Preparation and characterization of [Zn(L)₂] and [Ru(NO)Cl(L)₂] complexes (L = 8-hydroxyquinoline derivatives) with therapeutic potential

Contemporary medicinal chemistry recognizes heterocyclic ligands, notably quinoline derivatives, as a versatile scaffold for drug discovery. 8‑Hydroxyquinoline (8‑Hq) exhibits multifunctional biological activity, including antibacterial, antifungal, antineoplastic, and neuroprotective effects. In this study, we synthesized and structurally characterized Zn(II) and Ru(II) coordination complexes bearing 5‑chloro‑7‑iodo‑8‑hydroxyquinoline and 5‑SO3H‑8‑hydroxyquinoline ligands, targeting antineoplastic and antifungal applications. Syntheses were performed under controlled conditions with stoichiometries optimized for downstream biological assays. Isolated compounds—[Zn(5‑chloro‑7‑iodo‑8‑hydroxyquinoline)2], [Ru(NO)Cl(5‑chloro‑7‑iodo‑8‑hydroxyquinoline)2], Na[Ru(NO)Cl(5‑SO3‑8‑hydroxyquinoline)2], and Na[Zn(5‑SO3–‑8‑hydroxyquinoline)2]—display satisfactory yields and structural stability. Characterization by 1H NMR, FTIR, and UV–Vis spectroscopy corroborates bidentate chelation of the ligands through N and O donor atoms. 1H NMR spectra reveal aromatic proton deshielding, loss of the phenolic resonance, and ligand deprotonation, consistent with effective metal coordination. In vitro cytotoxicity assays and mechanistic studies are planned to identify promising candidates combining therapeutic potency with low toxicity.