X-ray crystal structure, ESR and potentiometric studies of copper(II) complexes with (2-pyridylmethyl, 3-pyridylmethyl) amine ligand

In this paper, we describe the coordinating behaviour of the (2-pyridylmethyl, 3-pyridylmethyl) amine ligand with the copper(II) ion. This ligand is bidentate and forms, in accordance with the pH values, 1:1 and 1:2 species (ratio metal:ligand). These species were characterized in aqueous solution by ESR spectroscopy and their overall stability constants were determined by potentiometric measurements. In solid state, we obtained the compounds [CuLHCl2](BF4) and [CuL2](BF4)2. In ESR spectroscopy, the first compound is characterized by an axial g tensor (g∥=2.268 and g⊥=2.091), whereas the second one is characterized by a rhombic g tensor (g1=2.185, g2=2.146 and g3=2.026). We crystallized the [CuLHCl2]Cl compound, in hydrochloric medium, from the [CuLHCl2](BF4) powder. The compound obtained is a pseudo octahedral dimeric system, in which each copper(II) is surrounded by two nitrogen atoms and four chloride ions. The intramolecular Cu–Cu distance is 3.859 Å.