CRYSTAL GROWTH & DESIGN 2002 VOL. 2, NO. 6 485-487
Communications An Unforeseen Chemical Rearrangement of Pyridinecarboxylate to Oxalate under Hydrothermal Conditions Afforded the First Oxalato and Isonicotinato Mixed-Ligand Guest-Inclusion Coordination Polymer Jack Y. Lu,* Jose Macias, Jiageng Lu, and Jared E. Cmaidalka Department of Chemistry, University of Houston-Clear Lake, Houston, Texas 77058 Received June 11, 2002;
Revised Manuscript Received August 21, 2002
ABSTRACT: The first oxalato and isonicotinato mixed-ligand guest-inclusion open-framework coordination polymer {[(H2O)2(oxa)Zn2(IN)2]‚2(H2O)} was synthesized from a chemical rearrangement of isonicotinate to oxalate under hydrothermal conditions: space group, P21/c; a ) 8.302(1), b ) 15.557(2), c ) 7.344 (1) Å, β ) 94.351(1)°, U ) 945.8(1) Å3, Z ) 2. Crystal engineering of two-dimensional (2-D) and threedimensional (3-D) open-framework coordination polymers has been an attractive area of research in recent years due to their potential properties in catalysis, molecular separations, and optoelectronic and magnetic materials.1,2 The synthetic strategies used for preparing functional coordination polymers have been rapidly advanced by a variety of synthetic pathways such as oxidation reactions,3 conventional solution methods,1 simultaneous substitution and reduction,4 and unexpected reduction reactions.5 While both unpredictable structures and rational designs can be achieved, such as those demonstrated recently,1-6 openframework coordination polymers constructed via chemical rearrangement of pyridinecarboxylate to oxalate has never been observed. Here we report the first isonicotinato and oxalato mixed-ligand guest-inclusion open-framework coordination polymer, {[(H2O)2(oxa)Zn2(IN)2]‚2(H2O)} (oxa ) C2O42-, IN ) isonicotinato) 1, synthesized from a chemical rearrangement of pyridinecarboxylate to oxalate in a selfassembly chemical process under hydrothermal conditions. The reaction of Zn(NO3)2‚6H2O (0.2974 g, 0.001 mol) with isonicotinic acid (0.1231 g 0.001 mol) and iodine (0.1269 g, 0.0005 mol) in the mole ratio of 2:2:1 under hydrothermal conditions at 120 °C for 4 days produced pale yellowish crystals of 1 with 21% yield. The crystals are characterized by elemental analysis, FTIR, X-ray powder diffraction, and single-crystal X-ray diffraction analysis.7 Elemental analysis, Calc. C, 31.40%; H, 3.01%; N, 5.23%. Found, C, 31.85%; H, 2.98%; N, 5.29%. FTIR (KBr, cm-1): 3350 (vs), 1670 (vs), 1610 (s), 1545 (s), 1425 (vs), 1310 (m), 1220, 1205, 1055 (m), 1010 (m), 867 (m), 800 (m), 770 (m), 695 (vs). The structure of 1 consists of one crystallographically distinct zinc atom that is surrounded by a bidentate oxalato group, a terminal water molecule, a pyridyl group of the IN unit, and a bidentate carboxylato-group of the IN unit (Figure 1). The geometry of the zinc atom has a severely
Figure 1. View of the complete coordination about Zn showing the atom numbering scheme. Thermal ellipsoids are 50% equiprobability envelopes, with hydrogen atoms as spheres of arbitrary diameter.
Figure 2. View of the complete coordination about Zn, with dashed lines to the centroids of the chelating ligands. The six angles about Zn range from 91.8 to 129.9°.
distorted octahedral shape since the angles around the zinc atom vary from 59.4(1) to 169.6(1)°. Alternatively, the geometry of the zinc coordination may be viewed as distorted tetrahedra where the angles around zinc atom range from 91.8 to 129.9° (Figure 2). The zinc metal centers are linked by both tetradentate oxalato-ligand and tridentate isonicotinato-ligand to form a large open-framework
10.1021/cg025539i CCC: $22.00 © 2002 American Chemical Society Published on Web 09/05/2002
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Figure 3. View of the six-sided ring which comprises the basic structural unit. Only one orientation of the disordered water is shown at each site.
Communications synthesize compound 1 by using mixed oxalate and isonicotinate ligands were successful with a higher yield of 67%. The reaction of Zn(NO3)2‚6H2O (0.2974 g, 0.001 mol) with isonicotinic acid (0.1231 g, 0.001 mol) and sodium oxalate (0.067 g, 0.0005 mol) in the mole ratio of 2:2:1 under hydrothermal conditions at 160 °C for 3 days produced colorless crystals of 1. The observed pale yellowish crystal color from the original synthesis of 1 is probably caused by contamination from the iodine-containing solution. Thermal analysis of 1 reveals that the compound 1 lost inclusion water molecules (6.75% in weight) below 150 °C; all water molecules were lost (13.5% in weight) below 180 °C, and the compound started decomposition process after about 380 °C. In summary, we have reported that an unforeseen unique chemical rearrangement under hydrothermal conditions resulted in a very stable open-framework polymer. Although the complicated chemical process may be unpredictable, the chemical rearrangement of pyridinecarboxylate to oxlalate has afforded unexpected chemical information under hydrothermal conditions. Acknowledgment. The authors thank the financial support from the Welch Foundation and assistance from Dr. J. D. Korp in crystallography. This work made use of MRSEC/TCSUH Shared Experimental Facilities supported by the National Science Foundation and the Texas Center for Superconductivity at the University of Houston.
Figure 4. View showing several rings forming a single layer with water molecules as guests.
Supporting Information Available: Crystallographic tables and CIF file are available free of charge via the Internet at http:// pubs.acs.org.
References
Figure 5. View of two rings from adjacent layers linked by hydrogen bonds, and hydrogen bonds with guest water molecules indicated by dashed lines.
unit where water molecules reside (Figure 3). The propagation of the open-framework unit afforded an extended noninterpenetrating 2-D open-framework with inclusion water molecules (Figure 4). The adjacent 2-D layers are linked by hydrogen bonds (O(5)-H(5A)‚‚‚O(3) 2.742(2), O(5)-H(5B)‚‚‚O(1) 2.765(2) Å) (Figure 5). Note that the chemical rearrangements in the reactions are unique. One-third of the building ligands in the structure of 1 are oxalates that are from the chemical rearrangements of the starting isonicotinate ligands. Although the carboxylate groups of pyridinecarboxylates can be released or replaced under hydrothermal conditions,4 the formation of oxalate from carboxylate groups under hydrothermal conditions has never been reported. The pressure under hydrothermal conditions is a necessary factor for the rearrangement. While this unique chemical rearrangement reaction is repeatable with similar yield at the given conditions, subsequent reactions attempted to
(1) See, for example, Bourne, S. A.; Lu, J.; Mondal, A.; Moulton, B.; Zaworotko, M. J. Angew. Chem., Int. Ed. 2001, 40, 2111. Carlucci, L.; Ciani, G.; Moret, M.; Proserpio, D. M.; Rizzato, S. Chem. Mater. 2002, 14, 12. Zhang, D.; Ding, L.; Xu, W.; Hu, H.; Zhu, D.; Huang, Y.; Fang, D. Chem. Commun. 2002, 44. Ciurtin, D. M.; Pschirer, N. G.; Smith, M. D.; Bunz, U. H. F.; zur Loye, H-C. Chem. Mater. 2001, 13, 2743. Batten, S. R.; Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1995, 117, 5385. (2) See, for example, Reineke, T. M.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Angew. Chem Int. Ed. Engl. 1999, 38, 2590. O’Keeffe, M.; Eddaoudi, M.; Li, H.; Reineke, T.; Yaghi, O. M. J. Solid State Chem. 2000, 152, 3. Lin, W.; Wang, Z.; Ma, L. J. Am. Chem. Soc. 1999, 121, 11249. Evans, O. R.; Wang, Z.; Xiong, R.; Foxman, B. M.; Lin, W. Inorg. Chem. 1999, 38, 2969. Pschirer, N. G.; Ciurtin, D. M.; Smith, M. D.; Bunz, U. H. F.; zur Loye, H-C. Angew. Chem. 2002, 114, 603. Forster, P. M.; Cheetham, A. K. Angew. Chem. Int. Ed. 2002, 41, 457. (3) Lu, J. Y.; Runnels, K. R. Inorg. Chem. Commun. 2001, 4, 678. Lu, J. Y.; Schauss, V. Eur. J. Inorg. Chem. 2002, 1945. (4) Lu, J. Y.; Babb, A. M. Inorg. Chem. 2002, 41, 1339. (5) Yaghi, O. M.; Li, H. J. Am. Chem. Soc. 1995, 117, 10401. Lu, J. Y.; Cabrera, B. R.; Wang, R.-J.; Li, J. Inorg. Chem. 1998, 37, 4480. (6) See, for example, Keller S. W.; Lopez, S. J. Am. Chem. Soc. 1999, 121, 6306. Keller, S. W. Angew. Chem., Int. Ed. Engl. 1997, 36, 247. Lu, J.; Mondal, A.; Moulton, B.; Zaworotko, M. J. Angew. Chem., Int. Ed. 2001, 40, 2113. Biradha, K.; Domasevitch, K. V.; Moulton, B.; Seward, C.; Zaworotko, M. J. Chem. Commun. 1999, 1327. Du, B.; Ding, E.; Meyers, E. A.; Shore, S. G. Inorg. Chem. 2001, 40, 3637. Du, B.; Meyers, E. A.; Shore, S. G. Inorg. Chem. 2001, 40, 4353. Lu, J. Y.; Babb, A. M. Chem. Commun. 2001, 821. Zhang, H.; Wang, X.; Zelmon, D. E.; Teo, B. K. Inorg. Chem. 2001, 40, 1501. Bu, X. H.; Chen, W.; Lu, S. L.; Zhang, R. H.; Liao, D. Z.; Shionoya, M.; Brisse, F.; Ribas, J. Angew. Chem., Int. Ed. Engl. 2001, 40, 3201. Lu, J. Y.; Babb, A. M. Inorg. Chem. 2001, 40, 3261. MacGillivray, L. R.; Groeneman, R. H.; Atwood, J. L. J. Am. Chem. Soc. 1998, 120, 2676. Zhang, H.; Wang, X.; Teo, B. K. J. Am. Chem. Soc. 1996, 118, 11813.
Communications (7) Crystal data for 1: FW, 535.03; monoclinic, space group, P21/c; cell dimensions a ) 8.302(1), b ) 15.557(2), c ) 7.344 (1) Å, β ) 94.351(1)°, U ) 945.8(1) Å3, Z ) 2, Fcalc ) 1.879 gcm-3, µ ) 2.605 mm-1, T ) 223(2) K. Reflections collected: 4958; independent reflections: 1734 [R(int) ) 0.0260]. Final R indices [I > 4σ(I)]: R1 ) 0.0224, wR2 ) 0.0622. The asymmetric unit consists of one-half formula unit, with the
Crystal Growth & Design, Vol. 2, No. 6, 2002 487 oxalate ligand situated about an inversion center. The interstitial water (type O6) is disordered over slightly different orientations, and the two positions having the highest occupancies were refined using ideal rigid bodies.
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