Green synthesis of colorimetric molecular probes based on Schiff base and computational study

Purpose This paper aims to synthesize a colorimetric molecular probe for Fe(III) based on a Schiff base, prepared by the condensation of 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid. Design/methodology/approach The synthesized probe was thoroughly characterized by empirical and theoretical methods, including FT-IR, UV–Vis and NMR spectroscopy, supported by Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations to investigate electronic properties and validate the sensing mechanism. Findings The probe exhibited a strong and selective response to Fe(III) ions in DMF/H2O, with a clear bathochromic shift (450 and 504 nm) consistent with a reduction of the HOMO–LUMO gap from 3.77 to 3.25 eV. TD-DFT calculations predicted transition energies at 454 and 498 nm, in excellent agreement with experiment. The selectivity was confirmed against competing metal ions [Ca(II), Al(III), Pb(II), Mn(II), Cr(III)], and real-sample testing in spiked tap showed high recoveries (98%). Originality/value This study demonstrates that Schiff-base-derived molecular probes can serve as sensitive and selective Fe(III) sensors, combining practical environmental applicability with fundamental insights into electronic structure. The findings highlight the potential role of such probes in organic optoelectronic and sensing applications.