Abstract
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)center dot 8H(2)O, 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)](2)(4+) cation and an uncoordinated cyclotetraphosphate counter-anion (P4O124-). 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 (T-N) lower than 2 K. The values of paramagnetic Curie-Weiss temperature (0(cw)) and the exchange parameter (J/K-B) emphasize the existence of an antiferromagnetic interaction between the neighboring copper ions. (C) 2012 Elsevier Inc. All rights reserved.