A Review on Synthesis and Biological Activities of 2‐Aminophenol‐Based Schiff Bases and Their Transition Metal Complexes

Abstract

ABSTRACT2‐Aminophenol‐based Schiff bases and their metal complexes have drawn a lot of interest because of their wide range of biological activity and their uses in several fields. These Schiff bases are synthesized through the condensation of 2‐aminophenol and various carbonyl compounds, and metal complexes formed easily by coordinating Schiff bases with transition metal ions possess a wide range of intriguing properties that have rendered them promising candidates in biomedical research. These compounds have a diverse array of captivating biological properties including antibacterial, antifungal, anticancer, and antioxidant actions. Their versatile nature and potential for tailored modifications hold the promise for innovative biomedical applications. Compared to standard antibiotics and other studied compounds, C2, C8–C11, and C116 complexes, along with L16 and L17 ligands, exhibit the highest antibacterial activity, while C3 and C115 complexes demonstrate the highest antifungal activity. The metal chelate formation of the ligands enhanced the antimicrobial activity by increasing their lipophilic nature. C66, C76, and C112 complexes and L39 ligand showed higher anticancer activity than standard anticancer drugs. The metal complexes have higher anticancer activity than the ligand due to improved permeability and cellular uptake. The anticancer activity of the complexes is related to the substituents of the Schiff base ligands. In compounds containing an electron‐withdrawing group (e.g., Cl or Br or NO2), the activity is obviously better than others. Ligands L1–L3 and L5, L6, and L32 demonstrated the most potent antioxidant activity, surpassing both metal complexes and standard conventional antioxidants. The ligands showed greater antioxidant activity than the metal complexes due to their capability of donating free protons to scavenge free radicals. More study is needed to fully explore the potential of 2‐aminophenol‐based Schiff bases and their transition metal complexes for the development of new drugs. This review summarizes different synthetic methods, biological activities, and the structure–activity relationship. This study aims to conduct further research on 2‐aminophenol‐based Schiff bases and their metal complexes.