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Molecular Recognition Directed Self-Assemblyof Supramolecular Liquid Crystalline Polymersfrom Complementary Chiral ComponentsBy Claudine Fouquey, Jean-M arie Lehn,*and Anne-Marie Levelut

Recognition processes occuring at the molecular level maylead to changes at the level of the material, thus expressingmolecular information on the macroscopic scale. This is thecase namely when the formation of a complementarysupramolecular pair E 3 induces the appearance of a liquidcrystalline phase.'']

If two (or more) units E or 3 are grafted onto a templateT, mixing TE, with the complementary T3,,, may lead to theself-assembly of a linear or cross-linked polymeric supra-molecular species (TE, ,T3,,,)" whose existence is conditionedby the molecular recognition directed association betweenthe E and 3 groups.[21Figure I represents schematically such

* + +

m E Z , T 3 2 ) .Fig. 1, Schematic representation of the formation of a polymeric supramolecu-lar species (TE,, T3,)" by association of tw o complementary ditopic compo-nents TE, and T3,.

[*I Prof. .I.-M. Lehn, Dr. C . FouqueyChimie des Interactions MolC.culairesCollkge de France11, Place Marcelin Berthelot, F-75005 Paris (France)Dr. A.-M. LevehtLaboratoire de Physique des Solides, Universite Paris-SudF-91405 Orsay Cedex (France)

[**I We thank Dr. Frunpise Livulunt for discussion of the optical textures.

a process in the case of two-site (ditopic) complementarycomponents TE, and T3,. The resulting supramolecularpolymeric material (TE,, T32)nmay present liquid crystallineproperties if suitable chains are introduced onto the compo-nents.

We now describe results obtained along these lines in thecase where T is a group derived from tartaric acid and thecomplementary units E, 3 are of uracil (U) and 2,6-diacyl-amino-pyridine (P) type. The formation of triply hydrogen-bonded complementary pairs by these units is well docu-mentedF3 and has been used in separation procedures[41in macrocyclic receptor molecules 'I and for inducing theappearance of supramolecular mesophases."] The tartaricacid (T) unit provides in addition the opportunity to investi-gate the effect of changes in chirality on the properties of thespecies formed.

The required components LP,, LU,, DP,, MP, and MU,derived from L(+),D(-) and meso (M) tartaric acid respec-tively, have been synthesized in a straightforward fashion.Alkylation of the L(+ -N,N,NN-tetramethyltartramideL-lL6]by treatment with NaH in DMF followed byC, ,H, ,OTS[ ~~ ave the bis-ether L-2 (80% ; mp

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hydrogen bonding in a way reminiscent of nucleic base pair-ing.[' '] Indeed, 131 mixtures of the complementary pairs(LP, +LU,) and (MP, +MU,) yielded definite com-pounds, different from their components, in the solvent freestate as well as in solution. In d,-THF they showed down-field shifts (of about 0.2-0.3 ppm for the L mixture) for theNH 'H-NMR signals with respect to the pure substances, asexpected [', 4, 'I if association occurs.["] Marked changesappeared likewise in the circular dichroism spectra of(LP, +LU,). The change of sign and large increase in inten-sity observed on going from THF ( A E , , ~=-1 .4 ;

=+4.0cm-'M-') to ethanol =-100;A C , ~ ~- 5 cm-'M-') solution may be related to aggre-gate formation due to low solubility in ethanol. Similarchanges were reported for mesophases of polynucle-otide~.[ '~I

Of particular interest are the phase transition properties ofthese materials and their mixtures. The thermal and opticalproperties have been studied by differential scanning micro-calorimetry and with a polarizing microscope. The tempera-tures and enthalpies of transition determined are listed inTable 1. It is seen that the pure compounds are solids pre-

Table 1. Temperatures and enthalpies of transition for compounds LU,, LP,,MU,, MP, and their 131 mixtures[a].Material Transition

T ["Cl AH [kcal mol- I]LU, K 216-220 I 11LP2 K 29;45; 58 1 3DP2 K 25-33; 43-54 I 3.5(DPz +LUz) K

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HNAO

P: U :HN 0

The spontaneous formation of microstructures from dif-ferent types of components has been reported, for instancehelical fibers from guanine nucleosides," lyomesophasesfrom diguanosine phosphates," 61 helical and tubular struc-tures from polymerizable lecithins," 71 helical superstructuresand fibers in lipid bilayers from chiral components,['*. andsuperhelical strands from phospholipid-nucleoside conju-gates.["] Molecular recognition affects the properties ofmolecular layers[z1*1 and electron donor-acceptor interac-tions may induce me so phase^.[^^^

The X-ray patterns of the viscous LL, DL and MM mix-tures indicate that they are hexagonal columnar mesophases.The diameter of the columns is nearly the same for the threesystems: - 7 A . A tentative description of the supramolec-ular organization is derived from X-ray diffraction data ob-tained with more or less aligned samples.

For the LL mixture, a period of c=3.45 A along thecolumn axis is indicated; this separation corresponds to thestacking distance between flat heterocyclic groups and iscompatible with a picture in which the base pairs are locatedin parallel planes oriented almost perpendicularly to the axisof the column. Moreover there is evidence that the pairs arearranged in a helicoidal structure with an estimated pitch ofC =12.8 and a mean diameter of 14.7A . Taking into ac-count the density of the material, our data are consistentwith a model in which the columns have a triple helix super-structure, made of three strands resulting from the polyasso-ciation of the two components TP, and TU, in a polymericfashion. O n each strand there are C/c=3.71 residues perturn (120", since it is a triple helix), each residue being alter-natively a (T/2)P.U(T/2) and a (T/2)U.P(T/2) sequence.'241A schematic representation of the supramolecular structure

is shown in Figure 3 (left). The distance between two succes-sive pairs (UP-PU) or (PU-UP) along a helical strand isabout 15 A, which is compatible with the lengths of the UTUand PTP components (in which the spacer groups separatingthe two heterocyclic bases are somewhat different).

For the M M mixture, the main period along the columnaxis is c =3.55 8,with a twofold superstructure. The da ta fita model built on three polymeric strands in a zigzag arrange-ment as shown in Figure 3 (right).

i147A {Fig. 3. Schematic representation of the columnar superstructures suggestedbyth e X-ray data for (LP,, LU,)., (left) and (MP,, MU,), (right); each spotrepresents a PU or UP base pair; spots of the same type belong to the samehelical strand of the triple helix; the dimensions are compatible with an arrange-ment of the PTP and UTU components along the strands indicated (see alsotext); the aliphat ic chains stick out of the cylinder, more or less perpendicularlyto its axis. For (LP,, LU,). a single helical strand and the full triple helix arerespectively represented on the bottom and at the top of the column. For (MP,,MU,)., the representation shown corresponds to the column cut parallel to itsaxis and flattened out.256 0 CH Verlug.~gesellschafimbH, 0 - 6 9 4 0 Weinheim. 990 093S-9648/90/OSOS-O256OZ.SO/O A d v . Mater . 2 (1 990) No. 5

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The LD mixture presents a mesophase with columns ofnearly the same characteristics. There are four residues perturn (120)but each of them has a different conformationinducing a fourfold superstructure in the residue sequence.

The fact that these three materials have different struc-tures shows the profound influence of chirality changes onthe superstructure formed.

The present results indicate that it is possible to engineermolecular components that may form liquid crystalline poly-m e r ~ [ ~ ~ ]f a supramolecular nature (or mesomorphic poly-molecular associations) by the self-assembly of complemen-tary subunits, thus expressing the recognition processoccurring on the molecular level via the formation of amacroscopic mesophase, whose properties may in additiondepend on the chirality of the components. They extendsupramolecular chemistry [l to the formation of polymericsupermolecules.[21The materials obtained also representmesophases resulting from a base pairing process of a biolog-ical type.[261Finally, the formation of these supramolecularmesophases by recognition induced self-assembly involves amolecular information dependent process that leads to thegeneration of intelligent (or informed) supramolecularmaterials.

Received: December 29, 1989

[I ] M.-J. Brienne, J. Gabard, J.-M. Lehn, I. Stibor, J . Chem. Soc. Chem. Com-mun. 1989, 1868.[2] The term polymer will he used here for designating a repetitive poly-molecular association.[3] See fo r instance: G. Simundza,T. D. Sakore, H. M. Sobell,J . M ol . Biol. 48(1970) 263; F. E. Scarhrough, H.-S. Shieh, D. Voet, Proc. Nut l . Acad. Sci .U S A 73 (1976) 3807.[4] B. Feibush, A. Figueroa, R. Charles, K. D. Onan, P. Feibush, B. L.Larger, J. Am. Chem. Soc. 108, (1986) 3310; B. Feibush, M. Saha, K.Onan, B. Karger, R. Giese, ibid. 109 (1987) 7531.[5] A. D. Hamilton, D. Van Engen, J . A m . Chem. SOC. 09 (1987) 5035; A. D.Hamilton, A. Muehldorf, S.-K. Chang, N . Pant, S. Goswami, D. VanEngen, J. Incl. Phen. Molec. Reco. Chem. 7 (1989) 27, and referencestherein.[6] D. Seebach, H. 0 . Kalinowski, W. Langer, G. Grass, E. M. Wilka, Org.Synth. 61 (1983) 24.[7] A. Anantanarayan, V. A. Carmichael, P. J. Dutton, T. M. Fyles, M. J.Pitre, Synlh. Commun. 16 (1986) 1771.[8] J.-P. Behr, J.-M. Girodeau, R. C. Hayward, J.-M. Lehn, J.-P. Sauvage,Helv. Chim. Acta 63 (1980) 2096.

191 K. L. Nagpal, J . Med. Chem. 15 (1972) 121.[lo] Prepared in four steps from 4-benzyloxy-2.6-diaminopyridine:iacetyl-ation (Ac,O, pyridine), hydrogenolysis of the benzyl group (H2 , Pd/C),alkylation with 2-bromoethylacetate (DMF, K,CO,), saponification (INNaOHIMeOH). D. G. Markees, V. C. Dewey, G. W Kidder, J. Med .Chem. I 1 (1968) 126.I l l ] A number of artificial analogues of dinucleotides have been reported, seefor instance: D. T. Browne, J. Eisinger, N. J. Leonard, J. Am. Chem. Soc.90 (1968) 7302; N. J. Leonard, Ace. Chem. Res. 12 (1979) 423; K.Golankiewicz, L. Celewicz, Polish J . Chem. 52 (1978) 1035; 1. Sasaki,M.-N. Dufour, A. Gaudemer, Nouv . J. Chim. 6 (1982) 341; I. Saito, H.Sugiyama, T. Matsuura, K. Fukuyama, Tetrahedron Lett. 1985, 4467;M. S. Kim and G. W Gokel, J . Chem. Sac. Chem. Commun. 1987,1686; T.Ishida, Y. Tokura, M. Shimamoto, M. Doi, M. Inoue, Chem. Pharni. Bull.

Jpn. 35 (1987) 1691; J. L. Sessler, D. Magdal, J. Hugdall,J. Incl. Phen. Mol .Reco. 7 (1989) 19; M . M. Harding, J.-M. Lehn, unpublished results, see inref. 27 ; for a polymeric analogue see: S. Hoffmann, W Witkowski, H.Schuhert, Z. Chem. 14 (1974) 154.[12] Much larger shifts of 1.5-2.0 ppm are found with respect to compoundscontaining a single U or P unit [I] , in line with earlier observations

ADVANCEDMATERIALS[I , 4, 51. This may indicate that the present substances containing two suchunits undergo autoassociation to some extent.[13] G. B. Lortkipanidze, Yu. M. Evdokimov, A . T. Demho, Ya. M .Varshavskii,Moi. B i d . { M os cow) 18 (1984) 466; Chem. Absir. 100 (1984)205164m; S. G. Skuridin, G.B. Lortkipdnidze, 0.R. Musaev, Yu. M.Evdokimov, Vysokomol. Soedin., Ser. A 27 (1985) 2266; Chem. Ahstr. 105(1986) 209302f; Yu. M. Evdokimov, S. G. Skuridin, N. M. Akimenko.ibid. 26 (1984) 2403; Chem. Abstr. 102 (1985) 149691h.

[I41 C. Viney, A . M. Donald, A . H. Windle, J. Muter. Sci. 18 (1983) 1136;A.M. Donald, A. H. Windle. ibid. 18 (1983) 1143; A.M. Donald, C.Viney, A. H. Windle, Polymer 24 (1983) 155; P. Navard, L Polym. Sci.,Polym. Phys. Ed . 24 (1986) 435.[I51 P. Tougard, J.-F. Chantot, W Guschlbauer, Biochim. Biophys Acta 308(1973) 9.[16] G. P. Spada, A. Carcuro, F. P. Colonna, A. Garbesi, G. Gottarelli, Liq .Crys t . 3 (1988) 651; P. Mariani, C. Mazabard, A. Garbesi,G. P. Spada, J.Am. Chem. Soc. 111 (1989) 6369.[I71 J. H. Georger, A. Singh, R. R. Price, J. M. Schnur, P. Yager, P. E. Schoen,J . Am. Chem. SOC.109 (1987) 6169.[IS] N. Nakashima, S . Asakuma, T. Kunitake, J. A m . Chem. Soc. 107 (1985)509.[I91 J.-H. Fuhrhop, P. Schnieder, E. Boekema, W. Helfrich, J . A m . Chem. SO C .I1 0 (1988) 2861.

[20] H. Yanagawa, Y Ogawa, H. Furuta, K. Tsuno, J. Am. Chem. SOC .11(1989) 4567; Chem. L e f t . 1989,403,[21] H. Ringsdorf, B. Schlarh, J. Venzmer, Angew. Chem. In t . Ed. Engl. 27(1988) 113; Angew. Chem. 100 (1988) 117.[22] E. M. Arnett, N. G. Harvey, P. L. Rose, Acc. Chem. Res. 22 (1989) 131.[23] K. Araya, Y. Matsunga, Bull. Chem. SOC. pn . 53 (1980) 3079; H. Rings-dorf, R. Wiistefeld, E. Zerta, M. Ebert, J. H. Wendorff, Anxew. Chem. I n t .Ed . Engl. 28 (1989) 914; Angew. Chem. 101 (1989) 934.[24] The X-ray data are rather intensitive to the doubling of the period inducedby the differences that actually exist between these two species. A singlestrand helical model would have a 3.53 8,pitch and 2.78 residues per turn,and is not compatible with the X-ray patterns , which also exclude a dimericl / l association of two components into a sort of supramolecular cage.[25] Fo r molecular liquid crystalline polymers see: H. Finkelmann, Angew.Chem. I n t . Ed . Engl. 26 (1987) 816; Angew. Chem. 99 (1987) 840.[26] For studies on biomesogens, see: S. Hoffmann, W Witkowski, Am. Chem.Soc. Synip. Ser . 74 (1978) 178; S. Hoffmann. 2. Chem. 27 (1987) 395.1271 J.-M. Lehn, Angew. Chem. I n t . Ed . Engl. 27 (1988) 89; Angew. Chem. 10 0(1988) 91.

Crystal Synthesis under Langmuir Monolayers **By Stephen Mann,* Brigid R . Heywood, Sundara Rajam,Justin B. A . Walker, Roger J . Davey, and J . Derek Birchall

We are currently exploring the potential of crystal synthe-sis under Langmuir monomolecular films. Our aims are todetermine the nature of the molecular recognition processesat inorganic-organic interfaces and to use chemically de-signed macromolecular surfaces as model systems forbiomineralization and in the crystal engineering of inorganic

[*] Dr. S. Mann, Dr. B. R. Heywood, S. Rajam, J. B. A. WalkerSchool of Chemistry, University of BathBath BA27AY (UK)Dr. R. J. DaveyICI plc, Chemicals and Polymers Ltd.Research and Technology DepartmentRuncorn, Cheshire WA7 4Q E (UK)Prof. J. D. BirchallICI Advanced MaterialsRuncorn, Cheshire WA7 4Q E (UK)[**I We thank Mr. J. M. Didymus for assistance with control experiments andMr. B.Chapman for help with X-ray diffraction measurements. The workwas supported by the SERC and ICI plc.

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