Stabilities and coordination modes of methionine in copper(II) mixed-ligand complexes with ethylenediamine, diethylenetriamine or N, N, N′, N′′, N′′-pentamethyldiethylenetriamine in aqueous solution

Solution equilibrium studies on the Cu(II)-polyamine-Methionine ternary systems (polyamine: ethylenediamine, diethylenetriamine, N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) have been performed by pH-potentiometry, UV-Vis spectrophotometry and EPR methods. Our spectroscopic results indicate the tetragonal geometry for the [Cu(en)(Met)]+, the geometry slightly deviated from square pyramidal for the [Cu(dien)(Met)]+ species and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me5dien)(Met)]+ species.