Thienopyrimidine‐derived multifunctional fluorescence sensor for the detection of Cu²⁺, Fe³⁺, and PPi in different solvents

Hydrazine substituted thienopyrimidine, a new fluorophore, was used to synthesize a novel Schiff base R1 as a chemosensor via the condensation with p ‐formyltriphenylamine, and the structure was confirmed using nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) analysis. When treated with Cu 2+ in dimethylsulfoxide (DMSO)/H 2 O buffer, R1 showed a phenomenon of fluorescence quenching, which was reversible with the action of ethylenediaminetetraacetic acid (EDTA). When treated with Fe 3+ in dimethylformamide (DMF)/H 2 O buffer, R1 exhibited the same phenomenon, but fluorescence was recovered with inorganic pyrophosphate (PPi) quantitatively. The complexation ratios for R1 ‐Cu 2+ and R1 ‐Fe 3+ were both 1:2, which were manifested by MS titrations and corresponding Job's plots. The limits of detection of R1 for Cu 2+ and Fe 3+ were 3.11 × 10 −8 and 1.24 × 10 −7 M, respectively. The sensing mechanism of R1 toward Cu 2+ and Fe 3+ was confirmed using density functional theory calculations and electrostatic potential analysis. Test strips of R1 were fabricated successfully for on‐site detection of Cu 2+ and Fe 3+ . In addition, R1 was applied to recognize Cu 2+ and Fe 3+ in actual water samples with satisfactory recovery.