Dissociation Kinetics of TMDTA and TMEDTA Complexes of Lanthanides

Abstract
The dissociation kinetics of TMDTA (trimethylenedinitrilotetraacetic acid) and TMEDTA (tetramethyl-enedinitrilotetraacetic acid) complexes of Ce(III), Eu(III), and Yb(III) ions have been studied in aqueous solution using Cu(II) ions as the scavenger in acetate buffer (I = 0.1 M) at 25°C. All the complexes exhibit acid-dependent and acid-independent pathways in a manner similar to LnDCTA complexes. The buffer concentration dependence of the rate of dissociation has also been investigated. The rates of dissociation of LnTMDTA and LnTMEDTA complexes are much faster than those of LnEDTA complexes. The chelate ring size effect is discussed by comparing the rate constants to those of analogous EDTA and DCTA systems.