Cation-induced supramolecular isomerism in the hydrogen-bonded network of secondary ammonium monocarboxylate salts: A new class of organo gelator and their structures

A series of secondary ammonium monocarboxylate salts have been prepared by reacting variously substituted cinnamic acids and benzoic acids with dibenzylamine. Gelation tests reveal that 19 salts (9 cinnamates and 10 benzoates) are moderate to good gelators of various organic fluids, including commercial fuels such as gasoline and diesel fuel. Structure-property correlation studies based on single-crystal structures of 18 salts indicate that the one-dimensional hydrogen-bonded network is indeed important for gelation. The conformational flexibility of the dibenzyl cation and various intra- and internetwork C-H center dot center dot center dot pi and C-H center dot center dot center dot O interactions appear to be responsible for the stabilization of the one-dimensional network in these salts. The gel fibrils in the xerogel state for 8 salts also adopt a 1D hydrogen-bonded network, as revealed by detailed X-ray powder diffraction studies, further supporting the importance of the one-dimensional network in the gelation process.