with Rint = 0.0751, 1.64 < θ < 26.50°, final R-factors: R1 = 0.0482 and wR2 = 0.1470 [for 3232 reflections with I > 2σ(I)], R1 = 0.0665, and wR2 = 0.1508 (for all data).
