Fluorogenic ferrocenyl Schiff base for Zn2+ and Cd2+ detection

A novel sensor based on acetylferrocene-containing Schiff base (ASB) was synthesized by reaction of α-chloroacetylferrocene and N-(salicylidene)-l-valinmethylester. The structure of the compound was characterized by using elemental analysis and Fourier-transform infrared (FT-IR), 1H nuclear magnetic resonance (NMR), and 13C NMR spectroscopy. Its metal-cation-sensing properties were investigated spectrofluorometrically. ASB served as selective chemosensor for Zn2+ and Cd2+ towards alkali, alkaline-earth, and various heavy-metal ions. It showed significant fluorescence enhancement for Zn2+ and Cd2+ ions, stemming from C=N isomerization and chelation-enhanced fluorescence. The binding modes of the complexes were determined to have 1:1 complexation stoichiometry, and the binding constants were calculated as (6.93 ± 0.25) × 106 M−1 for ASB·Zn2+ and (7.49 ± 0.18) × 105 M−1 for ASB·Cd2+ using the nonlinear curve-fitting method.