A new fluorescent-colorimetric chemosensor based on a Schiff base for detecting Cr3+, Cu2+, Fe3+ and Al3+ ions.

A new Schiff base derivative fluorescence-colorimetric chemosensor 2-hydroxy-5-[(2-hydroxy-1-naphthyl)methylideneamino]benzoic acid (H3L), has been designed and synthesized. H3L displayed high selectivity and sensitivity for detecting Cr3+, Cu2+, Fe3+ and Al3+ ions in DMF/H2O (v/v = 1/1) solution. When Cr3+, Cu2+ or Fe3+ ions were added, the solution of H3L in DMF/H2O exhibited different color changes. While with the addition of Fe3+ or Al3+ ions, the solution of H3L in DMF/H2O displayed different fluorescence responses. The bonding modes and bonding ratios of H3L and metal ions were explored by the Job's plot, 1H NMR titration, and electrospray ionization mass spectrometry (ESI-MS). The detection limits of H3L with Cr3+, Cu2+, Fe3+and Al3+ ions were 3.37 × 10-7 M, 4.65 × 10-7 M, 3.58 × 10-7 M and 4.89 × 10-7 M, respectively.