Synthesis and Characterization of Schiff Base Complexes and Their Applications

New water-soluble Schiff base complexes based on tridentate ligands, namely [N-(2-hydroxyethylamino)ethyl]-5-methoxysalicylaldimine (L1H) and 2-[(2-(2-hydroxyethylamino)ethylimino)methyl]phenol (L2H), containing O,N,O donor sets (imine, phenolate, and amine groups), were successfully synthesized and characterized. The study aimed to develop efficient and reusable catalysts for environmentally friendly oxidation processes, providing a sustainable alternative to traditional methods. Two dinuclear oxo-bridged complexes were obtained through the reaction of the corresponding metal salts with these Schiff base ligands under reflux in methanol, ensuring high yield and purity. In addition, a mononuclear complex was prepared by reacting the hydroxyethyl-functionalized Schiff base ligand with the appropriate metal precursor in ethanol, demonstrating the versatility of these ligands in forming stable metal complexes.

The catalytic activity of these complexes was systematically evaluated in the oxidation of various olefins in aqueous medium, using water as a green solvent and different oxidants. The reactions exhibited high conversion rates, excellent selectivity, and remarkable reusability over multiple catalytic cycles, highlighting the practical potential of these complexes. The study also demonstrated that the catalytic performance is significantly influenced by the nature of the oxidant, reaction temperature, and solvent polarity, providing insights for optimizing reaction conditions.

Overall, this work highlights the synthesis of structurally well-defined water-soluble Schiff base complexes as efficient and sustainable catalysts for organic transformations. Their excellent catalytic stability, recyclability, and environmental compatibility make them promising candidates for green and cost-effective oxidation processes in modern synthetic chemistry. These results clarify the chemical nature of the ligands and underline their role in enhancing catalytic performance.