STABILITY OF METAL-COMPLEXES WITH LIGANDS OF BIOLOGICAL INTEREST - DOPAMINE AND ADRENALINE

The composition and equilibrium constants of magnesium(II), cobalt(II) , nickel(II), copper(II), cadmium(II), lead(II) and iron(III) complexe s with two bidentate catechol ligands : dopamine and adrenaline, were studied in aqueous solution, by using protometric and spectrophotometr ic techniques. Both of the ligands give similar species, with very clo se equilibrium constants. The coordination degree of the metal ion is not greater than two, with the stability order Cu(II) > Pb(II) > Ni(II ) approximate to Co(II) approximate to Cd(II) > Mg(II). Iron(III) give s much more stable complexes with adrenaline, especially the Fe(H2L)(3 +) species in acidic medium.