Bis(thiophen-2-yl-methylene) Benzene-1, 4-Diamine as Fluorescent Probe for the Detection of Fe³⁺ in Aqueous Samples

A Schiff base bis(thiophen-2-yl-methylene)benzene-1, 4-diamine (L) was synthesized and used for selective and sensitive detection of Fe³⁺. L exhibited enhanced fluorescence response at excitation of 365 nm and emission wavelength of 440 nm for Fe³⁺. The formation of a 1:1 complex between L and Fe³⁺ was suggested by Job's plot by fluorescence titration and from optimized structures using Density functional theory (DFT). The fluorescence intensity was directly proportional to concentration of Fe³⁺ (R² = 0.999) with the detection limit of 3.8 × 10^-7 M and the binding constant of 1.20 × 10⁴ M^-1 at pH = 6.0. The probe was used to detect Fe³⁺ in different water samples with the percentage recovery of 99.7-103%. The interference of the other cations are < 5%.