A Phenalenone-based Fluorescent Probe for the Detection of Fe³⁺ ions

A phenalenone based "turn on" probe was developed for selective and sensitive detection of Fe³⁺ ions in aqueous solutions. The thiophene-2-carboxaldehyde (receptor unit) was integrated into the 6-amino-1-phenalenone (6-AP) (signal reporter unit) through the C = N bond formation. The probe, 6-APT, operated through subsequent hydrolysis of the C = N bond induced by the coordination of Fe³⁺ ions to the heteroatoms to form highly fluorescent 6-AP. The probe displayed remarkable characteristics such as rapid response time (< 1 min), high analyte selectivity, and low limit of detection (1.3 µM). The sensing approach offered an accurate method for the detection of Fe³⁺ ions in real water samples (tap water and drinking water). In addition to the fluorometric response, the presence of Fe³⁺ ions can be monitored under daylight by the change in the color of the solution. Importantly, this study is the first example of a phenalenone-based sensor developed for metal ion sensing in literature.