Organogelation of Diacetylene Cholesteryl Esters Having Two

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Articles Organogelation of Diacetylene Cholesteryl Esters Having Two Urethane Linkages and Their Photopolymerization in the Gel State Jun’ichi Nagasawa,* Masabumi Kudo, Shigenobu Hayashi, and Nobuyuki Tamaoki* National Institute of Advanced Industrial Science and Technology, Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan Received March 2, 2004. In Final Form: June 8, 2004 Various diacetylene cholesteryl esters having two urethane linkages were synthesized to study the relationship between their gelation properties and chemical structures. Most of these compounds form organogels in cyclohexane, and some compounds gelatinized hexane, diethyl ether, N,N-dimethylformamide, and ethanol. The cholesteryl moieties play an important role in gel formation, but IR spectroscopic measurements show that the main driving force for gelation is hydrogen bonding of the urethane groups. Upon UV irradiation, most of the gels polymerized to give polydiacetylenes, with concomitant changes from colorless to a variety of hues, such as dark blue, orange, and pink. The polymerization proceeds efficiently in cases where the gels change color to dark blue. The polymerization reached 52% chemical yield, with the quantum yield estimated to be at least 54. Solid-state NMR spectroscopy confirmed that polymerization in the gel state proceeds via 1,4-addition.

Introduction Low-molecular-weight gelators have attracted much attention in recent years.1 The gelators form fibrous aggregates through noncovalent interactions, and the fibrous structures intertwine to create three-dimensional networks. The driving forces behind the molecular aggregation are predominantly hydrogen-bonding, van der Waals, charge-transfer, dipole-dipole, π-π stacking, and coordination interactions. For example, the main driving force among amides,2 urethanes,3 ureas,4 and sugar derivatives5 is hydrogen bonding, with van der Waals forces dominant6 among steroid derivatives. Some gelators utilize two or more of these interactions.7 Gels have potential usefulness for preparation of new nanoscale * To whom correspondence should be addressed. Telephone/ Fax: +81-29-861-4673. E-mail: [email protected]; n.tamaoki@ aist.go.jp. (1) (a) Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133-3159. (b) Terech, P. Ber. Bunsen-Ges. Phys. Chem. 1998, 102, 1630-1643. (c) Abdallah, D. J.; Weiss, R. G. Adv. Mater. 2000, 12, 1237-1247. (2) (a) Kato, T.; Kutsuna, T.; Hanabusa, K.; Ukon, M. Adv. Mater. 1998, 10, 606-608. (b) Kamiyama, T.; Yasuda, Y.; Shirota, Y. Polym. J. 1999, 31, 1165-1170. (c) Makarevic´, J.; Jokic´, M.; Peric´, B.; Tomisˇic´, V.; Kojic´-Prodic´, B.; Zˇ inic´, M. Chem.sEur. J. 2001, 7, 3328-3341. (d) Schmidt, R.; Schmutz, M.; Michel, M.; Decher, G.; Me´sini, P. J. Langmuir 2002, 18, 5668-5672. (e) Miyawaki, K.; Harada, A.; Takagi, T.; Shibakami, M. Synlett 2003, 349-352. (f) George, M.; Weiss, R. G. Chem. Mater. 2003, 15, 2879-2888. (g) George, M.; Synder, S. L.; Terech, P.; Glinka, C. J.; Weiss, R. G. J. Am. Chem. Soc. 2003, 125, 10275-10283. (3) (a) Hanabusa, K.; Okui, K.; Karaki, K.; Kimura, M.; Shirai, H. J. Colloid Interface Sci. 1997, 195, 86-93. (b) Bhattacharya, S.; Acharya, S. N. G. Chem. Mater. 1999, 11, 3121-3132. (4) (a) Carr, A. J.; Melendez, R.; Geib, S. J.; Hamilton, A. D. Tetrahedron Lett. 1998, 39, 7447-7450. (b) Schoonbeek, F. S.; van Esch, J. H.; Wegewijs, B.; Rep, D. B. A.; de Haas, M. P.; Klapwijk, T. M.; Kellogg, R. M.; Feringa, B. L. Angew. Chem., Int. Ed. 1999, 38, 13931397. (c) de Loos, M.; Ligtenbarg, A. G. J.; van Esch, J.; Kooijman, H.; Spek, A. L.; Hage, R.; Kellogg, R. M.; Feringa, B. L. Eur. J. Org. Chem. 2000, 3675-3678. (d) Wang, G.; Hamilton, A. D. Chem. Commun. 2003, 310-311.

structures. On the other hand, diacetylene derivatives polymerize topochemically through 1,4-addition to form corresponding polydiacetylenes; this process occurs typically in the crystalline state8 and in two-dimensional crystal-like Langmuir-Blodgett (LB) films.9 Recently, examples of this type of polymerization occurring in (5) (a) Amanokura, N.; Yoza, K.; Shinmori, H.; Shinkai, S.; Reinhoudt, D. N. J. Chem. Soc., Perkin Trans. 2 1998, 2585-2592. (b) Amanokura, N.; Kanekiyo, Y.; Shinkai, S.; Reinhoudt, D. N. J. Chem. Soc., Perkin Trans. 2 1999, 1995-2000. (c) Yoza, K.; Amanokura, N.; Ono, Y.; Akao, T.; Shinmori, H.; Takeuchi, M.; Shinkai, S.; Reinhoudt, D. N. Chem.s Eur. J. 1999, 5, 2722-2729. (d) Jung, J. H.; John, G.; Masuda, M.; Yoshida, K.; Shinkai, S.; Shimizu, T. Langmuir 2001, 17, 7229-7232. (e) Jung, J. H.; Shinkai, S.; Shimizu, T. Chem.sEur. J. 2002, 8, 26842690. (6) (a) Murata, K.; Aoki, M.; Suzuki, T.; Harada, T.; Kawabata, H.; Komori, T.; Ohseto, F.; Ueda, K.; Shinkai, S. J. Am. Chem. Soc. 1994, 116, 6664-6676. (b) Mukkamala, R.; Weiss, R. G. Langmuir 1996, 12, 1474-1482. (c) Geiger, C.; Stanescu, M.; Chen, L.; Whitten, D. G. Langmuir 1999, 15, 2241-2245. (d) Lu, L.; Cocker, T. M.; Bachman, R. E.; Weiss, R. G. Langmuir 2000, 16, 20-34. (7) (a) Inoue, K.; Ono, Y.; Kanekiyo, Y.; Ishi-i, T.; Yoshihara, K.; Shinkai, S. J. Org. Chem. 1999, 64, 2933-2937. (b) Jung, J. H.; Ono, Y.; Shinkai, S. Tetrahedron Lett. 1999, 40, 8395-8399. (c) Amaike, M.; Kobayashi, H.; Shinkai, S. Bull. Chem. Soc. Jpn. 2000, 73, 2553-2558. (d) Ishi-i, T.; Iguchi, R.; Snip, E.; Ikeda, M.; Shinkai, S. Langmuir 2001, 17, 5825-5833. (e) Snip, E.; Koumoto, K.; Shinkai, S. Tetrahedron 2002, 58, 8863-8873. (f) Tamaru, S.; Uchino, S.; Takeuchi, M.; Ikeda, M.; Hatano, T.; Shinkai, S. Tetrahedron Lett. 2002, 3751-3755. (g) Kawano, S.; Fujita, N.; van Bommel, K. J. C.; Shinkai, S. Chem. Lett. 2003, 32, 12-13. (h) Suzuki, M.; Yumoto, M.; Kimura, M.; Shirai, H.; Hanabusa, K. Chem.sEur. J. 2003, 9, 348-354. (i) Babu, P.; Sangeetha, N. M.; Vijyakumar, P.; Maitra, U.; Rissanen, K.; Raju, A. R. Chem.sEur. J. 2003, 9, 1922-1932. (j) Suzuki, M.; Yumoto, M.; Kimura, M.; Shirai, H.; Hanabusa, K. Helv. Chim. Acta 2003, 86, 2228-2238. (8) (a) Ba¨ssler, H. In Advances in Polymer Science; Cantow, H.-J., Ed.; Springer-Verlag: Berlin, 1984; Vol. 63, pp 1-48. (b) Sixl, H. In Advances in Polymer Science; Cantow, H.-J., Ed.; Springer-Verlag: Berlin, 1984; Vol. 63, pp 49-90. (9) (a) Tieke, B. In Advances in Polymer Science; Springer-Verlag: Berlin, 1985; Vol. 71, pp 79-151. (b) Cira´k, J.; Barancˇok, D. Acta Phys. Slovaca 1995, 45, 479-490. (c) Huo, Q.; Russell, K. C.; Leblanc, R. M. Langmuir 1999, 15, 3972-3980.

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Figure 1. Synthesis and structures of dicholesteryl compounds.

unidimensional crystal-like systems have been reported for gel states2e,2f,3b,10 and in a fibril state.11 A diacetylene dicholesteryl ester having urethane linkages has been polymerized in the organogel state to form a stable blue organogel containing polydiacetylene nanowires.12 This gelator has two interaction sites: urethane moieties behaving as hydrogen-bonding sites and cholesteryl moieties as van der Waals interaction sites. Polydiacetylene nanowires are very attractive materials because conductive nanowires are important for interconnecting molecular devices in molecular electronics systems.13 To clarify the relationship between the chemical structure and the gelation or polymerization properties of this class of compounds, we synthesized dicholesteryl esters having a series of alkylene chains connecting the cholesteryl ester, the urethane linkage, and the diyne unit. Herein, we describe detailed studies on these compounds with respect to their gelling ability, hydrogen bonding (monitored by IR spectroscopy), polymerization yield, quantum yield, and polymerization mechanism (monitored by solid-state NMR spectroscopy). Results and Discussion Molecular Design and Synthesis. The gelator compounds have three components: two urethane groups, two cholesteryl groups, and a diacetylene unit. The urethane groups are expected to behave as sites for hydrogen bonding, and the cholesteryl groups are expected to assemble through van der Waals interactions. The diacetylene unit is a promising unit for polymerization. There are two kinds of alkylene spacers in the structure: one links a cholesteryl group to a urethane group, and the other links a diacetylene unit to a urethane group; these spacers are abbreviated in Figures 1 and 2 as X and (CH2)n, respectively. To investigate the effect that the structure has on the gelling and polymerizing properties, we synthesized compounds by varying the length and bulkiness of these spacers. In addition, we used two kinds of terminal groups, either cholesteryl units or alkyl chains, to verify the role of the cholesteryl unit. To (10) (a) Markowitz, M.; Singh, A.; Chang, E. L. Biochem. Biophys. Res. Commun. 1994, 203, 396-305. (b) Masuda, M.; Hanada, Y.; Yase, K.; Shimizu, T. Macromolecules 1998, 31, 9403-9405. (c) Inoue, K.; Ono, Y.; Kanekiyo, Y.; Hanabusa, K.; Shinkai, S. Chem. Lett. 1999, 429-430. (d) Masuda, M.; Hanada, T.; Okada, Y.; Yase, K.; Shimizu, T. Macromolecules 2000, 33, 9233-9238. (e) Huang, W. Y.; Matsuoka, S.; Kwei, T. K.; Okamoto, Y. Macromolecules 2001, 34, 7166-7171. (11) (a) Svenson, S.; Messersmith, P. B. Langmuir 1999, 15, 44644471. (b) Wang, G.; Hollingsworth, R. I. Adv. Mater. 2000, 12, 871-874. (12) Tamaoki, N.; Shimada, S.; Okada, Y.; Belaissaoui, A.; Kruk, G.; Yase, K.; Matsuda, H. Langmuir 2000, 16, 7545-7547. (13) Tour, J. M. Acc. Chem. Res. 2000, 33, 791-804.

Figure 2. Structures of mono- and non-cholesteryl compounds.

synthesize these compounds, we used three components: a diol featuring a diyne unit, two amino acid units, and two terminal units. In our previous synthetic method,12 we obtained a dicarboxylic acid by condensing a diynediol with butyl isocyanatoacetate, followed by hydrolysis, and then esterified it with cholesterol. Because the range of commercially available isocyanates is limited, we required a more general method that uses common intermediates for the preparation of the various derivatives. In this study, we formed the urethane linkages finally using carbonyldiimidazole, so that various amino acids could be utilized as spacer units. Diacetylene dicholesteryl compounds and diacetylene dialkyl compounds were synthesized by the condensation of cholesteryl or alkyl esters of amino acids and diynediols with carbonyldiimidazole. Diacetylene monocholesteryl compounds were synthesized by the condensation of cholesteryl esters of amino acids, dodecylamine, and diynediols with carbonyl diimidazole. This new synthetic route gave the gelators in good yields and allowed variations in the combinations of the synthetic partners. Gelation Behavior. The gelation was performed by dissolving the samples, heating them in a screw-capped bottle or cell, and then allowing them to stand at room temperature. The gelation of these compounds was tested in various solvents, as was the photopolymerization of the gel. The results are summarized in Tables 1 and 2. Cyclohexane is the best solvent for the gelation among the solvents examined. Some of the compounds gelatinized cyclohexane as low as 0.2-0.5 wt % (Table 3). Such compounds fall into the category of being among the most powerful known organogelators. The gel-sol phase transition temperature (Tgel) is shown in Table 3, too. The correlation is not observed in Tgel and the minimum concentration for gelation. Hexane is also a good solvent for gelation, when the compound is soluble in it. Some compounds gelatinized polar solvents, such as diethyl ether (3c), N,N-dimethylformamide (3e), and ethanol (3c, 3e, 4c, 4e). The gelation in hexane and in ethanol occurs when the spacer (CH2)n has n ) 3 or 4 but not when n ) 1 or 2. The length of the spacer also affects the gelation in cyclohexane, but the trend is not clear. In ethanol, gelation is limited to cases where the other spacer, X, is either (CH2)3 or CHCH3. Two pairs of diastereoisomers were synthesized to investigate steric effects: derivatives of D-alanine (3e and 4e) gelated at lower concentrations than those of L-alanine (3d and 4d). That is to say, the configuration of just one methyl group affects the gelation

Organogelation and Polymerization of Diacetylenes

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Table 1. Gelation and Photopolymerization of Dicholesteryl Compounds in Various Solventsa solvent hexane cyclohexane benzene chlorobenzene carbon tetrachloride diethyl ether ethyl acetate N,N-dimethylformamide acetonitrile ethanol methanol

1b I GP S S S S S S C C C

1c

2a

I GPb

I GP S S S C C C C C C

S S C C

2c

3a

I GPb S S S C S S I C C

I GPb S S C C S C C C

3b GP GP S S S C C S C C C

3c GP GP S S S GP S S C GP C

3d C GPb S S S S S S C GPb C

3e GP GP S S S S S G C GP C

4a GP GP S S S S S S C C C

4b I C S S S C C C I C C

4c

4d

4e

4f

GP GP S S S S C S C GP C

GPb

GP GP S S S S S

S S S S S S S S C C C

GPb S S S S S C C C C

c

C GP C

a The concentration of each compound is usually 1.0 wt %. G ) gel formed but did not polymerize on photoirradiation; GP ) gel formed and polymerized upon photoirradiation; C, S, or I ) gel did not form because of crystallization, solubilization, or insolubility, respectively. b The concentration is 2.0 wt %. c Gel-like precipitates formed.

Table 2. Gelation and Photopolymerization of Mono- and Non-cholesteryl Compounds in Various Solventsa solvent

5

6

7

8a

8e

9

10

hexane cyclohexane benzene chlorobenzene carbon tetrachloride diethyl ether ethyl acetate N,N-dimethylformamide acetonitrile ethanol methanol

GP GP S S S S S

GP GP S S S S S S C C C

S S

C C S S C C C S C C C

C C

C C

C C

C C

C C

C C

C C

C C

S S C S

S S C C

a The concentration of each compound is 1.0 wt %. GP ) Gel formed and polymerized upon photoirradiation; C or S ) gel did not form because of crystallization or solubilization, respectively.

Table 3. Minimum Concentration for Gelation and Tgel compound

solvent

minimum concentration for gelation [wt %]

1b 1c 2a 2c 3a 3b 3c 3d 3d 3e 4a 4c 4d 4d 4e 5 6

cyclohexane cyclohexane cyclohexane cyclohexane cyclohexane cyclohexane cyclohexane cyclohexane ethanol cyclohexane cyclohexane cyclohexane cyclohexane hexane cyclohexane cyclohexane cyclohexane

0.5 1.8 0.5 1.5 1.1 0.2 0.4 1.2 1.4 0.4 0.5 0.2 1.1 1.2 0.3 0.3 0.4

Tgel [°C] at 1.0 wt % 73 55a 56a 67 55 47.5 70 62

a Crystallization was also generated with the sol-gel phase transition.

ability; this methyl group is located between a urethane unit, which acts as a hydrogen-bonding site, and a cholesteryl group, which acts as a van der Waals interaction site, and must, therefore, affect the relative configuration of both sites. No gelation was observed in any solvents for compounds 4b and 4f. Compound 4b crystallizes easily, and 4f has a good solubility because of its bulky isobutyl side chain. Monocholesteryl compounds 5 and 6, which we synthesized for comparison with the excellent gelators 3b and 4a, also gelatinize cyclohexane and hexane at low concentrations. Another monocholesteryl compound (7), which is analogous to 6 but differs in the number of urethane units, does not show gelation ability. Compounds 5 and 6 have two urethane units, but 7 has just one. This result suggests the importance of

intermolecular hydrogen bonding at the two positions. The non-cholesteryl compounds 8a and 8e, which are analogous to the powerful gelators 4a and 4e, do not form gels, but instead they crystallize. These results suggest that at least one cholesteryl group is necessary for gelation to occur. In conclusion, both two-position hydrogen bonding and van der Waals interactions between cholesteryl groups are necessary in this class of compounds for gelation. We measured Fourier transform infrared (FTIR) spectra in these solvents to confirm the presence of hydrogen bonding in the gel state. Table 4 shows the FTIR spectra of compounds 1c, 2a, 2c, 3b, and 4f in solutions and in the gel state. The spectra of the cyclohexane gel of 1c, 2a, 2c, and 3b are characterized by signals at 3310-3322 and 1688-1693 cm-1, which we assign to the N-H and CdO stretching vibrations of hydrogen-bonded groups, and at 1727-1734 cm-1, assigned to the stretching vibration of free CdO units. There are no characteristic differences in IR spectra between stronger gelators (2a, 3b) and weaker gelators (1c, 2c). In the gel state, both urethane groups undergo hydrogen bonding. On the other hand, the FTIR spectra of isotropic solutions of 3b display CdO stretching vibrations at 1721 cm-1 in chloroform and at 1728 cm-1 in tetrahydrofuran and N-H stretching vibrations at 3454 cm-1 in chloroform; there is no evidence of hydrogen bonding in these solutions. Compound 4f, which does not form gels because its bulky isobutyl sidechain groups near the urethane units inhibit hydrogen bonding through steric hindrance, displays peaks at 1732 and 3439 cm-1 in cyclohexane for its free carbonyl and amino groups, respectively. It is clear from our observations of these infrared spectra that hydrogen bonding between the CdO and N-H units in two urethane units of neighboring molecules plays an important role in the gel formation process. Photopolymerization. We performed the photopolymerization of gels by irradiating them with light from a super-high-pressure mercury lamp. Most of the gels polymerized upon photoirradiation and changed their hue from colorless to a variety of colors: dark blue (3b, 4a, 5, and 6), purple (2a, 3a, and 4c), pink (1c), red (1b, 2c, 3e, and 4d), and orange (3c, 3d, and 4e). Figure 3 displays images of some of the gels before and after photoirradiation. The appearance of the colors implies that polydiacetylenes have been produced; the particular color depends on the effective delocalization length of the π-electrons in the polyenyne backbone,14 with blue polydiacetylenes having longer effective lengths than do red ones. Table 5 summarizes results of the irradiations conducted in cyclohexane and in crystalline states. There (14) Eckhardt, H.; Boudreaux, D. S.; Chance, R. R. J. Chem. Phys. 1986, 85, 4116-4119.

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Table 4. FTIR Spectra of Gels and Solutions

a

compound

state

1c 2a 2c 3b 3b 3b 4f 3b 3b

cyclohexane gel cyclohexane gel cyclohexane gel cyclohexane gel tetrahydrofuran solution chloroform solution cyclohexane solution xerogel before irradiation xerogel after irradiation

concentrationa [mmol dm-3]

νN-H [cm-1]

νCdO (ester) [cm-1]

νCdO (urethane) [cm-1]

14.0 (2.0) 14.4 (2.0) 13.7 (2.0) 5.0 (0.73) 5.0 (0.64) 5.0 (0.38) 5.0 (0.73)

3316 3310 3318 3322

1727 1727 1730 1734 1728 1721 1732 1734 1732

1693 1693 1693 1688 1728 1721 1732 1692 1691

b

3454 3439 3335 3325

Percentages by weight are given in parentheses. b Not observed.

Figure 3. Photographic images of cyclohexane gels: 3b (a) before and (b) after photoirradiation; (c) 3a, (d) 3c, (e) 4e, and (f) 5 after photoirradiation. Table 5. Colors of Cyclohexane Gels and Crystals Formed after Photoirradiation

a

compound

gel color

crystal color

1b 1c 2a 2c 3a 3b 3c 3d 3e 4a 4b 4c 4d 4e 4f 5 6 7

red pink purple red purple dark blue orange orange red dark blue

orange orange whitea red whitea purple pink pink red purple orange purple orange pink whitea purple purple whitea

purple red orange dark blue dark blue

Polymerization did not occur.

is a correlation between the color of the gel and the crystal when both are irradiated. For example, when the color of the crystal is purple, the color of the gel is dark blue or purple; when the color of the crystals is red or pink, the color of the gels is red or orange, respectively. Figure 4a presents the spectra of 3a, 3b, 3c, and 3e after irradiation; these compounds all have the same (CH2)3 spacer but possess different X spacers. The length of spacer X affects

Figure 4. (a) UV-vis spectra of the cyclohexane gels of 3a, 3b, 3c, and 3d after UV irradiation. Concentrations are 9.1 mmol dm-3 (3a), 2.0 mmol dm-3 (3b), 5.3 mmol dm-3 (3c), and 6.8 mmol dm-3 (3d). Irradiation times were 30 s (3a), 10 s (3b), 30 s (3c), and 40 s (3d). (b) UV-vis spectra of cyclohexane gels of 2a, 3a, and 4a after UV irradiation. Concentrations are 3.6 mmol dm-3 (2a), 9.1 mmol dm-3 (3a), and 6.8 mmol dm-3 (4a). Irradiation times were 5 s (2a), 30 s (3a), and 20 s (4a).

the color of the polymerized gel. Figure 4b displays the spectra of 2a, 3a, and 4a after irradiation; these compounds have different (CH2)n spacers but the same X spacer (i.e., CH2). Upon irradiation, compounds 2a and 3a gave purple gels; 4a gave a dark-blue gel. Compounds 2c, 3c, and 4c gave red, orange, and purple gels, respectively, upon irradiation. The lengths of both the (CH2)n and X spacers affect the colors of the polymerized gels. In conclusion, the gels that gave dark-blue or purple colors upon irradiation all have the characteristic feature that their (CH)n spacer is longer than their X spacer. In Figure 4, the coloring in the UV-vis spectra represents almost the saturation state. After irradiation, the absorbance of the dark-blue gels is larger than that of the nonblue gels; in addition, the polymerization of blue gels seems to occur faster than that of nonblue gels. All of the compounds that changed to dark blue gelatinized cyclohexane at a 0.5 wt % concentration or below. These molecules exhibit both the good aggregation required for gelation and a suitable assembly in the gel for the


Figure 5. Time profile for the polymerization of the cyclohexane gel of 3b at 7.3 mmol dm-3.

polymerization to proceed. The yield of polymerization was estimated by the weight of insoluble fractions, obtained upon diluting with dichloromethane and passing through a 0.2-µm filter, after irradiation with the light from a super-high-pressure mercury lamp. In the absorption spectra of 3b, the two peaks that appear at 622 and 574 nm after the first stage are shifted gradually to 637 and 588 nm upon photoirradiation. The yield of the polymer in the cyclohexane gel of 3b reached 52% after 5 min, as indicated in Figure 5; this yield is the highest obtained for diacetylene gels to be reported in the literature. The conversion of 3a, which gave a purple gel, was 0.9% after 5 min; the conversion of 3e, which gave a red gel, was 0.1% after 5 min. The filtrate was colorless in the case of 3b, but it was purple for 3a and yellow for 3e. The degree of polymerization of 3b could not be estimated by size-exclusion chromatography because of the lack of solubility in any solvent, but it seems to be larger than that of 3a and 3e. Compounds having methyl groups in side chains do not polymerize effectively even in the case of excellent gelation ability such as 4e. Perhaps side methyl groups prevent diacetylene moieties from suitable arrangement for polymerization. There is a close relation between the molecular assembly, the gelation ability of a compound, the polymerization yield, the polymerization rate, and the structure of the resulting polydiacetylene. For the gels that change to dark blue upon photoirradiation, the diacetylene moieties must be arranged adequately for polymerization (i.e., with a suitable distance between the diyne groups and a suitable angle between the diacetylene rods) because diacetylene polymerization is known to require strict structural alignments.15 We determined the quantum yield to evaluate the efficiency of the polymerizations. The 1 wt % gel of 3b in cyclohexane was irradiated with 254-nm light from a xenon lamp at low light intensity. The quantum yield must be estimated from the reaction rate at time ) 0, because the polymer also absorbs the 254-nm light and acts as a filter even at low polymerization yields. However, near time ) 0 the conversion is too small to measure the weight accurately. Therefore, the value obtained must be underestimated. The lower limit of the quantum yield is 54, which was calculated at the stage where the conversion was 5.4-5.8%. This report is the first to describe the quantum yield of photopolymerization of diacetylenes that form molecular aggregates in solvent. Some research groups have reported the quantum yields of several (15) (a) Baughman, R. H. J. Polym. Sci., Polym. Phys. Ed. 1974, 12, 1511-1535. (b) Enkelmann, V. In Advances in Polymer Science; Cantow, H.-J., Ed.; Springer-Verlag: Berlin, 1984; Vol. 63, pp 91-136.

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Figure 6. 13C CP/MAS NMR spectra of freeze-dried cyclohexane gels of 3b. The letter “S” designates spinning sidebands.

diacetylene compounds upon their UV polymerization in the solid state. The diacetylene 4BCMU (i.e., RCtC-Ct CR, where R is (CH2)4OCONHCH2COOC4H9) is known to be a highly UV-reactive compound.16 Using different methods, the quantum yield of 4BCMU in the solid state has been estimated by Bhattacharjee and Patel17 (g50), by Prock et al.18 (ca. 90 and ca. 70), and by Eckhardt et al.19 (ca. 60). The quantum yield of 3b in the gel state is comparable to that of 4BCMU in the solid state. 4BCMU has two urethane groups and can undergo hydrogen bonding in a manner similar to that of our compounds. Values of quantum yield ranging from 10-4 to 14 have been reported for films and crystals of other R1CtCCtCR2 diacetylene compounds, where R1 and R2 are two alkyl groups,20 two sulfonic esters,17,21 or a combination of an alkyl group and a carboxylic acid.22 These compounds have either one or no hydrogen bonding sites. The formation of hydrogen bonds on both sides of the diacetylene unit plays an important role in arranging it suitably for polymerization. We have clarified for the first time that diacetylenes polymerize upon UV irradiation in unidimensional molecular aggregates with high reactivity in a manner similar to that of 4BCMU in the solid state. The polymerization of diacetylene in a crystal occurs by 1,4-addition polymerization. The polymers we obtained after irradiation are insoluble in all solvents, so we measured solid-state 13C NMR spectra to confirm the type of reaction that occurs in the gel state. Figure 6 presents 13C cross-polarization/magic-angle spinning (CP/MAS) NMR spectra of freeze-dried cyclohexane gels of 3b obtained before and after irradiation for 3 min under conditions corresponding to those in Figure 5. The xerogels were not washed with any solvent, so the xerogel after irradiation contained both the polymer and the unreacted monomer. After irradiation, the intensity of the peaks at 65.6 and 77.9 ppm decreased and new peaks appeared at 106.3 and 130.5 ppm. The 13C NMR spectra of polydi(16) Chance, R. R.; Shand, M. L. J. Chem. Phys. 1980, 72, 948-952. (17) Bhattacharjee, H. R.; Patel, G. N. J. Photochem. 1981, 16, 8591. (18) (a) Prock, A.; Shand, M. L.; Chance, R. R. J. Chem. Phys. 1982, 76, 5834-5837. (b) Prock, A.; Shand, M. L.; Chance, R. R. Macromolecules 1982, 15, 238-241. (19) Eckhardt, H.; Prusik, T.; Chance, R. R. Macromolecules 1983, 16, 732-736. (20) Tieke, B.; Wegner, G. Makromol. Chem. 1978, 179, 1639-1642. (21) (a) Mondong, R.; Ba¨ssler, H. Chem. Phys. Lett. 1981, 78, 371374. (b) Bauer, H. D.; Materny, A.; Mu¨ller, I.; Schwoerer, M. Mol. Cryst. Liq. Cryst. 1991, 200, 205-223. (22) Fouassier, J. P.; Tieke, B.; Wegner, G. Isr. J. Chem. 1979, 18, 227-232.

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acetylenes have been studied extensively in solution23 and in the solid state.24 By comparing our spectra with those in the literature, we assign the peaks at 65.6 and 77.9 ppm to interior and exterior sp-hybridized carbon atoms, respectively, of the monomeric diacetylene unit; the peaks at 106.3 and 130.5 ppm are assigned to the sp- and sp2hybridized carbon atoms, respectively, of the polydiacetylene backbone. No other new peaks for sp- or sp2-hybridized carbon atoms are observed in the spectra after irradiation. This observation implies that a single reaction occurs predominantly and that this reaction must be 1,4-addition polymerization. This evidence is the first to indicate that 1,4-addition polymerization proceeds in gel states as well as in the crystal. The FTIR spectra of the gels after irradiation are almost the same as those obtained prior to irradiation (Table 3). Before irradiation, the spectrum of the xerogel of 3b formed in cyclohexane is characterized by bands at 3335 and 1692 cm-1, which we assign to the stretching vibrations of hydrogen-bonded N-H and CdO units, and at 1734 cm-1, assigned to the stretching vibration of free CdO units. After irradiation, these peaks are observed at 3325, 1691, and 1732 cm-1, respectively. The CtC stretching vibration could not be observed either before or after photoirradiation. Basically, the hydrogen-bonding character did not change after irradiation. The thermal stability of polymerized cyclohexane gels of 2a, 3b, 4a, and 4c was examined by heating them to 80 °C. When the polymerized gel of 2a was heated, the shape of the gel was broken, although the polymer was not dissolved. However, the polymerized gels of 3b, 4a, and 4c shrank but maintained the shape after heating, probably because the polymer yield was high enough and polymer fibers formed sufficiently entangled networks. The contraction of the polymerized gel began at the temperature at which the gel of monomers began to become the sol. The heating changed the color of the polymerized gels from purple to red (2a and 4c), from blue to red (4a), and from blue to purple in the case of the slightly polymerized gel of 3b. Surprisingly, the heating did not change the color of the sufficiently polymerized gel of 3b. The high thermal stability may reflect high yield of the polymerization. Morphology of Gels. Figure 7 presents scanning electron micrograph (SEM) images of freeze-dried gels of 3b and 4e formed in cyclohexane before and after irradiation. The gels have fibrous three-dimensional network structures; the width of the fibrils ranges from 20 to 50 nm. We do not observe any helical structures. No obvious differences are observed between the shapes before and after irradiation. Figure 8 displays a transmission electron micrograph (TEM) image of a cyclohexane gel of 3b; this image indicates that 3b assembles into ribbonlike structures having widths in the range of 100-300 nm. This TEM image may indicate the original form of the aggregate in the solvent; these ribbon structures may fold into the fibrous shape observed in the SEM images upon freeze-drying. (23) (a) Babbitt, G. E.; Patel, G. N. Macromolecules 1981, 14, 554557. (b) Plachetta, C.; Schultz, R. C. Macromol. Chem., Rapid. Commun. 1982, 3, 815-819. (c) Wenz, G.; Mu¨ller, M. A.; Schmidt, M.; Wegner, G. Macromolecules 1984, 17, 837-850. (24) (a) Havens, J. R.; Thakur, M.; Lando, J. M.; Koenig, J. L. Macromolecules 1984, 17, 1071-1074. (b) Galambos, A. F.; Stockton, W. B.; Koberstein, J. T.; Sen, A.; Weiss, R. A. Macromolecules 1987, 20, 3094-3097. (c) Tanaka, H.; Gomez, M. A.; Tonelli, A. E.; Thakur, M. Macromolecules 1989, 22, 1208-1215. (d) Lee, D.-C.; Sahoo, S. K.; Cholli, A. L.; Sandman, D. J. Macromolecules 2002, 35, 4347-4355.

Nagasawa et al.

Figure 7. Scanning electron micrographs of cyclohexane gels: (a) 3b and (b) 4e. The left- and right-hand images correspond to the states before and after photoirradiation, respectively.

Figure 8. A transmission electron micrograph of the cyclohexane gel of 3b.

Conclusions We have synthesized a variety of cholesteryl ester derivatives that have both urethane and diacetylene units. Most of these compounds, which have additionally either one or two cholesteryl groups, gelatinize cyclohexane at concentrations of 0.2-1.8 wt %. Some of these compounds also gelatinize hexane, diethyl ether, N,N-dimethylformamide, and ethanol. Gel formation is the result of hydrogen bonding between the N-H and CdO groups of the urethane units, and the structures are stabilized further by van der Waals interactions between cholesteryl groups. Each of the gels, except for one, polymerized upon photoirradiation of its gel state, causing its hue to change from colorless to dark blue, purple, red, orange, or pink. The length and structure of the spacers affect the gelation


and polymerization processes. The compounds that gave dark-blue gels upon irradiation are the ones that exhibit excellent gelation ability, high polymerization rates, and high polymerization conversions. The polymerization yield of the cyclohexane gel of 3b reached 52%, and we estimate the quantum yield to be at least 54. This example is the first in which the quantum yield after UV polymerization of a diacetylene in its aggregate state has been recorded. We also have provided the first evidence, suggested by solid-state 13C NMR spectroscopy, that these polymerizations in the gel state proceed by 1,4-addition. Experimental Section Instrumentation and Materials. Absorption spectra were recorded on a Shimadzu UV-2500PC spectrophotometer. 1H and 13C NMR spectra were measured using a JEOL JMN LA-600 spectrometer for solutions in CDCl3 containing tetramethylsilane as the internal standard. Solid-state 13C NMR spectra were measured using a Bruker ASX200 spectrometer. IR spectra were recorded on a Mattson Infinity Gold FTIR spectrometer. Fast atom bombardment mass spectrometry (FAB-MS) analysis was carried out using a JEOL DX303 mass spectrometer. The uncorrected melting points were determined on a Mettler Toledo FP82HT hot-stage apparatus equipped with a FP900/FP90 processor and an Olympus BH-2 microscope connected to a video system. Electron micrographs were obtained using a Topcon DS720 field emission scanning electron microscope and a Zeiss EM902A transmission electron microscope. Elemental analyses were measured using a CE Instruments EA1110 automatic elemental analyzer. Cholesteryl aminoacetate and cholesteryl L-alanate were synthesized in the manner reported by Lapatsanis et al.25 The synthesis of compound 4a has been described elsewhere.12 General Synthesis of N-tert-Butoxycarbonyl Amino Acid Esters. 1,1′-Carbonyldiimidazole (4.68 g, 30 mmol) was added to a solution of N-tert-butoxycarbonyl amino acid (30 mmol) in dichloromethane (20 mL) under a nitrogen atmosphere. The solution was stirred for 3 h at room temperature. A solution of cholesterol (7.73 g, 20 mmol) or 1-dodecanol (3.73 g, 20 mmol) in dichloromethane (30 mL) was added to the reaction mixture, and then stirring was continued for 2-5 days. The resulting solution was washed with water, 1 M HCl, and saturated NaCl solution, respectively, and then dried over sodium sulfate. After evaporation of the solvent, the residue was subjected to silica gel column chromatography using dichloromethane and ethyl acetate as an eluent. Cholesteryl 3-(tert-Butoxycarbonylamino)propionate. Obtained as a white solid (93% yield); mp 133.2-133.9 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.32 (2H, d, J ) 7.7 Hz, H-4), 2.49 (2H, t, J ) 5.9 Hz, CH2CO), 3.39 (2H, m, CH2NH), 4.63 (1H, m, H-3), 5.00 (1H, br s, NH), 5.38 (1H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 19.31, 21.04, 22.57, 22.83, 23.84, 24.29, 27.79, 28.02, 28.24, 28.41, 31.87, 31.91, 34.92, 35.80, 36.19, 36.60, 36.97, 38.13, 39.53, 39.74, 42.33, 50.04, 56.15, 56.70, 74.36, 79.32, 122.78, 139.55, 155.79, 171.91. Elemental Anal. Calcd for C35H59NO4: C, 75.36; H, 10.66; N, 2.51%. Found: C, 75.58; H, 10.62; N, 2.38%. Cholesteryl 4-(tert-Butoxycarbonylamino)butyrate. Obtained as a white solid (83% yield); mp 116.5-117.7 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.26-2.36 (4H, m, H-4, CH2CO), 3.16 (2H, m, CH2NH), 4.56-4.68 (2H, m, H-3, NH), 5.37 (1H, d, J ) 4.8 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 19.32, 21.04, 22.56, 22.82, 23.84, 24.29, 25.32, 27.79, 28.02, 28.24, 28.43, 31.88, 31.91, 32.01, 35.80, 36.20, 36.61, 36.99, 38.13, 39.53, 39.75, 40.01, 42.33, 50.05, 56.16, 56.71, 74.10, 79.19, 122.70, 139.62, 155.95, 172.71. Elemental Anal. Calcd for C36H61NO4: C, 75.61; H, 10.75; N, 2.45%. Found: C, 75.27; H, 10.72; N, 2.39%. Cholesteryl N-tert-Butoxycarbonyl-D-alaninate. Obtained as a white solid (81% yield); mp 117.2-118.1 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.04 (m, aliphatic), 2.34 (2H, d, J ) 7.7 Hz, H-4), 4.26 (1H, m, CHCO), 4.65 (1H, m, H-3), 5.05 (1H, (25) Lapatsanis, L.; Profilis, C.; Catsoulacos, P. J. Chem. Eng. Data 1980, 25, 287-289.

Langmuir, Vol. 20, No. 19, 2004 7913 br d, J ) 4.8 Hz, NH), 5.38 (1H, d, J ) 4.4 Hz, H-3). 13C NMR (CDCl3): δ 11.86, 18.73, 18.85, 19.31, 21.04, 22.56, 22.83, 23.84, 24.29, 27.63, 28.02, 28.23, 28.35, 31.85, 31.90, 35.80, 36.19, 36.57, 36.91, 37.99, 39.52, 39.73, 42.33, 49.39, 50.02, 56.14, 56.70, 74.99, 79.71, 122.90, 139.40, 155.11, 172.79. Elemental Anal. Calcd for C35H59NO4: C, 75.36; H, 10.66; N, 2.51%. Found: C, 75.37, H, 10.68; N, 2.40%. Cholesteryl N-tert-Butoxycarbonyl-L-leucinate. Obtained as a white solid (42% yield); mp 39.5-41.7 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.26-2.36 (2H, m, H-4), 4.26 (1H, m, CHCO), 4.65 (1H, m, H-3), 4.90 (1H, d, J ) 8.4 Hz, NH), 5.37 (1H, d, J ) 5.1 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.72, 19.32, 21.04, 22.03, 22.56, 22.83, 23.83, 24.29, 24.82, 27.71, 28.01, 28.24, 28.32, 31.85, 31.89, 35.79, 36.19, 36.59, 36.93, 37.98, 39.52, 39.72, 41.98, 42.32, 50.01, 52.25, 56.14, 56.69, 74.80, 79.66, 122.80, 139.47, 155.41, 172.90. Elemental Anal. Calcd for C38H65NO4: C, 76.08; H, 10.92; N, 2.33%. Found: C, 75.58; H, 10.62; N, 2.38%. Dodecyl tert-Butoxycarbonylaminoacetate. Obtained as a colorless oil (63% yield). 1H NMR (CDCl3): δ 0.88 (3H, t, J ) 7.0 Hz, CH3CH2), 1.18-1.38 (18H, m, aliphatic), 1.45 [9H, s, (CH3)3C], 1.63 (2H, quint, J ) 6.9 Hz, CH2CH2O), 3.88 (2H, d, J ) 5.5 Hz, CH2CO), 4.13 (2H, t, J ) 6.8 Hz, CH2O), 5.38 (1H, br s, NH). 13C NMR (CDCl3): δ 13.81, 22.41, 25.59, 28.03, 28.31, 28.98, 29.09, 29.25, 29.32, 29.37, 29.38, 31.66, 42.14, 65.05, 79.33, 155.56, 170.22. Elemental Anal. Calcd for C19H37NO4: C, 66.43; H, 10.86; N, 4.08%. Found: C, 66.52; H, 10.91; N, 4.02%. Dodecyl N-tert-Butoxycarbonyl-D-alaninate. Obtained as a colorless oil (66% yield). 1H NMR (CDCl3): δ 0.88 (3H, t, J ) 7.0 Hz, CH3CH2), 1.20-1.37 (18H, m, aliphatic), 1.38 (3H, d, J ) 7.3 Hz, CH3CH), 1.44 [9H, s, (CH3)3C], 1.64 (2H, quint, J ) 7.0 Hz, CH2CH2O), 4.11 (1H, dt, J ) 10.6, 6.6 Hz, CHHO), 4.14 (1H, dt, J ) 10.6, 6.6 Hz, CHHO), 4.30 (1H, m, CHCO), 5.19 (1H, br d, J ) 5.5 Hz, NH). 13C NMR (CDCl3): δ 13.97, 18.55, 22.56, 25.69, 28.20, 28.45, 29.10, 29.23, 29.38, 29.44, 29.50, 29.51, 31.79, 49.14, 65.26, 79.47, 155.01, 173.30. Elemental Anal. Calcd for C20H39NO4: C, 67.19; H, 10.99; N, 3.92%. Found: C, 67.48; H, 11.08; N, 3.79%. General Synthesis of Amino Acid Esters. Trifluoroacetic acid (4.8 g, 42 mmol) was added to a solution of the N-tertbutoxycarbonyl amino acid (7.0 mmol) in dichloromethane (20 mL), and then the mixture was stirred for 6 h at room temperature. The mixture was evaporated, and then 0.1 M NaOH solution and dichloromethane were added to the residue. The organic layer was separated and dried over sodium sulfate. After evaporation of the solvent, the residue was subjected to column chromatography (SiO2; chloroform/methanol, 5:1). Cholesteryl 3-Aminopropionate. Obtained as a white solid (63% yield); mp 100.5-101.7 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.32 (2H, d, J ) 7.7 Hz, H-4), 2.56 (2H, t, J ) 6.2 Hz, CH2CO), 3.08 (2H, t, J ) 6.0 Hz, CH2NH2), 3.82 (2H, br s, NH2), 4.63 (1H, m, H-3), 5.37 (1H, d, J ) 4.0 Hz, H-6). 13C NMR (CDCl ): δ 11.86, 18.72, 19.32, 21.04, 22.56, 22.82, 3 23.83, 24.28, 27.83, 28.01, 28.23, 31.86, 31.90, 35.79, 36.19, 36.60, 36.98, 37.93, 38.17, 38.26, 39.52, 39.73, 42.32, 50.02, 56.14, 56.69, 74.06, 122.71, 139.59, 172.10. Elemental Anal. Calcd for C30H51NO2: C, 78.72; H, 11.23; N, 3.06%. Found: C, 78.62; H, 11.18; N, 2.99%. Cholesteryl 4-Aminobutyrate. Obtained as a white solid (70% yield); mp 80.3-81.7 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.31 (2H, d, J ) 7.7 Hz, H-4), 2.33 (2H, t, J ) 7.5 Hz, CH2CO), 2.73 (2H, t, J ) 7.0 Hz, CH2NH2), 4.62 (1H, m, H-3), 5.37 (1H, d, J ) 4.8 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 19.33, 21.04, 22.56, 22.83, 23.84, 24.29, 27.81, 28.02, 28.24, 29.08, 31.87, 31.91, 32.12, 35.80, 36.19, 36.61, 37.00, 38.15, 39.52, 39.74, 41.60, 42.32, 50.04, 56.14, 56.70, 73.90, 122.65, 139.66, 172.99. Elemental Anal. Calcd for C31H53NO2: C, 78.92; H, 11.32; N, 2.97%. Found: C, 78.61; H, 11.23; N, 2.75%. Cholesteryl D-Alaninate. Obtained as a white solid (76% yield); mp 104.9-106.3 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.802.05 (m, aliphatic), 2.33 (2H, d, H-4), 3.50 (1H, q, J ) 7.1 Hz, CHCO), 4.63 (1H, m, H-3), 5.38 (1H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.87, 18.72, 19.33, 20.75, 21.05, 22.57, 22.82, 23.83, 24.29, 27.73, 28.02, 28.23, 31.87, 31.92, 35.80, 36.19, 36.60, 36.95, 38.08, 39.53, 39.73, 42.32, 50.03, 50.21, 56.15, 56.70, 74.45, 122.81,

7914


139.53, 176.08. Elemental Anal. Calcd for C30H51NO2: C, 78.72; H, 11.23; N, 3.06%. Found: C, 78.26; H, 11.15; N, 2.87%. Cholesteryl L-Leucinate. Obtained as a white solid (93% yield); mp 91.2-92.4 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.802.05 (m, aliphatic), 2.31 (2H, m, H-4), 3.42 (1H, dd, J ) 8.6, 5.7 Hz, CHCO), 4.64 (1H, m, H-3), 5.38 (1H, d, J ) 4.8 Hz, H-6). 13C NMR (CDCl3): δ 11.82, 18.69, 19.30, 21.01, 21.90, 22.54, 22.80, 22.94, 23.81, 24.25, 24.76, 27.73, 27.98, 28.20, 31.82, 31.87, 35.76, 36.16, 36.55, 36.94, 38.03, 39.49, 39.70, 42.28, 44.10, 49.99, 52.93, 56.11, 56.65, 74.27, 122.73, 139.46, 176.02. Elemental Anal. Calcd for C33H57NO2: C, 79.30; H, 11.49; N, 2.80%. Found: C, 79.01; H, 11.49; N, 2.61%. Dodecyl Aminoacetate. Obtained as a white solid (60% yield); mp 89.2-90.5 °C. 1H NMR (CDCl3): δ 0.88 (3H, t, J ) 7.1 Hz, CH3), 1.20-1.39 (18H, m, aliphatic), 1.50 (2H, br s, NH2), 1.63 (2H, quint, J ) 7.1 Hz, CH2CH2O), 3.41 (2H, s, CH2CO), 4.11 (2H, t, J ) 6.8 Hz, CH2O). 13C NMR (CDCl3): δ 13.81, 22.42, 25.63, 28.38, 28.99, 29.09, 29.25, 29.31, 29.37, 31.65, 43.70, 64.70, 174.07. Elemental Anal. Calcd for C14H29NO2: C, 69.09; H, 12.01; N, 5.75%. Found: C, 68.65; H, 11.94; N, 5.78%. Docecyl D-Alaninate. Obtained as a colorless oil (60% yield). 1H NMR (CDCl ): δ 0.88 (3H, t, J ) 7.0 Hz, CH ), 1.20-1.39 3 3 (21H, m, aliphatic), 1.56 (2H, br s, NH2), 1.64 (2H, quint, J ) 7.10 Hz, CH2CH2O), 3.54 (1H, q, J ) 7.0 Hz, CHCO), 4.09 (1H, dt, J ) 10.8, 6.8 Hz, CHHO), 4.12 (1H, dt, J ) 10.8, 6.8 Hz, CHHO). 13C NMR (CDCl3): δ 14.12, 20.76, 20.77, 22.70, 25.89, 28.62, 29.24, 29.35, 29.52, 29.57, 29.64, 31.93, 50.13, 65.07, 176.74. Elemental Anal. Calcd for C15H31NO2: C, 69.99; H, 12.14; N, 5.44%. Found: C, 69.77; H, 12.03; N, 5.27%. General Synthesis of Diacetylene Dicholesteryl Esters and Didodecyl Esters. 1,1′-Carbonyldiimidazole (324 mg, 2.0 mmol) was added to a solution of diynediol (1.0 mmol) in dry dichloromethane (20 mL), and then the resulting solution was stirred for 3 h at room temperature. The amino acid cholesteryl (or dodecyl) ester (2.0 mmol) was added to the mixture, and the stirring was continued for 3-5 days. The solution was washed sequentially with water and saturated NaCl solution and then dried over sodium sulfate. After evaporation of the solvent, the residue was subjected to column chromatography (SiO2; dichloromethane/ethyl acetate). The crude product was purified by crystallization from ethyl acetate or by precipitation from dichloromethane/ethanol. Dicholesteryl 3,3′-[2,4-Hexadiynylenebis(oxycarbonylamino)]dipropionate (1b). Obtained as a white solid (58% yield); decomposition > 165 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 2.32 (4H, d, J ) 8.1 Hz, H-4), 2.52 (4H, t, J ) 5.9 Hz, CH2CO), 3.45 (4H, q, J ) 5.9 Hz, CH2NH), 4.63 (2H, m, H-3), 4.73 (4H, s, tCCH2O), 5.33 (2H, t, J ) 5.7 Hz, NH), 5.38 (2H, d, J ) 4.8 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 19.31, 21.04, 22.56, 22.83, 23.84, 24.29, 27.78, 28.01, 28.23, 31.85, 31.91, 34.60, 35.80, 36.19, 36.58, 36.72, 36.95, 38.10, 39.52, 39.73, 42.32, 50.02, 52.78, 56.14, 56.70, 70.20, 74.13, 74.55, 122.84, 139.47, 155.13, 171.66. Elemental Anal. Calcd for C68H104N2O8: C, 75.79; H, 9.73; N, 2.60%. Found: C, 75.86; H, 9.77; N, 2.49%. Dicholesteryl 4,4′-[2,4-Hexadiynylenebis(oxycarbonylamino)]dibutyrate (1c). Obtained as a white solid (58% yield); decomposition > 138 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.31 (4H, d, J ) 7.7 Hz, H-4), 2.34 (4H, t, J ) 7.1 Hz, CH2CO), 3.24 (4H, q, J ) 6.5 Hz, CH2NH), 4.61 (2H, m, H-3), 4.73 (4H, s, tCCH2O), 4.99 (2H, br t, NH), 5.37 (2H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 19.32, 21.04, 22.56, 22.83, 23.84, 24.29, 25.01, 27.78, 28.01, 28.24, 31.86, 31.91, 35.80, 36.19, 36.59, 36.97, 38.11, 39.52, 39.74, 40.64, 42.32, 50.03, 52.74, 56.14, 56.70, 70.21, 74.15, 74.23, 76.82, 122.74, 139.56, 155.24, 172.61. Elemental Anal. Calcd for C70H108N2O4: C, 76.04; H, 9.85; N, 2.53%. Found: C, 76.00; H, 9.97; N, 2.36%. Dicholesteryl 3,5-Octadiynylenebis(oxycarbonylaminoacetate) (2a). Obtained as a white solid (48% yield); mp 210.8-212.9 °C. 1H NMR (CDCl ): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 3 2.33 (4H, d, J ) 7.7 Hz, H-4), 2.60 (4H, t, J ) 6.8 Hz, tCCH2), 3.94 (4H, d, J ) 5.5 Hz, CH2CO), 4.17 (4H, t, J ) 6.6 Hz, CH2O), 4.68 (2H, m, H-3), 5.23 (2H, br t, NH), 5.38 (2H, d, J ) 4.0 Hz, H-6). 13C NMR (CDCl3): δ 11.87, 18.73, 19.30, 20.14, 21.05, 22.56, 22.82, 23.86, 24.29, 27.72, 28.02, 28.23, 31.87, 31.92, 35.81, 36.21, 36.59, 36.93, 38.02, 39.54, 39.75, 42.34, 42.97, 50.05, 56.18, 56.71, 62.62, 66.54, 73.65, 75.45, 123.02, 139.32, 155.86, 169.27.

Nagasawa et al. Elemental Anal. Calcd for C68H104N2O8: C, 75.79; H, 9.73; N, 2.60%. Found: C, 75.79; H, 9.67; N, 2.50%. Dicholesteryl 4,4′-[3,5-Octadiynylenebis(oxycarbonylamino)]dibutyrate (2c). Obtained as a white solid (45% yield); mp 174.5186.9 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 2.31 (4H, d, J ) 7.7 Hz, H-4), 2.34 (4H, t, J ) 7.1 Hz, tCCH2), 2.58 (4H, t, J ) 6.2 Hz, CH2CO), 3.22 (4H, q, J ) 6.4 Hz, CH2NH), 4.14 (4H, t, J ) 6.4 Hz, CH2O), 4.61 (2H, m, H-3), 4.92 (2H, br s, NH), 5.37 (2H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 19.33, 20.21, 21.04, 22.57, 22.83, 23.85, 24.29, 25.15, 27.78, 28.01, 28.24, 31.86, 31.91, 35.80, 36.19, 36.60, 36.98, 38.12, 39.52, 39.74, 40.43, 42.32, 50.03, 56.15, 56.70, 62.17, 66.42, 73.82, 74.17, 122.73, 139.58, 156.03, 172.60. Elemental Anal. Calcd for C72H112N2O8: C, 76.28; H, 9.96; N, 2.47%. Found: C, 75.70; H, 9.53; N, 2.42%. Dicholesteryl 4,6-Decadiynylenebis(oxycarbonylaminoacetate) (3a). Obtained as a white solid (50% yield); mp 155.8-157.2 °C. 1H NMR (CDCl ): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 3 2.31-2.37 (8H, m, H-4, tCCH2), 3.93 (4H, d, J ) 5.1 Hz, CH2NH), 4.17 (4H, t, J ) 6.0 Hz, CH2O), 4.68 (2H, m, H-3), 5.18 (2H, t, J ) 4.8 Hz, NH), 5.38 (2H, d, J ) 3.7 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 15.99, 18.73, 19.29, 21.04, 22.56, 22.82, 23.84, 24.28, 27.71, 27.82, 28.01, 28.23, 31.85, 31.90, 35.79, 36.19, 36.56, 36.90, 38.01, 39.52, 39.72, 42.32, 42.94, 50.01, 56.14, 56.69, 63.77, 65.85, 75.38, 76.25, 122.99, 139.31, 156.27, 169.44. Elemental Anal. Calcd for C70H108N2O8: C, 76.04; H, 9.85; N, 2.53%. Found: C, 76.17; H, 9.81; N, 2.45%. Dicholesteryl 3,3′-[4,6-Decadiynylenebis(oxycarbonylamino]]dipropionate (3b). Obtained as a white solid (46% yield); mp 169.4-172.7 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.27-2.38 (8H, m, H-4, tCCH2), 2.51 (4H, t, J ) 5.7 Hz, CH_CO), 3.44 (4H, q, J ) 5.9 Hz, CH2NH), 4.13 (4H, t, J ) 5.9 Hz, CHQO), 4.63 (2H, m, H-3), 5.18 (2H, br s, NH), 5.38 (2H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.84, 15.98, 18.71, 19.29, 21.02, 22.55, 22.81, 23.82, 24.26, 27.76, 27.86, 27.99, 28.21, 31.83, 31.88, 34.71, 35.77, 36.17, 36.53, 36.56, 36.94, 38.09, 39.49, 39.71, 42.29, 50, 56.12, 56.67, 63.33, 65.78, 74.44, 76.29, 122.79, 139.46, 156.3, 171.78. Elemental Anal. Calcd for C72H112N2O8: C, 76.28; H, 9.96; N, 2.47%. Found: C, 76.58; H, 9.93; N, 2.42%. Dicholesteryl 4,4′-[4,6-Decadiynylenebis(oxycarbonylamino)]dibutyrate (3c). Obtained as a white solid (63% yield); mp 149.6150.7 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 2.26-2.40 (12H, m, H-4, tCCH2, CH2CO), 3.22 (4H, q, J ) 6.2 Hz, CH2NH), 4.12 (4H, t, J ) 5.9 Hz, CH2O), 4.61 (2H, m, H-3), 4.84 (2H, br s, NH), 5.37 (2H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.87, 16.05, 18.73, 19.33, 21.04, 22.57, 22.83, 23.84, 24.29, 25.18, 27.79, 27.91, 28.02, 28.24, 31.86, 31.91, 31.95, 35.80, 36.19, 36.60, 36.97, 38.13, 39.52, 39.74, 40.44, 42.32, 50.03, 56.15, 56.70, 63.34, 65.80, 74.17, 76.34, 122.73, 139.58, 156.44, 172.68. Elemental Anal. Calcd for C74H116N2O8: C, 76.51; H, 10.06; N, 2.41%. Found: C, 76.26; H, 9.88; N, 2.35%. Dicholesteryl N,N′-[4,6-Decanediynylenebis(oxycarbonyl)]di(L-alaninate) (3d). Obtained as a white solid (50% yield); mp 138.4-139.2 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.31 (4H, d, J ) 4.4 Hz, H-4), 2.35 (4H, t, J ) 7.0 Hz, tCCH2), 4.14 (4H, t, J ) 6.0 Hz, CH2O), 4.31 (2H, quint, J ) 7.3 Hz, CHCO), 4.65 (2H, m, H-3), 5.25 (2H, d, J ) 7.7 Hz, NH), 5.38 (2H, m, H-6). 13C NMR (CDCl3): δ 11.86, 15.99, 18.71, 18.87, 19.31, 21.03, 22.56, 22.82, 23.83, 24.28, 27.67, 27.84, 28.01, 28.22, 31.84, 31.91, 35.79, 36.18, 36.57, 36.90, 37.92, 39.52, 39.72, 42.31, 49.68, 50, 56.13, 56.67, 63.53, 65.82, 75.18, 76.27, 122.93, 139.32, 155.61, 172.49. Elemental Anal. Calcd for C72H112N2O8: C, 76.28; H, 9.96; N, 2.47%. Found: C, 76.30; H, 10.14; N, 2.39%. Dicholesteryl N,N′-[4,6-Decanediynylenebis(oxycarbonyl)]di(D-alaninate) (3e). Obtained as a white solid (54% yield); mp 150.5-152.2 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.27-2.40 (8H, m, tCCH2, H-4), 4.14 (4H, t, J ) 5.9 Hz, CH2O), 4.31 (2H, quint, J ) 7.1 Hz, CHCO), 4.65 (2H, m, H-3), 5.23 (2H, d, J ) 7.7 Hz, NH), 5.38 (2H, br s, H-6). 13C NMR (CDCl ): δ 11.86, 16.00, 18.73, 18.90, 19.32, 21.04, 3 22.56, 22.83, 23.84, 24.29, 27.63, 27.85, 28.02, 28.23, 31.85, 31.90, 35.79, 36.19, 36.56, 36.89, 37.96, 39.52, 39.73, 42.32, 49.69, 50.01, 56.14, 56.69, 63.53, 65.83, 75.21, 76.29, 122.98, 139.30, 155.59,

Organogelation and Polymerization of Diacetylenes 172.48. Elemental Anal. Calcd for C72H112N2O8: C, 76.28; H, 9.96; N, 2.47%. Found: C, 76.00; H, 9.97; N, 2.36%. Dicholesteryl3,3′-[5,7-Dodecadiynylenebis(oxycarbonylamino)]dipropionate (4b). Obtained as a white solid (56% yield); mp 179.2-179.4 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.29 (4H, t, J ) 7.0 Hz, tCCH2), 2.32 (4H, d, J ) 7.7 Hz, H-4), 2.51 (4H, t, J ) 5.9 Hz, CH2CO), 3.43 (4H, q, J ) 5.9 Hz, CH2NH), 4.06 (4H, t, J ) 6.2 Hz, CH2O), 4.63 (2H, m, H-3), 5.17 (2H, br s, NH), 5.38 (2H, d, J ) 3.7 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 18.73, 18.90, 19.31, 21.04, 22.56, 22.83, 23.84, 24.28, 24.77, 27.79, 28.01, 28.15, 28.23, 31.85, 31.91, 34.76, 35.79, 36.19, 36.59, 36.96, 38.11, 39.52, 39.73, 42.32, 50.02, 56.14, 56.70, 64.23, 65.70, 74.41, 74.48, 76.93, 122.83, 139.50, 156.50, 171.80. Elemental Anal. Calcd for C74H116N2O8: C, 76.51; H, 10.06; N, 2.41%. Found: C, 75.97; H, 9.93; N, 2.34%. Dicholesteryl4,4′-[5,7-Dodecadiynylenebis(oxycarbonylamino)]dibutyrate (4c). Obtained as a white solid (56% yield); mp 146.4147.0 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 2.24-2.38 (12H, m, H-4, tCCH2, CH2CO), 3.22 (4H, q, J ) 6.2 Hz, CH2NH), 4.05 (4H, t, J ) 6.2 Hz, CH2O), 4.61 (2H, m, H-3), 4.81 (2H, br s, NH), 5.37 (2H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.87, 18.73, 18.91, 19.33, 21.04, 22.57, 22.83, 23.84, 24.29, 24.81, 25.22, 27.79, 28.02, 28.17, 28.24, 31.86, 31.91, 35.80, 36.19, 36.60, 36.98, 38.13, 39.52, 39.74, 40.40, 42.33, 50.03, 56.15, 56.70, 64.18, 65.70, 74.16, 76.82, 122.72, 139.59, 156.62, 172.67. Elemental Anal. Calcd for C76H120N2O8: C, 76.72; H, 10.17; N, 2.35%. Found: C, 76.01; H, 10.03; N, 2.35%. Dicholesteryl N,N′-[5,7-Dodecadiynylenebis(oxycarbonyl)]di(L-alaninate) (4d). Obtained as a white solid (54% yield); mp 127.2-128.8 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.22-2.38 (8H, m, H-4, tCCH2), 4.07 (4H, t, J ) 6.0 Hz, CH2O), 4.31 (2H, quint, J ) 7.0 Hz, CHCO), 4.66 (2H, m, H-3), 5.22 (2H, br d, J ) 7.3 Hz, NH), 5.38 (2H, m, H-6). 13C NMR (CDCl ): δ 11.86, 18.73, 18.89, 19.32, 21.04, 22.56, 3 22.83, 23.84, 24.29, 24.75, 27.69, 28.02, 28.11, 28.24, 31.85, 31.91, 35.80, 36.19, 36.58, 36.91, 37.93, 39.52, 39.73, 42.33, 49.68, 50.01, 53.42, 56.14, 56.69, 64.42, 65.71, 75.16, 122.93, 139.35, 155.81, 172.54. Elemental Anal. Calcd for C72H112N2O8: C, 76.51; H, 10.06; N, 2.41%. Found: C, 76.65; H, 10.04; N, 2.33%. Dicholesteryl N,N′-[5,7-Dodecadiynylenebis(oxycarbonyl)]di(D-alaninate) (4e). Obtained as a white solid (65% yield); mp 148.2-149.5 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.802.05 (m, aliphatic), 2.30 (4H, t, J ) 6.8 Hz, tCCH2), 2.34 (4H, d, J ) 8.1 Hz, H-4), 4.08 (4H, t, J ) 5.9 Hz, CH2O), 4.31 (2H, m, CHCO), 4.65 (2H, m, H-3), 5.22 (2H, d, J ) 6.6 Hz, NH), 5.38 (2H, s, H-6). 13C NMR (CDCl3): δ 11.87, 18.73, 18.90, 19.32, 21.05, 22.57, 22.83, 23.85, 24.29, 24.76, 27.64, 28.02, 28.11, 28.24, 31.85, 31.91, 35.80, 36.19, 36.57, 36.90, 37.97, 39.53, 39.74, 42.33, 49.68, 50.02, 53.43, 56.15, 56.70, 64.42, 65.72, 75.18, 76.93, 122.97, 139.33, 155.81, 172.53. Elemental Anal. Calcd for C74H116N2O8: C, 76.51; H, 10.06; N, 2.41%. Found: C, 76.80; H, 10.05; N, 2.34%. Dicholesteryl N,N′-[5,7-Dodecadiynylenebis(oxycarbonyl)]di(L-leucinate) (4f). Obtained as a white solid (24% yield); mp 74.875.7 °C. 1H NMR (CDCl3): δ 0.68 (6H, s, H-18), 0.80-2.05 (m, aliphatic), 2.23-3.37 (8H, m, tCCH2, H-4), 4.07 (4H, t, J ) 6.2 Hz, CH2O), 4.31 (2H, m, CHNH), 4.65 (2H, m, H-3), 5.12 (2H, d, J ) 8.4 Hz, NH), 5.37 (2H, m, H-6). 13C NMR (CDCl3): δ 11.81, 18.68, 18.83, 19.27, 20.98, 21.90, 22.53, 22.78, 22.82, 23.79, 24.23, 24.52, 24.7, 27.66, 27.95, 28.05, 28.18, 31.79, 31.86, 35.74, 36.14, 36.52, 36.86, 37.92, 39.47, 39.68, 41.90, 42.26, 49.95, 52.48, 56.09, 56.63, 64.39, 65.70, 74.94, 122.8, 139.34, 156.12, 172.61. Elemental Anal. Calcd for C80H126N2O8: C, 77.25; H, 10.21; N, 2.25%. Found: C, 76.63; H, 10.22; N, 2.22%. Didodecyl 5,7-Dodecadiynylenebis(oxycarbonylaminoacetate) (8a). Obtained as a white solid (58% yield); mp 89.7-90.4 °C. 1H NMR (CDCl3): δ 0.88 (6H, t, J ) 7.0 Hz, CH3), 1.23-1.36 (36H, m, aliphatic), 1.54-1.67 (8H, m, aliphatic), 1.74 (4H, quint, J ) 7.0 Hz, CH2CH2O), 2.30 (4H, t, J ) 6.8 Hz, tCCH2), 3.96 (4H, d, J ) 5.1 Hz, CH2NH), 4.10 (4H, t, J ) 6.4 Hz, CH2O), 4.15 (4H, t, J ) 6.8 Hz, CH2O), 5.14 (2H, br s, NH). 13C NMR (CDCl3): δ 14.12, 18.87, 22.69, 24.71, 25.80, 28.07, 28.52, 29.21, 29.35, 29.49, 29.56, 29.63, 29.64, 31.91, 42.71, 64.69, 65.68, 156.44, 170.17. Elemental Anal. Calcd for C42H72N2O8: C, 68.82; H, 9.90; N, 3.82%. Found: C, 68.67; H, 9.77; N, 3.79%. Didodecyl N,N′-[5,7-Dodecadiynylenebis(oxycarbonyl)]di(Dalaninate) (8e). Obtained as a white solid (58% yield); mp 79.4-

Langmuir, Vol. 20, No. 19, 2004 7915 79.8 °C. 1H NMR (CDCl3): δ 0.88 (6H, t, J ) 6.8 Hz, CH3CH2), 1.20-1.37 (36H, m, aliphatic), 1.41 (6H, d, J ) 7.3 Hz, CH3CH), 1.56-1.67 (8H, m, aliphatic), 1.74 (4H, m, CH2CH2O), 2.29 (4H, t, J ) 6.8 Hz, tCCH2), 4.08 (4H, br t, J ) 5.9 Hz, CH2O), 4.12 (2H, dt, J ) 10.6, 6.9 Hz, CHHO), 4.15 (2H, dt, J ) 10.6, 6.9 Hz, CHHO), 4.35 (2H, quint, J ) 7.1 Hz, CH), 5.21 (2H, br d, J ) 6.6 Hz, NH). 13C NMR (CDCl3): δ 14.12, 18.89, 22.70, 24.75, 25.80, 28.10, 28.54, 29.21, 29.35, 29.51, 29.57, 29.63, 31.92, 49.59, 64.46, 65.64, 65.73, 76.92, 155.82, 173.19. Elemental Anal. Calcd for C44H76N2O8: C, 69.44; H, 10.07; N, 3.68%. Found: C, 69.39; H, 9.93; N, 3.61%. Synthesis of Compounds 5 and 9. 1,1′-Carbonyldiimidazole (1.30 g, 8.0 mmol) was added to a solution of 4,6-decadiyne1,10-diol (665 mg, 4.0 mmol) in dry dichloromethane (50 mL), and then the resulting solution was stirred for 3 h at room temperature. Cholesteryl 3-aminopropionate (4.0 mmol) and dodecylamine (4.0 mmol) were added to the mixture, and the stirring was continued for 3-5 days. The solution was washed with saturated NaCl solution and dried over sodium sulfate. After evaporation of the solvent, the residue was subjected to gel column chromatography (SiO2; dichloromethane/ethyl acetate). Compounds 3c (510 mg, 11% yield), 5, and 9 were obtained. Cholesteryl 3-{[10-(dodecylaminocarbamoyloxy)-4,6-decadiynyl]oxycarbonylamino}propionate (5). Obtained as a white solid (631 mg, 18% yield); mp 111.3-112.6 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.28-2.41 (6H, m, t CCH2, H-4), 2.51 (2H, t, J ) 5.7 Hz, CH2CO), 3.16 (2H, q, J ) 6.5 Hz, NHCH2CH2CH2), 3.44 (2H, q, J ) 5.8 Hz, NHCH2CH2CO), 4.13 (4H, t, J ) 5.7 Hz, CH2O), 4.60-4.67 (3H, m, H-3, NH), 5.18 (1H, br s, NH), 5.38 (1H, d, J ) 4.4 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 14.13, 16.04, 18.72, 19.31, 21.04, 22.56, 22.70, 22.82, 23.83, 24.29, 26.77, 27.79, 27.88, 27.94, 28.02, 28.23, 29.30, 29.35, 29.55, 29.59, 29.63, 29.65, 29.99, 31.85, 31.92, 34.73, 35.80, 36.19, 36.55, 36.59, 36.96, 38.12, 39.52, 39.73, 41.05, 42.32, 50.02, 56.14, 56.70, 63.19, 63.35, 65.75, 65.80, 74.48, 76.30, 76.40, 122.83, 139.49, 156.31, 156.41, 171.82. Elemental Anal. Calcd for C54H88N2O6: C, 75.30; H, 10.30; N, 3.25%. Found: C, 75.50; H, 10.20; N, 3.17%. 4,6-Decadiynylene Bis(dodecylcarbamate) (9). Obtained as a white solid (221 mg, 9% yield); mp 113.7-114.9 °C. 1H NMR (CDCl3): δ 0.88 (6H, t, J ) 7.0 Hz, CH3), 1.20-1.52 (m, aliphatic), 1.83 (4H, m, CH2CH2O), 2.34 (4H, t, J ) 6.6 Hz, tCCH2), 3.16 (4H, q, J ) 6.4 Hz, CH2NH), 4.13 (4H, t, J ) 5.9 Hz, CH2O), 4.66 (2H, br s, NH). 13C NMR (CDCl3): δ 14.13, 16.05, 22.70, 26.77, 27.95, 29.30, 29.35, 29.56, 29.59, 29.63, 29.66, 29.99, 31.93, 41.06, 63.21, 65.77, 76.37, 156.42. Elemental Anal. Calcd for C36H64N2O4: C, 73.42; H, 10.95; N, 4.76%. Found: C, 73.48; H, 10.76; N, 4.61%. Synthesis of Compounds 6 and 10. Compounds 4a (13% yield), 6, and 10 were obtained from 5,7-dodecadiyne-1,12-diol, cholesteryl aminoacetate, and dodecylamine in the same manner as described for the synthesis of compounds 5 and 9. Cholesteryl [12-(dodecylaminocarbamoyloxy)-5,7-dodecadiynyl]oxycarbonylaminoacetate (6). Obtained as a white solid (23% yield); mp 107.8-108.4 °C. 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.30 (4H, t, J ) 6.8 Hz, tCCH2), 2.33 (2H, d, J ) 8.1 Hz, H-4), 3.15 (2H, q, J ) 6.2 Hz, NHCH2CH2), 3.93 (2H, d, J ) 5.1 Hz, NHCH2CO), 4.06 (2H, t, J ) 6.0 Hz, CH2OCO), 4.10 (2H, t, J ) 6.2 Hz, CH2OCO), 4.64 (1H, br s, NHCH2CH2), 4.68 (1H, m, H-3), 5.16 (1H, br s, NHCH2CO), 5.38 (1H, d, J ) 4.0, H-6). 13C NMR (CDCl3): δ 11.86, 14.12, 18.72, 18.88, 18.91, 19.29, 21.04, 22.56, 22.70, 22.82, 23.83, 24.28, 24.73, 24.83, 26.77, 27.71, 28.01, 28.09, 28.22, 29.30, 29.35, 29.56, 29.59, 29.63, 29.65, 30.01, 31.85, 31.90, 31.92, 35.79, 36.19, 36.56, 36.91, 38.01, 39.52, 39.72, 41.04, 42.32, 42.94, 50.01, 56.14, 56.69, 64.06, 64.65, 65.66, 65.74, 75.36, 122.98, 139.32, 156.45, 156.61, 169.49. Elemental Anal. Calcd for C55H90N2O6: C, 75.47; H, 10.36; N, 3.20%. Found: C, 75.12; H, 10.28; N, 3.22%. 5,7-Dodecadiynylene Bis(dodecylcarbamate) (10). Obtained as a white solid (15% yield); mp 91.2-91.5 °C. 1H NMR (CDCl3): δ 0.88 (6H, t, J ) 7.0 Hz, CH3), 1.19-1.35 (36H, m, aliphatic), 1.48 (4H, m, CH2), 1.59 (4H, m, CH2), 1.71 (4H, m, CH2), 2.29 (4H, t, J ) 6.8 Hz, tCCH2), 3.16 (4H, q, J ) 6.4 Hz, CH2NH), 4.06 (4H, t, J ) 6.0 Hz, CH2O), 4.62 (2H, br s, NH). 13C NMR (CDCl3): δ 14.12, 18.91, 22.70, 24.83, 26.77, 28.20, 29.30, 29.35, 29.56, 29.59, 29.63, 29.65, 30.01, 31.92, 41.04, 64.05, 65.66, 156.61.

7916


Elemental Anal. Calcd for C38H68N2O4: C, 73.98; H, 11.11; N, 4.54%. Found: C, 73.99; H, 10.85; N, 4.47%. Synthesis of Cholesteryl 5,7-Icosadiynyloxycarbonylaminoacetate (7). 1,1′-Carbonyldiimidazole (357 mg, 2.2 mmol) was added to a solution of 5,7-icosadiyn-1-ol (639 mg, 2.2 mmol) in dichloromethane (30 mL), and then the mixture was stirred for 2 h at room temperature. Cholesteryl aminoacetate (976 mg, 2.2 mmol) was added to the solution, and the stirring was continued for 4 days. The solution was washed sequentially with water and saturated NaCl solution, and then it was dried over sodium sulfate. After evaporation of the solvent, the residue was subjected to column chromatography (SiO2; dichloromethane/ ethyl acetate, 10:1). Compound 7 was obtained as a wax (1.18 g, 71% yield). 1H NMR (CDCl3): δ 0.68 (3H, s, H-18), 0.80-2.05 (m, aliphatic), 2.24 (2H, t, J ) 7.1 Hz, tCCH2), 2.29 (2H, t, J ) 6.8 Hz, tCCH2), 2.33 (2H, d, J ) 8.1 Hz, H-4), 3.93 (2H, d, J ) 5.5 Hz, CH2CO), 4.10 (2H, t, J ) 6.4 Hz, CH2O), 4.68 (1H, m, H-3), 5.14 (1H, br t, NH), 5.38 (1H, d, J ) 4.0 Hz, H-6). 13C NMR (CDCl3): δ 11.86, 14.13, 18.73, 18.91, 19.21, 19.30, 21.04, 22.57, 22.70, 22.83, 23.84, 24.29, 24.76, 27.72, 28.02, 28.10, 28.24, 28.34, 28.88, 29.12, 29.36, 29.49, 29.64, 29.67, 31.85, 31.91, 31.93, 35.80, 36.19, 36.57, 36.92, 38.02, 39.53, 39.73, 42.33, 42.95, 50.02, 56.15, 56.70, 64.68, 65.13, 65.85, 75.36, 76.58, 77.89, 122.98, 139.32, 156.45, 169.48. Elemental Anal. Calcd for C50H81NO4: C, 79.00; H, 10.74; N, 1.84%. Found: C, 78.73; H, 11.06; N, 1.78%. Gelation and Polymerization Test. The gelator and solvent were placed in a screw-capped bottle or in a screw-capped quartz cell and heated until the solid dissolved. The solution was then

Nagasawa et al. cooled to room temperature on standing. For estimation of the gel-sol phase transition temperature (Tgel), ca. 0.1 mL of a hot solution was put in a screw-capped quartz cell having a 1-mm light path. The cell was left at room temperature until gelation completed and was then immersed horizontally in a water bath. The temperature was raised at 1 °C min-1. The Tgel was defined as the temperature at which the gel disappeared. The photoirradiation of the gel was performed using a 500-W super-highpressure mercury lamp (Ushio USH-500D) without using filters. Determination of Polymer Yield. A 1 wt % cyclohexane gel in a quartz cell having a 10-mm light path was irradiated with light from a 500-W super-high-pressure mercury lamp. After irradiation, the reaction mixture was diluted with dichloromethane and filtered using a 0.2-µm filter unit. The yield was calculated from the weight of the insoluble fraction. Determination of Quantum Yield. A 1 wt % cyclohexane gel in a quartz cell having a 10-mm light path was irradiated using the 254-nm light from a 150-W xenon lamp (SX-150) equipped with a M10 monochromator (Bunkoh-Keiki Co. Ltd.). The number of photons absorbed by the sample was determined using potassium ferrioxalate actinometry. The light absorbed was 3.23 × 10-11 einsteins s-1. The irradiated mixture was diluted with dichloromethane and filtered using a 0.2-µm filter unit. The conversion was calculated from the weight of the insoluble fraction. The quantum yield was calculated from the data obtained at 5.4-5.8% conversion.

LA049459N

Organogelation of Diacetylene Cholesteryl Esters Having Two

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