Schiff Base–Derived Colorimetric Chemosensor for Fe 3+ Detection: Synthesis, Mechanistic Insights, and Real‐World Applications in Water Quality Monitoring

A Schiff base colorimetric chemosensor (H 2 L), synthesized from 2‐hydroxy‐1‐naphthaldehyde and anthranilic acid, was developed for selective Fe 3+ detection. In a DMF:H 2 O (9:1, v/v) medium, H 2 L exhibited a distinct and selective response to Fe 3+ among common competing cations, producing a visible color change from yellow to black and a new broad absorption band at 504 nm. Job’s plot indicated a 1:1 binding stoichiometry, and the association constant was 2.87 × 10 4 M −1 . The sensor showed a low detection limit of 3.71 μM by UV–Vis titration, and its practical applicability was validated by spike–recovery analysis in real water samples (recoveries 91.04%–100.94%). A paper‐strip assay enabled rapid on‐site screening with smartphone image analysis, achieving an LOD of 50.7 μM. These results highlight H 2 L as a simple and effective platform for Fe 3+ monitoring in water‐relevant matrices.