Cholesterol linked benzothiazole: a versatile gelator for detection of picric acid and metal ions such as Ag+, Hg2+, Fe3+ and Al3+ under different conditions

Abstract

Cholesterol-appended benzothiazole 1 has been designed and synthesized. Compound 1 exhibits gelation in different solvents. The benzothiazole and cholesteryl motifs play a pivotal role in aggregation in organic solvents involving π-stacking and hydrophobic interactions, respectively. As an application, the nitrobenzene gel with good rheological properties has been noted to be useful in molecular recognition studies of multiple analytes ranging from neutral to ionic in nature. It selectively recognizes picric acid (PA) over a series of nitroaromatics by exhibiting a gel-to-sol phase transition with a distinguishable color change from pale yellow to deep yellow. On the other hand, the nitrobenzene gel shows selective recognition potential for Ag⁺ and Hg²⁺ ions through a gel-to-sol phase transition and the cations are distinguished by F⁻. The gelator 1 also reveals a measurable selective interaction with picric acid over a series of nitroaromatics in CH₃CN containing 1% CHCl₃. In CH₃CN containing 1% CHCl₃, compound 1 further shows affinity towards Fe³⁺, Al³⁺ and Hg²⁺ with distinctive features.