A highly selective colorimetric chemosensor for sequential detection of Fe³⁺ and pyrophosphate in aqueous solution

A novel colorimetric chemosensor 1 was designed and synthesized for Fe^3+/2+ and pyrophosphate (PPi). Sensor 1 showed highly selective and sensitive naked-eye color change to Fe³⁺ and Fe²⁺ from yellow to brown in a near-perfect aqueous solution. The detection limits of sensor 1 to Fe³⁺ and Fe²⁺ were estimated to be 0.51 μM and 1.15 μM, respectively, which were much lower than the environmental protection agency guideline (5.37 μM) in drinking water. Significantly, sensor 1 could be used for analytical quantification of Fe³⁺ in real water samples. Moreover, the resulting 1-Fe³⁺ complex could sense pyrophosphate through naked-eye over various anions especially including phosphate-based anions, showing recovery from 1-Fe³⁺ to 1 via demetallation. The detection limit of pyrophosphate was determined to be 6.11 μM in aqueous solution. The sensing mechanisms for Fe^3+/2+ and PPi were proposed by UV–vis titrations, Job plots, and ESI-mass spectrometry analyses.