CRYSTAL GROWTH & DESIGN
Tunable Two-Component Host System with Multiple Chiral Points Composed of Cyclohexanediamine and 1,1′-Binaphthyl-2,2′-dicarboxylic Acid
2007 VOL. 7, NO. 9 1676-1678
Yoshitane Imai,*,† Kakuhiro Kawaguchi,† Katuzo Murata,† Tomohiro Sato,‡ Reiko Kuroda,‡,§ and Yoshio Matsubara*,† Department of Applied Chemistry, Faculty of Science and Engineering, Kinki UniVersity, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan, JST ERATO-SORST Kuroda Chiromorphology Team, 4-7-6 Komaba, Meguro-ku, Tokyo 153-0041, Japan, and Department of Life Sciences, Graduate School of Arts and Sciences, The UniVersity of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan ReceiVed June 5, 2007; ReVised Manuscript ReceiVed July 31, 2007
ABSTRACT: A tunable supramolecular host system with multiple chiral points was developed by combining (1S,2S)-1,2-cyclohexanediamine and (R)-1,1′-binaphthyl-2,2′-dicarboxylic acid. Many supramolecular organic host compounds have been reported that include guest molecules.1 In cases in which the guest molecules are chiral, most hosts employed for chiral recognition and enantioselective reactions consist of only one molecule.2 In such chiral host systems, there has been an increased demand to modulate the size and shape of the chiral cavity in order to incorporate various guest molecules. Moreover, in order to increase the chiral recognition ability for various guest molecules, chiral recognition by multiple chiral points is needed in the host system. To meet these demands, supramolecular organic host systems composed of two or three molecules have been developed.3 Recently, we reported a tunable supramolecular host system with multiple chiral points that capitalized on a hydrogen- and ionicbonded network composed of a diamine and a dicarboxylic acid derivative.4 In these systems, chiral (1R,2R)-diphenylethylenediamine was used as the diamine compound. The advantage of these host systems is that modifications of the shape and properties of the cavity can easily be accomplished by changing the component molecules. In this paper, we report the formation and crystal structure of a tunable supramolecular host system with multiple chiral points consisting of a novel diamine and a dicarboxylic acid derivative. The complexation behavior, crystal structure and guest inclusion mechanism were studied when (1S,2S)-1,2-cyclohexanediamine ((1S,2S)-1) was used instead of (1R,2R)-diphenylethylenediamine. For the dicarboxylic acid portion, acids that have internal symmetry axes were used, i.e., the achiral diphenic acid (2) and chiral (S)- or (R)-1,1′-binaphthyl-2,2′dicarboxylic acids ((S)- or (R)-3) (see Chart 1). To study the guest inclusion mechanism, we used three simple n-alkyl alcohols with different alkyl chains (methanol (MeOH), ethanol (EtOH) and n-propanol (n-PrOH)) as guest molecules. The complexation behavior of the (1S,2S)-1/2 host system was studied. The formation of an inclusion complex was attempted by crystallization from three types of guest solutions containing (1S,2S)-1 and 2.5 Although a complex was obtained from EtOH solution in our previous work with (1R,2R)-diphenylethylenediamine and 2,4 an inclusion complex was not obtained from all solutions with the (1S,2S)-1/2 system. Therefore, the naphthalenecontaining dicarboxylic acid derivatives, chiral (S)- or (R)-3, were used instead of 2. When the formation of inclusion complexes was attempted, differences in complexation behavior were observed according to the chiralities of 1 and 3. In the case of (1S,2S)-1 and (S)-3, an inclusion complex did not form from all guest solutions.5 However, in the case of (1S,2S)-1 and (R)-3, inclusion complexes * To whom correspondence should be addressed. E-mail: y-imai@ apch.kindai.ac.jp (Y.I.);
[email protected] (Y.M.). Fax: 81-6-67272024 (Y.I.); Tel: 1-6-6730-5880 (ext. 5241) (Y.I.). † Kinki University. ‡ JST. § The University of Tokyo.
Chart 1
(I for the MeOH system (14 mg), II for the EtOH system (12 mg), and III for the n-PrOH system (11 mg))6 were obtained by crystallization from each solution.5 To study the mechanism of this two-component host system, we performed X-ray analysis on obtained crystals. The structure of crystal I is shown in Figure 1.7 Crystal I is constructed from (1S,2S)-1 (green molecules in Figure 1) and (R)-3 (blue molecules in Figure 1). The stoichiometry of complex I is 1:1:1:1 (1S,2S)-1:(R)-3:H2O:MeOH and the space group is P212121. This crystal has a columnar supramolecular hydrogen- and ionic-bonded network around the 21-axis and along the a-axis (parts a and b of Figure 1). The network is formed mainly by the ammonium hydrogen of one protonated amine and the carboxylate oxygen of a carboxylic acid anion. The included water molecules (Figure 1, indicated by purple balls) link the two carboxyl groups through hydrogen bonds and contribute to the maintenance of the column frame. Chiral cavities are formed by self-assembly of this 21 column (Figure 1c). In this cavity, the guest MeOH molecule (Figure 1, indicated in red or as a red space-filling molecule) is trapped and partially imbedded in the column linking the amine-H+ of (1S,2S)-1 and the included water molecule through a hydrogen bond. In complex I, because the cavities are formed by self-assembly of 21 columns without strong interactions, it is expected that the size and shape of the cavities can be tuned by the packing structure of the 21 columns. The crystal structure of II including EtOH was analyzed (see the Supporting Information, Figure ESI-1).8 X-ray analysis revealed that the stoichiometry of this complex is the same as that of I, i.e., 1:1:1:1 (1S,2S)-1:(R)-3:H2O:EtOH, with the same space group of P212121. These crystals share a characteristic 21 column structure, as in crystal I (see the Supporting Information, parts a and b in Figure ESI-1). Also in this complex, chiral cavities are formed by self-assembly of 21 columns (see the Supporting Information, parts c and d in Figure ESI-1). As expected, the size of the cavity changes according to the size of the guest molecule. As the alkyl chain of the n-alkyl alcohol becomes longer (from MeOH to EtOH), the distances between the (R)-3 molecules along the column (A, Figure 1a) shorten slightly from 8.92 to 8.88 Å, and the torsion angles of (R)-3 decrease from 94.57 to 91.87°. On the other hand, the distance between columns (B, Figure 1d) becomes greater (10.29 and 10.45 Å for I and II, respectively).
10.1021/cg070507m CCC: $37.00 © 2007 American Chemical Society Published on Web 08/11/2007
Communications
Crystal Growth & Design, Vol. 7, No. 9, 2007 1677
Figure 2. Crystal structure of complex III. (a) Basic unit composed of (1S,2S)-1 and (R)-3 observed along the a-axis. (b) Basic unit parallel to the a-axis. (c) 2D layered structure unit composed of basic unit observed along the a-axis. (d) Packing structure observed along the a-axis. Colored arrows show naphthalene-naphthalene edge-to-face interactions. Figure 1. Crystal structure of complex I. Water molecules are shown as purple balls. (a) Column structure is parallel to the a-axis. (b) View down the a-axis. (c) Packing structure observed along the c-axis. (d) Packing structure observed along the a-axis.
Next, the inclusion mechanism of complex III including n-PrOH molecules was studied. Interestingly, the packing style of complex III is dramatically changed from that of complexes I and II. The crystal structure of complex III is shown in Figure 2.9 X-ray analysis revealed that the stoichiometry of this complex is 1:2:3 (1S,2S)-1:(R)-3:n-PrOH, with the space group of P212121. In this crystal, two (R)-3 molecules (blue molecules in Figure 2) are connected by hydrogen and ionic bonds with a carboxyl group through (1S,2S)-1 (green molecules in Figure 2) and included n-PrOH molecules (red molecules in Figure 2), forming the basic unit (Figure 2a). This unit is connected along the a-axis by two types of naphthalene-naphthalene edge-to-face interactions (Figure 2b, indicated by blue and purple arrows, 2.77 and 2.70 Å, respectively). Moreover, along the c-axis, this unit is connected by three types of naphthalene-naphthalene edge-to-face interactions (Figure 2c, indicated by blue, purple, and orange arrows, 2.94, 2.80, and 2.79 Å, respectively), and a 2D layered network structure is
formed by self-assembly of this unit (Figure 2c). In this complex, two kinds of chiral channel-like cavities are formed by self-assembly of this 2D layered network structure along the a-axis (Figure 2d, indicated by orange and purple circles). In these channel-like cavities, the guest n-PrOH molecules (Figure 2d, indicated as orange and purple space-filling molecules) are trapped along the direction of the cavity by hydrogen bonds between one of the amino groups of (1S,2S)-1 and the hydroxyl group of n-PrOH and between the carboxyl group of (R)-3 and the hydroxyl group of n-PrOH. This result shows that not only the size of the cavity but also the style of the cavity can be dramatically changed according to the guest molecule in this system. In conclusion, a chiral cavity with multiple chiral points was successfully formed by self-assembly of two types of component units composed of chiral (1S,2S)-1 and (R)-3. One is a 21 column structure and the other is a 2D layered network structure. This chiral host system can include guest molecules by changing the style of the component unit (21 column structure or 2D layered network structure) according to the guest molecule. Moreover, the size of the cavity changes according to the guest molecules. Therefore, tunable chiral cavities of this type can accommodate various guest
1678 Crystal Growth & Design, Vol. 7, No. 9, 2007
Communications
molecules and have great potential in enantioselective molecular recognition or in asymmetric reactions. (5)
Acknowledgment. We thank Dr. M. Seki of Tanabe Seiyaku Co., Ltd. for providing the sample. Supporting Information Available: X-ray crystallographic reports (CIF) of complexes I-III and crystal structure of complex II (PDF). This information is available free of charge via the Internet at http://pubs.acs.org.
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References (1) Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Eds. Inclusion Compounds; Academic Press: New York, 1984; Vols. 1-3. Walba, D. M.; Clark, N. A.; Razavi, H. A.; Parmar, D. S. In Inclusion Phenomenon and Molecular Recognition; Atwood, J. L., Ed.; Plenum Press: New York, 1990. Lehn, J.-M., Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Vogtle, F., Eds. ComprehensiVe Supramolecular Chemistry; Pergamon Press: Oxford, U.K., 1996; Vols. 1-11. (2) Akazome, M.; Noguchi, M.; Tanaka, O.; Sumikawa, A.; Uchida, T.; Ogura, K. Tetrahedron 1997, 53, 8315. Akazome, M.; Ueno, Y.; Ooiso, H.; Ogura, K. J. Org. Chem. 2000, 65, 68. Akazome, M.; Senda, K.; Ogura, K. J. Org. Chem. 2002, 67, 8885. Akazome, M.; Hirabayashi, A.; Ogura, K. Tetrahedron 2004, 60, 12085. (3) Kobayashi, Y.; Kodama, K.; Saigo, K. Org. Lett. 2004, 6, 2941. Kodama, K.; Kobayashi, Y.; Saigo, K. Chem.sEur. J. 2007, 13, 2144. (4) Imai, Y.; Sato, T.; Kuroda, R. Chem. Commun. 2005, 3289. Imai, Y.; Takeshita, M.; Sato, T.; Kuroda, R. Chem. Commun. 2006, 1070. Imai, Y.; Kawaguchi, K.; Sato, T.; Kuroda, R.; Matsubara, Y.
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Tetrahedron Lett. 2006, 47, 7885. Imai, Y.; Kawaguchi, K.; Murata, K.; Sato, T.; Kuroda, R.; Matsubara, Y. Chem. Lett. 2007, 812. A mixture of (1S,2S)-1 (10 mg, 0.088 mmol) and dicarboxylic acid derivatives (0.088 mmol) was dissolved in n-alkyl alcohol solution (2-3 mL) and left to stand at room temperature. After a few days, several colorless crystals were produced. This weight is the total crop of obtained crystals in one batch. Crystal data for I: C6H14N2‚C22H14O4‚H2O‚CH4O, M ) 506.58 orthorhombic, space group P212121, a ) 8.9189(5) Å, b ) 10.2904(5) Å, c ) 27.9198(14) Å, U ) 2562.5(2) Å3, Z ) 4, Dc ) 1.313 g cm-3, µ(Mo KR) ) 0.092 mm-1, 22726 reflections measured, 5949 unique, final R(F2) ) 0.0399 using 5432 reflections with I > 2.0σ(I), R(all data) )0.0452, T ) 120(2) K. Crystal data for II: C6H14N2‚C22H14O4‚H2O‚C2H6O, M ) 520.61 orthorhombic, space group P212121, a ) 8.8746(5) Å, b ) 10.4445(6) Å, c ) 28.2830(15) Å, U ) 2621.6(3) Å3, Z ) 4, Dc ) 1.319 g cm-3, µ(Mo KR) ) 0.092 mm-1, 16376 reflections measured, 6007 unique, final R(F2) ) 0.0443 using 5552 reflections with I > 2.0σ(I), R(all data) )0.0485, T ) 120(2) K. Crystal data for III: C6H14N2‚2C22H14O4‚3C3H8O, M ) 979.14 orthorhombic, space group P212121, a ) 9.1854(6), b ) 15.1465(11), c ) 36.763(3) Å, U ) 5114.7(6) Å3, Z ) 4, Dc ) 1.272 g cm-3, µ(Mo KR) ) 0.087 mm-1, 31926 reflections measured, 11675 unique, final R(F2) ) 0.0497 using 10434 reflections with I > 2.0σ(I), R(all data) )0.0571, T ) 120(2) K.
CG070507M
