A novel bisazo 5-[5-(4,6-dioxo-2-thioxo-hexahydro-pyrimidin-5ylazo)-naphthalen-1-ylazo]-2-mercapto-1H-pyrimidine-4,6-dione (H 4 L) ligand has been synthesized from diazotization coupling between naphthalene-1,5diamine and 2-thiobarbituric acid. Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Fe(III) chelates were prepared. All prepared compounds were characterized by different techniques. The azo groups did not participate in chelation according to the infrared spectra, whereas the thioamide group did participate. The azo dye ligand coordinated with all metallic ions in a neutral−keto−thiol structure and behaved as a bi-and tridentate moiety. Zinc, manganese, and iron chelates had an octahedral structure, while nickel and cobalt chelates had a tetrahedral structure, but the copper chelate had a square pyramidal geometry. The thermal behavior of all prepared compounds was investigated and thermokinetic parameters were also discussed. X-ray diffraction (XRD) data reflected that Fe(III) and Zn(II) complexes were crystalline while the Cu(II) complex was amorphous. Calcination of the Fe(III) complex at 600 °C yielded a nanosized Fe 2 O 3 crystalline phase, elucidated by XRD and transmission electron microscope. The novel azo dye and some of its chelates were tested against HepG-2. The Fe 2 O 3 nanooxide showed remarkable activity against the HepG-2 cell line rather than its precursor Fe(III) complex. Co(II) had a higher antioxidant activity than the other investigated complexes. In both activities, the Cu(II) complex did not show any activity. Molecular modeling and some theoretical studies were validated, and the experimental results were interpreted.