Amide/urea-based simple fluorometric receptors for iodide and Hg2+ ions in aqueous medium: Aggregation induced emission and DFT studies

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 325; p. 125134
• Main Authors: Ghosh, Suprava, Malakar, Chandi C., Pahari, Pallab, Kumar Atta, Ananta
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.01.2025
• Subjects: AIE; DFT; Fluorescence; Hg2+ ions; Iodide ions; Urea-based; Fluorescence; Urea-based; DFT; Iodide ions; AIE; Hg2+ ions
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2024.125134

[Display omitted] •Amide and urea-based fluorometric receptors 1 and 2 were reported for I− and Hg2+ ions in aqueous medium.•Receptor 2 exhibited aggregation-induced emission at high pH.•Stern-Volmer plots and DFT studies explain fluorescence quenching with the presence of iodide ions.•Fluorescence turn-on phenomena were observed after adding Hg2+ ions to the iodide complexes of the receptors.•Practical utilities for detecting I− and Hg2+ ions were highlighted. Herein, we report pyrene-tagged amide and urea-based sugar derivatives 1 and 2 in a simple synthetic pathway to recognize I− and Hg2+ ions. Both molecules showed absorbance and fluorescence selectivity towards iodide ions in THF/H2O (7/3, v/v) medium. The selectivity and sensitivity of 2 for iodide ions are superior to 1 due to more H-bond donors in 2. Interestingly, fluorometric receptor 2 exhibited aggregation-induced emission (AIE) at higher pH with a remarkable fluorometric color change. The AIE phenomenon might be explained by the self-association of 2 after forming imine functionality in the alkali medium. The Stern-Volmer plot showed the fluorescence quenching constant of each receptor with an iodide ion and indicated the quenching pathway. The LODs of 1 and 2 for iodide ions were evaluated as 0.84 and 0.17 µM, respectively. The 1:1 binding stoichiometry of 1 or 2 with iodide was found from the Job plot and verified by measuring the complex mass. Further, the complexes of each receptor with I− ions can detect Hg2+ ions selectively by fluorescence turn-on method with low sensitivities (LODs: 0.008 µM for 1 and 0.01 µM for 2). DFT results were used to understand the binding mode of receptors 1 and 2 with iodide ions and the quenching process in the aqueous THF medium. The real application of the receptors was established for the recovery of iodide and Hg2+ ions from natural water samples.