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Torres, S ; Martins, JA ; André, JP ; Pereira, GA ; Kiraly, R ; Brücher, E ; Helm, L ; Tóth, E ; Geraldes, CFGC

H5EPTPACH2OH : Synthesis, relaxometric characterization and H-1 NMR studies of the solution dynamics of its Ln(III) complexes

European Journal of Inorganic Chemistry (35) 5489-5499

par Administrateur - publié le

Abstract :

The synthesis and characterization of a new metal chelator, 4-(S)-hydroxymethyl-3,6,10-tri(carboxymethyl)-3,6,10-triaza-dodecanedioic acid (H(5)EPTPACH(2)OH), is reported. Protonation constants for the ligand H(5)EPTPACH(2)OH and for the previously reported H(5)EPTPAC16 have been determined by potentiometry, which reveals that both ligands display slightly higher protonation constants relative to that of the ligand DTPA(5-). The stability constant for the [Gd(EPTPACH(2)OH)(H2O)](2-) complex has also been determined by potentiometry. The obtained value (log K-GdL = 16.7) is two orders of magnitude lower than that for the [Gd(EPTPA)(H2O)](2-) complex, which indicates the destabilizing effect of the pendant hydroxymethyl group at the EPTPA backbone. The microscopic protonation scheme has been deduced from the pH dependence of the H-1 NMR spectra of both H(5)EPTPACH(2)OH and H5EPTPAC16 ligands.