Copper(II) complexation by (pyridinyl)aminomethane-1,1-diphosphonic acid derivatives; spectroscopic and potentiometric studies

The complex formation between copper(II) and (pyridinyl)aminomethane-1,1-diphosphonic acid derivatives was studied by means of pH-potentiometry, spectroscopic methods (UV–Vis, EPR) and mass spectrometry (MS). The bisphosphonate ligands form polynuclear Cu3HxL3 (x = 4 ,3, 2, 1, 0, −1) species besides the mononuclear 1:1 and 1:2 metal-to-ligand molar ratio complexes. Two phosphonate groups are basic binding sites for the metal ion. It is suggested that in the polynuclear complexes the ligands adopt chelating and bridging modes via the four oxygen atoms of the two phosphonate groups.

The complex formation between copper(II) and (pyridinyl)aminomethane-1,1-diphosphonic acid derivatives was studied by means of pH-potentiometry, spectroscopic methods (UV–Vis, EPR) and mass spectrometry (MS). It is suggested that the bisphosphonic ligands form a trinuclear Cu3HxL3 (x = 4, 3, 2, 1, 0, −1) species besides the mononuclear 1:1 and 1:2 metal-to-ligand molar ratio complexes.Figure optionsDownload as PowerPoint slideResearch highlights
► The complex formation of copper(II) and bisphosphonic acid derivatives was studied.
► Stability constants and stoichiometry of complexes formed were determined.
► EPR and MS suggest that the bisphosphonic ligands form a polynuclear species.