Crystal structure, spectroscopic, magnetic and electronic structure studies of a novel Cu(II) amino acid complex [Cu(l-arg)2(H2O)]2(P4O12)·8H2O

Single crystals of a novel copper (II) complex with the amino acid l-arginine (l-arg) and cyclotetraphosphate, [Cu(l-arg)2(H2O)]2(P4O12)·8H2O, were prepared in aqueous solution and were characterized by X-ray diffraction, spectroscopy (diffuse reflectance, UV–vis and IR) and thermal analysis. Magnetic measurements and electronic structure calculations were also performed. Crystal structure determination reveals that this compound has a nonsymmetrical atomic arrangement, containing mainly a binuclear [Cu(l-arg)2(H2O)]24+ cation and an uncoordinated cyclotetraphosphate counter-anion (View the MathML sourceP4O124−). The tetravalent cation contains two independent Cu(II) ions in two different chemical environments. This compound exhibits an antiferromagnetic (AFM) to paramagnetic (PM) phase transition at a temperature (TN) lower than 2 K. The values of paramagnetic Curie–Weiss temperature (θcw) and the exchange parameter (J/KB) emphasize the existence of an antiferromagnetic interaction between the neighboring copper ions.