Hippuric acid–appended aminothiazole derivatives as ion-responsive metallogelators for visual detection of Ce³⁺

Abstract

A new class of hippuric acid–appended aminothiazole derivatives (1a–4a) was synthesized and systematically evaluated as potential ion‑responsive gelators in the presence of lanthanides such as Ce³⁺, Pr³⁺, Sm³⁺, and Eu³⁺, as well as other metal ions. Most metal–ligand interactions resulted in precipitates, crystalline solids, or clear solutions; however, ligand 2a uniquely induced gelation upon exposure to Ce³⁺ ions. Substituent effects were found to be decisive: a methyl group at the 4‑position of the thiazole ring strongly promoted gel formation, whereas methyl substitution at the 5‑position, phenyl substitution, or the absence of a methyl group exerted a weaker influence. This selective ion responsive gelation establishes a simple supramolecular platform for Ce³⁺ recognition. Importantly, ligand 2a enables rapid, instrument free, on site visual screening of highly contaminated samples, offering a practical and environmentally relevant approach for qualitative or semi quantitative monitoring. While not intended as a highly sensitive analytical method, this strategy highlights the trade-off between simplicity and detection limits compared to more sophisticated instrumental techniques, positioning it as a robust first line tool for environmental sensing applications.