Cholesterol-based diazine derivative: selective sensing of Ag+ and Fe3+ ions through gelation and the performance of metallogels in dye and picric acid adsorption from water

Abstract

Cholesterol appended diazine derivative 1 on a 4-hydroxybenzaldehyde scaffold has been designed and synthesized. The compound having diazine as a metal ion binding site forms nice gels with Ag⁺ and Fe³⁺ ions over a series of other metal ions from CHCl₃/CH₃OH (3 : 1, v/v). Strong hydrophobic interaction owing to the presence of cholesterol has a marked contribution in aggregation. The SEM image reveals fibrillar to globular porous microstructures. The true nature of the gels is determined from a rheological study. The Ag⁺ and Fe³⁺-gels are distinguishable with the aid of tetrabutylammonium chloride, tetrabutylammonium bromide or fluoride and ammonium thiocyanate. There is no interference of Fe²⁺ ions in the detection of Fe³⁺ ions. The presence of Fe²⁺ ions in solution can successfully be ascertained through gelation of 1 in the specified solvent upon adding external oxidising agents such as m-CPBA. As an application, both the Ag⁺- and Fe³⁺-gels of 1 act as good adsorbents for adsorption of uranine dye and picric acid from aqueous solution. In this process, the metallogels are recyclable and exhibit excellent efficiency.