Formation of homo- and heteronuclear complexes of 1-hydroxyethylidene-1,1-diphosphonic acid with Mn^II and Fe^III in aqueous solutions

Abstract

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Systems based on 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), iron(iii)—HEDP and manganese(ii)—iron(iii)—HEDP, were studied by pH-potentiometry combined with mathematical modeling and NMR. Diverse and highly stable heteronuclear iron manganese complexes were found to exist in the heteronuclear system. The formation of the MnH3L23–, FeMnH3L20, Fe2MnHL33–, and MnL2– complexes was established. The relaxation efficiency coefficient REC2 (relaxivity) of these complexes was evaluated at ~2000 mol–1 s–1 L. Therefore, these systems hold promise as MRI contrast agents.