A new azo Schiff-base ligand, (N1Z,N2Z)-N1,N2-bis(4-((Z)4-hydroxy naphthalen-1-yl)diazenyl)-(1,5-dimethy-2-phenyl-1H-pyrazol-3(2H)-ylidene) benzene-1,2-diamine, has been synthesized from coupling (N1Z,N2Z)-N1,N2-bis(4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-ylidene)benzene-1,2-diamine with 1-naphthol. Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), carbon nuclear magnetic resonance (13C-NMR) technique, ultraviolet-visible spectroscopy (UV-Vis), mass analysis, molar conductance and magnetic susceptibility were used to characterize the structures of the new ligand and their transition metal complexes. The complexes were found to have the general formula (M)(L)Cl2 where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), (M)(L)Cl3 where M = Au(III), and (M)(L)Cl2Cl where M = Fe(III). The FTIR results demonstrated that the coordination sites were the azomethine nitrogen and azo nitrogen atoms of the azo Schiff-base ligand. The electronic spectral and magnetic measurement data indicated that the complexes exhibited octahedral geometry, except the Au(III) complex suggested a square planar geometry around the central metal ion. The results showed the highest inhibitory effect for gold the complex. The effect of biological screening of the gold complex on human colon cancer cell line LS-174 was investigated. The gold complex was observed to have the highest inhibitory effect.