Enclathration of Aromatic Molecules by the O-H‚‚‚N Supramolecular Adducts of Racemic-bis-β-naphthol and 4,4′-Bipyridine Kumar Biradha* and Goutam Mahata Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India Received July 12, 2004;
CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 1 61-63
Revised Manuscript Received August 25, 2004
ABSTRACT: Racemic-bis-β-naphthol (rac-BN) reacts with 4,4′-bipyridine (BIPY) to form two types of supramolecular adducts via O-H‚‚‚N hydrogen bonds. One of those adducts consists of a cyclic aggregate formed by two molecules of rac-BN and two molecules of BIPY, while the other consists of a 1D-chain in which BIPY and rac-BN arrange alternately through O-H‚‚‚N hydrogen bonds. Interestingly, both these adducts have shown a remarkable ability to form continuous channels that enclathrate aromatic guest molecules such as benzene, toluene, p-xylene, biphenyl, naphthalene, and anthracene. Hydrogen bonds play a key role in the formation of stable and well-defined supramolecular synthons that in turn lead to predefined structures and properties.1 Phenols and pyridine moieties are known to form a variety of supramolecular aggregates via O-H‚‚‚N hydrogen bonds. In particular, the aggregation of resorcinol and phloroglucinol units with various substituted pyridine molecules and with 4,4′-bipyridine are well exploited.2 In this communication, we report the enclathration of aromatic guest molecules such as benzene, toluene, p-xylene, biphenyl, naphthalene, and anthracene by the O-H‚‚‚N aggregates of racemic-bisβ-naphthol (rac-BN) and 4,4′-bipyridine (BIPY). Recently, rac-BN and 1,4-benzoquinone molecules were shown to form supramolecular aggregates via O-H‚‚‚O hydrogen bonds to include several aromatic guest molecules.3 In the present study, we found that rac-BN and BIPY form three types of aggregates depending on the presence of guest molecules. The polar guest molecule such as toluene templated a 1D-chain, which assembles further into polar layers, whereas the nonpolar guest molecules such as benzene, biphenyl, naphthalene, p-xylene, and anthracene templated a tetrameric cyclic aggregate. Further, a nonaromatic guest molecule such as 1,4-dioxane was not enclathrated in the crystal lattice but forms a different tetrameric aggregate in which only one of the pyridyl units of bipy is involved in O-H‚‚‚N hydrogen bonds.4 Crystals of rac-BN:BIPY‚toluene, 1, suitable for singlecrystal X-ray diffraction were grown in toluene (10 mL) by taking 1:1 equivalents of rac-BN (0.10 mmol; 28.6 mg) and BIPY (0.10 mmol, 15.6 mg).5 The single-crystal analysis of the structure reveals the formation of 1D-chains via O-H‚‚‚N hydrogen bonds (H‚‚‚N, O‚‚‚N, O-H‚‚‚N, 1.74 Å, 2.785 Å, 152°, 1.73 Å, 2.743 Å, 161°), which run along crystallographic a-axis (Figure 1a). These 1D-chains form a layer in the ab-plane with the thickness of 10 Å, half of the c-axis, by packing on each other such that there is a cross-arrangement of chains (Figure 1b). The layer does not contain an inversion center and therefore is constituted by only a single enantiomer. The supramolecular forces between the chains are edge-to-face aromatic interactions between rac-BN and BIPY (Figure 1c). Further, the layers in 1 pack on each other along the c-axis such that there exists continuous channels to accommodate guest molecules and also an inversion center between the layers; therefore, every alternate layer corresponds to only one of the enantiomers (Figure 2a). The * To whom correspondence should be addressed. Fax: +91-3222282252. Tel: +91-3222-283346. E-mail:
[email protected].
Figure 1. Illustrations for the crystal structure of 1: (a) a 1D O-H‚‚‚N hydrogen bond chain between rac-BN and BIPY; (b) cross-packing of the 1D chains to form a layer; for the sake of clarity the chains are represented in two colors and hydrogen atoms were not shown; (c) edge-to-face aromatic interactions between rac-BN and BIPY.
asymmetric unit contains two-half equivalents of toluene molecules per rac-BN:BIPY, and both these molecules are found to be in a similar type of disorder as shown in Figure 2c and occupy 27% of the crystal volume.6 Crystals of the complex 2(rac-BN):2(BIPY)‚biphenyl, 2, obtained by taking rac-BN (0.10 mmol, 28.6 mg), BIPY (0.10 mmol, 15.6 mg), and biphenyl (0.60 mmol, 92.4 mg) in a 1:1:6 ratio in acetonitrile (10 mL). Its crystal structure indicated the formation of a tetrameric cyclic aggregate via O-H‚‚‚N hydrogen bonds (H‚‚‚N, O‚‚‚N, O-H‚‚‚N 1.90 Å; 2.760 Å; 167°; 1.83 Å, 2.743 Å, 166°; Figure 3a).7 The aggregate sits on an inversion center and therefore is constituted by both the enantiomers of rac-BN. They pack on each other through edge-to-face aromatic interactions, between rac-BN and BIPY (Figure 3b,c), in the direction of the crystallographic b-axis to form a layer in the bc-plane with a thickness of 16 Å, the length of the a-axis. It is interesting to note that a similar type of edge-to-face aromatic interactions were found in the case of 1. Further, these layers enclathrate biphenyl guest molecules through aromatic interactions as shown in Figure 3c, and biphenyl molecules occupy 22% of the crystal volume.
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Figure 2. Illustration for the crystal structure 1 (a) packing of the layers and enclathration of guest molecules in the channels (toluene molecules were shown in space filling mode); (b) column of the guest molecules, disordered toluene, which are occupied in the channels; (c) model of the toluene disorder.
Communications
Figure 4. Illustration for crystal structure 3; (a) O-H‚‚‚N hydrogen-bonded 0D-aggregate; (b) packing of 0D-aggregates via edge-to-face aromatic interactions (b) view along a-axis; (c) view along c-axis.
and BIPY. The similarities in these interactions are apparent from the almost equal lengths of b-axis in 1 and 2 and a-axis in 3. The O-H‚‚‚N supramolecular aggregates observed in crystal structures of 1 and 2 can be regarded as supramolecular isomers as both the aggregates possess the same set of molecular components but different superstructures.1g,2j,9 The related studies on chiral-bis-βnaphthols are underway in our laboratory. Supporting Information Available: Crystallographic information files (CIF) and ORTEP drawings and crystallographic tables for 1, 2, and 3. This material is available free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. We thank the DST (SR/S1/OC-36/ 2002) for research funding and for X-ray diffractometer facility. G.M. thanks CSIR for research fellowship
References
Figure 3. Illustrations for the crystal structure of 2: (a) tetrameric cyclic aggregate of rac-BN and BIPY via O-H‚‚‚N hydrogen bonds; (b) edge-to-face aromatic interactions between rac-BN and BIPY; (c) enclathration of biphenyl (space-filling mode) by rac-BN and BIPY layers (cylinder mode); the middle layer was colored for the sake of identifying cyclic aggregates.
A similar reaction to the above reactions but in the presence of nonaromatic guest molecule, 1,4-dioxane, resulted in the formation of crystals of a different product rac-BN.2(BIPY), 3, without the inclusion of guest molecule. In 3, each rac-BN is connected to two BIPY units through O-H‚‚‚N hydrogen bonds to form a 0D-aggregate (H‚‚‚N, O‚‚‚N, O-H‚‚‚N: 1.76 Å; 2.730 Å, 159°; 1.78 Å, 2.700 Å, 162°, Figure 4a).8 The pyridine rings in both BIPY units which does not involve in O-H‚‚‚N hydrogen bonds, form C-H‚‚‚N hydrogen bonds with naphthyl C-H groups (H‚‚‚N, C‚‚‚N, C-H‚‚‚N: 2.88 Å, 3.700 Å, 147°, 2.71 Å, 3.502 Å, 143°). The O-H‚‚‚N hydrogen-bonded aggregates pack on each other via edge-to-face aromatic interactions (Figure 4b,c) in a fashion similar to the above two structures. The repeat occurrence of edge-to-face aromatic interactions between rac-BN and BIPY in a similar fashion in all three structures indicates that this recognition motif can be termed as a supramolecular synthon between rac-BN
(1) (a) Desiraju, G. R. Crystal Engineering, The Design of Organic Solids; Elsevier: Amsterdam, 1989; (b) Lehn, J. M. Supramolecular Chemistry: Concepts and Perspectives; VCH: Weinheim, Germany, 1995; (c) Philp, D.; Stoddart, J. F. Angew. Chem., Int. Ed. Engl. 1996, 35, 1154; (d) Steed, J.; Atwood, J. L.; Supramolecular Chemistry; John Wiley & Sons: New York, 2000; (e) Desiraju, G. R. In Stimulating Concepts in Chemistry; Vo¨gtle, F., Stoddart, J. F., Shibasaki, M., Eds.; Wiley-VCH: Weinheim, Germany, 2000; p 293; (f) Holman, K. T.; Pivovar, A. M.; Swift, J. A.; Ward, M. D. Acc. Chem. Res. 2001, 34, 107; (g) Zaworotko, M. J. Chem. Commun. 2001, 1; (h) Aakero¨y, C. B.; Beatty, A. M.; Helfrich, B. A. Angew. Chem., Int. Ed. 2001, 40, 3240; (i) Aakero¨y, C. B. Acta Crystallogr. 1997, B53, 569; (j) Biradha, K. CrystEngComm 2003, 5, 274. (2) (a) Ma, B.-Q.; Coppens, P. Chem. Commun. 2003, 504; (b) Ma, B.-Q.; Coppens, P. Chem. Commun. 2003, 412; (c) Hamilton, T. D.; Papaefstathiou, G. S.; MacGillivray, L. R. J. Am. Chem. Soc. 2002, 124, 11606; (d) Ma, B.-Q.; Zhang, Y.; Coppens, P. Cryst. Growth Des. 2002, 2, 7; (e) Ma, B.Q.; Zhang, Y.; Coppens, P. Cryst. Growth Des. 2001, 1, 271; (f) Tanaka, T.; Tasaki, T.; Aoyama, Y. J. Am. Chem. Soc. 2002, 124, 12453; (g) MacGillivray, L. R.; Reid, J. L.; Ripmeester, J. A. CrystEngComm 1999, 1, 1350; (h) Wheatley, P. S.; Lough, A. J.; Ferguson, G.; Glidewell, C. Acta Crystallogr. 1999, C55, 1489; (i) Lavender, E. S.; Glidewell, C.; Ferguson, G. Acta Crystallogr. 1998, C54, 1637; (j) Biradha, K.; Zaworotko, M. J. J. Am. Chem. Soc. 1998, 120, 6431; (k) Ferguson, G.; Glidewell, C.; Lough, A. J.; McManus, G. D.; Meehan, P. R. J. Mater. Chem. 1998, 8, 2339.
Communications (3) (a) Cheung, E. Y.; Kitchin, S. J.; Harris, K. D. M.; Imai, Y.; Tajima, N.; Kuroda, R. J. Am. Chem. Soc. 2003, 125, 14658; (b) Kuroda, R.; Imai, Y.; Tajima, N. Chem. Commun. 2002, 2848; (c) Toda, F.; Senzaki, M.; Kuroda, R. Chem. Commun. 2002, 1788. (4) Here we describe only one example for each type; the detailed characterization and structural analyses of all the other crystals are in progress and will be published later. (5) The single-crystal data was collected on Bruker-Nonius Mach3 CAD4 X-ray diffractometer that uses graphite monochromated Mo KR radiation (λ ) 0.71073 Å) by ω-scan method. The structure was solved by direct methods and refined by least-squares methods on F2 using SHELX-97. Non-hydrogen atoms were refined anisotropically and hydrogen atoms were fixed at calculated positions and refined using a riding model. Crystal data 1: C37H30N2O2, M ) 534.63, monoclinic, space group ) C2/c; a ) 29.950(6); b ) 9.809(2); c ) 19.848(4) Å, β ) 93.59(3)°; U ) 5820(2), Z ) 8, Dc ) 1.220 g cm-3, R1 ) 0.0636, wR2 ) 0.2257.
Crystal Growth & Design, Vol. 5, No. 1, 2005 63 (6) Spek, A. L.; PLATON, A Multipurpose Crystallographic Tool; Utrecht University, Utrecht, The Netherlands, 2002. (7) Crystal data 2: C36H27N2O2, M ) 519.60, monoclinic, space group ) P2(1)/c; a ) 16.218(2); b ) 9.536(2); c ) 17.675(4) Å, U ) 2728.9(9), Z ) 4, Dc ) 1.265 g cm-3, R1 ) 0.0575, wR2 ) 0.1862. (8) Crystal data 3: C40H30N4O2, M ) 598.68, monoclinic, space group ) P2(1)/n; a ) 9.894(2); b ) 18.022 (4); c ) 18.045(4) Å, U ) 3157.8(11), Z ) 4, Dc) 1.259 g cm-3, R1 ) 0.0764, wR2 ) 0.2992. (9) (a) Kumar, V. S. S.; Pigge, F. C.; Rath, N. P. Cryst. Growth Des. 2004, 4, 651; (b) Biradha, K.; Seward; C.; Zaworotko, M. J. Angew. Chem., Int. Ed. 1999, 38, 492; (c) Gudbjartson, H.; Biradha, K.; Poirier, K. M.; Zaworotko, M. J. J. Am. Chem. Soc. 1999, 121, 2599; (d) Biradha, K.; Zaworotko, M. J. Cryst. Eng. 1998, 1, 67.
CG049761U
