Transition metal complexes of N,N-dimethylthreonine: Stability and UV/Vis spectra

Acidity (dehydronation) constants of N,N-dimethylthreonine (DMT) and stability constants of its complexes with Cu+2, Ni+2, and Co+2 were determined in aqueous solution by means of potentiometric titration. UV/Vis spectra were also taken during the titration. It is suggested thatDMT acts as a bidentate ligand toward copper(II) by engaging either (a) amino and carboxyl groups (in [Cu(DMT)] and [Cu(DMT)2]), or, (b) upon dehydronation, amino and hydroxyl groups (in [Cu(DMT)H−1], [Cu(DMT)2H−1], and [Cu(DMT)2H−2]). It is suggested that the coordination in threoninato andallo-threoninato complexes is similar to that described under (a).