Bidirectional association of branched noncovalent complexes of tetrazoles and 1,3,5-tris(4,5-dihydroimidazol-2-yl)benzene in solution

Journal of Organic Chemistry

Volumn 64, Issue 17, 1999, Pages 6425-6433

  Kraft, Arno ^a,c   Osterod, Frank ^a,c   Fröhlich, Roland ^b  

^a HEINRICH HEINE UNIVERSITY   (Germany)

^b UNIVERSITY OF MÜNSTER   (Germany)

^c HERIOT WATT UNIVERSITY   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

BENZENE DERIVATIVE; TETRAZOLE DERIVATIVE;

ARTICLE; BINDING AFFINITY; COMPLEX FORMATION; CRYSTAL STRUCTURE; NUCLEAR MAGNETIC RESONANCE; ORGANIC CHEMISTRY; VAPOR;

EID: 0033588141     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo990830z     Document Type: Article

References (67)

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5. For recent examples, see: (a) Yang, J.; Marenday, J.-L.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1994, 35, 3665-3668. (b) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995, 28, 37-44. (c) Marsh, A.; Silvestri, M.; Lehn, J.-M. Chem. Commun. 1996, 1527-1528. (d) Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Science 1996, 271, 1095-1098. (e) Huck, W. T. S.; Hulst, R.; Timmerman, P.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1997, 36, 1006-1008. (f) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276, 384-389. (g) Zimmerman, S. C.; Wang, Y.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1998, 120, 2172-2173. (h) Kenda, B.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1998, 37, 3152-3156. (i) Park, H. S.; Lin, Q.; Hamilton, A. D. J. Am. Chem. Soc. 1999, 121, 8-13.
6. For recent examples, see: (a) Yang, J.; Marenday, J.-L.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1994, 35, 3665-3668. (b) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995, 28, 37-44. (c) Marsh, A.; Silvestri, M.; Lehn, J.-M. Chem. Commun. 1996, 1527- 1528. (d) Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Science 1996, 271, 1095-1098. (e) Huck, W. T. S.; Hulst, R.; Timmerman, P.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1997, 36, 1006-1008. (f) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276, 384-389. (g) Zimmerman, S. C.; Wang, Y.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1998, 120, 2172-2173. (h) Kenda, B.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1998, 37, 3152-3156. (i) Park, H. S.; Lin, Q.; Hamilton, A. D. J. Am. Chem. Soc. 1999, 121, 8-13.
7. For recent examples, see: (a) Yang, J.; Marenday, J.-L.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1994, 35, 3665-3668. (b) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995, 28, 37-44. (c) Marsh, A.; Silvestri, M.; Lehn, J.-M. Chem. Commun. 1996, 1527- 1528. (d) Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Science 1996, 271, 1095-1098. (e) Huck, W. T. S.; Hulst, R.; Timmerman, P.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1997, 36, 1006-1008. (f) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276, 384-389. (g) Zimmerman, S. C.; Wang, Y.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1998, 120, 2172-2173. (h) Kenda, B.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1998, 37, 3152-3156. (i) Park, H. S.; Lin, Q.; Hamilton, A. D. J. Am. Chem. Soc. 1999, 121, 8-13.
8. For recent examples, see: (a) Yang, J.; Marenday, J.-L.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1994, 35, 3665-3668. (b) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995, 28, 37-44. (c) Marsh, A.; Silvestri, M.; Lehn, J.-M. Chem. Commun. 1996, 1527- 1528. (d) Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Science 1996, 271, 1095-1098. (e) Huck, W. T. S.; Hulst, R.; Timmerman, P.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1997, 36, 1006-1008. (f) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276, 384-389. (g) Zimmerman, S. C.; Wang, Y.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1998, 120, 2172-2173. (h) Kenda, B.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1998, 37, 3152-3156. (i) Park, H. S.; Lin, Q.; Hamilton, A. D. J. Am. Chem. Soc. 1999, 121, 8-13.
9. For recent examples, see: (a) Yang, J.; Marenday, J.-L.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1994, 35, 3665-3668. (b) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995, 28, 37-44. (c) Marsh, A.; Silvestri, M.; Lehn, J.-M. Chem. Commun. 1996, 1527- 1528. (d) Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Science 1996, 271, 1095-1098. (e) Huck, W. T. S.; Hulst, R.; Timmerman, P.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1997, 36, 1006-1008. (f) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276, 384-389. (g) Zimmerman, S. C.; Wang, Y.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1998, 120, 2172-2173. (h) Kenda, B.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1998, 37, 3152-3156. (i) Park, H. S.; Lin, Q.; Hamilton, A. D. J. Am. Chem. Soc. 1999, 121, 8-13.
10. For recent examples, see: (a) Yang, J.; Marenday, J.-L.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1994, 35, 3665-3668. (b) Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res. 1995, 28, 37-44. (c) Marsh, A.; Silvestri, M.; Lehn, J.-M. Chem. Commun. 1996, 1527- 1528. (d) Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Science 1996, 271, 1095-1098. (e) Huck, W. T. S.; Hulst, R.; Timmerman, P.; van Veggel, F. C. J. M.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1997, 36, 1006-1008. (f) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276, 384-389. (g) Zimmerman, S. C.; Wang, Y.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1998, 120, 2172-2173. (h) Kenda, B.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1998, 37, 3152-3156. (i) Park, H. S.; Lin, Q.; Hamilton, A. D. J. Am. Chem. Soc. 1999, 121, 8-13.
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18. a values are large enough for proton transfer to be expected in polar solvents. In fact, neutralization takes place in aqueous solution on combining 1 and 3 equiv of a water-soluble tetrazole.
19. a values are large enough for proton transfer to be expected in polar solvents. In fact, neutralization takes place in aqueous solution on combining 1 and 3 equiv of a water-soluble tetrazole.
20. (a) Kraft, A.; Fröhlich, R. Chem. Commun. 1998, 1085-1086.
21. (b) Kraft, A. J. Chem. Soc., Perkin Trans. 1 1999, 705-714.
22. For a related report on carboxylic acid complexes with a tris(tetrahydropyrimidine) base see: (c) Kraft, A.; Reichert, A. Tetrahedron 1999, 55, 3923-3930.
23. Such a strategy has previously been used for ensuring the solubility of shape-persistent dendrimers and other large disk-shaped molecules: (a) Moore, J. S. Acc. Chem. Res. 1997, 30, 402-413. (b) Palmans, A. R. A.; Vekemans, J. A. J. M.; Fischer, H.; Hikmet, R. A.; Meijer, E. W. Chem. Eur. J. 1997, 3, 300-307.
24. Such a strategy has previously been used for ensuring the solubility of shape-persistent dendrimers and other large disk-shaped molecules: (a) Moore, J. S. Acc. Chem. Res. 1997, 30, 402-413. (b) Palmans, A. R. A.; Vekemans, J. A. J. M.; Fischer, H.; Hikmet, R. A.; Meijer, E. W. Chem. Eur. J. 1997, 3, 300-307.
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31. For applications of tetrazoles as intermediates in the synthesis of 1,3,4-oxadiazole-based electron-transporting materials, see: (a) Bettenhausen, J.; Strohriegl, P. Macromol. Rapid Commun. 1996, 17, 623-631. (b) Bettenhausen, J.; Strohriegl, P. Adv. Mater. 1996, 8, 507-510.
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35. An alternative binding geometry for some or all of the tetrazole ligands cannot be entirely excluded where the heterocycle's second and third nitrogen atoms hydrogen bond to the imidazoline-NH groups. Although we failed to obtain crystals of a tetrazole complex other than 12a that were suitable for X-ray crystallography, such a binding arrangement was found in the crystal structures of two related complexes between a tetrazole and 1,3,5-tris(3,4,5,6-tetrahydropyrimidin-2-yl)benzene (A. Kraft, R. Fröhlich, unpublished results).
36. A similar observation has been made for polymeric amidine bases which adhere to phosphated and passivated metal surfaces: Wulff, G.; Schönfeld, R. Adv. Mater. 1998, 10, 957-959.
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40. 3OD), and suggests that tetrazole complexes dissociate completely in these solvents.
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45. stacking was furthermore consistent with the increase in molar mass measured by VPO.
46. 2 triplet of 12g or the AA′XX′ signals of the para-disubstituted phenylenes of 12h) became then apparent at higher concentration (that is, when stack formation started to play a role), and were attributed to hindered rotation around the aryl-tetrazole C-C single bond. For a previous discussion of the rotational barrier around the C(aryl)-C(tetrazolate) bond, see: Alkorta, I.; Rozas, I.; Elguero, J. J. Chem. Soc., Perkin Trans. 2 1998, 2671-2675.
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49. After being heated from room temperature to above the melting point, complex 12g exhibited a very fine texture. Slow (between 0.2 and 0.5 °C/min) cooling from the isotropic liquid phase resulted in the growth of homeotropic digitized stars. Such a dendritic growth was followed by the development of birefringent pseudofocal conic or fanlike textures. Although this is characteristic for the formation of a columnar liquid-crystalline mesophase, the required low cooling rates caused rapid decomposition and discoloration that led to the disappearance of the developing texture owing to a continuous drop in the clearing temperature (Kraft, A.; Osterod, F.; Peters, L.; Reichert, A. Polym. Mater. Sci. Eng. 1999, 80, 18-19). Investigations toward the improvement of thermal stability and X-ray diffraction studies of potentially liquid-crystalline carboxylic acid and tetrazole complexes with 1 are underway.
50. Pesak, D. J.; Moore, J. S. Angew. Chem., Int. Ed. Engl. 1997, 36, 1636-1639.
51. Similarly, a polystyrene-oligothiophene-polystyrene triblock copolymer also shows aggregation in solution owing to an extended planar π-system: Hempenius, M. A.; Langeveld-Voss, B. M. W.; van Haare, J. A. E. H.; Janssen, R. A. J.; Sheiko, S. S.; Spatz, J. P.; Möller, M.; Meijer, E. W. J. Am. Chem. Soc. 1998, 120, 2798-2804.
52. This is illustrated by a crystal structure of 5-(4-hydroxyphenyl)-tetrazole: Gallardo, H.; Begnini, I. M.; Vencato, I. Acta Crystallogr. 1997, C53, 143-144.
53. C.f. Tokuhisa, H.; Era, M.; Tsutsui, T. Adv. Mater. 1998, 10, 404-407.
54. It should be taken into account that π-π interactions between electron-deficient aromatic systems (such as with the 1,3,4-oxadiazole-containing ligand 11a) are very favorable and may equally promote stacking interactions: (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525-5534. (b) Zhang, J.; Moore, J. S. Ibid. 1992, 114, 9701-9702. (c) Cozzi, F.; Cinquini, M.; Annuziata, R.; Siegel, J. S. Ibid. 1993, 115, 5330-5331. (d) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-1586. (e) Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019-1027. (f) Tobe, Y.; Utsumi, N.; Kawabata, K.; Naemura, K. Tetrahedron Lett. 1996, 37, 9325- 9328.
55. It should be taken into account that π-π interactions between electron-deficient aromatic systems (such as with the 1,3,4-oxadiazole- containing ligand 11a) are very favorable and may equally promote stacking interactions: (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525-5534. (b) Zhang, J.; Moore, J. S. Ibid. 1992, 114, 9701-9702. (c) Cozzi, F.; Cinquini, M.; Annuziata, R.; Siegel, J. S. Ibid. 1993, 115, 5330-5331. (d) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-1586. (e) Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019-1027. (f) Tobe, Y.; Utsumi, N.; Kawabata, K.; Naemura, K. Tetrahedron Lett. 1996, 37, 9325- 9328.
56. It should be taken into account that π-π interactions between electron-deficient aromatic systems (such as with the 1,3,4-oxadiazole- containing ligand 11a) are very favorable and may equally promote stacking interactions: (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525-5534. (b) Zhang, J.; Moore, J. S. Ibid. 1992, 114, 9701-9702. (c) Cozzi, F.; Cinquini, M.; Annuziata, R.; Siegel, J. S. Ibid. 1993, 115, 5330-5331. (d) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-1586. (e) Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019-1027. (f) Tobe, Y.; Utsumi, N.; Kawabata, K.; Naemura, K. Tetrahedron Lett. 1996, 37, 9325- 9328.
57. It should be taken into account that π-π interactions between electron-deficient aromatic systems (such as with the 1,3,4-oxadiazole- containing ligand 11a) are very favorable and may equally promote stacking interactions: (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525-5534. (b) Zhang, J.; Moore, J. S. Ibid. 1992, 114, 9701-9702. (c) Cozzi, F.; Cinquini, M.; Annuziata, R.; Siegel, J. S. Ibid. 1993, 115, 5330-5331. (d) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-1586. (e) Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019-1027. (f) Tobe, Y.; Utsumi, N.; Kawabata, K.; Naemura, K. Tetrahedron Lett. 1996, 37, 9325- 9328.
58. It should be taken into account that π-π interactions between electron-deficient aromatic systems (such as with the 1,3,4-oxadiazole- containing ligand 11a) are very favorable and may equally promote stacking interactions: (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525-5534. (b) Zhang, J.; Moore, J. S. Ibid. 1992, 114, 9701-9702. (c) Cozzi, F.; Cinquini, M.; Annuziata, R.; Siegel, J. S. Ibid. 1993, 115, 5330-5331. (d) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-1586. (e) Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019-1027. (f) Tobe, Y.; Utsumi, N.; Kawabata, K.; Naemura, K. Tetrahedron Lett. 1996, 37, 9325- 9328.
59. It should be taken into account that π-π interactions between electron-deficient aromatic systems (such as with the 1,3,4-oxadiazole- containing ligand 11a) are very favorable and may equally promote stacking interactions: (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525-5534. (b) Zhang, J.; Moore, J. S. Ibid. 1992, 114, 9701-9702. (c) Cozzi, F.; Cinquini, M.; Annuziata, R.; Siegel, J. S. Ibid. 1993, 115, 5330-5331. (d) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-1586. (e) Shetty, A. S.; Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019-1027. (f) Tobe, Y.; Utsumi, N.; Kawabata, K.; Naemura, K. Tetrahedron Lett. 1996, 37, 9325-9328.
60. Stacking interactions are also well-known for columnar liquid-crystalline mesophases of suitably substituted condensed aromatic compounds. For recent examples, see: (a) Reference 8b. (b) van de Craats, A. M.; Warmann, J. M.; Müllen, K.; Geerts, Y.; Brand, J. D. Adv. Mater. 1998, 10, 36-38. Columnar liquid-crystalline mesophases were already reported for a number of self-assembled compounds: (c) Mariani, P.; Mazabard, C.; Garbesi, A.; Spada, G. P. J. Am. Chem. Soc. 1989, 111, 6369-6373. (d) Kleppinger, R.; Lillya, C. P.; Yang, C. J. Am. Chem. Soc. 1997, 119, 4097-4102. (e) Beginn, U.; Zipp, G.; Möller, M.; Johansson, G.; Percec, V. Macromol. Chem. Phys. 1997, 198, 2839-2852. (f) Suárez, M.; Lehn, J.-M.; Zimmerman, S. C.; Skoulios, A.; Heinrich, B. J. Am. Chem. Soc. 1998, 120, 9526-9532 and references therein.
61. Stacking interactions are also well-known for columnar liquid- crystalline mesophases of suitably substituted condensed aromatic compounds. For recent examples, see: (a) Reference 8b. (b) van de Craats, A. M.; Warmann, J. M.; Müllen, K.; Geerts, Y.; Brand, J. D. Adv. Mater. 1998, 10, 36-38. Columnar liquid-crystalline mesophases were already reported for a number of self-assembled compounds: (c) Mariani, P.; Mazabard, C.; Garbesi, A.; Spada, G. P. J. Am. Chem. Soc. 1989, 111, 6369-6373. (d) Kleppinger, R.; Lillya, C. P.; Yang, C. J. Am. Chem. Soc. 1997, 119, 4097-4102. (e) Beginn, U.; Zipp, G.; Möller, M.; Johansson, G.; Percec, V. Macromol. Chem. Phys. 1997, 198, 2839-2852. (f) Suárez, M.; Lehn, J.-M.; Zimmerman, S. C.; Skoulios, A.; Heinrich, B. J. Am. Chem. Soc. 1998, 120, 9526-9532 and references therein.
62. Stacking interactions are also well-known for columnar liquid- crystalline mesophases of suitably substituted condensed aromatic compounds. For recent examples, see: (a) Reference 8b. (b) van de Craats, A. M.; Warmann, J. M.; Müllen, K.; Geerts, Y.; Brand, J. D. Adv. Mater. 1998, 10, 36-38. Columnar liquid-crystalline mesophases were already reported for a number of self-assembled compounds: (c) Mariani, P.; Mazabard, C.; Garbesi, A.; Spada, G. P. J. Am. Chem. Soc. 1989, 111, 6369-6373. (d) Kleppinger, R.; Lillya, C. P.; Yang, C. J. Am. Chem. Soc. 1997, 119, 4097-4102. (e) Beginn, U.; Zipp, G.; Möller, M.; Johansson, G.; Percec, V. Macromol. Chem. Phys. 1997, 198, 2839-2852. (f) Suárez, M.; Lehn, J.-M.; Zimmerman, S. C.; Skoulios, A.; Heinrich, B. J. Am. Chem. Soc. 1998, 120, 9526-9532 and references therein.
63. Stacking interactions are also well-known for columnar liquid- crystalline mesophases of suitably substituted condensed aromatic compounds. For recent examples, see: (a) Reference 8b. (b) van de Craats, A. M.; Warmann, J. M.; Müllen, K.; Geerts, Y.; Brand, J. D. Adv. Mater. 1998, 10, 36-38. Columnar liquid-crystalline mesophases were already reported for a number of self-assembled compounds: (c) Mariani, P.; Mazabard, C.; Garbesi, A.; Spada, G. P. J. Am. Chem. Soc. 1989, 111, 6369-6373. (d) Kleppinger, R.; Lillya, C. P.; Yang, C. J. Am. Chem. Soc. 1997, 119, 4097-4102. (e) Beginn, U.; Zipp, G.; Möller, M.; Johansson, G.; Percec, V. Macromol. Chem. Phys. 1997, 198, 2839-2852. (f) Suárez, M.; Lehn, J.-M.; Zimmerman, S. C.; Skoulios, A.; Heinrich, B. J. Am. Chem. Soc. 1998, 120, 9526-9532 and references therein.
64. Stacking interactions are also well-known for columnar liquid- crystalline mesophases of suitably substituted condensed aromatic compounds. For recent examples, see: (a) Reference 8b. (b) van de Craats, A. M.; Warmann, J. M.; Müllen, K.; Geerts, Y.; Brand, J. D. Adv. Mater. 1998, 10, 36-38. Columnar liquid-crystalline mesophases were already reported for a number of self-assembled compounds: (c) Mariani, P.; Mazabard, C.; Garbesi, A.; Spada, G. P. J. Am. Chem. Soc. 1989, 111, 6369-6373. (d) Kleppinger, R.; Lillya, C. P.; Yang, C. J. Am. Chem. Soc. 1997, 119, 4097-4102. (e) Beginn, U.; Zipp, G.; Möller, M.; Johansson, G.; Percec, V. Macromol. Chem. Phys. 1997, 198, 2839-2852. (f) Suárez, M.; Lehn, J.-M.; Zimmerman, S. C.; Skoulios, A.; Heinrich, B. J. Am. Chem. Soc. 1998, 120, 9526-9532 and references therein.
65. Stacking interactions are also well-known for columnar liquid- crystalline mesophases of suitably substituted condensed aromatic compounds. For recent examples, see: (a) Reference 8b. (b) van de Craats, A. M.; Warmann, J. M.; Müllen, K.; Geerts, Y.; Brand, J. D. Adv. Mater. 1998, 10, 36-38. Columnar liquid-crystalline mesophases were already reported for a number of self-assembled compounds: (c) Mariani, P.; Mazabard, C.; Garbesi, A.; Spada, G. P. J. Am. Chem. Soc. 1989, 111, 6369-6373. (d) Kleppinger, R.; Lillya, C. P.; Yang, C. J. Am. Chem. Soc. 1997, 119, 4097-4102. (e) Beginn, U.; Zipp, G.; Möller, M.; Johansson, G.; Percec, V. Macromol. Chem. Phys. 1997, 198, 2839-2852. (f) Suárez, M.; Lehn, J.-M.; Zimmerman, S. C.; Skoulios, A.; Heinrich, B. J. Am. Chem. Soc. 1998, 120, 9526-9532 and references therein.
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