The new azo dye was prepared from the reaction of the diazonium salt derived from 3-aminophenol with 2- hydroxyquinoline, then it was used to prepare a series of complexes with the chlorides of cobalt, chromium, copper, nickel, platinum, palladium and ammonium molybdate. The ligand was identified by a proton and carbon nuclear magnetic resonance spectroscopy, and the compounds were collected. The prepared materials were subjected to infrared, ultraviolet-visible, and mass spectrometry, as well as thermogravimetric analysis, differential calorimetry, and elemental analysis. Conductivity, magnetic susceptibility, metal content, and chlorine content of the complexes were also measured. The results showed that the ligand behaves in a trigonal behavior, and the proposed formula for it was correct, and that the complexes gave tetrahedral and octahedral shapes, except for palladium, square planar shape was given. The results also showed that the complexes contain water within the coordination field and that all of them are non-electrolytes. The dyeused the complexes prepared from it to determine their ability to inhibit free radicals by measuring their ability as antioxidants using DPPH as a free radical and ascorbic acid as a standard substance, and determining the value of IC50, as it was found that the ligand had a high ability to inhibit free radicals, and the ability to inhibit the complexes varied according to the value of IC50. The results are as follows (H2L > Ascorbic acid > Cu-complex > Mo-complex > Pt-complex > Ni-complex > Pd-complex)
