The azo dye (LH) was used to synthesize a series of complexes with Fe(III), Co(II), Ru(III), and Rh(III) metal ions. The ligand (LH) was synthesized by the condensation reaction between tryptamine and 2-hydroxyquinoline. Due to the presence of effective donor atoms (-N=N- azo and OH hydroxyl groups), the ligand was subsequently refluxed with various metal ions, leading to the formation of nonelectrolytic [M:L] (1:2). These compounds were characterized using 1H and 13C-NMR, FT-IR, UV–Vis, mass spectrometry, TGA, DSC, and C.H.N. analysis, along with conductivity, magnetic susceptibility, and metal and chlorine content measurements. The results indicated that the ligand acts as a bidentate, with the complexes adopting an octahedral geometry. All of the complexes were found to be nonelectrolytes. The effectiveness of both compounds in inhibiting free radicals was evaluated by measuring their antioxidant activity. DPPH was used as the free radical, and gallic acid served as the standard substance. The IC 50 value for each sample was determined. The ligand showed a higher ability to inhibit free radicals compared to the complexes. Moreover, the inhibition ability of the complexes varied according to their IC50 values. The ligand, along with the Co(II), Rh(III), and Ru(III) complexes, was assessed for anticancer activity against MCF-7 breast cancer cells at five different concentrations. The results indicated that the ligand had the highest inhibition with an IC50 value of 49.86 μg/mL. In comparison, the Co complex exhibited an IC 50 of 86.67 μg/mL, the Rh(III) complex had 106 μg/mL, the Fe(III) complex showed 112 μg/mL, and the Ru(III) complex had 124 μg/mL. These results demonstrate that the ligand exhibited a higher inhibition value than the metal complexes.
