Insight into the Dynamics of Lanthanide-DTPA Complexes As Revealed by Oxygen-17 NMR.

Luca Fusaro, Francesca Mocci, Robert N. Muller, Michel. Luhmer

Research output: Contribution to journalArticlepeer-review


DTPA chelates of various diamagnetic and paramagnetic lanthanide(III) metal ions, as well as the chem. similar DTPA chelate of Y3+, were studied in aq. soln. by variable temp. 17O NMR with the aim of characterizing their internal dynamics. As a consequence of poor chem. shift dispersion and fast quadrupole relaxation, no dynamic exchange process could be detected for the diamagnetic complexes nor for the Sm-DTPA complex. In contrast, the spectra recorded for the Eu-DTPA complex show chem. exchange due to the well-known racemization process and, at high temp., feature signal broadening that reveals a fluxional process involving the interchange of the coordinated and noncoordinated oxygen atoms of the carboxylate groups. The spectra recorded for the Pr-DTPA complex feature coalescence events due to such a fluxional process, which is ascribable to the rotation of the carboxylate groups. The activation free energy barriers detd. exptl. are remarkably lower than the calcd. activation barriers recently reported for the rotation of the carboxylate groups of various Ln-DOTA complexes. Furthermore, the smallest activation free energy measured for the Pr-DTPA complex, about 45 kJ mol-1, is significantly lower than the activation free energy characterizing the racemization process. The fluxional behavior of the carboxylate groups is, however, not expected to significantly affect the residence time of the water mol. coordinated to the metal ion. [on SciFinder(R)]
Original languageEnglish
Pages (from-to)8455-8461
Number of pages7
JournalInorganic Chemistry
Issue number15
Publication statusPublished - 2012
Externally publishedYes


  • dynamics lanthanide DTPA complex oxygen 17 NMR
  • contrast agent NMR MRI


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