Pyridoxal-based low molecular weight progelator as a new chemosensor for the recognition of Ag+ and Hg2+ under different conditions

Abstract

Pyridoxal-based low molecular weight progelator 1 has been designed and synthesized for the selective visual detection of Ag⁺ ions through sol-to-gel conversion. Compound 1 shows excellent gelation property with desired gel stiffness only in the presence of Ag⁺ ions over a series of other metal ions in 1 : 1 (v/v) aqueous solvent system miscible with organic solvents such as DMSO, DMF, and dioxane, and validates the visual detection of Ag⁺ ions. The gel properties were studied by FTIR, UV-Vis, scanning electron microscopy (SEM), and rheology measurements. Minimum gelation concentration was found to be 3 mg mL⁻¹. While Ag⁺-induced metallogel in DMSO/H₂O is thermally reversible, it is irreversible in the DMF/H₂O system. The model compound 2, devoid of hydroxyl groups, did not show gelation under identical conditions and established the role of pyridoxal moiety in 1. In addition, compound 1 exhibits the selective sensing of Hg²⁺ ions over a series of metal ions in the solution phase, as established by UV-Vis, fluorescence, and ¹H NMR studies.