Potentiometric Investigation of the Formation of 1:1 and 1:2 Complexes of Ed (Ⅲ), Nd (Ⅲ) and Pr (Ⅲ) with 3-4, Dihydroxyphenylalanine and 3-4, Dihydroxyphenylethylamine in Aqueous Solution

摘要

Interaction of catacholamines namely 3-4, -dihyroxyphenylalanine (DOPA) and 3-4, dithydroxyphenyiethylamine (Dopamine) with Ed (Ⅲ), Nd (Ⅲ) and Pr (Ⅲ) ions have been studied in aqueous 0.1M KCl by potentiometry at 25℃. The acid dissociation constants of the protonated ligands DOPA (H_4L) and Dopamine (H_3L) are determined and the stepwise formation constants for the formation of different protonated and normal 1:1 and 1:2 complexes have been calculated. The possible coordination sites of DOPA and Dopamine co-ordinate to metal ions at different pH values are explained.