The azo ligand of guanine namely 8-[2-methoxyphenylazo]-guanine (MPAG) was prepared and characterized by elemental analysis, mass spectroscopy, 1H-NMR, FTIR and UV-vis spectroscopies. The Cu(II) and Zn(II) complexes of MPAG ligand were prepared under mole ratio equal to 2:1 as MPAG ligand to metal ions and characterized by 1H-NMR, FTIR, UV-vis, XRD powder and mass spectroscopies and elemental analysis, magnetic susceptibility as well as molar conductance. The solvents did not have a signifi cant eff ect on the NAPAG ligand, and the MPAG ligand exhibited potential changes under diff erent pH values. The MPAG ligand may be utilized as a colorimetric sensor for the particles of Co2+, Ni2+, Cu2+ and Zn in watery solutions. The MPAG ligand is tridentate and the complexes are electrolyte and octahedral.