C-H‚‚‚O Hydrogen Bonding Induced Guest Inclusion and Supramolecular Isomerism in 1,3,5-Tris(4-cyanobenzoyl)benzene V. S. Senthil Kumar, F. Christopher Pigge,* and Nigam P. Rath Department of Chemistry & Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, Missouri 63121-4499
CRYSTAL GROWTH & DESIGN 2004 VOL. 4, NO. 4 651-653
Received December 10, 2003
W This paper contains enhanced objects available on the Internet at http://pubs.acs.org/crystal. ABSTRACT: Crystallization of 1,3,5-tris(4-cyanobenzoyl)benzene (1) from EtOAc, MeNO2, and 3-pentanone results in formation of isostructural inclusion complexes mediated by weak hydrogen bonding interactions involving aryl C-H donors and heteroatom acceptors from nitrile, carbonyl, and nitro groups. The solvent guests occupy interlayer channels within a porous triaroylbenzene host network. The study of host-guest inclusion complexes continues to receive a great deal of attention, and often these supramolecular composites may be regarded as prototypical examples of microporous solids.1 Additionally, inclusion complexes may provide valuable insight into the design of functional materials including separation devices, catalysts, chemical sensors, nonlinear materials, magnets, and solid-state reaction platforms.2-4 While it is difficult to predict the occurrence (let alone structure) of inclusion complexes, crystal engineering of open networks using coordination polymers, flexible organic molecular frameworks, or both has resulted in the realization of designed inclusion hosts. For example, ligands such as analogues of 4,4′-bipyridine and trimesic acid have been utilized to great effect in the synthesis of porous coordination polymers,5,6 while triphenoxytriazines have been found to self-assemble into organic hexagonal channel-type inclusion hosts.2 Other examples of inclusion hosts designed through incorporation of hydrogen bonding functional groups into rigid symmetrical frameworks have also been reported.1,7 The successful design of inclusion hosts operative in the absence of metal-ligand interactions, strong hydrogen bonding, or both, however, remains problematic. In some instances an inclusion host will form a number of tractable crystalline complexes with various guests (usually solvent molecules), and in this regard, the occurrence of inclusion complexes is superficially comparable to polymorphism.8 The frequency at which polymorphism and solvent inclusion occur combined with the need to develop a better understanding and control of these phenomena are of great contemporary interest in the area of crystal engineering.9 Recently, we reported the structural characterization of 1, a triaroylbenzene derivative found to
exhibit concomitant polymorphism.10 Herein we report that 1 also serves as an inclusion host toward three different solvent guests that each possess a hydrogen bond acceptor. The three inclusion complexes are isostructural and are * To whom correspondence should be addressed. E-mail: piggec@ jinx.umsl.edu. Phone: (314) 516-5340. Fax: (314) 516-5342.
Figure 1. C-H‚‚‚O and C-H‚‚‚N mediated 2D lamellar pattern in 1‚EtOAc. Guest molecules have been omitted for clarity. W A rotatable 3D image of Figure 1 is available in PDB format suitable for viewing with the CHIME plug-in.
mediated by various weak solid-state host-guest C-H‚‚‚ O/N hydrogen bonds. The network topology of 1 in these complexes differs from those observed in the previously characterized polymorphic modifications,10 so the inclusion of guest molecules appears to play an important role in influencing supramolecular isomerism in the triaroylbenzene host. As part of continuing studies exploring the solid-state properties of triaroylbenzenes,11 single crystals of 1 (obtained from acetone/H2O solution) were examined by X-ray diffraction. Compound 1 was found to adopt two concomitant crystalline modifications consisting of a hexagonal network in one case and a ladder network in the other.10 Neither modification contained any guest solvates. Crystallization of 1 from EtOAc, however, afforded single crystals of different morphology, and X-ray diffraction analysis revealed the formation of a host-guest inclusion complex between 1 and EtOAc (1:1 stoichiometry, space group P1 h ).12,13 Moreover, the network structure displayed by host molecules 1 was found to differ significantly from previously observed topologies. As shown in Figure 1, a single cyanobenzoyl ring of 1 self-assembles via a pair of centrosymmetric C-H‚‚‚O and C-H‚‚‚N hydrogen bonds (H‚‚‚O 2.52 Å, C-H‚‚‚O 131.1°, H‚‚‚N 2.57 Å, C-H‚‚‚N 166.0°, C-H distances are neutron-normalized) resulting in a lamellar 2D pattern along [001]. The central arene ring and another cyanobenzoyl ring are oriented in the third dimension and act as pillars between adjacent layers. EtOAc guest molecules reside in interlayer channels formed
10.1021/cg034252y CCC: $27.50 © 2004 American Chemical Society Published on Web 05/27/2004
652
Crystal Growth & Design, Vol. 4, No. 4, 2004
Figure 2. Two views of 1‚EtOAc: (a) down the crystallographic c axis; (b) down the crystallographic a axis. H-bonding interactions have been omitted for clarity. W A rotatable 3D image of Figure 2 is available in PDB format suitable for viewing with the CHIME plug-in.
down the c axis by inversion and translation-related benzoyl rings (Figure 2). Two atoms of the EtOAc guests are disordered (carbonyl carbon and ester oxygen). The carbonyl oxygen of each EtOAc guest participates in relatively strong bifurcated C-H‚‚‚O hydrogen bonding interactions with aromatic C-H donors of the host (Figure 3a). Phenyl rings engaged in π stacking interactions14 and various host-host and guest-host hydrogen bonding further stabilizes the inclusion complex. Crystallization of 1 from nitromethane (MeNO2) and 3-pentanone also resulted in inclusion complex formation. The crystal structures of 1‚MeNO2 (1:1.5) and 1‚3-pentanone (1:1) were found to be isomorphous with 1‚EtOAc
Communications and exhibited identical host network arrangements (with the exception of a second disordered MeNO2 guest present at 50% occupancy). In all the three cases, bifurcated hydrogen bonds between guest acceptors (carbonyl, nitro group) and host C-H moieties were observed (Figure 3). Conformational mobility and the flexible nature of C-H‚‚‚O and C-H‚‚‚N hydrogen bonding undoubtedly play crucial roles in promoting the supramolecular isomerism observed in 1.15,16 The specific host-guest interactions in the inclusion complexes described above, however, appear to enforce an architectural rigidity on host network 1 that is lacking in the absence of guest. Thus, guest inclusion effectively controls conformational (and by extension supramolecular) isomerism in this system. The importance of host-guest solid-state hydrogen bonding in influencing the formation of the observed host network is difficult to quantify, but network interconversions facilitated by weak hydrogen bonding have been reported in other recent studies.17 While it is not yet known how far the inclusion host ability of 1 will extend, attempts to obtain crystalline samples from solvents devoid of H-bond acceptors (e.g., CHCl3, CH2Cl2, C6H6) have been unsuccessful. It should be noted, however, that the possibility that guest inclusion simply facilitates more efficient packing (as a function of size and shape, irrespective of weak H-bonding interactions) cannot be excluded from consideration. Indeed, the identification of polymorphic modifications in solvate-free 1 suggests that optimal crystalline packing may be difficult to achieve in the absence of included guests.18 The design of artificial organic zeolites is of great contemporary interest in the crystal engineering community and may lead to novel separation/molecular storage devices and catalysts.6,9 The pillared lamellar structure observed in connection with this study may be significant, then, in that the ability of triaroylbenzenes to assemble into potentially functional materials is established. Thermochemical characterization of the inclusion complexes described above is underway, as is work aimed at defining the factors responsible for poylmorphism and pseudopolymorphism in 1 and its congeners. Efforts directed toward further exploiting the propensity of triaroylbenzenes to form extended supramolecular networks continues. The incorporation of triaroylbenzene derivatives into more robust crystalline assemblies (for example, as components of coordination polymers) with the goal of achieving stable open networks is also a subject of ongoing research.19 In conclusion, the inclusion complexes formed between 1 and various solvents imbued with H-bond acceptors further demonstrates the significant role weak hydrogen bonding can play in influencing (and enforcing) supramolecular isomerism. In addition, this work further highlights the versatility of triaroylbenzene derivatives as useful
Figure 3. The host-guest bifurcated C-H‚‚‚O hydrogen bonding in (a) 1‚EtOAc (2.47 Å, 177.0° and 2.285 Å, 165.3°), (b) 1‚3-pentanone (2.49 Å, 136.6° and 2.44 Å, 142.2°), and (c) 1‚MeNO2 (2.70 Å, 172.0° and 2.51 Å, 159.8°).
Communications
Crystal Growth & Design, Vol. 4, No. 4, 2004 653
probes for the study of important supramolecular solidstate phenomena. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research (ACS PRF No. 37468AC4).
(12)
Supporting Information Available: X-ray data with details of refinement procedure (cif files). This material is available free of charge via the Internet at http://pubs.acs.org.
References (1) Comprehensive Supramolecular Chemistry; Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Vo¨gtle, F., Eds.; Pergamon: Oxford, U.K., 1996; Vol. 6. (2) Nangia, A. Curr. Opin. Solid State Mater. Sci. 2001, 5, 115122. (3) (a) MacGillivray, L. R.; Atwood, J. L. Angew. Chem., Int. Ed. 1999, 38, 1018-1033. (b) Langley, P. J.; Hulliger, J. Chem. Soc. Rev. 1999, 28, 279-291. (c) Aoyama, Y. Top. Curr. Chem. 1998, 198, 131-161. (4) (a) Toda, F. Aust. J. Chem. 2001, 54, 573-582. (b) Frisˇcˇicˇ, T.; MacGillivray, L. R. Chem. Commun. 2003, 1306-1307. (5) (a) Zaworotko, M. J. Chem. Commun. 2001, 1-9. (b) Bourne, S. A.; Lu, J.; Moulton, B.; Zaworotko, M. J. Chem. Commun. 2001, 861-862. (6) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; Keefe, M. O.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319-330. (7) For examples, see: (a) Inclusion Compounds; Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Eds.; Oxford University Press: Oxford, U.K., 1991; Vol. 4. (b) Bishop, R. Synlett 1999, 1351. (8) (a) Desiraju, G. R. Science 1997, 278, 404-405. (b) Bernstein, J. Polymorphism in Molecular Crystals; Clarendon: Oxford, U.K., 2002. (9) Desiraju, G. R. Crystal Engineering: The Design of Organic Solids; Elsevier: Amsterdam, 1989. (10) Kumar, V. S. S.; Pigge, F. C.; Rath, N. P. New J. Chem. 2003, 27, 1554-1556. (11) (a) Kumar, V. S. S.; Pigge, F. C.; Rath, N. P. CrystEngComm 2004, 6, 102-105. (b) Pigge, F. C.; Ghasedi, F.; Zheng, Z.; Rath, N. P.; Nichols, G.; Chickos, J. S. J. Chem. Soc., Perkin Trans. 2 2000, 2458-2464. (c) Pigge, F. C.; Zheng, Z.; Rath,
(13)
(14) (15) (16)
(17)
(18)
(19)
N. P. New J. Chem. 2000, 24, 183-185. (d) Pigge, F. C.; Ghasedi, F.; Rath, N. P. Tetrahedron Lett. 1999, 40, 80458048. Crystals of 1‚EtOAc, 1‚3-pentanone, and 1‚MeNO2 were grown by slow evaporation of neat solutions (room temperature). 1‚EtOAc: (C30H15N3O3)‚(C4H7O2), P1 h , a ) 8.7512(9), b ) 11.2046(11), c ) 14.7252(14) Å, R ) 89.930(5)°, β ) 85.400(5)°, γ ) 71.494(5)°, V ) 1364.3(2) Å3, Z ) 2, Dc ) 1.347 g cm-3, T ) 165 K, F(000) ) 576, λ ) 0.710 73 Å, µ ) 0.092, R1 ) 0.0613 for 5129 Fo > 2σ(Fo), wR ) 0.1726. 1‚ 3-pentanone: (C30H15N3O3)‚(C5H10O), P1 h , a ) 8.3516(4), b ) 11.5882(5), c ) 14.8865(7) Å, R ) 88.831(3)°, β ) 85.666(3)°, γ ) 76.197(3)°, V ) 1395.11(11) Å3, Z ) 2, Dc ) 1.313 g cm-3, T ) 165 K, F(000) ) 576, λ ) 0.710 73 Å, µ ) 0.087, R1 ) 0.0442 for 4219 Fo > 2σ(Fo), wR ) 0.0945. 1‚MeNO2: (C30H15N3O3)‚(CH3NO2)1.5, P1 h , a ) 8.782(1), b ) 11.036(1), c ) 14.664(2) Å, R ) 88.95(1)°, β ) 84.30(1)°, γ ) 70.60(1)°, 3 V ) 1333.8(2) Å , Z ) 2, Dc ) 1.387 g cm-3, T ) 165 K, F(000) ) 576, λ ) 0.710 73 Å, µ ) 0.099, R1 ) 0.0631 for 4818 Fo > 2σ(Fo), wR ) 0.195. The terms “host” and “guest” are used to delineate the molecular components of these inclusion complexes. The triaroylbenzene 1 has arbitrarily been assigned the role of “host”. Hunter, C. A. Chem. Soc. Rev. 1994, 23, 101-109. Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in Structural Chemistry and Biology; Oxford University Press: Oxford, U.K., 1999. (a) Moulton, B.; Zaworotko, M. J. Chem. Rev. 2001, 101, 1629-1658. (b) Ma, B.-Q.; Coppens, P. Chem. Commun. 2003, 504-505. (c) MacGillivray, L. R.; Reid, J. L.; Ripmeester, J. A. Chem. Commun. 2001, 1034-1035. (d) MacGillivray, L. R.; Papaefstathiou, G. S.; Reid, J. L.; Ripmeester, J. A. Cryst. Growth Des. 2001, 1, 373-375. (a) Thaimattam, R.; Xue, F.; Sarma, J. A. R. P.; Mak, T. C. W.; Desiraju, G. R. J. Am. Chem. Soc. 2001, 123, 44324445. (b) Kumar, V. S. S.; Nangia, A.; Kirchner, M. T.; Boese, R. New. J. Chem. 2003, 27, 224-226. For additional discussions along these lines, see: (a) Aakero¨y, C. B.; Beatty, A. M.; Helfrich, B. A.; Nieuwenhuyzen, M. Cryst. Growth Des. 2003, 3, 159-165. (b) Soldatov, D. V.; Ripmeester, J. A. Chem.sEur. J. 2001, 7, 2979-2994. Pigge, F. C.; Burgard, M. D.; Rath, N. P. Cryst. Growth Des. 2003, 3, 331-337.
CG034252Y
