A Highly Fluorescent Pyrene-Based Sensor for Selective Detection Of Fe 3+ 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 3  M -1 . 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 3+ in drinking water (0.3 mg/L). The presence of 14 other metal ions such Co 2+ , Cr 3+ , Cu 2+ , Fe 2+ , Hg 2+ , Pb 2+ , K + , Ni 2+ , Mg 2+ , Cd 2+ , Ca 2+ , Mn 2+ , Al 3+ , and Zn 2+ did not interfere with the detection of Fe(III) ions. The fluorescence life-time of the receptor PEBD with and without Fe 3+ ion was found to be 1.097 × 10 -9  s and 0.9202 × 10 -9  s respectively. Similarly, the quantum yield of the receptor PEBD with Fe 3+ and without Fe 3+ 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.