Pyridine hydrazide glycoconjugate-based gelators: Facile synthesis and exploring their application in iodide sensing

Abstract

Detection of iodide (I−) holds great importance because of its crucial role in various biological activities in the human body. However, its selective detection using small molecular systems has not been as well-explored as metal complex and metal-framework structures, which are expensive and difficult to synthesize. Here, we have reported the synthesis of a novel class of 4,6-O-protected sugar-pyridine hydrazide derivatives in an environmentally benign condition with moderate yield. The overall characterization was done using NMR, HRMS, single-crystal XRD, and DFT studies. Anomeric forms of the N-glucosylamines were assigned from NMR spectroscopy and single-crystal XRD studies. The selective sensing ability towards I− of the synthesized derivatives has been confirmed through colourimetry, UV–Vis and 1H NMR titration and gelation studies. The 4,6-O-butylidene derivatives 6(a–c) were utilized because of their better solubility for the selective detection of iodide ion in solution, whereas 4,6-O-benzylidene derivatives 7(a–c) were used for the same in gel state for their enhanced gelation ability. Furthermore, the morphology of the xerogels have been analyzed through SEM and the thermal ability has been determined by DSC spectra. The experimental studies suggest that the iodide anion takes part in self-assembly formation with the sugar-pyridine hydrazide derivatives through C–H···I− interaction, which, along with H-bonding, π–π stacking, van der Waal force of interaction enhances the gel formation.