A Perspective on Salen/Salen‐Type N/O‐Donor Ligands and Their Zn/Cd Complexes Biological (Antimicrobial/Anticancer) Activities: Research Progress and Future Challenges

ABSTRACT

From a coordination chemistry perspective, Salen/Salen‐type N/O/S‐donor ligands are a class of Schiff bases of considerable significance, particularly for the synthesis of transition‐metal complexes and for their biological activities, including antimicrobial and cytotoxicity. Such ligands have an imine (─CH═N) and an ─OH group in their structural framework, which are highly responsible for their biological activities, while the phenyl ring enhances lipophilicity and antimicrobial activity. The present perspective explores Salen/Salen‐type Schiff base ligands and their Zinc (Zn)/Cadmium (Cd) complexes across multiple dimensions. The review encompasses research progress between 2014 and 2025. Moreover, the perspectives critically presented the ligand in depth concepts, including its synthesis, limitations of synthetic methodologies, yields, coordination aspects, compartmental classification, and characterization techniques. It thoroughly assesses future research outcomes, covering the potential of Salen‐analogous S / Se compound synthesis and the biological applications of ligands or their Zinc (Zn)/Cadmium (Cd) complexes. The perspective concludes with a valuable guide for the next generation of researchers, especially for Salen/Salen‐type ligands and their Zinc (Zn)/Cadmium (Cd) complexes in coordination chemistry. The review summarizes the synthetic methodologies, characterization, DFT, biological activities, and future challenges of Salen/Salen‐type ligands. The biological and toxic activities were further explained using molecular docking, Structure‐activity relationship (SAR), and ADME/T.