Synthesis and Characterization of Novel 1,8-Naphthalimide Derivatives and Their Application in Metal Ion Detection

A series of N-butyl-1,8-naphthalimide derivatives substituted at the C4 position were synthesized via a three-step reaction sequence involving nucleophilic substitution and acylation. The products were characterized by IR and 1H and 13C NMR spectroscopy and mass spectrometry. The structure of compound 4f was validated by single crystal X-ray diffraction analysis. Compound 4f crystallizes in a monoclinic space group P21/c with a = 17.080 (3), b = 15.900 (3), c = 7.9210 (16) Å, α = 90.00°, β = 91.12 (3)°, γ = 90.00°, and V = 2150.7 (7) Å3. The synthesized compounds were screened for fluorescence responses to various metal ions. Only compound 4d exhibited a selective response, showing a 13.5% fluorescence quenching upon the addition of Fe3+ and demonstrating excellent efficiency in detecting Fe3+. Therefore, this work is expected to provide a promising fluorescent probe for the detection of Fe3+.