3.4. Metal-Chelating Effect

The ultraviolet/visible (UV/Vis) spectra were recorded in methanol using a path length of 1 cm, at room temperature on a Varian CARY100 spectrophotometer (Agilent Technologies, Santa Clara, California, United States) from a range of 200 nm to 500 nm (software CaryWin UV, v. 3.0). The metal-chelating effect was evaluated by described procedures [36] with stock solutions (1.0 × 10⁻⁴ M) in methanol. Iron (III) and copper (II) solutions were prepared in a concentration of 1.0 × 10⁻³ M from FeCl₃ and CuCl₂ in deionized water. Briefly, sequential additions of 33 μL of metal ion solution were performed to 3 mL of compounds 1, 2, and 3.