Rapid, Sensitive, and Selective "ON-OFF" Detection of Fe³⁺ Ions Using Novel Acetalophanes and Their Applications in Real Samples

Three novel acetalophanes 1a-c have been designed, synthesized and characterized. The receptors 1b-c, featuring bulky anthracene groups, displayed significant selectivity for Fe3+ ions, resulting in a turn-off fluorescence mode in a DMF-buffer solution. Conversely, the non-steric probe 1a could serve as a versatile sensor for the simultaneous detection of Fe3+ and Cu2+ ions in MeOH-buffer solution. The sensing mechanism for the capability of 1a was demonstrated to be different, as evidenced by the addition of cyanide ions. The probes with Fe3+ exhibited a sensing mechanism that resulted in the deprotection of acetals to the corresponding starting materials, as confirmed by H-1 NMR, IR spectra and TLC analysis. The attractive features of these practical and efficient sensors are selectivity, sensitivity (limit of detection = 0.15 mu M by 1a, 0.16 mu M by 1b and 0.14 mu M by 1c), rapid response (less than 5 s). The on-site monitoring of various real samples, including well water, apricot, and green tea, proved to be successful for the quantitative and cost-effective detection of Fe3+. The method demonstrated good precision, even in the presence of other interfering materials.