A Highly Fluorescent Pyrene-Based Sensor for Selective Detection Of Fe Ion in Aqueous Medium: Computational Investigations.

In this work, we introduce a highly selective and sensitive fluorescent sensor based on pyrene derivative for Fe(III) ion sensing in DMSO/water media. 2-(pyrene-2-yl)-1-(pyrene-2-ylmethyl)-1H-benzo[d]imidazole (PEBD) receptor was synthesized via simple condensation reaction and confirmed by spectroscopic techniques. The receptor exhibits fluorescence quenching in the presence of Fe(III) ions at 440 nm. ESI-MS and Job's method were used to confirm the 1:1 molar binding ratio of the receptor PEBD to Fe(III) ions. Using the Benesi-Hildebrand equation the binding constant value was determined as 8.485 × 10 M. Furthermore, the limit of detection (LOD, 3σ/K) value was found to be 1.81 µM in DMSO/water (95/5, v/v) media. According to the Environmental Protection Agency (EPA) of the United States, it is lower than the acceptable value of Fe in drinking water (0.3 mg/L). The presence of 14 other metal ions such Co, Cr, Cu, Fe, Hg, Pb, K, Ni, Mg, Cd, Ca, Mn, Al, and Zn did not interfere with the detection of Fe(III) ions. The fluorescence life-time of the receptor PEBD with and without Fe ion was found to be 1.097 × 10 s and 0.9202 × 10 s respectively. Similarly, the quantum yield of the receptor PEBD with Fe and without Fe ion was calculated, and found as 0.05 and 0.25 respectively. Computational studies of the receptor PEBD were carried out with density functional theory (DFT) using B3LYP/ 6-311G (d, p), LANL2DZ level of theory.