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

Abstract

AbstractChiral 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.