Coordination Chemistry and Antifungal Activity of Metal Complexes: Thiazolidinine Ligands with Co and Ni Transition Metals

Abstract

Thiazolidinone derivatives constitute an important class of heterocyclic compounds that have attracted considerable attention in medicinal and coordination chemistry because of their diverse biological activities and versatile coordination behavior. The presence of heteroatoms such as nitrogen, oxygen, and sulfur within the thiazolidinone ring enables effective chelation with transition metal ions, particularly cobalt(II) and nickel(II). Complexation often enhances the biological efficacy of ligands by increasing lipophilicity, membrane permeability, and metal-mediated biochemical interactions. The present study reviews the coordination chemistry of thiazolidinone ligands with Co(II) and Ni(II) ions and examines the antifungal properties of the resulting metal complexes. Emphasis is placed on ligand design, synthesis, coordination modes, structural characterization, antifungal mechanisms, and structure–activity relationships. The discussion integrates established theories of coordination chemistry, including Crystal Field Theory, Ligand Field Theory, Chelation Theory, and Overtone’s Concept–Tweedy’s Chelation Theory. Available evidence demonstrates that cobalt and nickel complexes generally exhibit superior antifungal activity compared with free thiazolidinone ligands, indicating their potential as promising candidates for future antifungal drug development...