CRYSTAL GROWTH & DESIGN
Supramolecular Grid and Layer Architectures. Hydrogen Bonds and Halogen-Halogen Interactions Influenced by Bromo-, Chloro-, and Cyano-Substituted Anilic Acids
2004 VOL. 4, NO. 3 585-589
Md. Badruz Zaman, Konstantin A. Udachin, and John A. Ripmeester* Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada Received July 18, 2003;
Revised Manuscript Received November 6, 2003
ABSTRACT: Supramolecular reactions were performed between 2,2′-bipyrimidine (BPM) and 2,5-substituted cyanoand haloanilic acids [cyananilic acid (CNA), chloranilic acid (ClA), and bromanilic acid, (BrA)] under identical reaction conditions in methanol and a mixture of acetonitrile and methanol. The cyano and hydroxyl functional units of CNA in supramolecular compound 1 are hydrogen-bonded through water molecules and form a two-dimensional network with a grid motif. The grid cavities are occupied by BPM molecules, which are strongly linked by water molecules that connect to the CNA network. The supramolecular architecture of 1 thus consists of a three-dimensional hydrogen-bonded network. The 1:1:2 (H2O) compound 2 has intermolecular O-H‚‚‚O and O-H‚‚‚N hydrogen bonds: (i) ClA‚‚‚H2O‚‚‚BPM linked along the diagonal line of the bc-plane and (ii) BPM‚‚‚H2O‚‚‚BPM connected along the b-axis. This structure includes strong Cl‚‚‚Cl interactions at 3.34 Å, which generate a three-dimensional packing arrangement as strengthened by acid‚‚‚acid interaction. A new class of hydrogen-bonded 1:1:4 (H2O) supramolecular compound 3 is formed from BPM, BrA, and water molecules, where structure formation is directed by O-H‚‚‚O and O-H‚‚‚N hydrogen bonds, as well as weaker C-H‚‚‚O and C-H‚‚‚Br interactions between BPM and BrA. Remarkable Br‚‚‚Br interactions at 3.68 Å are observed that are similar to the Cl‚‚‚Cl interactions in 2. The three supramolecular compounds have been prepared with the specific aim of assessing a new donor-acceptortype of hydrogen-bonded interactions to control the architecture of organic solids for the further invention of supramolecular solid-state materials. Introduction
Scheme 1
Understanding the role of noncovalent forces is a major challenge for the rational design of well-defined supramolecular structures and materials.1 Such interactions often control structurally important attributes of the crystal and also are responsible for possible functional properties, which in the long run may lead to applications as porous solids for chemical recognition and sensing, and in supramolecular aggregates for potential applications in diverse areas including the burgeoning field of nanotechnology.2,3 One of our aims is to assemble supramolecular solid materials where directionality, reversibility, and the possibility of controlling the strength of the interactions are influenced by alternating the number of hydrogen bonds and other noncovalent interactions.4 It is therefore important to identify new supramolecular synthons5 that involve donor and acceptor molecules able to form conventional pairwise hydrogen bonds in the structurally dominant polymeric moieties.6 Here we take advantage of the carbonyl, hydroxyl, halide, and cyanide groups of substituted benzoquinone-type molecules with dihydroxy groups, anilic acids, that interact in a noncovalent fashion to conserve specific and persistent supramolecular synthons.7 The acids in question have strong electron-accepting properties and possess both hydrogenbonding and ionic interaction sites. Moreover, these planar molecules may give a variety of ionic species (Scheme 1) differing in the number of protons (0-4) and charge (mainly -2 e δ e 0). * To whom correspondence should be addressed.
[email protected], Fax: +1-613-998-7833.
The self-assembly of anilic acids, to the best of our knowledge, has not been used before in the design and synthesis of new materials for organic crystal engineering. In this report, we explore for the first time selfcomplementary building blocks using cyano-, chloro-, and bromo-substituted cyananilic acid (CNA), chloranilic acid (ClA), and bromanilic acid (BrA), respectively. These acids are associated with water molecules and four hydrophilic N-containing organic component 2,2′-bipyrimidine (BPM),8 and form three crystalline solids 1-3 that are isolated as supramolecular grid networks (1) and supramolecular layer architectures (2 and 3).9 A new family of organic frameworks is created by non-hydrogen-bridged Br‚‚‚Br, Cl‚‚‚Cl, CN‚‚‚O, and O‚‚‚O contacts (see Scheme 2 below) resulting from substituted groups of anions and/or water molecules, but do not form direct contact between pyridyl cation and Scheme 2
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10.1021/cg034134a CCC: $27.50 Published 2004 by the American Chemical Society Published on Web 03/30/2004
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Figure 1. Space-filling view of two-dimensional hydrogenbonded grid architecture of 1. Stick-and-ball presentation of the guest, BPM, occupies the cavity of the grid and is hydrogen bonded with the host network.
Figure 2. The two-dimensional hydrogen-bonded sheet architecture of 2. Hydrogen atoms are omitted for clarity. Red circles are water molecules.
anions, although the packing motif of the crystal structure is stabilized by cation-anion attraction. As mentioned above, the focal points of our supramolecular systems are the anilic acids.10 To realize our goals, we exploit anilic acids that react readily with a variety of electron-donors and proton-acceptors to form supramolecular compounds that contain robust and reproducible halogen-halogen and hydrogen-bonded interactions (Scheme 2). The hydrogen-bond motifs in the CNA links in I and II are seen in the acid‚‚‚H2O‚‚‚acid interaction. By reacting chloro- and bromo-substituted anilic acids (ClA and BrA) with BPM, we see preferential interactions between Cl‚‚‚Cl (III) and Br‚‚‚Br (IV) and the supramolecules are completed through a self-complementary anion‚‚‚anion interaction. These examples establish that a small number of specific intermolecular interactions can contribute to a large part of the stabilization energy of the molecular crystal.11
Figure 3. (a) Packing of ClA in 2. Red lines show the Cl‚‚‚Cl interaction of 3.34 Å. (b) Packing of BrA in 3. Yellow lines show the Br‚‚‚Br contact of 3.68 Å.
Results and Discussion The supramolecular compound 1 crystallizes in the monoclinic P21/c space group, molecules of CNA and BPM are located on inversion centers, and water molecules are in general positions. The compound has a 1:1:2 (CNA/BPM/H2O) stoichiometric ratio with transfer of two CNA acidic protons to the BPM nitrogens. The hydrogen atom positions in this complex were identified from Fourier difference map and further refined isotropically. The C-O bond and hydrogen-bond lengths were taken in consideration.6 The cyano-functional group and the carboxy units of CNA in 1 are hydrogen bonded through water molecules [CtN‚‚‚H-O (dN‚‚‚O and θN‚‚‚H-O ) 2.88 Å and 160.0°) and O-H‚‚‚O (dO‚‚‚O and θO‚‚‚H-O ) 2.53 Å and 137.3°; 2.64 Å and 134.5°)] and form a grid motif in a self-assembled two-dimensional network (Figure 1). The organic grid cavities are occupied with BPM molecules, which again hydrogen bonded with CNA-linked water molecules [O-H‚‚‚N (dO‚‚‚N ) 2.73 and 2.78 Å)] of the grid network (Figure
Figure 4. View down the b-axis, with two-dimensional layered architecture of 3. Blue and red lines show the hydrogen bonds.
1). Such host-guest hydrogen-bonded interactions are rarely reported in the literature.12 The supramolecular architecture of 1 thus constitutes a virtual threedimensional hydrogen-bonding network. The CNA component forms an alternating stacking arrangement with BPM along the crystallographic b-axis in two different planes. The supramolecular compound 2 crystallizes in the monoclinic C2/c space group, molecules ClA are located on inversion center, BPM on 2-fold axis, and water is
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Figure 5. MDSC curves of 1 (green), 2 (navy), and 3 (maroon). Melting temperatures are observed at 155.51, 112.61, and 77.97 °C for 1, 2, and 3, respectively.
located in general position. The geometry and the CdO, C-OH, and C-C bond distances are consistent with those of a typical neutral ClA.5b,6 The complex of 2 reveals that the stoichiometric ratio of ClA/BPM/H2O is 1:1:2. The components ClA and BPM are strongly hydrogen bonded with water molecules and form a twodimensional sheet-type network along the ab-plane (see Figure 2). In fact, four pyridyl N-atoms are favorably stacked in a columnar alignment through O-H‚‚‚N (dO‚‚‚N ) 2.88 and 2.93 Å) hydrogen bonds with water molecules, which again hydrogen bond in a bifurcated manner [O-H‚‚‚O (dO‚‚‚O ) 2.52 and 3.03 Å)] with two carbonyl O-atoms of the ClA. Additional inspection of the supramolecular packing revealed that the crystal lattice is further directed by strong Cl‚‚‚Cl interactions13 that strengthens the columnar structure appropriate for polymer formation. An interesting tetrachloro interaction (3.34 and 3.71 Å) is one of the rare examples of a supramolecular tetrameric Cl4 synthon (Scheme 2; III) and is observed in the crystallographic bc-plane (Figure 3a). The noncovalent Br‚‚‚Br distances (3.68 Å, van der Waals radius of Br is 1.85 Å) are seen in the crystal packing pattern of 3. A view down the a-axis (Figure 3b) shows that Br atoms aggregate through Br‚‚‚Br interactions to form a supramolecular trimeric Br3 synthon (Scheme 2; IV).14 The supramolecular compound 3 crystallizes in the monoclinic C2/c space group, molecules BrA are located on inversion center, BPM on 2-fold axis, and water is located in general position. The geometry of BrA has similar CdO, C-OH, and C-C bond distances as compared to those in a previously reported BrA complex.6 The stoichiometric ratio of this compound is 1:1:4 (H2O) and is prepared from BrA and BPM components in the same reaction system that was applied for 1 and 2. Similar to 2, BrA and BPM are strongly hydrogen bonded with water molecules as O-H‚‚‚O (dO‚‚‚O ) 2.46 Å) and O-H‚‚‚N (dO‚‚‚N ) 2.83 Å), respectively. Moreover, three water molecules are linked to each other by O-H‚‚‚O hydrogen bonds (dO‚‚‚O ) 2.73 Å). In addition,
the component BPM is associated with two water molecules along the a-axis and BrA with one of the water molecules along the c-axis and they form twodimensional supramolecular polymer sheets in the crystallographic ac-plane (Figure 4). The C-H‚‚‚O and C-H‚‚‚Br distances are 3.41 and 3.76 Å, respectively, and are regarded as donor‚‚‚acceptor interactions. In crystals of 2 and 3, robust restricted dimensional hydrogen-bonded networks that include significant halogen-halogen and/or CH-π interactions are observed. These function cooperatively to align columns that lead to the observed polymer formation. In the layered crystals, the formation of molecular sheets also assists with polymer formation.4 To check for phase purity of the self-assembled cocrystal phases 1-3, bulk crystalline samples were characterized in the solid-state by TGA, modulated DSC (MDSC), and powder X-ray diffraction.15 When performing MDSC on crystalline solids 1, 2, and 3 melting temperatures were observed to be 156, 113, and 78 °C (Figure 5), respectively, which are rather lower than the thermal degradation temperatures observed from TGA. To try and understand the complex DSC patterns, sample pans were crimped before being placed in the heat flow chamber to avoid complications from sample loss by evaporation. This yielded the exothermic peaks in the reversible heat flow as shown in Figure 5. However, nonreversible heat flow experiments showed that these features disappear, which indicates that all processes observed are reversible. Moreover, extra endothermic peaks are seen around 50-55 °C for 1, and at 104 °C and 50 °C for 2 and 3, respectively, to indicate reorganization of the crystals to different phases.12,16 The bulk compounds were checked by X-ray powder diffraction (Figure 6) out to high angles. The expected reflections, as calculated from single crystal data, were observed, as well as some extra reflections indicating that small quantities of other phases were present. Since these extra reflections are few, we take this to mean that the small amounts of the extraneous materi-
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Experimental Section
Figure 6. Powder X-ray diffraction patterns of 1 (a), 2 (b), and 3 (c). Arrows in each pattern indicate the position of lowintensity reflections that were observed in addition to those that correspond to calculated positions derived from the singlecrystal data. (a) 9.4° for 1 (b) 7.8°, 8.4°, and 13.1° for 2 (c) 8.3° for 3. (Calculated patterns are illustrated in Supporting Information.)
als were structurally related polymorphs or pseudopolymorphs. As the DSC shows weak endotherms at quite low temperatures (∼50 °C), it is likely that these could easily form via a solid-solid phase transition.17 Two important similarities exist in the powder patterns of 1-3. All show additional low-intensity reflections between 7.8° and 9.4°; as well, two extra reflections were observed for 2, one above 10°. We also see weak overlapping reflections in the region from 26° to 29°, particularly for 2 and 3. These results suggest that there may be relatively rich phase diagrams for these compounds that will require further investigation.18 Conclusions In this study, we have shown that the appropriate stacking of anilic acids is indispensable for the process of polymer formation. Specifically, the hydrogen-bonding network of the sheet-type structures, 2 and 3, implies a head-to-head arrangement of ClA and BrA at a suitable distance for halogen-halogen interaction. This suggests that polarization and/or charge-transfer related to the halogen atoms play a significant role in the intermolecular interactions. The complementary pairing studies taking place here in the presence of strong hydrogen-bonding and nonbonding motifs bodes well for the development of new supramolecular architectures.19
Starting Materials. The procedure for the preparation of 2,5-dicyano-3,6-dihydroxy-1,4-benzoquinone (CNA) was developed in our laboratory. 2,2′-Bipyrimidine (BPM) was prepared according to the literature.8 Other compounds 2,5-dibromo3,6-dihydroxy-1,4-benzoquinone (BrA) and 2,5-dichloro-3,6dihydroxy-1,4-benzoquinone (CLA) were commercially available and purified by the usual methods. All the solvents were distilled before use. General Procedures for the Preparation of Single Crystals. Method I: equimolar amounts (0.03-0.10 mmol) of anilic acids and BPM were placed in the bottom of an H-shaped tube and filled with 1:1 mixture of acetonitrile/methanol (10-25 mL). Crystals suitable for single-crystal X-ray diffraction grew over a period of between 3 and 30 days at room temperature, Method II: a solution of the acid (0.05-0.10 mmol) in freshly distilled hot methanol (5-15 mL) was mixed with a solution of the BPM base (0.05-0.10 mmol) in a distilled hot methanol (5-10 mL). Within a week, red crystals suitable for singlecrystal X-ray diffraction appeared in the flask. The appearance of the single crystals: 1: Brown prismatic crystals were prepared by method I; yield 96%. 2: Reddish rod crystals were prepared by method I and method II; yield 92%. 3: Red plate crystals were prepared by method I and method II; yield 87%. Thermogravimetric Analyses. TGA experiments were carried out on a TA Instruments 2050 (V5.4A) under flowing nitrogen (40 mL/min flow rate). Compounds 1-3 were heated from 50 to 500 °C at a rate of 5 °C/min. MDSC (Modulated DSC) experiments were performed using a 2920 Modulated Differential Scanning calorimeter (TA Instruments). Operation condition: equilibration at -150 °C, isothermal for 15 min, modulate ( 1 °C every 60 s, ramp 5 °C/min to 210 °C. X-ray Crystallographic Analysis. Single-crystal diffraction experiments were performed with crystals, or chips cut there from, taken from under their respective mother liquors and cooled immediately to -100 °C. A Siemens SMART CCDdiffractometer equipped with graphite-monochromated MoKR radiation, λ ) 0.7107 Å) was used to collect diffraction data. Preliminary unit cell parameters were determined using 60 or more frame ω scans, 0.3° wide, starting at three different φ positions. Full data set was collected using the ω scan mode over the 2θ range of 3-58°. Coverage of the unique sets was over 99%. An empirical absorption correction utilized the SADABS routine associated with the diffractometer. The final unit cell parameters were obtained using the entire data set. All non-hydrogen atoms were refined anisotopically and all hydrogen atoms were clearly localized in the Fourier maps and refined isotropically. The structures were solved and refined with the SHELXTL software package.20 Crystal Data for 1. C16H12N6O6, fw ) 384.32, monoclinic, space group P21/c, a ) 7.0936(7), b ) 8.5462(8), c ) 14.1966(14) Å, β ) 109.1470(10), V ) 813.03(14) Å3, Z ) 2, Dc ) 1.570 g cm-3, F(000) ) 396, µ(Mo KR) ) 0.124 mm-1, crystal dimensions ) 0.40 × 0.35 × 0.10 mm3, Of the 5601 reflections collected, 1061 were unique. Final R1 ) 0.0294 and wR2 ) 0.0798, GOF ) 1.072 for 883 data with I > 2σ(I). Crystal Data for 2. C20H20Cl2N4O4, fw ) 451.30, monoclinic, space group C2/c, a ) 25.790(2), b ) 3.7148(3), c ) 17.2252(14) Å, β ) 100.081(2), V ) 1624.8(2) Å3, Z ) 2, Dc ) 1.922 g cm-3, F(000) ) 468, µ(Mo KR) ) 0.222 mm-1, crystal dimensions ) 0.50 × 0.35 × 0.20 mm3, Of the 8907 reflections collected, 2076 were unique. Final R1 ) 0.0387 and wR2 ) 0.0797, GOF ) 0.951 for 1491 with I > 2σ(I). Crystal Data for 3. C14H16Br2N4O8, fw ) 528.13, monoclinic, space group C2/c, a ) 19.7690(19), b ) 3.7834(4), c ) 24.983(2) Å, β ) 93.919(2), V ) 1864.2(3) Å3, Z ) 4, Dc ) 1.882 g cm-3, F(000) ) 1048, µ(Mo KR) ) 4.401 mm-1, crystal dimensions ) 0.35 × 0.30 × 0.15 mm3, Of the 10216 reflections collected, 2412 were unique. Final R1 ) 0.0382 and wR2 ) 0.0857, GOF ) 0.988 for 1899 data with I > 2σ(I). X-ray powder diffraction patterns (XRD) were recorded at room temperature on a Scintag XDS2000 diffractometer, using
Supramolecular Grid and Layer Architectures graphite monochromatized Cu KR radiation (λ ) 1.79 Å) in the θ -θ scan mode. Samples were scanned over a range 10° < 2θ < 30°, with a 30 s accumulation time at an increment of 0.02° in 2θ, giving a total acquisition time for each sample of approximately 12 h. The pattern was generated from the single-crystal data using the SHELXTL ’97 XPOW software.
Acknowledgment. We thank Professor K. Nakasuji and Professor Y. Morita of Osaka University for supplying 2,5-dicyano-3,6-dihydroxy-1,4-benzoquinone. M.B.Z. thanks NSERC for visiting fellowships. This work was supported by National Research Council of Canada. Supporting Information Available: CIF files for three single crystals together with powder XRD and TGA (PDF). These materials are available free of charge via the Internet at http://pubs.acs.org.
References (1) Prins, L. J.; Reinhoudt, D. N.; Timmerman, P. Angew. Chem., Int. Ed. 2001, 40, 2382-2426. (2) (a) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. Rev. 2000, 100, 853-908. (b) Chui, S. S.-Y.; Lo, S. M.-F.; Chartmant, J. P. H.; Orpen, A. G.; Williams, I. D. Science 1999, 283, 1148-1150. (c) Noro, S-i.; Kitaura, R.; Kondo, M.; Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Yamashita, M. J. Am. Chem. Soc. 2002, 124, 2568-2583. (d) Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jin, Y. J.; Kim, K. Nature 2000, 404, 982-986. (3) For hydrogen-bond-mediated self-assembled nanoscale structures, see recent reviews for organic nanotubes: (a) Fenniri, H.; Mathivanan, P.; Vidale, K. L.; Sherman, D. M.; Hallenga, K.; Wood, K. V.; Stowell, J. G. J. Am. Chem. Soc. 2001, 123, 3854-3855. (b) Bong, D. T.; Clark, T. D.; Granja, J. R.; Ghadiri, M. R. Angew. Chem., Int. Ed. 2001, 40, 988-1011. (4) Brunsveld, L.; Folmer, B. J. B.; Meijer, E. W.; Sijbesma, R. P. Chem. Rev. 2001, 101, 4071-4097. (5) (a) Desiraju, G. R. Angew. Chem., Int. Ed. 1995, 34, 23112327. (b) Zaman, M. B.; Tomura, M.; Yamashita, Y. Chem. Commun. 1999, 999-1000 (6) Zaman, M. B.; Tomura, M.; Yamashita, Y. J Org. Chem. 2001, 66, 5987-5995.
Crystal Growth & Design, Vol. 4, No. 3, 2004 589 (7) (a) Reddy, D. S.; Ovchinnikov, Y. E.; Shishkin, O. V.; Struchkov, Y. T.; Desiraju, G. R. J. Am. Chem. Soc. 1996, 118, 4085-4089. (b) Kuduva, S. S.; Craig, D. C.; Nangia, A.; Desiraju, G. R. J. Am. Chem. Soc. 1999, 121, 1936-1944. (c) Yamochi, H.; Nakamura, S.; Saito, G.; Zaman, M. B.; Toyoda, J.; Morita, Y.; Nakasuji, K.; Yamashita, Y. Synth. Met. 1999, 102, 1729. (8) 2,2′-Bipyrimidine (BPM) has an efficient capability for a proton-acceptor mediated electron-donor and acts here as a guest or countercation. For a high-yield synthetic method, see Vlad, G.; Horvath, I. T. J. Org. Chem. 2002, 67, 65506552. (9) Simanek, E. E.; Tsoi, A.; Wang, C. C. C.; Whitesides, G. M.; McBride, M. T.; Palmore, G. T. R. Chem. Mater. 1997, 9, 1954-1961 (10) S. Kitagawa, S. Kawata Coord. Chem. Rev. 2002, 224, 1134. (11) Dauber, P.; Hagler, A. T. Acc. Chem. Res. 1980, 13, 105-112. (12) Beketov, K.; Weber, E.; Ibragimov, B. T.; Seidel, J.; Ko¨hnke, K. Adv. Mater. 2000, 12, 664-667. (13) Madhavi, N. N. L.; Desiraju, G. R.; Bilton, C.; Haward, J. A. K.; Allen, F. H. Acta Crystallogr., Sect. B: Struct. Sci. 2000, 56, 1063-1070. (14) Jetti, R. K. H.; Xue, F.; Mak, T. C. W.; Nangia, A. Cryst. Eng. 1999, 2, 215-224. (15) The organic frameworks of 1-3 were not soluble in common organic solvents and fluorine-containing polar solvents. Therefore, the bulk crystalline samples were characterized in the solid state by TGA, MDSC, and XRD. (16) Bershtein, V. A.; Egorov, V. M. Differential Scanning Calorimetry of Polymers; English Ed.; Ellis Horwood: New York, 1994. (17) Harris, K. M. D.; Tremayne, M.; Kariuki, B. M. Angew. Chem., Int. Ed. 2001, 40, 1626-1651. (18) Simanek, E. E.; Tsoi, A.; Wang, C. C. C.; Whitesides, G. M.; McBride, M. T.; Palmore, G. T. R. Chem. Mater. 1997, 9, 1954-1961. (19) Study on other polymer properties, such as fabrication of nanoscale fiber and composition, is under way. Sijbesma, R. P.; Beijer, F. H.; Brunsveld, L.; Folmer, B. J. B.; Hirschberg, J. H. K. Ky; Lange, R. F. M.; Lowe, J. K. L.; Meijer, E. W. Science 1997, 278, 1601-1604. (20) Sheldrick, G. M. SHELXTL, Version 6.10; Bruker AXS Inc., Madison, Wisconsin, USA, 2000.
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