Biphenyl Bis(amino alcohol) Oxalamide Gelators: Complex Gelation Involving Coupled Equilibria, Central‐to‐Axial Chirality Transfer, Dia­stereoisomer Interconversion, and Self‐Sorting

Abstract

Chiral gelators 3 and 4, with two valinol‐ or leucinol‐oxalamido arms attached to the 2,2′‐positions of the proatropisomeric biphenyl group, were prepared, and their gels were studied. Compound (R,R)‐3 in the solution and gel states forms a mixture of major [(R,aR,R)‐3] and minor [(R,aS,R)‐3] diastereomers due to central‐to‐axial chirality transfer. 1H NMR studies of its toluene gel provide evidence of diastereomer interconversion and self‐sorting, which results in exclusive incorporation of (R,aR,R)‐3 into the gel network. Gels formed in the 10–3 M concentration range show an irregular Tg/concentration dependence, which is in contrast to those formed in the 10–2 M concentration range. The peculiar properties of the former gels may be explained by kinetic effects due to the presence of coupled equilibria comprising diastereomer interconversion and (R,aR,R)‐3 self‐assembly where the rate of gelation becomes dependent on the rate of formation of the gelling (R,aR,R)‐3 from the nongelling (R,aS,R)‐3.

The Effect of Branched Alkyl Chain Length on the Properties of Supramolecular Organogels from Mono-N-Alkylated Primary Oxalamides

“…Oxalamide compounds are of considerable interest due to their potential in biomedical applications [34][35][36][37][38][39][40][41][42][43][44][45], catalysis [46][47][48], foods [49], and self-assembling behavior to form gels [50][51][52][53][54][55][56]. The oxalamide functional group consists of two amide groups next to each other in reverse mode, connected by two consecutive carbonyl groups, which has been extensively used as supramolecular synthon to generate LMWGs [50][51][52][53][54][55][56][57][58].…”

“…Oxalamide compounds are of considerable interest due to their potential in biomedical applications [34][35][36][37][38][39][40][41][42][43][44][45], catalysis [46][47][48], foods [49], and self-assembling behavior to form gels [50][51][52][53][54][55][56]. The oxalamide functional group consists of two amide groups next to each other in reverse mode, connected by two consecutive carbonyl groups, which has been extensively used as supramolecular synthon to generate LMWGs [50][51][52][53][54][55][56][57][58]. A variety of bis, homo and hetero-functionalized bolaform, oxalamide-based gelators have been reported over the past two decades [50][51][52][53][54][55][56], while only two reports of mono-functionalized, primary oxalamide gelators exist to date [57,58].…”

“…The oxalamide functional group consists of two amide groups next to each other in reverse mode, connected by two consecutive carbonyl groups, which has been extensively used as supramolecular synthon to generate LMWGs [50][51][52][53][54][55][56][57][58]. A variety of bis, homo and hetero-functionalized bolaform, oxalamide-based gelators have been reported over the past two decades [50][51][52][53][54][55][56], while only two reports of mono-functionalized, primary oxalamide gelators exist to date [57,58]. Thus the present study aims to report new LMWGs based on mono-N-alkylated primary oxalamides (Scheme 1) and evaluate the effect of different sized, branched tail-groups on the supramolecular gelation behavior and gel properties.…”

An Encyclopedic Compendium on Chemosensing Supramolecular Metal‐Organic Gels

“…[291] Their antimicrobial applications [292] can be explored as biomedical coating materials. [293] Myriad gelators scaffolds are available based on phenolic, [294] amide functionality [295] or carboxylate moeity, [296] acylhydrazone, [297] nucleoside: [298] guanosine, [299] sugar, [300] Schiff base, [301] naphthalene diimide, [302] bis(L-Leu-oxalamide), [303] bis(amino alcohol)oxalamide, [304,305] bisphenol A, [306] 1,3 : 2,4-dibenzylidenesorbitol, [307] barbiturate [308] amino acids viz. histidine [309] or alanine-based, [45] peptide/ peptidomimetics, [21,49] steroid, [7] other nitrogen-based [310] benzimadzole, terpyridine, and so on.…”

Oxalamide-Bridged Ferrocenes: Conformational and Gelation Properties and In Vitro Antitumor Activity

“…The systematic work of Žinić et al on the gelation properties of bis­(amino acid) ( I ) and bis­(amino alcohol) oxalamide ( II ) gelators (Figure a) showed that gelation is governed by strong and directional intermolecular hydrogen bonding of the oxalamide units. Moreover, the symmetrical oxalamides that contained achiral amino acids or were meso diastereomers crystallized in contrast to those containing chiral amino acids or amino alcohols, which tended to form gels in certain solvents. ,− …”