A rhodamine–bistriazole based fluorescent and colorimetric sensor containing a phenyl linker for Fe(III) detection

A rhodamine-based fluorescent sensor bearing 1,2-phenylenediamine linked to a bistriazole moiety was designed and synthesized through the copper(I)-catalyzed click chemistry. The bistriazole-based sensor containing an aromatic linker was highly selective toward Fe³⁺, among other metal ions in MeCN/H₂O (1:9 v/v, pH 7.0). Upon the addition of Fe³⁺, the solution of the sensor changed from colorless to pink and fluorescence emission increased 614-fold, visually observed within 5 min. For the titration experiments, the absorption and fluorescence intensity were distinctly enhanced with the increasing concentrations of Fe³⁺ and the limit of detection (LOD) was calculated to be 0.15 μM. The binding ratio of the sensor–Fe³⁺ complex was a 1:1 ratio, confirmed by the Job’s plot. Besides, the optimized condition of the sensor for Fe³⁺ recognition was investigated in a pH range of 5.0–7.0.