Synthesis of Coumarinylhydrazone Fluorescent Probe and its Relay Recognition of Cu²⁺ and HPO₄²⁻

A novel coumarinylhydrazone fluorescent probe L was designed and synthesized from 4-(diethylamino)salicylaldehyde, its structure was characterized by NMR, IR. Fluorescence emission spectra showed that in ethanol solution, probe L could form a 1:1 complex L-Cu²⁺ with Cu²⁺ to realize the "turn-off" detection of Cu²⁺ with high specificity and sensitivity (3.7 × 10^–7 mol/L). Meanwhile, the complex L-Cu²⁺ had a specific fluorescence-enhanced response to HPO₄²⁻ with a detection limits down to 5.6 × 10^–7 mol/L and was resistant to the effects of many common anions (NO₂⁻, N₃⁻, CO₃²⁻, SO₃²⁻, HPO₄²⁻, I⁻, Br⁻, F⁻, HCO₃⁻, SO₄²⁻, NO₃⁻, Cl⁻, CH₃COO⁻, Cr₂O₇²⁻, S₂O₃²⁻, P₂O₇⁴⁻). Detection mechanism could be HPO₄²⁻ captured Cu²⁺ of the complex and released the free ligand L. At last, the complex L-Cu²⁺ was successfully applied to the determination of HPO₄²⁻ in different environmental water samples, and the spiked recoveries ranged from 98.05% to 108.18% and the relative standard deviations of 0.75% ~ 2.9%, which had good application prospects.

A new coumarin acyl hydrazone fluorescent probe L was designed and synthesized, which could specifically recognize Cu2+ and HPO42- in a relay manner. In addition, the probe had good prospects for practical applications.