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A new organogelator based on 1,3,5-tris(phenylisoxazolyl)benzene
Synthetic Metals 159 (2009) 821–826
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A new organogelator based on 1,3,5-tris(phenylisoxazolyl)benzene Takeharu Haino ∗ , Hiroshi Saito Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
a r t i c l e
i n f o
Article history: Received 21 November 2008 Received in revised form 24 December 2008 Accepted 10 January 2009 Available online 8 February 2009 Keywords: Gel Self-assembly Aromatic stacking
a b s t r a c t 1,3,5-Tris(phenylisoxazolyl)benzene derivatives possessing polar and nonpolar side chains were synthesized. The microscopic gel morphology was confirmed by using FESEM, TEM, and XRD measurements. The amphiphilic nature of the tris(phenylisoxazolyl)benzene derivative gives rise to the lamellar structure, responsible for the formation of the fibrous bundles. The intertwined networks of the bundles immobilize the alcoholic solvents, and result in the formation of the organogels. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Organogels are thermally reversible viscoelastic materials, formed by the self-assembly of gelators via noncovalent interactions [1–6]. The aggregation of gelators forms the entangled fibers, giving rise to the three-dimensional network. Solvent molecules are immobilized in voids of the network, which is responsible for gelation. Some amide [7], urea [8] and saccharide [9] derivatives, and steroid [10] compounds have been reported as a gelator, and their gelation behaviors have been intensively studied so far. Recently, low-molecular-weight gelators have received much attention not only for their gelation behavior, but also for their formation of welldefined nanostructures such as fibers, sheets and helical structures via self-assembly. In particular, the nanostructures formed by conjugated molecules have been widely studies for the construction of functional materials [11–14]. Small aromatics, such as benzene, phenylene, and triphenylene create nanometric unique organization with the aid of hydrogen bonding to afford a new class of functional supramolecular assemblies. There is a limited number of the small aromatic gelators that can assemble to form fibrous gels without hydrogen bonds in organic solvents [15–19]. Previously, we have reported that tris(phenylisoxazolyl)benzene derivatives act as a good gelator of various organic solvents. [20] The solution studies of the assembly for the gelators have revealed that the molecular stacks driven by the local dipole–dipole interactions of the isoxazole moieties are responsible for the formation of the fibrous morphology in their gel state.
∗ Corresponding author. Tel.: +81 82 424 7427; fax: +81 82 424 0724. E-mail address: [email protected] (T. Haino). 0379-6779/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2009.01.017
In this paper, we demonstrate that macromolecular properties and solid state organization of the molecular stacks are uniquely modulated by the amphiphilic nature of the side chains. Tris(phenylisoxazolyl)benzene derivatives 1–4 possessing alkyl chains and polar triethyleneglycol monomethyl ether (mTEG) or methoxy groups as the side chains are synthesized, and their selfassembling behaviors in bulk and solution are studied (Fig. 1). 2. Results and discussion The synthesis of tris(phenylisoxazolyl)benzenes 1–4 is shown in Scheme 1. 1,3-Dipolar cycloaddition of 1,3,5-triethynylbenzene 5 with the nitriloxide prepared in situ from hydroximinoyl chloride 6 by treatment of triethylamine gave compound 9. Subsequent treatment of 9 with hydroximinoyl chloride 7 [21] and triethylamine afforded desired product 1 in 74% yield. The nitriloxide resulted from hydroximinoyl chloride 12 reacted with 9 to produce product 3 in 76% yield. Reaction of 7 and 5 with triethylamine led to compound 10, which was converted to compound 2 through the reaction with 6 in 31% yield. Reaction of 5 with hydroximinoyl chloride 8 [21] in the presence of triethylamine gave 11. Following reaction with 7 afforded compound 4 in 70% yield. The gelation ability of compounds 1–4 was studied in a variety of organic solvents (Table 1). Compound 1 selectively formed the gels only in the alcoholic solvents, whereas compounds 2 and 3 did not act as a gelator in the solvents. Compound 4 produced the gels in some of the alcoholic solvents. These results indicate the role of the side chains in the gelation ability. The two mTEG side chains of 2 increase its solubility in a variety of solvents; thus, the strong solvation of the two mTEG chains probably brings about the low intermolecular affinity in the self-association. As compared with the gelation properties of 1, 3 and 4, the two long alkyl chains and
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Scheme 1. Synthesis of the unsymmetric tris(phenylisoxazolyl)benzene derivatives.
Fig. 1. Unsymmetrical tris(phenylisoxazolyl)benzene derivatives 1–4.
one mTEG group are necessary incorporation on the aromatic core for creating a good gelator; in fact, the absence of the decyloxy group takes away the gelation ability from 3 while the incorporation of methoxy group instead of mTEG one obviously reduces the stability of the gels of 4. To gain a macroscopic aspect of the gels, the butanol xerogels of 1 and 4 were studied by using field emission scanning electron microscopy. The FESEM images of the xerogels of 1 display the formation of the three-dimensional entangled networks (Fig. 2a) in which the tape-like morphology is observed with widths of
Fig. 2. FESEM images of the xerogels of 1 (a and b) and 4 (c and d) from butanol, and the film prepared from butanol solution of 3 (e and f).
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Fig. 3. TEM images (a and b) of the xerogel of 1, and the electron diffraction (c) of b.
500–1500 nm (Fig. 2b). The xerogels of 4 create the fibrous morphology (Fig. 2c), and the fibers with diameters of 150–300 nm bundle and create the network (Fig. 2d). Both the xerogels have the well-developed structures with many voids responsible for hold-
Table 1 Gelation properties of 1–4 in a variety of solvents. Solvent
1
2
3
4
Ethanol Propanol iso-Propanol Allyl alcohol Propargyl alcohol 1-Butanol 2-Methyl-l-propanol 2-Butanol tert-Butanol tert-Amyl alcohol 1-Hexanol 1-Octanol 1-Decanol 1-Dodecanol Benzyl alcohol Hexane Cycrohexane Benzene Chloroform Ether Acetone Ethylacetate Acetonitrile THF DMF DMSO
I S S P G(20) G(25) G(10) P G(10) P G(30) G(30) G(30) G(30) S I I S S S S S I S S S
S S S S S S S S S S S S S S S I S S S S S S S S S S
P S S S S S P P P S P P P P S I P P S S S S P S S S
I S S P P G(35) G(20) P pG P pG pG pG PG P I G(8) S S P S S I S P S
G: gel; pG: partial gel; S: solution; I: insoluble; P: precipitation. The critical gelation concentration (mg mL−1 ) is shown in a parenthesis.
ing and immobilizing solvent molecules. In contrast, the images of 3 show the lumps without forming any well-defined structures (Fig. 2e and f). This microscopic aspect of the xerogels provides that the three-dimensional networks formed by the intertwined fibers immobilize the organic solvents and result in the formation of the gels. Transmission electron microscopy (TEM) observation of the xerogel of 1 gives an insight into the higher level of the molec-
Fig. 4. 1 H NMR spectra of 1 at the concentration of: (a) 0.48 mmol L−1 , (b) 1.4 mmol L−1 , (c) 5.8 mmol L−1 , (d) 25 mmol L−1 , and (e) 50 mmol L−1 at 290 K in chloroform-d1 .
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Fig. 5. XRD patterns of the xerogels of: (a) 1 and (b) 4, and the film (c) of 3.
ular arrangement. Fig. 3a shows well developed network made up of the tape-like fibers with width of about 300 nm (Fig. 3b), the electron diffraction pattern of which display well-defined diffraction spots with d-spacing of 4.2 Å (Fig. 3c), suggesting that compound 1 assembles to form the loose stacks via – stacking interaction. The – stacking interaction of the tris(phenylisoxazolyl) benzene unit in solution is evidenced by the self-association study using 1 H NMR spectroscopy. When the chloroform solution of 1 was concentrated from 0.48 to 50 mmol L−1 , the aromatic protons shifted upfield (Fig. 4). Nonlinear curve fitting analysis [22] gave self-association constant (KE = 3.6 ± 0.2 L mol−1 ) and estimated induced upfield shifts of the aromatic protons (Ha,b : −1.07, Hc,d : −0.84, He,f : −0.78, Hg : −0.50, and Hh : −0.60 ppm). The other derivatives 2–4 also formed the molecular stacks with the association constants (2: 2.8 ± 0.3 L mol−1 , 3: 2.8 ± 0.2 L mol−1 , 4: 4.4 ± 0.2 L mol−1 ) and the upfield shifts of their aromatic protons. This is indicative of the formation of the molecular stacks in which the aromatic protons are shielded by the aromatic rings of the adjacent molecules. XRD measurements were performed on the xerogels of compounds 1, 3 and 4 to investigate their assembled structures in the gel state. The XRD pattern of the xerogel of 1 show the periodical reflection peaks at d-spacings 27.6 and 13.8 Å in small-angle region (Fig. 5a); the ratio of 1:1/2 indicates that 1 indeed assembles into a lamellar organization [23–29]. Additionally, the XRD pattern in the wide-angle region displays the diffuse band originated from the molten long alkyl chain, and the reflection peak at d-spacing 3.92 Å is typical – stacking. The long spacing 27.6 Å is compatible with the fully extended molecular length (Fig. 6a) of 1; thus, assembling of the molecules gives rise to the fibrous stacks that bundle to form the tape-like morphology (Fig. 7). In contrast, the XRD pattern of the xerogel 4 exhibits only broad and weak peak at 20.6 Å (Fig. 5b) that matches the molecular length (Fig. 6b), suggesting that a loose lamellar organization seems to be maintained. In the case of the film of 3, any periodicity is not found; perhaps the shorter alkyl chains are unable to create van der Waals interactions enough to give rise to a bundle of the molecular stacks of 3. 3. Conclusion
Fig. 6. Molecular modeling of 1 and 4 calculated by MacroModel V. 9.1. The alkyl chains are omitted for clarity.
In summary, we have demonstrated the systematic investigation of the gelation properties for tris(phenylisoxazolyl)benzene
Fig. 7. Plausible molecular array of 1 in a lamellar organization.
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possessing the polar and nonpolar alkyl chains. Compounds 1–4 assemble to form the molecular stacks in solution; however, further stacking to create the macromolecular morphology needs the assistance of the van der Waals interaction of the long alkyl chains and microphase separation induced by mTEG groups. 4. Experimental 4.1. General All chemicals were used without further purification unless otherwise specified. Proton and carbon NMR spectra were recorded on Varian Mercury-300 or JEOL LAMBDA-500 spectrometers. IR spectra were obtained on a JASCO FT/IR-420S. UV–vis absorption spectra were measured on a JASCO V-560 spectrometer. Mass spectra were reported with a JEOL JMX-SX 102A. Melting points were measured with Yanagimoto micro-melting point apparatus and uncorrected. Elemental analyses were performed on a PerkinElmer 2400CHN elemental analyzer. FESEM was performed on a Hitachi S-5200 system. TEM images were obtained on a JEOL JEM-2010. XRD measurements were carried out by using RIGAKU RINT-2100V. 4.2. Gelation test Compounds 1–4 were placed in capped glass tube with a solvent, heated until the solid was dissolved. The mixture was slowly cooled to room temperature, and left for 2 h at this temperature. The formation of gels was confirmed by the absence of fluid solvents when the glass tube was inverted. 4.2.1. 4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy} benzohydroximinoyl chloride (6) To a solution of 4-{2-[2-(2-methoxyethoxy)-ethoxy]ethoxy}benzaldehyde oxime in DMF (2.6 mL) was added N-chlorosuccinimide (388 mg, 2.60 mmol). After stirred at room temperature for 1 h, the reaction mixture was poured into 10 volumes of water and extracted with ether. The organic layer was washed three times with water, dried over Na2 SO4 , and concentrated under vacuum to give yellow oil (772 mg, 96%). 1 H NMR (300 MHz, CDCl3 ): d 7.75 (d, 2H, J = 9.0 Hz), 6.91 (d, 2H, J = 9.0 Hz), 4.14–4.18 (m, 2H), 3.85–3.90 (m, 2H), 3.67–3.79 (m, 6H), 3.53–3.57 (m, 2H), 3.38 (s, 3H). 4.2.2. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-diethynylbenzene (9) To a solution of 5 (3.49 g, 23.24 mmol) and 6 (1.54 g, 5.05 mmol) in CH2 Cl2 (230 mL) was added triethylamine (2.1 mL, 15 mmol). After stirred at room temperature for 48 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (80% AcOEt–hexane) to give the white solid (1.44 g, 70%). mp 128 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 7.89 (d, 2H, J = 1.2 Hz), 7.76 (d, 2H, J = 8.7 Hz), 7.64 (t, 1H, J = 1.2 Hz), 7.00 (d, 2H, J = 8.7 Hz), 6.80 (s, 1H), 4.17–4.22 (m, 2H), 3.87–3.92 (m, 2H), 3.64–3.77 (m, 6H), 3.52–3.57 (m, 2H), 3.37 (s, 3H), 3.17 (s, 2H). 13 C NMR (75 MHz, CDCl3 ): ı 168.0, 162.6, 160.3, 136.6, 129.2, 128.1, 128.0, 123.4, 121.3, 115.0, 98.3, 81.6, 79.1, 71.9, 70.8, 70.6, 70.5, 69.6, 67.5, 59.0. IR (KBr): 3247, 3126, 2925, 2912, 2887, 2867, 1614, 1569, 1531, 1444, 1428, 1386, 1355, 1307, 1294, 1280, 1253, 1189, 1141, 1130, 1102, 1067, 1038, and 1024 cm−1 . HRMS (FAB; M+H+ ) calcd. for C26 H26 NO5 432.1811, found 432.1793. Anal. calcd. for C26 H25 NO5 ·0.25H2 O: C, 71.63; H, 5.90; N, 3.21. Found: C, 71.64; H, 5.93; N, 3.14.
825
4.2.3. 1-[3-(4-Decyloxyphenyl)isoxazol-5-yl]-3,5diethynylbenzene (10) To a solution of 5 (1.92 g, 12.78 mmol) and 7 (864 mg, 2.77 mmol) in CH2 Cl2 (120 mL) was added triethylamine (1.16 mL, 8.31 mmol). After stirred at room temperature for 12 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (10% AcOEt–hexane) to give the white solid (1.14 g, 96%). mp 118 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 7.91 (d, 2H, J = 1.2 Hz), 7.77 (d, 2H, J = 8.7 Hz), 7.66 (t, 1H, J = 1.2 Hz), 6.98 (d, 2H, J = 8.7 Hz), 6.81 (s, 1H), 4.01 (t, 2H, J = 7.2 Hz), 3.17 (s, 2H), 1.81 (quint, 2H, J = 7.2 Hz), 1.20–1.51 (m, 14H), 0.88 (t, 3H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.0, 162.7, 160.7, 136.6, 129.2, 128.1, 128.0, 123.5, 120.9, 114.8, 98.3, 81.7, 79.0, 68.1, 31.9, 29.5, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1. IR (KBr): 3292, 3254, 2923, 2850, 1613, 1565, 1528, 1444, 1428, 1385, 1308, 1295, 1253, 1177, 1118, 1057, and 1016 cm−1 . HRMS (FAB; M+H+ ) calcd. for C29 H32 NO2 426.2433, found 426.2418. Anal. calcd. for C29 H31 NO2 : C, 81.85; H, 7.34; N, 3.29. Found: C, 81.59; H, 7.34; N, 3.20. 4.2.4. 1-[3-(4-Methoxyphenyl)isoxazol-5-yl]-3,5diethynylbenzene (11) To a solution of 5 (1.81 g, 12.05 mmol) and 8 (224 mg, 1.21 mmol) in CH2 Cl2 (200 mL) was added triethylamine (0.52 mL, 3.63 mmol). After stirred at room temperature for 72 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (10% AcOEt–hexane) to give the white solid (271 mg, 75%). mp 182 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 7.91 (d, 2H, J = 1.2 Hz), 7.89 (d, 2H, J = 8.7 Hz), 7.66 (t, 1H, J = 1.2 Hz), 6.99 (d, 2H, J = 8.7 Hz), 6.81 (s, 1H), 3.87 (s, 3H), 3.17 (s, 2H). 13 C NMR (75 MHz, CDCl3 ): ı 168.1, 162.7, 161.2, 136.6, 129.3, 128.3, 128.1, 123.5, 121.2, 114.4, 98.4, 81.7, 79.0, and 55.4. IR (KBr): 3285, 3219, 2964, 2933, 2838, 1613, 1581, 1567, 1530, 1445, 1424, 1388, 1295, 1261, 1176, and 1029 cm−1 . HRMS (FAB; M+H+ ) calcd. for C20 H14 NO2 300.1025, found 300.1040. Anal. calcd. for C20 H13 NO2 ·0.25H2 O: C, 79.06; H, 4.48; N, 4.61. Found: C, 79.11; H, 4.30; N, 4.68. 4.2.5. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-bis[3-(4-decyloxyphenyl)isoxazol-5-yl]benzene (1) To a solution of 9 (92 mg, 0.218 mmol) and 7 (253 mg, 0.811 mmol) in CH2 Cl2 (40 mL) was added triethylamine (0.22 mL, 1.62 mmol). After stirred at room temperature for 24 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (80% AcOEt–hexane) and recrystallized from isopropyl alcohol to give the white solid (159 mg, 74%). mp 82 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.34 (s, 3H), 7.83 (d, 6H, J = 8.7 Hz), 7.06 (s, 3H), 7.02 (d, 6H, J = 8.7 Hz), 4.16–4.21 (m, 2H), 4.03 (t, 4H, J = 7.2 Hz), 3.87–3.92 (m, 2H), 3.66–3.80 (m, 6H), 3.55–3.57 (m, 2H), 3.39 (s, 3H), 1.82 (quint, 4H, J = 7.2 Hz), 1.21–1.57 (m, 28H), 0.89 (t, 6H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl ): ı 168.1, 168.0, 162.9, 162.8 160.8, 160.4, 3 129.2, 128.2, 123.8, 121.2, 120.8, 115.0, 114.9, 98.7, 71.9, 70.9, 70.7, 70.6, 69.6, 68.1, 67.5, 59.0, 31.9, 29.6, 29.4, 29.3, 29.2, 26.0, 22.7, and 14.1. IR (KBr): 2961, 2850, 1613, 1560, 1526, 1469, 1435, 1388, 1297, 1255, 1175, 1115, and 1020 cm−1 . HRMS (FAB; M+H+ ) calcd. for C60 H76 N3 O9 982.5582, found 982.5565. Anal. calcd. for C60 H75 N3 O9 : C, 73.37; H, 7.70; N, 4.28. Found: C, 73.09; H, 7.71; N, 4.19. 4.2.6. 1,3-Bis[3-(4-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy} phenyl)isoxazol-5-yl]-5-[3-(4-decyloxyphenyl)isoxazol-5yl]benzene (2) To a solution of 10 (1.14 g, 2.68 mmol) and 6 (2.68 g, 8.71 mmol) in CH2 Cl2 (50 mL) was added triethylamine (2.37 mL, 17.42 mmol). After stirred at room temperature for 24 h, the reaction mixture was concentrated under vacuum. The crude product was purified
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by column chromatography on silica gel (AcOEt) and recrystallized from ethanol and water (9:1) to give the white solid (1.05 g, 31%). mp 69–70 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.27 (s, 3H), 7.81 (d, 6H, J = 8.4 Hz), 7.03 (s, 3H), 6.99 (d, 6H, J = 8.4 Hz), 4.12 − 4.30 (m, 4H,), 3.89 (t, 2H, J = 7.2 Hz), 3.86–3.91 (m, 4H), 3.66 − 3.80 (m, 12H), 3.54 − 3.57 (m, 4H), 3.39 (s, 6H), 1.82 (quint, 2H, J = 7.2 Hz), 1.21 − 1.57 (m, 14H), 0.89 (t, 3H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.1, 168.0, 162.9, 162.8 160.8, 160.4, 129.2, 128.2, 123.8, 121.2, 120.8, 115.0, 114.9, 98.7, 71.9, 70.9, 70.7, 70.6, 69.6, 68.1, 67.5, 59.0, 31.9, 29.6, 29.4, 29.3, 29.2, 26.0, 22.7, and 14.1. IR (KBr): 2920, 2867, 1612, 1561, 1525, 1469, 1436, 1388, 1298, 1254, 1177, 1114, 1064, and 1020 cm−1 . HRMS (FAB; M+H+ ) calcd. for C57 H70 N3 O12 988.4960, found 988.4976. Anal. calcd. for C57 H69 N3 O12 ·0.5H2 O: C, 68.65; H, 7.08; N, 4.21. Found: C, 68.69; H, 6.95; N, 4.15. 4.2.7. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-bis[3-(4-hexyloxyphenyl)isoxazol-5-yl]benzene (3) To a solution of 9 (600 mg, 1.42 mmol) and 12 (1.34 g, 5.22 mmol) in CH2 Cl2 (30 mL) was added triethylamine (1.54 mL, 11.36 mmol). After stirred at room temperature for 48 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (50% AcOEt–hexane) and recrystallized from isopropyl alcohol to give the white solid (940 mg, 76%). mp 41–43 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.34 (s, 3H), 7.84 (d, 6H, J = 8.7 Hz), 7.06 (s, 3H), 7.02 (d, 6H, J = 8.7 Hz), 4.21 (t, 2H, J = 4.8 Hz), 4.03 (t, 4H, J = 7.2 Hz), 3.86–3.91 (m, 2H), 3.66–3.80 (m, 6H), 3.54–3.57 (m, 2H), 3.39 (s, 3H), 1.82 (quint, 4H, J = 7.2 Hz), 1.21–1.57 (m, 12H), 0.89 (t, 6H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.1, 168.0, 162.8, 162.7, 160.8, 160.4, 129.1, 128.2, 123.8, 121.2, 120.8, 115.0, 114.8, 98.7, 71.9, 70.9, 70.7, 70.6, 69.6, 68.1, 67.5, 59.0, 31.6, 29.2, 25.7, 22.6, and 14.0. IR (KBr): 2931, 2870, 1614, 1559, 1525, 1458, 1436, 1387, 1295, 1251, 1176, 1116, and 1025 cm−1 . HRMS (FAB; M+H+ ) calcd. for C52 H60 N3 O9 870.4330, found 870.4328. Anal. calcd. for C52 H59 N3 O9 ·0.5H2 O: C, 71.05; H, 6.88; N, 4.78. Found: C, 70.79; H, 6.78; N, 4.72. 4.2.8. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-bis[3-(4-methoxyphenyl)isoxazol-5-yl]benzene (4) To a solution of 11 (100 mg, 0.33 mmol) and 7 (320 mg, 0.811 mmol) in CH2 Cl2 (20 mL) was added triethylamine (0.22 mL, 1.03 mmol). After stirred at room temperature for 24 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (10% AcOEt–hexane) and recrystallized from isopropyl alcohol to give the white solid (200 mg, 70%). mp 131 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.16 (s, 3H), 7.74–7.77 (m, 6H), 6.87–6.96 (m, 9H), 3.97 (t, 4H,
J = 7.2 Hz), 3.84 (s, 3H), 1.80 (quint, 4H, J = 7.2 Hz), 1.30–1.66 (m, 28H), 0.90 (t, 6H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.0, 167.9, 162.8, 162.7, 161.1, 160.8, 129.1, 128.2, 123.6, 121.0, 120.8, 114.9, 114.3, 98.7, 68.1, 55.2, 31.9, 29.7, 29.6, 29.4, 29.2, 26.0, 22.7, and 14.1. IR (KBr): 2922, 2852, 1611, 1525, 1466, 1431, 1387, 1295, 1255, 1175, 1114, and 1027 cm−1 . HRMS (FAB; M+H+ ) calcd. for C54 H64 N3 O6 850.4795, found 850.4793. Anal. calcd. for C54 H63 N3 O6 : C, 76.29; H, 7.47; N, 4.94. Found: C, 76.15; H, 7.52; N, 4.92. Acknowledgements This work was supported by Grant-in-Aids for Scientific Research (No. 18350065) of JSPS, and a Grant-in-Aid for Science Research (No. 19022024) in Priority Area “Super-Hierarchical Structures” from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. We acknowledge financial support from the Murata, Ogasawara, Iketani, and Inamori Foundations. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
P. Terech, R.G. Weiss, Chem. Rev. 97 (1997) 3133. J.H. van Esch, R.M. Kellogg, B.L. Feringa, Angew. Chem., Int. Ed. 39 (2000) 2264. O. Gronwald, S. Shinkai, Chem. Eur. J. 7 (2001) 4328. L.A. Estroff, A.D. Hamilton, Chem. Rev. 104 (2004) 201. N. Sangeetha, U. Maitra, Chem. Soc. Rev. 34 (2005) 821. M. George, R.G. Weiss, Acc. Chem. Res. 39 (2006) 489. K. Hanabusa, K. Okui, K. Karaki, T. Koyama, H. Shirai, J. Chem. Soc., Chem. Commun. 18 (1992) 1371. J.H. van Esch, F. Schoonbeek, M. De Loos, H. Kooijman, A.L. Spek, R.M. Kellogg, B.L. Feringa, Chem. Eur. J. 5 (1999) 937. S. kiyonaka, S. Shinkai, I. Hamachi, Chem. Eur. J. 9 (2003) 976. K. Murata, M. Aoki, T. Suzuki, T. Harada, H. Kawabata, T. komori, F. Ohseto, K. Ueda, S. Shinkai, J. Am. Chem. Soc. 116 (1994) 6664. F.J.M. Hoeben, P. Jonkheijm, E.W. Meijer, A.P.H.J. Schenning, Chem. Rev. 105 (2005) 1491. A.P.H.J. Schenning, E.W. Meijer, Chem. Commun. (2005) 3245. T. Ishi-i, S. Shinkai, Topic Curr. Chem. 258 (2005) 119. A. Ajayaghosh, V. Praveen, Acc. Chem. Res. 40 (2007) 644. F. Placin, M. Colomes, J.-P. Desvergne, Tetrahedron Lett. 38 (1997) 2665. G. Clavier, M. Mistry, F. Fages, J.L. Pozzo, Tetrahedron Lett. 40 (1999) 9021. J. Mamiya, K. Kanie, T. Hiyama, T. Ikeda, T. Kato, Chem. Commun. (2002) 1870. F. Würthner, S. Yao, U. Beginn, Angew. Chem., Int. Ed. 42 (2003) 3247. B.K. An, D.S. Lee, J.S. Lee, Y.S. Park, H.S. Song, S.Y. Park, J. Am. Chem. Soc. 126 (2004) 10232. T. Haino, M. Tanaka, Y. Fukazawa, Chem. Commun. (2008) 468. M. Tanaka, T. Haino, K. Ideta, K. Kubo, A. Mori, Y. Fukazawa, Tetrahedron 63 (2007) 652. R.B. Martin, Chem. Rev. 96 (1996) 3043. M. Kölbel, F.M. Menger, Chem. Commun. (2001) 275. J.H. Jung, S. Shinkai, T. Shimizu, Chem. Eur. J. 8 (2002) 2684. S.M. Park, Y.S. Lee, B.H. Kim, Chem. Commun. (2003) 2912. G. John, J.H. Jung, M. Masuda, T. Shimizu, Langmuir 20 (2004) 2060. S. Tanaka, M. Shirakawa, K. Kaneko, M. Takeuchi, S. Shinkai, Langmuir 21 (2005) 2163. A.J. Lampkins, O. Abdul-Rahim, H. Li, R.K. Castellano, Org. Lett. 7 (2005) 4471. F. Camerel, B. Donnio, C. Bourgogne, M. Schmutz, D. Guillon, P. Davidson, R. Ziessel, Chem. Eur. J. 12 (2006) 4261.
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Synthetic Metals journal homepage: www.elsevier.com/locate/synmet
A new organogelator based on 1,3,5-tris(phenylisoxazolyl)benzene Takeharu Haino ∗ , Hiroshi Saito Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
a r t i c l e
i n f o
Article history: Received 21 November 2008 Received in revised form 24 December 2008 Accepted 10 January 2009 Available online 8 February 2009 Keywords: Gel Self-assembly Aromatic stacking
a b s t r a c t 1,3,5-Tris(phenylisoxazolyl)benzene derivatives possessing polar and nonpolar side chains were synthesized. The microscopic gel morphology was confirmed by using FESEM, TEM, and XRD measurements. The amphiphilic nature of the tris(phenylisoxazolyl)benzene derivative gives rise to the lamellar structure, responsible for the formation of the fibrous bundles. The intertwined networks of the bundles immobilize the alcoholic solvents, and result in the formation of the organogels. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Organogels are thermally reversible viscoelastic materials, formed by the self-assembly of gelators via noncovalent interactions [1–6]. The aggregation of gelators forms the entangled fibers, giving rise to the three-dimensional network. Solvent molecules are immobilized in voids of the network, which is responsible for gelation. Some amide [7], urea [8] and saccharide [9] derivatives, and steroid [10] compounds have been reported as a gelator, and their gelation behaviors have been intensively studied so far. Recently, low-molecular-weight gelators have received much attention not only for their gelation behavior, but also for their formation of welldefined nanostructures such as fibers, sheets and helical structures via self-assembly. In particular, the nanostructures formed by conjugated molecules have been widely studies for the construction of functional materials [11–14]. Small aromatics, such as benzene, phenylene, and triphenylene create nanometric unique organization with the aid of hydrogen bonding to afford a new class of functional supramolecular assemblies. There is a limited number of the small aromatic gelators that can assemble to form fibrous gels without hydrogen bonds in organic solvents [15–19]. Previously, we have reported that tris(phenylisoxazolyl)benzene derivatives act as a good gelator of various organic solvents. [20] The solution studies of the assembly for the gelators have revealed that the molecular stacks driven by the local dipole–dipole interactions of the isoxazole moieties are responsible for the formation of the fibrous morphology in their gel state.
∗ Corresponding author. Tel.: +81 82 424 7427; fax: +81 82 424 0724. E-mail address: [email protected] (T. Haino). 0379-6779/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2009.01.017
In this paper, we demonstrate that macromolecular properties and solid state organization of the molecular stacks are uniquely modulated by the amphiphilic nature of the side chains. Tris(phenylisoxazolyl)benzene derivatives 1–4 possessing alkyl chains and polar triethyleneglycol monomethyl ether (mTEG) or methoxy groups as the side chains are synthesized, and their selfassembling behaviors in bulk and solution are studied (Fig. 1). 2. Results and discussion The synthesis of tris(phenylisoxazolyl)benzenes 1–4 is shown in Scheme 1. 1,3-Dipolar cycloaddition of 1,3,5-triethynylbenzene 5 with the nitriloxide prepared in situ from hydroximinoyl chloride 6 by treatment of triethylamine gave compound 9. Subsequent treatment of 9 with hydroximinoyl chloride 7 [21] and triethylamine afforded desired product 1 in 74% yield. The nitriloxide resulted from hydroximinoyl chloride 12 reacted with 9 to produce product 3 in 76% yield. Reaction of 7 and 5 with triethylamine led to compound 10, which was converted to compound 2 through the reaction with 6 in 31% yield. Reaction of 5 with hydroximinoyl chloride 8 [21] in the presence of triethylamine gave 11. Following reaction with 7 afforded compound 4 in 70% yield. The gelation ability of compounds 1–4 was studied in a variety of organic solvents (Table 1). Compound 1 selectively formed the gels only in the alcoholic solvents, whereas compounds 2 and 3 did not act as a gelator in the solvents. Compound 4 produced the gels in some of the alcoholic solvents. These results indicate the role of the side chains in the gelation ability. The two mTEG side chains of 2 increase its solubility in a variety of solvents; thus, the strong solvation of the two mTEG chains probably brings about the low intermolecular affinity in the self-association. As compared with the gelation properties of 1, 3 and 4, the two long alkyl chains and
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Scheme 1. Synthesis of the unsymmetric tris(phenylisoxazolyl)benzene derivatives.
Fig. 1. Unsymmetrical tris(phenylisoxazolyl)benzene derivatives 1–4.
one mTEG group are necessary incorporation on the aromatic core for creating a good gelator; in fact, the absence of the decyloxy group takes away the gelation ability from 3 while the incorporation of methoxy group instead of mTEG one obviously reduces the stability of the gels of 4. To gain a macroscopic aspect of the gels, the butanol xerogels of 1 and 4 were studied by using field emission scanning electron microscopy. The FESEM images of the xerogels of 1 display the formation of the three-dimensional entangled networks (Fig. 2a) in which the tape-like morphology is observed with widths of
Fig. 2. FESEM images of the xerogels of 1 (a and b) and 4 (c and d) from butanol, and the film prepared from butanol solution of 3 (e and f).
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Fig. 3. TEM images (a and b) of the xerogel of 1, and the electron diffraction (c) of b.
500–1500 nm (Fig. 2b). The xerogels of 4 create the fibrous morphology (Fig. 2c), and the fibers with diameters of 150–300 nm bundle and create the network (Fig. 2d). Both the xerogels have the well-developed structures with many voids responsible for hold-
Table 1 Gelation properties of 1–4 in a variety of solvents. Solvent
1
2
3
4
Ethanol Propanol iso-Propanol Allyl alcohol Propargyl alcohol 1-Butanol 2-Methyl-l-propanol 2-Butanol tert-Butanol tert-Amyl alcohol 1-Hexanol 1-Octanol 1-Decanol 1-Dodecanol Benzyl alcohol Hexane Cycrohexane Benzene Chloroform Ether Acetone Ethylacetate Acetonitrile THF DMF DMSO
I S S P G(20) G(25) G(10) P G(10) P G(30) G(30) G(30) G(30) S I I S S S S S I S S S
S S S S S S S S S S S S S S S I S S S S S S S S S S
P S S S S S P P P S P P P P S I P P S S S S P S S S
I S S P P G(35) G(20) P pG P pG pG pG PG P I G(8) S S P S S I S P S
G: gel; pG: partial gel; S: solution; I: insoluble; P: precipitation. The critical gelation concentration (mg mL−1 ) is shown in a parenthesis.
ing and immobilizing solvent molecules. In contrast, the images of 3 show the lumps without forming any well-defined structures (Fig. 2e and f). This microscopic aspect of the xerogels provides that the three-dimensional networks formed by the intertwined fibers immobilize the organic solvents and result in the formation of the gels. Transmission electron microscopy (TEM) observation of the xerogel of 1 gives an insight into the higher level of the molec-
Fig. 4. 1 H NMR spectra of 1 at the concentration of: (a) 0.48 mmol L−1 , (b) 1.4 mmol L−1 , (c) 5.8 mmol L−1 , (d) 25 mmol L−1 , and (e) 50 mmol L−1 at 290 K in chloroform-d1 .
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Fig. 5. XRD patterns of the xerogels of: (a) 1 and (b) 4, and the film (c) of 3.
ular arrangement. Fig. 3a shows well developed network made up of the tape-like fibers with width of about 300 nm (Fig. 3b), the electron diffraction pattern of which display well-defined diffraction spots with d-spacing of 4.2 Å (Fig. 3c), suggesting that compound 1 assembles to form the loose stacks via – stacking interaction. The – stacking interaction of the tris(phenylisoxazolyl) benzene unit in solution is evidenced by the self-association study using 1 H NMR spectroscopy. When the chloroform solution of 1 was concentrated from 0.48 to 50 mmol L−1 , the aromatic protons shifted upfield (Fig. 4). Nonlinear curve fitting analysis [22] gave self-association constant (KE = 3.6 ± 0.2 L mol−1 ) and estimated induced upfield shifts of the aromatic protons (Ha,b : −1.07, Hc,d : −0.84, He,f : −0.78, Hg : −0.50, and Hh : −0.60 ppm). The other derivatives 2–4 also formed the molecular stacks with the association constants (2: 2.8 ± 0.3 L mol−1 , 3: 2.8 ± 0.2 L mol−1 , 4: 4.4 ± 0.2 L mol−1 ) and the upfield shifts of their aromatic protons. This is indicative of the formation of the molecular stacks in which the aromatic protons are shielded by the aromatic rings of the adjacent molecules. XRD measurements were performed on the xerogels of compounds 1, 3 and 4 to investigate their assembled structures in the gel state. The XRD pattern of the xerogel of 1 show the periodical reflection peaks at d-spacings 27.6 and 13.8 Å in small-angle region (Fig. 5a); the ratio of 1:1/2 indicates that 1 indeed assembles into a lamellar organization [23–29]. Additionally, the XRD pattern in the wide-angle region displays the diffuse band originated from the molten long alkyl chain, and the reflection peak at d-spacing 3.92 Å is typical – stacking. The long spacing 27.6 Å is compatible with the fully extended molecular length (Fig. 6a) of 1; thus, assembling of the molecules gives rise to the fibrous stacks that bundle to form the tape-like morphology (Fig. 7). In contrast, the XRD pattern of the xerogel 4 exhibits only broad and weak peak at 20.6 Å (Fig. 5b) that matches the molecular length (Fig. 6b), suggesting that a loose lamellar organization seems to be maintained. In the case of the film of 3, any periodicity is not found; perhaps the shorter alkyl chains are unable to create van der Waals interactions enough to give rise to a bundle of the molecular stacks of 3. 3. Conclusion
Fig. 6. Molecular modeling of 1 and 4 calculated by MacroModel V. 9.1. The alkyl chains are omitted for clarity.
In summary, we have demonstrated the systematic investigation of the gelation properties for tris(phenylisoxazolyl)benzene
Fig. 7. Plausible molecular array of 1 in a lamellar organization.
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possessing the polar and nonpolar alkyl chains. Compounds 1–4 assemble to form the molecular stacks in solution; however, further stacking to create the macromolecular morphology needs the assistance of the van der Waals interaction of the long alkyl chains and microphase separation induced by mTEG groups. 4. Experimental 4.1. General All chemicals were used without further purification unless otherwise specified. Proton and carbon NMR spectra were recorded on Varian Mercury-300 or JEOL LAMBDA-500 spectrometers. IR spectra were obtained on a JASCO FT/IR-420S. UV–vis absorption spectra were measured on a JASCO V-560 spectrometer. Mass spectra were reported with a JEOL JMX-SX 102A. Melting points were measured with Yanagimoto micro-melting point apparatus and uncorrected. Elemental analyses were performed on a PerkinElmer 2400CHN elemental analyzer. FESEM was performed on a Hitachi S-5200 system. TEM images were obtained on a JEOL JEM-2010. XRD measurements were carried out by using RIGAKU RINT-2100V. 4.2. Gelation test Compounds 1–4 were placed in capped glass tube with a solvent, heated until the solid was dissolved. The mixture was slowly cooled to room temperature, and left for 2 h at this temperature. The formation of gels was confirmed by the absence of fluid solvents when the glass tube was inverted. 4.2.1. 4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy} benzohydroximinoyl chloride (6) To a solution of 4-{2-[2-(2-methoxyethoxy)-ethoxy]ethoxy}benzaldehyde oxime in DMF (2.6 mL) was added N-chlorosuccinimide (388 mg, 2.60 mmol). After stirred at room temperature for 1 h, the reaction mixture was poured into 10 volumes of water and extracted with ether. The organic layer was washed three times with water, dried over Na2 SO4 , and concentrated under vacuum to give yellow oil (772 mg, 96%). 1 H NMR (300 MHz, CDCl3 ): d 7.75 (d, 2H, J = 9.0 Hz), 6.91 (d, 2H, J = 9.0 Hz), 4.14–4.18 (m, 2H), 3.85–3.90 (m, 2H), 3.67–3.79 (m, 6H), 3.53–3.57 (m, 2H), 3.38 (s, 3H). 4.2.2. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-diethynylbenzene (9) To a solution of 5 (3.49 g, 23.24 mmol) and 6 (1.54 g, 5.05 mmol) in CH2 Cl2 (230 mL) was added triethylamine (2.1 mL, 15 mmol). After stirred at room temperature for 48 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (80% AcOEt–hexane) to give the white solid (1.44 g, 70%). mp 128 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 7.89 (d, 2H, J = 1.2 Hz), 7.76 (d, 2H, J = 8.7 Hz), 7.64 (t, 1H, J = 1.2 Hz), 7.00 (d, 2H, J = 8.7 Hz), 6.80 (s, 1H), 4.17–4.22 (m, 2H), 3.87–3.92 (m, 2H), 3.64–3.77 (m, 6H), 3.52–3.57 (m, 2H), 3.37 (s, 3H), 3.17 (s, 2H). 13 C NMR (75 MHz, CDCl3 ): ı 168.0, 162.6, 160.3, 136.6, 129.2, 128.1, 128.0, 123.4, 121.3, 115.0, 98.3, 81.6, 79.1, 71.9, 70.8, 70.6, 70.5, 69.6, 67.5, 59.0. IR (KBr): 3247, 3126, 2925, 2912, 2887, 2867, 1614, 1569, 1531, 1444, 1428, 1386, 1355, 1307, 1294, 1280, 1253, 1189, 1141, 1130, 1102, 1067, 1038, and 1024 cm−1 . HRMS (FAB; M+H+ ) calcd. for C26 H26 NO5 432.1811, found 432.1793. Anal. calcd. for C26 H25 NO5 ·0.25H2 O: C, 71.63; H, 5.90; N, 3.21. Found: C, 71.64; H, 5.93; N, 3.14.
825
4.2.3. 1-[3-(4-Decyloxyphenyl)isoxazol-5-yl]-3,5diethynylbenzene (10) To a solution of 5 (1.92 g, 12.78 mmol) and 7 (864 mg, 2.77 mmol) in CH2 Cl2 (120 mL) was added triethylamine (1.16 mL, 8.31 mmol). After stirred at room temperature for 12 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (10% AcOEt–hexane) to give the white solid (1.14 g, 96%). mp 118 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 7.91 (d, 2H, J = 1.2 Hz), 7.77 (d, 2H, J = 8.7 Hz), 7.66 (t, 1H, J = 1.2 Hz), 6.98 (d, 2H, J = 8.7 Hz), 6.81 (s, 1H), 4.01 (t, 2H, J = 7.2 Hz), 3.17 (s, 2H), 1.81 (quint, 2H, J = 7.2 Hz), 1.20–1.51 (m, 14H), 0.88 (t, 3H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.0, 162.7, 160.7, 136.6, 129.2, 128.1, 128.0, 123.5, 120.9, 114.8, 98.3, 81.7, 79.0, 68.1, 31.9, 29.5, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1. IR (KBr): 3292, 3254, 2923, 2850, 1613, 1565, 1528, 1444, 1428, 1385, 1308, 1295, 1253, 1177, 1118, 1057, and 1016 cm−1 . HRMS (FAB; M+H+ ) calcd. for C29 H32 NO2 426.2433, found 426.2418. Anal. calcd. for C29 H31 NO2 : C, 81.85; H, 7.34; N, 3.29. Found: C, 81.59; H, 7.34; N, 3.20. 4.2.4. 1-[3-(4-Methoxyphenyl)isoxazol-5-yl]-3,5diethynylbenzene (11) To a solution of 5 (1.81 g, 12.05 mmol) and 8 (224 mg, 1.21 mmol) in CH2 Cl2 (200 mL) was added triethylamine (0.52 mL, 3.63 mmol). After stirred at room temperature for 72 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (10% AcOEt–hexane) to give the white solid (271 mg, 75%). mp 182 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 7.91 (d, 2H, J = 1.2 Hz), 7.89 (d, 2H, J = 8.7 Hz), 7.66 (t, 1H, J = 1.2 Hz), 6.99 (d, 2H, J = 8.7 Hz), 6.81 (s, 1H), 3.87 (s, 3H), 3.17 (s, 2H). 13 C NMR (75 MHz, CDCl3 ): ı 168.1, 162.7, 161.2, 136.6, 129.3, 128.3, 128.1, 123.5, 121.2, 114.4, 98.4, 81.7, 79.0, and 55.4. IR (KBr): 3285, 3219, 2964, 2933, 2838, 1613, 1581, 1567, 1530, 1445, 1424, 1388, 1295, 1261, 1176, and 1029 cm−1 . HRMS (FAB; M+H+ ) calcd. for C20 H14 NO2 300.1025, found 300.1040. Anal. calcd. for C20 H13 NO2 ·0.25H2 O: C, 79.06; H, 4.48; N, 4.61. Found: C, 79.11; H, 4.30; N, 4.68. 4.2.5. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-bis[3-(4-decyloxyphenyl)isoxazol-5-yl]benzene (1) To a solution of 9 (92 mg, 0.218 mmol) and 7 (253 mg, 0.811 mmol) in CH2 Cl2 (40 mL) was added triethylamine (0.22 mL, 1.62 mmol). After stirred at room temperature for 24 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (80% AcOEt–hexane) and recrystallized from isopropyl alcohol to give the white solid (159 mg, 74%). mp 82 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.34 (s, 3H), 7.83 (d, 6H, J = 8.7 Hz), 7.06 (s, 3H), 7.02 (d, 6H, J = 8.7 Hz), 4.16–4.21 (m, 2H), 4.03 (t, 4H, J = 7.2 Hz), 3.87–3.92 (m, 2H), 3.66–3.80 (m, 6H), 3.55–3.57 (m, 2H), 3.39 (s, 3H), 1.82 (quint, 4H, J = 7.2 Hz), 1.21–1.57 (m, 28H), 0.89 (t, 6H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl ): ı 168.1, 168.0, 162.9, 162.8 160.8, 160.4, 3 129.2, 128.2, 123.8, 121.2, 120.8, 115.0, 114.9, 98.7, 71.9, 70.9, 70.7, 70.6, 69.6, 68.1, 67.5, 59.0, 31.9, 29.6, 29.4, 29.3, 29.2, 26.0, 22.7, and 14.1. IR (KBr): 2961, 2850, 1613, 1560, 1526, 1469, 1435, 1388, 1297, 1255, 1175, 1115, and 1020 cm−1 . HRMS (FAB; M+H+ ) calcd. for C60 H76 N3 O9 982.5582, found 982.5565. Anal. calcd. for C60 H75 N3 O9 : C, 73.37; H, 7.70; N, 4.28. Found: C, 73.09; H, 7.71; N, 4.19. 4.2.6. 1,3-Bis[3-(4-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy} phenyl)isoxazol-5-yl]-5-[3-(4-decyloxyphenyl)isoxazol-5yl]benzene (2) To a solution of 10 (1.14 g, 2.68 mmol) and 6 (2.68 g, 8.71 mmol) in CH2 Cl2 (50 mL) was added triethylamine (2.37 mL, 17.42 mmol). After stirred at room temperature for 24 h, the reaction mixture was concentrated under vacuum. The crude product was purified
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by column chromatography on silica gel (AcOEt) and recrystallized from ethanol and water (9:1) to give the white solid (1.05 g, 31%). mp 69–70 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.27 (s, 3H), 7.81 (d, 6H, J = 8.4 Hz), 7.03 (s, 3H), 6.99 (d, 6H, J = 8.4 Hz), 4.12 − 4.30 (m, 4H,), 3.89 (t, 2H, J = 7.2 Hz), 3.86–3.91 (m, 4H), 3.66 − 3.80 (m, 12H), 3.54 − 3.57 (m, 4H), 3.39 (s, 6H), 1.82 (quint, 2H, J = 7.2 Hz), 1.21 − 1.57 (m, 14H), 0.89 (t, 3H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.1, 168.0, 162.9, 162.8 160.8, 160.4, 129.2, 128.2, 123.8, 121.2, 120.8, 115.0, 114.9, 98.7, 71.9, 70.9, 70.7, 70.6, 69.6, 68.1, 67.5, 59.0, 31.9, 29.6, 29.4, 29.3, 29.2, 26.0, 22.7, and 14.1. IR (KBr): 2920, 2867, 1612, 1561, 1525, 1469, 1436, 1388, 1298, 1254, 1177, 1114, 1064, and 1020 cm−1 . HRMS (FAB; M+H+ ) calcd. for C57 H70 N3 O12 988.4960, found 988.4976. Anal. calcd. for C57 H69 N3 O12 ·0.5H2 O: C, 68.65; H, 7.08; N, 4.21. Found: C, 68.69; H, 6.95; N, 4.15. 4.2.7. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-bis[3-(4-hexyloxyphenyl)isoxazol-5-yl]benzene (3) To a solution of 9 (600 mg, 1.42 mmol) and 12 (1.34 g, 5.22 mmol) in CH2 Cl2 (30 mL) was added triethylamine (1.54 mL, 11.36 mmol). After stirred at room temperature for 48 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (50% AcOEt–hexane) and recrystallized from isopropyl alcohol to give the white solid (940 mg, 76%). mp 41–43 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.34 (s, 3H), 7.84 (d, 6H, J = 8.7 Hz), 7.06 (s, 3H), 7.02 (d, 6H, J = 8.7 Hz), 4.21 (t, 2H, J = 4.8 Hz), 4.03 (t, 4H, J = 7.2 Hz), 3.86–3.91 (m, 2H), 3.66–3.80 (m, 6H), 3.54–3.57 (m, 2H), 3.39 (s, 3H), 1.82 (quint, 4H, J = 7.2 Hz), 1.21–1.57 (m, 12H), 0.89 (t, 6H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.1, 168.0, 162.8, 162.7, 160.8, 160.4, 129.1, 128.2, 123.8, 121.2, 120.8, 115.0, 114.8, 98.7, 71.9, 70.9, 70.7, 70.6, 69.6, 68.1, 67.5, 59.0, 31.6, 29.2, 25.7, 22.6, and 14.0. IR (KBr): 2931, 2870, 1614, 1559, 1525, 1458, 1436, 1387, 1295, 1251, 1176, 1116, and 1025 cm−1 . HRMS (FAB; M+H+ ) calcd. for C52 H60 N3 O9 870.4330, found 870.4328. Anal. calcd. for C52 H59 N3 O9 ·0.5H2 O: C, 71.05; H, 6.88; N, 4.78. Found: C, 70.79; H, 6.78; N, 4.72. 4.2.8. 1-[3-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl) isoxazol-5-yl]-3,5-bis[3-(4-methoxyphenyl)isoxazol-5-yl]benzene (4) To a solution of 11 (100 mg, 0.33 mmol) and 7 (320 mg, 0.811 mmol) in CH2 Cl2 (20 mL) was added triethylamine (0.22 mL, 1.03 mmol). After stirred at room temperature for 24 h, the reaction mixture was concentrated under vacuum. The crude product was purified by column chromatography on silica gel (10% AcOEt–hexane) and recrystallized from isopropyl alcohol to give the white solid (200 mg, 70%). mp 131 ◦ C. 1 H NMR (300 MHz, CDCl3 ): ı 8.16 (s, 3H), 7.74–7.77 (m, 6H), 6.87–6.96 (m, 9H), 3.97 (t, 4H,
J = 7.2 Hz), 3.84 (s, 3H), 1.80 (quint, 4H, J = 7.2 Hz), 1.30–1.66 (m, 28H), 0.90 (t, 6H, J = 7.2 Hz). 13 C NMR (75 MHz, CDCl3 ): ı 168.0, 167.9, 162.8, 162.7, 161.1, 160.8, 129.1, 128.2, 123.6, 121.0, 120.8, 114.9, 114.3, 98.7, 68.1, 55.2, 31.9, 29.7, 29.6, 29.4, 29.2, 26.0, 22.7, and 14.1. IR (KBr): 2922, 2852, 1611, 1525, 1466, 1431, 1387, 1295, 1255, 1175, 1114, and 1027 cm−1 . HRMS (FAB; M+H+ ) calcd. for C54 H64 N3 O6 850.4795, found 850.4793. Anal. calcd. for C54 H63 N3 O6 : C, 76.29; H, 7.47; N, 4.94. Found: C, 76.15; H, 7.52; N, 4.92. Acknowledgements This work was supported by Grant-in-Aids for Scientific Research (No. 18350065) of JSPS, and a Grant-in-Aid for Science Research (No. 19022024) in Priority Area “Super-Hierarchical Structures” from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. We acknowledge financial support from the Murata, Ogasawara, Iketani, and Inamori Foundations. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]
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