An Unusual Interweaving in a 3-Fold Interpenetrated Pillared-Layer Zn

Jun 7, 2012 - ABSTRACT: This communication describes a unique inter- weaving of a pyridyl-based long linear spacer ligand, 1,4-bis[2-(4-...
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An Unusual Interweaving in a 3-Fold Interpenetrated Pillared-Layer Zn(II) Coordination Polymer with a Long Spacer Ligand Published as part of the Crystal Growth & Design virtual special issue In Honor of Prof. G. R. Desiraju In-Hyeok Park,† Kihwan Kim,† Shim Sung Lee,*,† and Jagadese J. Vittal*,†,‡ †

Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701, South Korea Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543

‡

S Supporting Information *

ABSTRACT: This communication describes a unique interweaving of a pyridyl-based long linear spacer ligand, 1,4-bis[2-(4pyridyl)ethenyl]benzene (bpeb), in the triply interpenetrated pillarlayer porous coordination polymer [Zn2(ndc)2(bpeb)]·DMF·3H2O (where ndc = 2,6-naphthalenedicarboxylate) containing a paddlewheel secondary building unit (SBU) with α-Po topology. When the dicarboxylate is changed diethylpyrocarbonate (DEPC) from ndc to biphenyl-4,4′-dicarboxylate (bpdc), the reaction furnished a completely different 3-fold interpenetrating three-dimensional coordination polymer [Zn3(bpdc)3(bpeb)]·0.5DMSO·1.5H2O having a uninodal eight connected network structure with hexagonal bipyramidal SBUs.

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rystal engineering of coordination polymers has now reached a stage where the design component has fairly matured and the main focus of interest is slowly shifting from design strategies to exploration and understanding the structure−function− property relationships.1,2 In other words, by choosing appropriate metal ions or metal clusters and spacer ligands, the connectivity, topology, cavities, channels, interpenetration as well as bringing reactive functional groups close together in the lattice can be in principle controlled in the coordination network structures.1 However, in the crystallization process, the kinetic factors still influence and dominate the outcome of the connectivity and topology of the coordination polymers. The crystals have the normal tendency to maximize their packing density. As a result, the voids are usually filled by guest solvent molecules, uncoordinated ligand molecules or counterions, or interpenetration occurs.3 This is a common phenomena observed in the porous coordination polymers (PCPs) or metal−organic frameworks (MOFs).1 When the length of the linear spacer is increased, the three-dimensional (3D) coordination polymers tend to interpenetrate, and if the structure is already interpenetrated, the degree of interpenetration usually increases with the length of the spacer ligand.4 In their pioneering work, Robson and Batten classified a number of different types of interpenetrations that occur in coordination polymers.5 We have been interested in the longer spacer ligand 1,4bis[2-(4-pyridyl)ethenyl]benzene (bpeb) as it contains a pair of CC bonds that can be potentially used for [2 + 2] cycloaddition reactions, and the distance between the two nitrogen atoms ca. 16 Å is suitable for making MOFs. This ligand has already been extensively used by Lang and co-workers as well as others to © 2012 American Chemical Society

Figure 1. (a) Atom labeling in the paddle-wheel core of 1. Symmetry operators A = x, y − 1, z and B = 1 + x, y, z. (b) A view showing the coordination geometry around Zn(II) in 1. (c) A portion of the (4,4) connectivity in 1.

synthesize a number of interesting coordination polymers.6−10 During investigations, we observed two different types of Received: May 3, 2012 Revised: June 4, 2012 Published: June 7, 2012 3397

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Figure 2. (a) A perspective view of the pcu topology showing the wavy conformation of the bpeb ligand in 1. (b) Interweaving of three different bpeb ligands over ndc anions. (c) Another view of the threading of bpeb ligands over ndc anions. (d) A schematic representation of the 3-fold interpenetration in 1.

interpenetrations in different parts of the 3-fold interpenetrated pillared-layer [Zn2(ndc)2(bpeb)]·DMF·3H2O (where ndc = 2,6naphthalenedicarboxylate) structure α-Po (also called NaCl, ReO3 or pcu) topology. On the other hand, under similar reaction conditions [Zn3(bpdc)3(bpeb)]·0.5DMSO·1.5H2O (where bpdc = biphenyl-4,4′-dicarboxylate) furnished a completely different structure based on an eight connected network structure containing hexagonal bipyramidal secondary building units (SBUs) and trigonal prismatic nodes. The details of our investigations are described in this paper. The yellow block-shaped crystals of [Zn 2 (ndc) 2 (bpeb)]·DMF·3H2O (1) were obtained from the solvothermal reaction between Zn(NO3)2, ndc, and bpeb in 1:1:1 molar ratio at 110 °C.11 The compound crystallized in the space group P1̅ and the asymmetric unit consists of a [Zn2(ndc)2(bpeb)] and a disordered DMF and three disordered water molecules.12 The SBU is made up of a well-known paddle-wheel structure comprising a Zn2(O2C−)4 unit (Figure 1a), and the connectivity extends to form a (4,4) layer structure in the ab plane (Figure 1b). The Zn···Zn distances (13.073 and 13.083 Å which are the lengths of a and b of the unit cell) and Zn−Zn−Zn angles (84.2 and 95.8°) indicate a slightly distorted square arrangement.

In each square-pyramidal ZnO4N core, the apical position is occupied by an N atom of bpeb ligand. The connectivity of these bpeb ligands in the c-direction furnished a highly distorted pillared-layer 3D structure with α-Po topology (Figure 2a). The distance between the centers of the paddlewheel units along the bpeb pillar is 22.846 Å. The Zn(bpeb) chains are highly corrugated which can understood from the deviation of the linearity of the N1−Zn1−Zn2 and Zn1−Zn2− N2 angles, 173.0 and 172.9°. Further, the Zn1 and Zn2 atoms are away from the planes of pyridyl rings they were bonded to by 0.29 and 0.21 Å, respectively. In other words, bpeb−Zn− Zn−bpeb looks like a bow (with an angle of 17.2°) which extends along the c-direction to form a wavy conformation. As a consequence, interweaving occurs. Three wavy bpeb ligands from the adjacent cubes interweave over the ndc ligands along the a-axis to form fabriclike sheets in the ac plane (Figure 2b) leading to a triply interpenetrated structure (Figure 2c). Such interweaving has been observed only in two-dimensional (2D) structures with highly corrugated and flexible spacer ligands.5 Here the behavior of the linear spacer ligand bpeb is quite unusual. To the best of our knowledge such interweaved 3-fold interpenetration has not been observed in the well-known uninodal α-Po topology.1d,5a The Schläfli symbol for 1 has been 3398

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Figure 3. (a) Atom labeling in the [Zn3(O2C-R)6(bpeb)] core. Symmetry operators: A = 1/2 + x, 1/2 − y, 1/2 − z; B = 2 − x, 1 − y, 1 − z and C = 3/2 − x, 1/2 + y, 3/2 − z. (b) A view of the [Zn3(bpdc)3(bpeb)] SBU in 2 (c) A portion of the (3,3) triangular grid formed by [Zn3(bpdc)3].

Figure 4. (a) A view showing the trigonal prismatic topology in 2. (b) A schematic diagram of the topology present in 2. (c) A schematic representation of the 3-fold interpenetration in 2.

found to be {412.63}. Despite interpenetration the total potential solvent area volume is 849.1 Å3 (34.5% per unit cell volume), as calculated by PLATON.13

In order to understand the generality of the formation of unusual interweaving with the longer spacer ligand bpeb, another synthesis was carried out under similar experimental conditions 3399

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but with a more linear dicarboxylate, bpdc instead of ndc. Block-shaped yellow single crystals were obtained in 54% yield.14 X-ray crystallographic analysis15 revealed that the asymmetric unit consists of half of the formula in [Zn3(bpdc)3(bpeb)], and the crystallographic inversion center at Zn2 generates the SBU. In the Zn3(bpdc)3 unit, the three zinc(II) atoms are arranged in a linear fashion and three carboxylate ligands bridge each Zn2 pair such that the central Zn2 has a distorted octahedral geometry with a ZnO6 core as shown in Figure 3a. Each “terminal” Zn1 atom in the linear trinuclear complex has the tetrahedral geometry and bonded to three oxygen atoms, O1, O5, and O3A (symmetry operator: A = 1/2 + x, 1/2 − y, 1/2 − z) from three bpdc ligands. In this description the weak interaction of Zn1 with O6 (2.69 Å) is not considered. The two pyramidal-shaped ZnO3 cores at in the Zn3 rod are staggered but facing each other as shown in Figure 3a. As a result they interdigitate and the Zn3(O2C-R)6 core has highly distorted D3d point group symmetry. The other end of the six carboxylates of the bpdc ligands in the Zn3(bpdc)3 unit are connected to six different Zn(II) atoms occupying approximately the corners of a regular hexagon in the [101] plane. This connectivity from the six connecting Zn3(O2C-R)6 units provides a layer structure made up of (3,3) triangular grids as shown in Figure 3b. In the [Zn3(O2C-R)6(py)2] SBU, the tetrahedral geometry of each Zn1 is completed by an N atom of the bpeb ligand. The two bpeb ligands in the [Zn3(bpdc)3(bpeb)] cluster make this an eight-connector node with hexagonal bipyramidal geometry. To the best of our knowledge, such an SBU seems to be very rare. This leads to the formation of trigonal prismatic pillaredlayer network structure (Figure 4) with Schläfli symbol {36.418.53.6}. The Zn2···Zn2 distances in the Zn3 triangle are 14.36, 14.36, and 14.52 Å, while Zn2···Zn2 distance along the bpeb pillar is 26.946 Å and as the consequence these structures are triply interpenetrated as shown in Figure 4c. Despite interpenetration, the overall structure has some voids and the total potential solvent area volume was found to be 802.7 Å3 (25.2% per unit cell volume), as determined from PLATON.13 A quick look at the conformation of the Zn-bpeb polymer chain in 2 revealed that it does not have wavy conformation as in 1 and behaves like any other bpeb spacer ligands reported in the literature so far.6−10 To summarize, a pyridyl-based long linear spacer bpeb forms a unique interweaved 3-fold interpenetrated pillared-layer structure having the well-known pcu topology. Although a number of 3D coordination polymeric structures with pcu network topology have been observed with a control on the interpenetration, interweaving has not been observed to the best of our knowledge. When the slightly bulkier dicarboxylate ndc has been replaced by a longer spacer ligand bpdc, a completely different 3D network with a rare trigonal prismatic structure made from an eight-connected SBU has been obtained. It appears that this unusual interpenetrating structure could be synthesized only from the unique combination of ndc and bpeb ligands, probably dictated by the kinetic factors. We are currently investigating various experimental conditions to produce supramolecular isomers of 1 to investigate their gas storage behavior.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +82 55-772-1483. Fax: +82 55-753-7614. E-mail: sslee@ gnu.ac.kr (S.S.L.). Tel: +65 6516 2975. Fax: +65 6779 1691. E-mail: [email protected] (J.J.V.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the World Class University (WCU) project (R32-20003) and J.J.V. thanks the Ministry of Education, Science & Technology (S. Korea) for the WCU Chair Professorship. We also thank Dr. Goutam K. Kole for his interest in this project.

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REFERENCES

(1) (a) Desiraju, G. R.; Vittal, J. J.; Ramanan, A. Crystal Engineering. A Textbook; World Scientific: Singapore, 2011; (b) Farrusseng, D., Ed. Metal-Organic Frameworks − Applications from Catalysis to Gas Storage; Wiley-VCH Verlag: Weinheim, Germany, 2011; (c) MacGillivray, L. R., Ed. Metal-Organic Frameworks. Design and Application; John Wiley & Sons: New Jersey, USA, 2010; (d) Batten, S. R.; Neville, S. M.; Turner, D. R. Coordination Polymers - Design, Analysis and Application; RSC Publishing: Cambridge, UK, 2009. (2) (a) Zhou, H.-C.; Long, J. R.; Yaghi, O. M. Chem. Rev. 2012, 112, 673−674 and papers in this issue. (b) Long, J. R.; Yaghi, O. M. Chem. Soc. Rev. 2009, 38, 1213−1214 and papers in this issue. (c) Biradha, K.; Su, C.-Y.; Vittal, J. J. Cryst. Growth Des. 2011, 11, 875−886. (d) Kuppler, R. J.; Timmons, D. J.; Fang, Q.-R.; Li, J.-R.; Makal, T. A.; Young, M. D.; Yuan, D.; Zhao, D.; Zhuang, W.; Zhou, H-.C. Coord. Chem. Rev. 2009, 253, 3042−3066. (e) Zaworotko, M. J. New J. Chem. 2010, 34, 2355−2356. (f) Stock, N.; Biswas, S. Chem. Rev. 2012, 112, 933−969. (3) (a) Moulton, B.; Zaworotko, M. J. Chem. Rev. 2001, 101, 1629− 1658. (b) Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem., Int. Ed. 2004, 43, 2334−2375. (c) Brammer, L. Chem. Soc. Rev. 2004, 33, 476−489. (d) Kitagawa, S.; Matsuda, R. Coord. Chem. Rev. 2007, 251, 2490−2509. (4) (a) Uemura, T.; Kitagawa, S. Top. Curr. Chem. 2010, 293, 155− 173. (b) Farha, O. K.; Hupp, J. T. Acc. Chem. Res. 2010, 43, 1166− 1175. (c) Ferey, G. Chem. Soc. Rev. 2009, 37, 191−214. (d) Horike, S.; Shimomura, S.; Kitagawa, S. Nat. Chem. 2010, 1, 695−704. (e) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Science 2002, 295, 469−472. (f) Zhang, J.; Wojtas, L.; Larsen, R. W.; Eddaoudi, M.; Zaworotko, M. J. J. Am. Chem. Soc. 2009, 131, 17040−17041. (g) Klein, N.; Senkovska, I.; Gedrich, K.; Stoeck, U.; Henschel, A.; Mueller, U.; Kaskel, S. Angew. Chem., Int. Ed. 2009, 48, 9954−9957. (5) (a) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460−1494. (b) Batten, S. R. CrystEngComm 2001, 18, 1−7. (6) Liu, D.; Ren, Z.-G.; Li, H.-X.; Chen, Y.; Lang, J.-P.; Li, N.-Y.; Abrahams, B. F. Angew. Chem., Int. Ed. 2010, 49, 4767−4770. (7) Liu, D.; Ren, Z.-G.; Li, H.-X.; Chen, Y.; Wang, J.; Zhang, Y.; Lang, J.-P. CrystEngComm 2010, 12, 1912−1919. (8) Liu, D.; Li, H.-X.; Liu, L.-L.; Wang, H.-M.; Li, N.-Y.; Ren, Z.-G.; Lang, J.-P. CrystEngComm 2010, 12, 3708−3716. (9) Liu, D.; Chang., Y.-J.; Lang, J.-P. CrystEngComm 2011, 13, 1851− 1857. (10) (a) Huang, K.-L.; Liu, X.; Liang, G.-M. Inorg. Chim. Acta 2009, 362, 1565−1570. (b) Domasevitch, K. C.; Sieler, J.; Rusanov, E. B.; Chernega, A. N. Z. Anorg. Allg. Chem. 2002, 628, 51−56. (11) Preparation of [Zn2(ndc)2(bpeb)]·DMF·3H2O (1). A mixture of bpeb (20.2 mg, 0.071 mmol), H2ndc (15.2 mg, 0.070 mmol), and Zn(NO3)2·4H2O (18.5 mg, 0.071 mmol) dissolved in DMF (1.5 mL),

ASSOCIATED CONTENT

S Supporting Information *

TGA curves, XRPD patterns, crystal structures, and X-ray crystallographic information files (CIF) for 1 and 2. These 3400

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DMSO (1 mL), and H2O (1.5 mL) were placed in a 5-mL glass tube, and then 2−3 drops of 0.1 M NaOH solution were added. The tube was sealed and kept at 110 °C for 48 h, followed by cooling to room temperature over 5 h. Yellow block-shaped crystals 1 suitable for X-ray analysis were obtained. (21.3 mg, yield 33% based on bpeb). Anal. Calcd for [C47H37N3O10Zn2]: C, 60.40; H, 3.99; N, 4.50. Found: C, 60.45; H, 4.01; N, 4.29%. IR (KBr pellet, cm−1) 3060, 3031, 2919, 2854, 1653, 1610, 1559, 1406, 1360, 1200, 1030, 963, 833, 781, 554. (12) Crystal data for 1 (CCDC-879801): C47H41N3O12Zn2, fw = 970.57, triclinic, P1̅, a = 13.0735(3), b = 13.0828(3), c = 15.6584(3) Å, α = 82.741(1), β = 68.059(1), γ = 84.188(1)°, V = 2460.03(9) Å3, Z = 2, Dx = 1.31 g·cm−3, Rint = 0.0474, GOF = 1.106, R1 = 0.0679, and wR2 = 0.1908 for 7909 of reflections with I > 2σ(I). (13) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; University of Ultrecht: Ultrecht, The Netherlands, 2003. (14) Preparation of [Zn3(bpdc)3(bpeb)]·0.5DMSO·1.5H2O (2). A mixture of bpeb (20.1 mg, 0.070 mmol), H2bpdc (17.1 mg, 0.071 mmol), and Zn(NO3)2·4H2O (18.4 mg, 0.070 mmol) dissolved in DMF (2 mL) and DMSO (1 mL) were placed in a 5-mL glass tube, and then 2−3 drops of 0.1 M NaOH solution were added. The tube was sealed and kept at 110 °C for 48 h, followed by cooling to room temperature over 5 h. Yellow block-shaped crystals 2 suitable for X-ray analysis were obtained (48.60 mg, yield 54% based on bpeb). Anal. Calcd for [C63H46N2O14S0.5Zn3]: C, 59.71; H, 3.66; N, 2.21; Found: C, 60.35; H, 3.50; N, 2.64%. IR (KBr pellet, cm−1) 3032, 2921, 2850, 1675, 1608, 1545, 1395, 1223, 11203, 1178, 1093, 1055, 1028, 958, 858, 838, 773, 704, 679, 616, 555. (15) Crystal data for 2 (CCDC-879802): C64H62N2O16S1Zn3, fw = 1343.33, monoclinic, P21/n, a = 11.2055(2), b = 14.5219(3), c = 20.0027(4) Å, β = 101.338(1)°, V = 3191.42(11) Å3, Z = 2, Dx = 1.398 g·cm−3, Rint = 0.0297, GOF = 1.048, R1 = 0.0417, and wR2 = 0.1202 for 5497 of reflections with I > 2σ(I).

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