Molecular recognition directed self‐assembly of supramolecular liquid crystalline polymers from complementary chiral components

Abstract

Recognition processes occuring at the molecular level may lead to changes at the level of the material, thus expressing molecular information on the macroscopic scale. This is the case namely when the formation of a complementary supramolecular pair E 3 induces the appearance of a liquid crystalline phase. ''] If two (or more) units E or 3 are grafted onto a template T, mixing TE, with the complementary T3,,, may lead to the self-assembly of a linear or cross-linked polymeric supramolecular species (TE, ,T3,,,)" whose existence is conditioned by the molecular recognition directed association between the E and 3 groups.[21 Figure I represents schematically such * + + mEZ,T32).Fig. 1, Schematic representation of the formation of a polymeric supramolecular species (TE,, T3,)" by association of two complementary ditopic components TE, and T3,. [**I We thank Dr. Frunpise Livulunt for discussion of the optical textures. a process in the case of two-site (ditopic) complementary components TE, and T3,. The resulting supramolecular polymeric material (TE,, T32)n may present liquid crystalline properties if suitable chains are introduced onto the components. We now describe results obtained along these lines in the case where T is a group derived from tartaric acid and the complementary units E, 3 are of uracil (U) and 2,6-diacylamino-pyridine (P) type. The formation of triply hydrogenbonded complementary pairs by these units is well documentedF3 -and has been used in separation procedures[41 in macrocyclic receptor molecules ['I and for inducing the appearance of supramolecular mesophases."] The tartaric acid (T) unit provides in addition the opportunity to investigate the effect of changes in chirality on the properties of the species formed. The required components LP,, LU,, DP,, MP, and MU, derived from L( +), D( -) and meso (M) tartaric acid respectively, have been synthesized in a straightforward fashion. Alkylation of the L( + )-N,N,NN-tetramethyltartramide L-lL6] by treatment with NaH in DMF followed by C,,H,,OTS[~~ gave the bis-ether L-2 (80%; mp < 50°C; from hexane; [a]:' = + 45", c = 0.1, CHCl,), which was hydrolyzed with aqueous HCI (25 %) at reflux[*] to the diacid L-3 (65 YO; mp 76 "C; from hexane; [a];5 = + 14.7", c = 0.9, CHC1,). Treatment of L-3 with PCI, in CH,C1, (18 h, rt)['] gave the corresponding bis-acid chloride which by reaction with 6-hydroxymethyl uracil['] (in HMPA) and with 2,6-diacetylamino-4-(hydroxyethyl)oxy-pyridine~101 (in DMF) in the presence of 4-dimethylaminopyridine (2 eq.; 2 h; rt) afforded respectively the desired compounds LU, (50 %, [a];5 = + 37", c = 0.5, THF) and LP, (27%; [a];' = + 25.5", c = 0.5, THF) after purification by chromatography and crystallization from THF and aqueous ethanol respectively. Following the same reaction sequence D( -) tartaric acid gave DP, (23 %; [a];' = -25.4", c = 0.5, THF). RCOCH(OR)CH(OR)COR' 1 2 3 R = H, R = N(CH,), R = C,,H,,, R' = N(CH3), R = C,,H,,, R' = OH The corresponding compounds derived from meso-tartaric acid were obtained in a similar ...

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…38,39,[64][65][66] LC polymeric complex 12 was prepared through the formation of triple hydrogen bonds. 38,65 The influence of chirality on the mesomorphic behavior of the supramolecular polymers was studied. In a similar manner to the hydrogen-bonded side-chain LC polymers, 37,50-63 main-chain LC polymer 13 was synthesized by using hydrogen bonds between pyridines and benzoic acids.…”

“…The concept of hydrogen-bonded liquid crystals [29][30][31][32][33][34][35][36][37][38][39][40] has been extended to halogen-bonded LC complexes [73][74][75] because of the similarities of these non-covalent interactions. Halogen-bonded main-chain LC polymers were obtained by self-assembly of bifunctional halogen-bonding molecules.…”

“…In addition to hydrogen bonds, [29][30][31][32][33][34][35][36][37][38][39][40] halogen bonds, 74,75 and ionic interactions, 15,[86][87][88][89][90][91][92][93][94] charge-transfer interactions were applied for the preparation of supramolecular LC polymers. 95,96 Ringsdorf et al 95 used charge-transfer interactions between electron-rich triphenylene and 2,4,7-trinitrofluorenone units to produce LC discotic polymers.…”

“…1,2,29,30 Supramolecular hydrogen-bonded LC polymers emerged by introducing supramolecular chemistry into the design of LC polymers. [31][32][33][34][35][36][37][38][39] These polymers were firstly prepared through the formation of complementary hydrogen bonds by Kato and Frechet 37 and Lehn, 38 respectively. They exhibit LC phases in their bulk states.…”

Photoinduced transformations of stiff-stilbene-based discrete metallacycles to metallosupramolecular polymers

“…Supramolecular polymers can be defined as dynamically reversible polymeric arrays (29)(30)(31)(32)(33)(34)(35)(36)(37) that form from the explicit manipulation of noncovalent forces between monomeric units (38)(39)(40)(41)(42)(43). Supramolecular polymer chemistry can readily complement coordination-driven self-assembly, as exemplified by our efforts to design hierarchical supramolecular polymerizations of discrete organoplatinum(II) metallacycles, thus accessing novel supramolecular polymeric materials, such as macroscopic hexagonal supramolecular polymer fibers (44), dendronized organoplatinum(II) metallacyclic polymers (45), and a responsive, cavity-cored supramolecular polymer network metallogel (46).…”