Chiral Gelators Constructed from 11‐Aminoundecanoic (AUDA), Lauric and Amino Acid Units. Synthesis, Gelling Properties and Preferred Gelation of Racemates vs. the Pure Enantiomers

Abstract

A new class of efficient low molecular weight gelator molecules has been designed by combining 11‐aminoundecanoic acid (AUDA), lauric acid and aromatic and aliphatic amino acid units in the same molecule. This yields a special class of fatty acid amphiphiles with core chiral centres and hydrogen bonding sites. Some of the compounds with terminal carboxylic acid and sodium carboxylate functions exhibited ambidextrous gelation properties, being able to form gels both with highly polar solvents (water, DMSO) and also with highly lipophilic solvents, including two hydrocarbon fuels. At variance with several recent observations that the enantiomers are generally more efficient gelators than the corresponding racemates, some of the racemic gelators prepared in this work were found to be capable of gelling up to 16 times larger volumes of certain solvents than the pure enantiomers. Temperature‐dependent FTIR and 1H NMR studies of the gels formed by derivatives with terminal carboxylic acid groups and lipophilic solvents revealed that intermolecular hydrogen bonding between amidic and carboxylic acid units was involved in the self‐assembly of gel aggregates. Additional strong stabilization of the aggregates was observed in the gelators possessing terminal sodium carboxylate groups, and this was attributed to the electrostatic and ion‐dipole interactions between the sodium carboxylate groups. This additional stabilization appears to be responsible for considerably higher thermal stability of the latter gels in relation to those formed by gelators with terminal carboxylic acid groups. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Reversible Luminescent Gels Containing Metal Complexes

“…[46] The gelators 1 and 2 were synthesized according to an improved and more precise procedure with regard to the previous reported methodology (see Experimental). [26,[47][48][49][50] 1 and 2 are able to solidify DMF and water, respectively. Compound 1 forms a DMF gel by cooling of the hot solution (5 mg of 1 dissolved by heating in 1 mL of freshly distilled solvent) to room temperature.…”

Gelation Ability of Novel Oxamide‐Based Derivatives Bearing a Stilbene as a Photo‐Responsive Unit

“…In order to modulate the solvent gelation tendencies, a series of derivatives with modified terminal functions were prepared. Based on the strong stabilisation of gel aggregates observed in gelators possessing terminal sodium carboxylate groups, [22] the preparation of sodium salts of the corresponding carboxylic acids was carried out, and owing to the good gelation ability of monoalkyloxamide amphiphiles, [23] some derivatives containing a long lipophilic chain, (C 12 ) either bound directly to an oxamide fragment or as an oxyalkyl substituent on a stilbene unit, were also synthesised. Due to the fact that the stereogenic centre in the oxamide-based gelator molecule contributes to its gelation tendency, [17][18][19] an amino acid (-leucine) was included in the structure of some derivatives.…”

Inner Surface Chirality of Single‐Handed Twisted Carbonaceous Tubular Nanoribbons

“…1). 27 Single-handed twisted 4,4′biphenylene-bridged polybissilsesquioxane tubular nanoribbons and single-layered nanoribbons were prepared according to the literature. 26 The pH values were controlled by adding NaOH.…”

“…The characterization and self-assembly behavior of these LMWGs have been reported. 26,27,35 The single-handed twisted 4,4′biphenylene-bridged polybissilsesquioxane tubular nanoribbons and single-layered nanoribbons were prepared at pH = 11.6 with ethanol/water volume ratios of 1.8/2.2 and 1.5/2.5, respectively. The FESEM and TEM images of the nanoribbons are shown in Figures 2 and 3.…”