Abstract

Two new chromogenic Schiff base ligands were synthesized by the condensation reaction of 4,4’-diaminodiphenylmethane as a primary amine with 2-hydroxy-3-methoxybenzaldehyd and 4-hydroxy-3-methoxybenzaldehyde. The structures of the compounds were characterized by elemental analysis, FT-IR, and 1H NMR. The complexation behavior of the ligands towards some transition metal ions (Fe3+, Co2+, Ni2+, Cu2+, Ag+, Pb2+ and Sn2+) was studied using UV-Vis spectrophotometry. The effects of some experimental parameters on the complex formation such as solvent, metal ions and ligand concentrations were investigated. Both ligands exhibited excellent chromogenic properties towards the complexation with Fe3+ ions over other studied metal ions in DMSO. The addition of Fe3+ions to both ligands gave rise to a large bathochromic shift (from 400 to 610 nm). Thus, resulting in a change of color from orange to green (610nm) and from yellow to green (630nm) for both ligands, respectively, which provided a naked-eye detection of Fe3+ ions in addition to spectroscopic detection. Job’s continuous variation and mole ratio methods were used to determine the stoichiometry of ligands-Fe3+ complexes. Stability constants of the 1:1 (ligand : metal) complexes were found to be equivalent to 5.7×105 and 1.3 ×105, for both complexes, respectively.