Potent antimicrobial, antifungal, and antioxidant properties of ruthenium, rhodium, and iridium complexes with hydrazinyl-thiazolyl coumarin derivatives targeting Klebsiella pneumoniae, Candida albicans, and Fusarium solani

A series of nine transition metal complexes of the type [(arene)M{κ²(N∩N’)L}Cl] [M = Ru, Rh, Ir; arene = p-cymene/pentamethyl cyclopentadienyl (Cp*), L = N,N-bidentate coumarin thiazole-based ligand) were synthesized in good yields via reactions between metal precursors [(p-cymene)RuCl₂]₂ and [Cp*MCl₂]₂ (M = Rh/Ir) with hydrazinyl thiazolyl coumarin ligands (L1, L2, L3) in a 1:2 ratio under ambient conditions. The compounds were characterized by various spectroscopic technique like IR, 1H NMR, 13C NMR, mass and UV–visible.The molecular structures of complexes 1, 4, and 7 were confirmed by X-ray crystallography. Antibacterial, antifungal, and antioxidant evaluations revealed that complex 5 exhibited superior antimicrobial activity against Klebsiella pneumoniae, complex 2 outperformed Miconazole against Candida albicans, and ligand L1 and complex 1 were most effective against Fusarium solani. Complexes 1 and 7 demonstrated strong antioxidant activity, comparable to ascorbic acid. [Display omitted] Upon the reaction of metal precursors [(arene)MCl2]2 (M = Ru, Ir, Rh) with hydrazinyl thiazolyl coumarin based ligands (L1, L2, and L3) in a 1:2 (M:L) ratio, yielded neutral complexes.