Crystallized Water: Internal and External Ice Fragments in Polycyclic Hosts Sung Ok Kang, Douglas Powell,† Victor W. Day, and Kristin Bowman-James* Department of Chemistry, UniVersity of Kansas, 1251 Wescoe Hall DriVe, Lawrence, Kansas 66045 ReceiVed December 4, 2006
CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 4 606-608
ABSTRACT: Two crystal structures of cyclic water hexamers are reported, one with a bicyclic cryptand and the other with a tricyclic host. In the bicycle structure, the water molecules lie between the cryptands. In the tricycle structure, the hexameric water cluster is almost totally encapsulated within the host framework. Because water is so essential to life on Earth, water clusters have been the subject of extensive experimental and theoretical research.1,2 A number of discrete water clusters including tetramers,3 pentamers,4 hexamers,5-13 octamers,14 decamers,15,16 and higherorder clusters17 have been identified. In most of the crystallographically characterized instances, the clusters lie within channels formed by a host matrix or between hosts. An exception is the recently reported trapped decameric water cluster held inside a selfassembled palladium-based cage.16 Cyclic water hexamers are of special interest because they are the smallest repeat unit of the Ih form of ice. From theoretical studies, the five hexameric water conformations of lowest energy are the ring, book, bag, cage, and prism.1 In host lattices, water clusters have been most commonly found in the chair,5-9 sometimes in the planar ring8,10 or boat,5,9,11 but rarely in the book12 and cage conformations.13 Furthermore, most of the reported hosts for water clusters have been simple organic or transition-metal-based compounds. Here, we report two crystal structures of cyclic water hexamers with the rarer macrocyclic hosts. In one, the water molecules lie between their bicyclic hosts (L1); in the second, a hexameric water cluster is almost totally encapsulated within a tricyclic host framework (L2).
Figure 1. Perspective views of the water clusters showing (a) the external water hexamers linking cryptands L1 via hydrogen bonds and (b, c) two views of the hexamer inside the cavity of L2.
Bicycle L118 and tricycle L219 have the same pyridine straps but different dimensionalities and were prepared as previously reported. Crystals of the water complexes suitable for X-ray diffraction were grown by slow evaporation of a solution of CH3CN in the presence of excess nBu4N+NO3- for L1 and nBu4N+Clfor L2. The resulting crystalline products were not the anticipated anion complexes but were instead the free aquated ligands, L1‚ (H2O)6‚H2O20 and L2‚(H2O)6‚2H2O20, both containing hexameric cyclic arrays of water. The hexameric water arrays of the heptahydrated bicycle L1 are centered about the noncentrosymmetric origin of the unit cell (Figure 1). The unit cell contains just one formula unit so the * Corresponding author. Email:
[email protected]. Tel: 785-864-3669. Fax: 785-864-5396. † Present address: Department of Chemistry, University of Oklahoma, 620 Parrington Oval, Norman, OK 73019.
Figure 2. Hydrogen-bonding motifs showing bonds outside of the water hexamer (top views) and conformations (bottom views) of the trapped cyclic hexamer in hosts for (a) L1 and (b) L2.
10.1021/cg0608817 CCC: $37.00 © 2007 American Chemical Society Published on Web 02/22/2007
Communications
Crystal Growth & Design, Vol. 7, No. 4, 2007 607
Figure 3. Packing diagram of (a) L1‚(H2O)6‚H2O and (b) L2‚(H2O)6‚2H2O showing the hexameric array in relationship to the hosts.
hexameric water rings lay between, and are hydrogen-bonded to, the amido cryptand hosts in adjacent unit cells. One ring oxygen atom (O1W) is also hydrogen-bonded to the seventh water molecule (O7W). The remaining hydrogen atom of O7W is linked to the carbonyl oxygen atom of a cryptand amide. O7W also forms acceptor hydrogen bonds with two amide nitrogen atoms. The water cluster forms five donor hydrogen bonds to oxygen atoms of cryptand carbonyl groups, one donor bond to a cryptand amine nitrogen atom, and six acceptor hydrogen bonds to amide nitrogen atoms. The six water molecules in the ring in L1 are hydrogen-bonded to each other with O‚‚‚O distances ranging from 2.744(2) to 2.862(2) Å (Ih ice: O‚‚‚O ) 2.759 Å; Figure 2). Four of the O‚‚‚O‚‚‚O angles in the ring are near the 109.3° seen for the Ih form of ice; they range from 102.0(1) to 115.3(1)°. The other two, subtended at O3W and O6W, are quite large with values of 138.8(1) and 140.8(1)°. The protons on both of these water molecules are hydrogen-bonded to carbonyl oxygen atoms of two different cryptand ligands (Figure 2a, top view). The six-membered water ring adopts a folded envelope (or chaise lounge) conformation with O1W being displaced by 0.81 Å from the mean plane (coplanar to within 0.07 Å) of the other five water oxygen atoms (Figure 2a, bottom view). The “flap” of the envelope makes a dihedral angle of 28.8° with the “body”. In L2, the hexameric water cluster threads through the cavity of the tricycle. This flattened chair is sandwiched between the two tetraamide macrocyclic rings. The water molecules in the ring form donor hydrogen bonds with two macrocycle amine nitrogen atoms and acceptor hydrogen bonds with eight amide nitrogen atoms of the macrocycle. This centrosymmetric six-membered water ring is slightly larger than the tricycle cavity, and two of its water molecules (O3W and O3W′) protrude slightly outside the tricycle periphery (parts b and c of Figure 1). The four protons on these two water molecules form donor hydrogen bonds to carbonyl oxygen atoms of tricycles in adjacent unit cells. The three independent O‚‚‚O separations in the L2 water ring average 2.876 Å. Independent O‚‚‚O‚‚‚O angles are 105.52(4), 119.15(4), and 129.52(4)°. One feature of common interest between the two structures is the manner in which the hydrogen bonds are formed within the six-membered ring. There are nine possible modes of arranging these bonds in a circular arrangement of six water molecules.7 These include homodromic (same direction chain), three antidromic (two counter-running chains), and five heterodromic (randomly orientated chains).7,21 The circular hydrogen-bonding interactions of the water hexamers observed in hosts L1 and L2 make up two of the heterodromic possibilities. For L1, O3W and O6W lie on a pseudomirror plane for the ring hydrogen bonds. For L2, a crystallographic
inversion center requires opposing waters to be bonded with the same directionality within the ring. The packing views of L1 and L2, looking down the b-axis with the c-axis running horizontally, clearly show the position of the water hexamer in relationship to the macrocycles (Figure 3). In the bicyclic cryptands, the hexameric array of water molecules acts as a spacer between the cryptands (Figure 3a). However, in Figure 3b, the hexamer is intertwined within the tricyclic cavity. In conclusion, multicyclic hosts, in this case amide-based, with the ability to organize hydrogen-bond donors and acceptors represent promising new candidates for “freezing” water in crystalline lattices. The larger tricycle, L2, possesses the capability to almost encapsulate the water cluster, whereas the water acts as the glue linking cryptands in L1. Although there are now many examples of water clusters, these two multicyclic hosts represent possible prototypes for the stabilization of higher-order water clusters. Acknowledgment. The authors thank the National Science Foundation (CHE-0316623) for support of this work and purchase of the X-ray diffractometer (CHE-0079282). Supporting Information Available: Crystallographic data (CIF) and crystallographic information. This material is available free of charge via the Internet at http://pubs.acs.org.
References (1) Ludwig, R. Angew. Chem., Int. Ed. 2001, 40, 1808-1827. (2) (a) Mascal, M.; Infantes, L.; Chisholm, J. Angew. Chem., Int. Ed. 2006, 45, 32-36. (b) Ugalde, J. M.; Alkorta, I.; Elguero, J. Angew. Chem., Int. Ed. 2000, 39, 717-721. (3) (a) Zuhayra, M.; Kampen, W. U.; Henze, E.; Soti, Z.; Zsolnai, L.; Huttner, G.; Oberdorfer, F. J. Am. Chem. Soc. 2006, 128, 424-425. (b) Long, L.-S.; Wu, Y.-R.; Huang, R.-B.; Zheng, L.-S. Inorg. Chem. 2004, 43, 3798-3800. (c) Pal, S.; Sankaran, N. B.; Samanta, A. Angew. Chem., Int. Ed. 2003, 42, 1741-1743. (4) Ma, B.-Q.; Sun, H.-L.; Gao, S. Chem. Commun. 2004, 2220-2221. (5) Rodrı´guez-Cuamatzi, P.; Vargas-Dı´az, G.; Ho¨pfl, H. Angew. Chem., Int. Ed. 2004, 43, 3041-3044. (6) (a) Liao, Y.-C.; Jiang, Y.-C.; Wang, S.-L. J. Am. Chem. Soc. 2005, 127, 12794-12795. (b) Doedens, R. J.; Yohannes, E.; Khan, M. I. Chem. Commun. 2002, 62-63. (c) Custelcean, R.; Afloroaei, C.; Vlassa, M.; Polverejan, M. Angew. Chem., Int. Ed. 2000, 39, 30943096. (d) Ye, B.-H.; Ding, B.-B.; Weng, Y.-Q.; Chen, X.-M. Inorg. Chem. 2004, 43, 6866-6868. (e) Ghosh, S. K.; Bharadwaj, P. K. Inorg. Chem. 2003, 42, 8250-8254. (f) Mukhopadhyay, U.; Bernal, I. Cryst. Growth Des. 2005, 5, 1687-1689. (g) Prasad, T. K.; Rajasekharan, M. V. Cryst. Growth Des. 2006, 6, 488-491. (h) Tadokoro, M.; Fukui, S.; Kitajima, T.; Nagao, Y.; Ishimaru, S.; Kitagawa, H.; Isobe, K.; Nakasuji, K. Chem. Commun. 2006, 12741276.
608 Crystal Growth & Design, Vol. 7, No. 4, 2007 (7) Foces-Foces, C.; Cano, F. H.; Martı´nez-Ripoll, M.; Faure, R.; Roussel, C.; Claramunt, R. M.; Lo´pez, C.; Sanz, D.; Elguero, J. Tetrahedron: Asymmetry 1990, 1, 65-86. (8) Wang, J.; Zheng, L.-L.; Li, C.-J.; Zheng, Y.-Z.; Tong, M.-L. Cryst. Growth Des. 2006, 6, 357-359. (9) Michaelides, A.; Skoulika, S.; Bakalbassis, E. G.; Mrozinski, J. Cryst. Growth Des. 2003, 3, 487-492. (10) (a) Moorthy, J. N.; Natarajan, R.; Venugopalan, P. Angew. Chem., Int. Ed. 2002, 41, 3417-3420. (b) Ghosh, S. K.; Bharadwaj, P. K. Angew. Chem., Int. Ed. 2004, 43, 3577-3580. (c) Zhao, B.; Cheng, P.; Chen, X.; Cheng, C.; Shi, W.; Liao, D.; Yan, S.; Jiang, Z. J. Am. Chem. Soc. 2004, 126, 3012-3013. (d) Jiang, Y.-Q.; Xie, Z.-X. Supramol. Chem. 2005, 17, 291-296. (e) Luna-Garcı´a, R.; Damia´nMurillo, B. M.; Barba, V.; Ho¨pfl, H.; Beltra´n, H. I.; Zamudio-Rivera, L. S. Chem. Commun. 2005, 5527-5529. (11) (a) Saha, B. K.; Nangia, A. Chem. Commun. 2006, 1825-1827. (b) Ghosh, S. K.; Bharadwaj, P. K. Inorg. Chem. 2004, 43, 5180-5182. (c) Park, K.-M.; Kuroda, R.; Iwamoto, T. Angew. Chem., Int. Ed. 1993, 32, 884-886. (12) Ma, B.-Q.; Sun, H.-L.; Gao, S. Chem. Commun. 2005, 2336-2338. (13) Febles, M.; Pe´rez-Herna´ndez, N.; Pe´rez, C.; Rodrı´guez, M. L.; Foces-Foces, C.; Roux, M. V.; Morales, E. Q.; Buntkowsky, G.; Limbach, H.-H.; Martı´n, J. D. J. Am. Chem. Soc. 2006, 128, 1000810009. (14) (a) Atwood, J. L.; Barbour, L. J.; Ness, T. J.; Raston, C. L.; Raston, P. L. J. Am. Chem. Soc. 2001, 123, 7192-7193. (b) Blanton, W. B.; Gordon-Wylie, S. W.; Clark, G. R.; Jordan, K. D.; Wood, J. T.; Geiser, U.; Collins, T. J. J. Am. Chem. Soc. 1999, 121, 3551-3552. (15) (a) Barbour, L. J.; Orr, G. W.; Atwood, J. L. Nature 1998, 393, 671673. (b) Barbour, L. J.; Orr, G. W.; Atwood, J. L. Chem. Commun. 2000, 859-860. (c) Mukhopadhyay, U.; Bernal, I. Cryst. Growth Des. 2006, 6, 363-365. (16) Yoshizawa, M.; Kusukawa, T.; Kawano, M.; Ohhara, T.; Tanaka, I.; Kurihara, K.; Niimura, N.; Fujita, M. J. Am. Chem. Soc. 2005, 127, 2798-2799.
Communications (17) (a) Lakshminarayanan, P. S.; Suresh, E.; Ghosh, P. Angew. Chem., Int. Ed. 2006, 45, 3807-3811. (b) Lakshminarayanan, P. S.; Suresh, E.; Ghosh, P. J. Am. Chem. Soc. 2005, 127, 13132-13133. (c) Ma, B.-Q.; Sun, H.-L.; Gao, S. Angew. Chem., Int. Ed. 2004, 43, 13741376. (d) Ghosh, S. K.; Bharadwaj, P. K. Inorg. Chem. 2004, 43, 6887-6889. (e) Mu¨ller, A.; Krickemeyer, E.; Bo¨gge, H.; Schmidtmann, M.; Botar, B.; Talismanova, M. O. Angew. Chem., Int. Ed. 2003, 42, 2085-2090. (f) Raghuraman, K.; Katti, K. K.; Barbour, L. J.; Pillarsetty, N.; Barnes, C. L.; Katti, K. V. J. Am. Chem. Soc. 2003, 125, 6955-6961. (18) (a) Kang, S. O.; Llinares, J. M.; Powell, D.; VanderVelde, D.; Bowman-James, K. J. Am. Chem. Soc. 2003, 125, 10152-10153. (b) Kang, S. O.; VanderVelde, D.; Powell, D.; Bowman-James, K. J. Am. Chem. Soc. 2004, 126, 12272-12273. (19) Kang, S. O.; Powell, D.; Day, V. W.; Bowman-James, K. Angew. Chem., Int. Ed. 2006, 45, 1921-1925. (20) Crystal data for L1‚(H2O)6‚H2O: C33H53N11O13, M ) 811.86, triclinic, P1, a ) 10.369(5) Å, b ) 10.416(5) Å, c ) 11.099(5) Å, R ) 64.144(1)°, β ) 71.293(1)°, γ ) 63.249(1)°, V ) 951.7(1) Å3, Z ) 1, dcalcd ) 1.417 g cm-3, T ) 100(2) K, F(000) ) 432, λ(MoKR) ) 0.110 mm-1, 10 046 independent reflections (11641 measured), wR2 ) 0.114, R1 ) 0.043, and GOF on F2 ) 1.046. Crystal data for L2‚(H2O)6‚2H2O: C48H76N16O16, M ) 1133.25, triclinic, P1h, a ) 10.649(1) Å, b ) 11.789(1) Å, c ) 11.946(1) Å, R ) 88.667(3)°, β ) 81.501(3)°, g ) 64.577(3)°, V ) 1338.3(2) Å3, Z ) 1, dcaldc ) 1.400 g cm-3, T ) 100(2) K, F(000) ) 601, λ(Mo-KR) ) 0.106 mm-1, 7602 independent reflections (13 613 measured), wR2 ) 0.137, R1 ) 0.048, and GOF on F2 ) 1.061. (21) Saenger, W. Nature 1979, 279, 343-344.
CG0608817
