Formation of oligonuclear complexes between copper(II) and 1-hydroxyethane-1,1-diphosphonic acid

The complex formation between Cu(II) and 1-hydroxyethane-1,1-diphosphonic acid was studied by means of pH-potentiometry and spectroscopy (UV–Vis and EPR). Speciation revealed the formation of a trinuclear complex [Cu3A3]6− besides the mononuclear 1:1 and 1:2 species. In the complex [Cu3A3]6− , which is not formed with other diphosphonic derivatives, the ligands adopt chelating and bridging modes via the four O atoms of the two phosphonates, the alcoholic-OH groups remaining in the protonated form.