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

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.