Secondary Ammonium Dicarboxylate (SAD)A Supramolecular Synthon in Designing Low Molecular Weight Gelators Derived from Azo-Dicarboxylates

The supramolecular synthon namely secondary ammonium
dicarboxylate
(SAD) synthon has been exploited to design a new series of low molecular
weight gelators (LMWGs) derived from azobenzene-4,4′-dicarboxylic
acid and azobenzene-4,4′-diacrylic acid, and various secondary
amines. Single crystal structures of six such salts exclusively established
the presence of SAD synthon. Two such salts namely, dicyclohexylammonium
azobenzene-4,4′-diacrylate (2.DCHA) and dihexylammonium
azobenzene-4,4′-diacrylate (2.DHA) displayed intriguing
gelation properties. Powder X-ray diffraction in combination with
single crystal X-ray data established existence of SAD synthon in
the structure of the gel network of 2.DCHA. UV-irradiation
of the salts as well as the gel did not show any trans–cis isomerization of the azo-moiety.