Selective aqueous fluorescent probes for metal ions based on benzoyl hydrazone derivatives

Three novel fluorescent compounds were synthesized and employed as fluorescent probes for detecting different metal ions selectively. The naphthol-based probe (I) exhibited weak fluorescence in water, which was enhanced in the presence of Al3+ ions due to the complexation between I and Al3+. In addition, the coumarin-based probe (II) and quinolone-based probe (III) could selectively detect Cu2+ ions and Zn2+ ions, respectively. Unlike the changes in the fluorescence spectra of I and III upon Al3+ ion and Zn2+ ion addition, the fluorescence intensity of II decreased dramatically after Cu2+ ions were added into the aqueous solution. This is due to the fact that different mechanisms occurred in the recognition process for metal ions. Colorimetric monitoring of these processes was also feasible.