Nonpolymeric Hydrogelator Derived from N-(4-Pyridyl)isonicotinamide

Abstract

A series of pyridyl amides derived from isonicotinic acid, nicotinic acid, and benzoic acid have been synthesized. Only N-(4-pyridyl)isonicotinamide 1 is found to be an efficient hydrogelator with a minimum gelator concentration of 0.37 wt %. A wide range of concentrations (0.37-20 wt %) could be used to form hydrogels. The other amides, namely, N-(3-pyridyl)isonicotinamide 2, N-(2-pyridyl)isonicotinamide 3, N-(phenyl)isonicotinamide 4, N-(4-pyridyl)nicotinamide 5, N-(3-pyridyl)nicotinamide 6, and N-(4-pyridyl)benzamide 7, did not show any gelation properties. Fourier transform infrared spectroscopy, variable temperature 1H NMR, single-crystal diffraction and X-ray powder diffraction (XRPD), and scanning electron microscopy have been used to characterize the gel. Single-crystal diffraction and XRPD studies indicate that the morph responsible for gel formation is different from that in its bulk solid and xerogel.