A theoretical study based on the optimum angle and distance between salen Schiff base and Zn (II), Cd (II) and Hg (II) ions was conducted. These investigations were carried out based on ab-initio calculations, to estimate the pair wise interaction energy between the two molecules. In this study the geometries of metal complexes of Zn (II), Cd (II) and Hg (II) ions with salen Schiff base were studied.