A new pyridoxal-derived gelator for selective recognition of CN− and F− under different conditions

Abstract

A pyridoxal-based new supramolecular gelator 1 is designed and synthesized. Its gelation properties have been tested in various solvents. The gelator 1 forms gels in DMSO/H₂O (10 : 1, v/v) and DMF/H₂O (10 : 1, v/v). The DMF/H₂O (10 : 1, v/v) gel shows a highly cross-linked fibrous morphology and good viscoelastic properties. The gel matrix has been utilized for efficient ‘naked eye’ detection of CN⁻ and F⁻ ions through a phase transition with a colour change. While the DMF : H₂O gel of 1 is broken in the presence of CN⁻, the gel-to-gel colour change takes place upon contact with F⁻ and AcO⁻ ions. The use of Ca²⁺ distinguishes F⁻ from AcO⁻. In solution, ratiometric changes in absorbance for 1 with CN⁻ and F⁻ over other anions are noted with a distinct colour change. Even in emission, a considerable decrease in the intensity of 1 is observed with both the ions. Importantly, the changes are pronounced with CN⁻ compared to F⁻. The anion responsive nature of 1 in the solid state is verified using Merrifield resin-hooked bead 1a. A theoretical study is done to correlate with the experimental findings.