Accelerating water exchange in GdIII–DO3A-derivatives by favouring the dissociative mechanism through hydrogen bonding

[Abstract] The GdIII-complexes of DO3A-acetophenone and ortho- or para- hydroxyacetophenone ligands have been investigated to assess the effect of the presence of a phenol group on the relaxivity and on the water exchange rate of these potential MRI contrast agents. H-Bonding between the ortho-phenol(ate) groups and the water molecules involved in the dissociative exchange mechanism is shown to speed up the water exchange rate by stabilizing the eight-coordinate transition state.This work was carried out under the EU COST Action CA15209 "European Network on NMR Relaxometry". The authors thank Centro de Supercomputación de Galicia (CESGA) for providing the computer facilitie