A Unique Case of ′in Situ’ Bifluoride Triggered Formation of Supramolecular Organogels Using Isophthalamide Hydrogen Bond Donating Receptors

A novel isopthalamide based receptor H2L2 featuring two p-benzoic acid units has been synthesised and its anion binding properties analysed by 1H-NMR spectroscopy in DMSO-d6/0.5 % H2O. As expected, in the presence of tetrabutylammonium (TBA) fluoride the deprotonation of the carboxylic acid moieties was observed. However, the deprotonated receptor L22− was able to bind the in situ formed HF2− via the formation of H-bonds with the amide NHs. When H2L2 was dissolved in THF and 4 equivalents of TBAF were added in CH3CN a unique sol-gel transition occurred giving rise to a stable thixotropic supramolecular gel. Theoretical calculations elucidated the gelation mechanism and strongly support the findings observed experimentally.