Bioactive Properties of Schiff Base Ligands and Metal Complexes Containing Polycyclic Aromatic Hydrocarbons: A Comprehensive Review

Abstract Adequate healthcare and the economy have been negatively impacted by antibiotic‐resistant infections in the population and the healthcare system. The development of newly synthesized drug moieties with an improved and acceptable therapeutic index is urgently needed. Schiff bases (SBs) and their metal complexes (MCs) are flexible molecules, and it was synthesized from the condensation of a carbonyl compound and an amino compound. Moreover, Schiff base structure developed from different kinds of donor atoms like N, O, and S, makes them well‐suited ligands in coordination chemistry. The developed complexes are versatile pharmacophores for designing and creating a significant biologically active lead compound. In this review, we discussed the synthesis of SBs and their MCs using different techniques and their important biological applications. First, this review starts with a brief introduction of SBs and MCs, followed by different synthesis approaches. It summarizes the last 5 years reports of SBs and MCs in different biological activities such as anti‐bacterial, antioxidant, anticancer, anti‐inflammatory, and anti‐fungal applications. Metal complexes containing active functional groups such as ─OH and ─SH exhibit enhanced antibacterial activity and improved permeability through the lipid layers of cell membranes compared to their free ligands. Metal complexes containing halogen groups exhibit enhanced antifungal properties. The anticancer efficacy of metal complexes is significantly influenced by factors such as the length of the N‐alkyl chain, molecular planarity, reduced metal ion charge, and metal chelating capabilities, all of which play crucial roles in inhibiting cancer cell growth. Metal complexes, particularly those of Zn(II) and Cu(II), incorporating electron‐withdrawing groups on phenolic ligands and exhibiting hyperconjugative effects, demonstrate enhanced antioxidant activity. Also, it emphasizes the latest developments in Schiff base coordination chemistry and their prospective use as a bioactive core.