1-Hydroxyalkane-1,1-diyldiphosphonates as potent chelating agents for metal ions. Potentiometric and spectroscopic studies of copper(II) coordination

Potentiometric and spectroscopic (EPR and absorption) studies have shown that two phosphonic groups bound to the same carbon atom serve as a very powerful binding site for Cu2+ ion in spite of the very high negative charge centred on these groups. The steric effects as well as a high negative charge enforce unusual geometries around the metal ion and the formation of 1:2 complexes is less favourable. These features of the diphosphonic moiety mean that alkoxo-bridged dimer formation via the adjacent hydroxyl groups is less likely.