Polychromatic Butterfly‐Shaped Thiopyrimidine‐Derived Schiff Base Probe for Sequentially Detecting Trace In ³⁺ and Fe ³⁺ and Application

A polychromatic butterfly-shaped Schiff base probe DSP was designed and synthesized based on 2, 5-thiophenedicarboxaldehyde and 4-hydrazineyl-5, 6, 7, 8-tetrahydrobenzo [4, 5]thieno[2, 3-d]pyrimidine. DSP could monitor In³⁺ and Fe³⁺ sequentially, accompanied by the "yellow-orange-light green" multicolored change under the naked eye and the "off-on-off" fluorescence performance under the UV lamp in DMF/H₂O = 9/1. DSP showed high sensitivity and selectivity toward In³⁺ and Fe³⁺ in the presence of other metal ions with detection limits of 42 and 68 nM, respectively. The complex stoichiometry of DSP with target ions was determined to be 1:2 via Job's plot analysis, which was further verified by ESI-MS titration and theoretical calculations. DSP has been validated as a promising tool for detecting In³⁺ and Fe³⁺ in real-world water samples. Furthermore, a DSP test strip has been successfully developed, enabling on-the-spot detection of In³⁺ and Fe³⁺.