Fluorescence “Turn-off” Sensing of Iron (III) Ions Utilizing Pyrazoline Based Sensor: Experimental and Computational Study

A simple pyrazoline-based ‘‘turn off’’ fluorescent sensor 5-(4-methoxyphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1 H -pyrazole (PFM) was synthesized and well characterized by different techniques such as FT-IR, 1 H-NMR, 13 C-NMR, and mass spectrometry. The synthesized sensor PFM was utilized for the detection of Fe 3+ ions. Fluorescence emission selectively quenched by Fe 3+ ions compared to other metal ions (Mn 2+ , Al 3+ , Fe 2+ , Hg 2+ , Cu 2+ , Co 2+ , Ni 2+ , Cd 2+ , Pb 2+ , and Zn 2+ ) via paramagnetic fluorescence quenching and showed good anti-interference ability over the existence of other tested metals. Under optimum conditions, the fluorescence intensity of sensor quenched by Fe 3+ in the range of 0 to 3 μM with detection limit of 0.12 μM. Binding of Fe 3+ ions to PFM solution were studied by fluorescent titration, revealed formation of 1:1 PFM-Fe metal complex and binding constant of complex was found to be of 1.3 × 10 5 M −1 . Further, the fluorescent sensor has been potentially used for the detection of Fe 3+ in environmental samples (river water, tap water, and sewage waste water) with satisfactory recovery values of 99–101%. Graphical abstract