Complexes of EDTA in aqueous solutions. Structural aspects from a 13C NMR relaxation study

Abstract

¹³ C NMR relaxation times T₁ of the carboxylate groups in EDTA and its complexes with Mg(II), Ca(II), Zn(II) and Al(III) ions in aqueous solutions were measured at different magnetic field strengths, allowing the determination of the contribution of the chemical shift anisotropy mechanism to the total relaxation rate and, consequently, the shielding tensor (chemical shift) anisotropy of these nuclei. A discussion of these values in relation to the possible structure of these species in solution and a comparison with the values obtained in the solid state were performed.