This new azo dye 7-(3-hydroxy-phenylazo)-quinoline-8-ol was subsequently used to prepare a series of complexes with the chlorides of Fe, Co, Zn, Ru, Rh and Cd. The compounds identified by 1H and 13C-NMR, FT-IR, UV-Vis, mass spectroscopy, as well as TGA, DSC, and C.H.N., conductivity, magnetic susceptibility, metal and chlorine content. The results showed that the ligand behaves in a trigonal behavior, and that the complexes gave tetrahedral, except for Fe, Ru and Rh octahedral was given, that all of them are non-electrolytes. The effectiveness of both the compounds in inhibiting free radicals was evaluated by the ability to act as an antioxidant was measured using DPPH as a free radical and gallic acid as a standard substance, the IC50 value was determined, because the ligand was found to have a higher ability to inhibit free radicals, and the ability to inhibit the complex varied according to the IC50 value. Cobalt, zinc and ruthenium complexes were evaluated as anticancer agents breast cancer MCF-7 in five concentration, the results showed that the IC50 value for Zn was 43.38 µg/mL, while the ruthenium complex gave 63.57, cobalt complex gave 93.84 µg/mL, meaning that the Zn-complex gave a higher inhibition value than Ru and Co. KEY WORDS: Antioxidant, Azo dye complexes, 8-Hydroxyquinoline, Anticancer Bull. Chem. Soc. Ethiop. 2025, 39(5), 859-875. DOI: https://dx.doi.org/10.4314/bcse.v39i5.5
