A new azo dye, 5,5-[1,2-phenylenebis(2,1-biazenediyl)]bis[8-quinolino], was synthesized by reacting the diazonium salt of o-phenylenediamine with 8-hydroxyquinoline. The ligand was subsequently used to prepare a series of metal complexes with V(IV), Fe(III), Cr(III), Mn(II), Mo(VI), and Ru(III). The ligand was characterized using 1H and 3C-NMR spectroscopy, while the metal complexes were analyzed using UV-Vis, FT-IR, and mass spectrometry, along with thermal analysis (TGA, DSC), (C.H.N.), conductivity measurements, magnetic susceptibility, and metal and chlorine content analysis, the results indicated that the ligand exhibits tetracoordination. The complexes predominantly formed octahedral geometries, except for the vanadium complex, which exhibited a square pyramidal structure. Furthermore, all complexes were found to be non-electrolytes. The antioxidant activity of all the compounds were evaluated using DPPH as a free radical and gallic acid as a reference standard. The inhibition efficiency of the complexes varied according to their IC50 values. Additionally, the compounds were tested for antibacterial activity against Escherichia coli and Bacillus spp. and for antifungal activity against Penicillium, Aspergillus niger, Fusarium, and Trichoderma at two different concentrations. The results revealed varying degrees of bacterial and fungal growth inhibition compared to the control