An overview of the synthesis, structure, biological activity and catalytic application of bis(salicylidine) complexes of cobalt

Bis(salicylidene) Schiff base ligands and their cobalt complexes have been widely studied owing to their structural versatility, stability, and multifunctional applications. Cobalt occupies a distinctive role among transition metals due to its earth-abundance, variable oxidation states, and biological relevance. This review provides a comprehensive overview of the synthesis strategies, structural features, biological activities, and catalytic applications of cobalt bis(salicylidene) complexes. Particular emphasis is placed on the relationship between ligand coordination, stereoelectronic effects, and the resulting functional properties. These complexes have shown promising activity in antimicrobial and anticancer studies, as well as efficiency in oxidation and polymerization catalysis. Looking forward, cobalt bis(salicylidene) chemistry is expected to expand into new areas such as photocatalysis, CO₂ reduction, and sustainable energy applications. Furthermore, systematic exploration of structure–activity relationships in biological systems and the integration of computational approaches (DFT, docking) are anticipated to accelerate the rational design of complexes with enhanced catalytic and biomedical potential. The less explored applications of these complexes are also highlighted.