Water-soluble Schiff base ligands and metal complexes: an overview considering green solvent.

The water-soluble metal complexes with Schiff base (SB) ligands are of great interest to green chemistry researchers due to their stability, cost-effectiveness, eco-friendly, electron-donating ability, and various applications. They have high potential to express their biological activity including anti-inflammatory, anticancer, antibacterial, antifungal, antioxidant, and DNA binding and cleavage. In the recent era, transition metal complexes have played a significant role in different processes such as hydrogenation, carbonylation, oxidation, reduction, epoxidation, hydrolysis, decomposition, and polymerization reactions in industry. However, their limited aqueous solubility may be the major limitation to their potential catalytic, industrial, and clinical applications. In industrial catalytic processes, it has been proven that water can be used as a solvent to minimize the environmental effect of different reactions as well as simple and complete separation. Water is a green solvent, flexible, non-toxic, safe, readily available, environmentally harmless, and inexpensive. Attaching different substituents on Schiff bases enhances the water solubility and catalytic activity. Studies on water-soluble SB complexes will explore these aspects and their prospects for the future evolution of their diverse applications.