1H NMR study of the intramolecular rearrangements of the complexes of 2‐hydroxypropane‐1,3‐diaminetetraacetic acid with metal ions

The kinetics of the intramolecular processes of barium(II), zinc(II), cadmium(II) and lanthanum(III) complexes with 2‐hydroxypropane‐1,3‐diaminetetraacetic acid (HPDTA) were investigated by 1H NMR spectrometry. A novel result, the slow Δ, Λ conversion process at room temperature for Zn and LaHPDTA chelates, was observed. The best fittings of the experimental spectra were obtained by computer analysis. These indicate that the activation energy of the Δ, Λ conversion process increases with increasing electrostatic potential for these chelates.