NUCLEAR MAGNETIC-RESONANCE STUDIES OF DIAMAGNETIC METAL-DIETHYLENETRIAMINEPENTAACETATE COMPLEXES

The 1H NMR and 13C NMR spectra of the alkaline earth and diamagnetic rare earth metal complexes of DTPA are discussed in terms of the labilities of the metal-oxygen and metal-nitrogen bonds. The various resonance splitting patterns observed in the alkaline earth spectra are correlated with the patterns predicted for possible hexadentate structures involving all three nitrogen donors and averaging for the other three coordination sites by four of the ligand carboxylate groups. A heptadentate structure is proposed for the complexes of DTPA with the lanthanides in which the unbound ligand group is the lone acetate group of the middle nitrogen. © 1979, American Chemical Society. All rights reserved.