Tailor-making of desired assemblies from well-designed monomers: use of calix4arene conformers as building blocks

摘要

J. CHEM. SOC. PERKIN TRANS. I 1993 Tailor-making of Desired Assemblies from Well-designed Monomers: Use of CalixC4larene Conformers as Building Blocks Susumu Arimori, Takeshi Nagasaki and Seiji Shinkai * Department of Organic Synthesis, Faculty of Engineering, Kyushu University, Fukuoka 872, Japan Water-soluble, conformationally-immobilized calix4arenes with cone and 1.3-alternate conformations (cone-I and 1.3-alternate-l , respectively) have been synthesized. In aqueous solution cone-I, with a cone-shaped surface, aggregated into micelles with 20-40 8, diameter whereas 1.3- alternate-1, with a cylindrical surface, could not form such aggregates for concentrations up to 0.010 mol dm-3. In aqueous solution, amphiphilic compounds tend to aggregate so that they can reduce the surface area in contact with water molecules.The energy gain thus obtained is the origin of a hydrophobic force.rsquo; The concept suggests that if the hydro- phobic surface shape of the monomer is different, the resultant aggregate may have different three-dimensional architecture. Thus a desired architecture may be tailor-made by skillfully designing the hydrophobic surface shape of the building block. In the formation of synthetic bilayer membranes, for example, Kunitake eta1.2demonstrated that the aggregation morphology can be partly regulated by the shape of the hard segment inserted into the central part of the amphiphile. For several years, we and others have been accumulating basic knowledge about the syntheses of various calixC4larene conformer^.^ It has been established that introduction of 0-substituents bulkier than an ethyl group (e.g.propyl group) can inhibit the conformational isomerism which occurs via the oxygen-through-the-annulus r~tation.~,~ We here noticed that the surface shape of each conformer is quite different, so that a cone .7: they will aggregate into different three-dimensional architec- tures when they are dispersed into aqueous solution.This idea has already been realized by Regen et al.677 and others8*9 in a two-dimensional monolayer system. Among calixC41arene conformers, the surface shape of the cone and 1,3-alternate forms is particularly different: cone-calix4arene has a lsquo;conersquo;- shaped surface rsquo;rsquo; which will aggregate into a globular micelle Fig.I (a) whereas 1,3-aIternate-calix(4)arenehas a cylindrical surface 5*10.1 which will aggregate into a two-dimensional lamella Fig. I(b). To test this hypothesis, we synthesized water-soluble, conformationally-immobilized 5,11,17,23-tetra- kis(trimethylammoniomethyl)-25,26,27,28-tetrapropoxycal~x-4arene tetrachloride with a cone conformation or with a 1,3-alternate conformation (cone-1 or I ,3-alternate-1, respec- tively). Physical characterizations have shown that in aqueous solution cone-1 forms a micellar structure with a hydrophobic domain inside whereas 1,3-alternate-l does not form any detectable aggregate structure. Preparations of cone- and 1,3-alternate-25,26,27,28-tetra-(a) aggregation ? t +++++ +++++ 7, 3-alternare Fig.1 Expected aggregation modes for cone-shaped cone-I (a)and cylindrical 1,3-alternate-l (b) 888 J. CHEM. SOC. PERKIN TRANS. 1 1993 R'K I4K !famp;j OR 1.3-alternate-1 II I T T II II cone-150t k+ . **.*..I . . . . *.*.*.' . . .....*I . . .**...I . ...-.-40 ' IO-~ lo4 10" Catixarene/moI dm-3 Surface tension plotted against concentration of 1 at 17 "C propoxycalix4arenes have been described previously.5*1 Chloromethylation and subsequent quaternization were con- ducted in a similar manner to those described for 25,26,27,28- tetramethoxycalix4arene. Cone-1 and 1,3-alternate-l were identified by 'H NMR spectroscopy and elemental analysis.* We examined the aggregate formation of cone-1 and 1,3- alternate-1 by three independent methods.Surface tension (Wilhelmy method) of aqueous 1 was measured at 17 "C in 'pure' water.l4 As shown in Fig. 2, the surface tension for cone-1 abruptly decreased at around rnol dm-3 whereas that for 1,3-alternate-1 was almost constant for up to lo4 mol dm-3. In Fig. 3 we illustrate the fluorescence intensity of a hydrophobic probe, 2-anilinonaphthalene in the presence of 1. It is seen from this figure that in the presence of cone-1 the fluorescence intensity abruptly increases at 1.O x mol dmP3 whereas in the presence of 1,3-alternate-l the fluorescence intensity remains constant. The light-scattering measurement (Otsuka Electronics DLS-700) of aqueous 1 at 30deg;C established that cone-1 (0.010 mol dm-3) aggregates into particles with 20-40 A diameter.Examination of CPK molecular models suggests that the length of the long axis of cone-1 is about 15 A. Thus, each particle should consist of several (probably, less than 10) * Cone-1: m.p. (decomp.) 235 "C; d,(D,O; DSS standard; 25 "C; 250 MHzj 1.03 (12 H, t, CCH,), 2.01 (8 H, m, CH, in Pr"), 2.91 (36 14, s, KOR .. w cone l13-altemate 2.0 I I0.5I 0.0 1.o 2.0 3.0 Calixarenex 1O5 /mot dm-3 Fig. 3 Fluorescence intensity of 2-anilinonaphthalene (1 .OO x rnol dm-,) at 450 nm plotted against concentration of 1; 30deg;C excitation wavelength 3 15 nm molecules. In contrast, we could not find any perceptible particle for 1,3-alternate-l (0.010 mol dm-3) by the light- scattering method.The fact that even a particle with 20 8, diameter cannot be found allows us to conclude that 1,3-alternate-1 exists discretely as a monomer even at 0.010 rnol dm-3. We consider that the interaction among cylindrical hydrophobic surfaces of 1,3-alternate-l is not strong enough to maintain the lamellar structure by molecular aggregation. We believe that the formation of the lamellar structure will be realized by introduction of a proper hydrophobic group into 1,3-alternate-l. The foregoing findings consistently support the view that cone-shaped cone-1 forms micellar aggregates at around lop5 rnol dm whereas cylindrical 1,3-alternate-l does not form such aggregates for concentrations up to lop2 mol dmP3.This difference implies that the aggregation mode is well regulated by the surface shape designed on the basis of calixC41arene conformers. It is known that calixC41arene conformers can be modified by various substituents 3*4.15*16 and some of them are useful as a 'core' of starburst dendrimer~.'~.'~ We believe, therefore, that the basic skeleton of calixC41arene conformers is useful for the design of new surface shapes, which will eventually lead to the regulation of the three-dimensional architecture of molecular assemblies. NCH,), 3.44and 4.57 (4 H each, d each, ArCH,Arj, 4.01 (8 H, t, OCH,), 4.23(8H,s,NCH2jand6.97(8H,s,ArH)(Found:C,64.65;H,8.15;N, 5.35. C56H88Cl,N40.H,0 requires C, 64.59; H, 8.73; N, 5.38). 1,3- Alternate-1: m.p.(decomp.) 269 "C; d,(D,O; DSS standard; 25 "C; References 250 MHz) 0.89 (12 H, t, CCH,), 1.56 (8 H, m, CH, in PP), 3.02 (36 H, s, I C. Tanford, TheHydrophobic Effect,Wiley, New York, 1973. 2 T. Kunitake, Y. Okahata, M. Shimomura, S. Yasunami andNCH,),3.72(8H,t,OCH,),3.95(8H,s,NCH2),4.35(8H,s,ArCH,Ar) 1981,103,5401.and 7.36 (8 H, s, ArH) (Found: C, 63.98; H, 8.35; N, 5.2. K. Takarabe, J. Am. Chem. SOC., C,,H,,CI,N40,.2H,0 requires C, 63.49; H, 8.77; N, 5.29). The water 3 K. Iwamoto, K. Araki and S. Shinkai, Tetrahedron,1991,47,4325. content in these samples has been confirmed by a Karl Fischer titration. 4 K. Iwamoto, K. Araki and S. Shinkai, J. Org. Chem.,1991,56,4955. J. CHEM. SOC. PERKIN TRANS. I 1993 5 W. Verboom, S.Datta, Z. Asfari, S. Harkema and D. N. Reinhoudt, J. Org. Chrm., 1992,57, 5394. 6 M. A. Markowitz, R. Bielski and S. L. Regen, Langmuir, 1989,5,276. 7 M. Conner, V. Janout and S. L. Regen, J. Am. Chem. SOC., 1993,115, 1178. 8 Y. Ishikawa, T. Kunitake, T. Matsuda, T. Otsuka and S. Shinkai, J. Chem. Soc., Chem. Commun., 1989,736. 9 Y. Nakamoto, G. Kallinowski, V. Bohmer and W. Vogt, Langmuir, 1989,5, 11 16. 10 J. L. Atwood and S.G. Bott, Top. Inclusion SOC., 1991,3,199and refs. cited therein. 1 I K. Fujimoto, N. Nishiyama, H. Tsuzuki and S. Shinkai, J. Chem. Soc.. Perkin Trans. 2, 1992,643. 12 A. Ikeda. T. Nakasaki, K. Araki and S. Shinkai, Tetrahedron, 1992, 48, 1059. 13 T. Nagasaki, K. Sisido, T. Arimura nnd S. Shinkai, Tetrahedron, 1992,48,797. 14 For the method of the measurement see S. Shinkai. S. Mori, H. Koreishi, T. Tsubaki and 0.Manabe, J. Am. Chem. Soc., 1986, 108,2409. 15 C. D. Gutsche, Culixarenes,Royal Society ofchemistry, Cambridge, 1989. 16 J.-D. van Loon, A. Arduini, L. Coppi, W. Verboom, A. Pochini, R. Ungaro, S. Harkema and D. N. Reinhoudt, J. Org. Chem., 1990, 55, 5639. 17 S. Shinkai, H. Kawabata, T. Matsuda, H. Kawaguchi and 0.Manabe, Bull. Chem. SOC.Jpn., 1990,63, 1272. 18 G. R. Newkome, Y. Hu, M. J. Saunders and F. R. Fronczek, Tetrahedron Lett., 199I, 32, 1 133. Paper 3/00899A Received1 5th February 1993 Accepted Is1 March 1993