Synthesis, crystal structure and magnetic properties of a new dinuclear copper(II) amino acid complex Cu-2(L-arg)(2)(mu-HPO4-O)(mu-HPO4-O,O ')(mu-OH) (-)center dot(H3O)(+)center dot(H2O)(6)

Agradecimentos: We thank Dr. E.E. Castellano (Instituto de Física de São Carlos – USP) for X-ray data collection and to Dr. Mireille Perec (INQUIMAE, University of Buenos Aires and CONICET) for helpful comments on the manuscript. We also thank to the Spanish Research Council (CSIC) for providing some of us with free-of-charge licenses to the Cambridge Structural Database [32], [33], [34]. The work in Brazil was supported by FUNAPE, CNPq, FAPERJ and CAPES. The work in Argentina was supported by Grants CAI+D-UNL, PIP 5274 and ANPCyT PICT 06-13782. M.C.G.P. and R.C. are members of CONICET Abstract: A novel dinuclear copper(II) complex with the amino acid L-arginine (L-arg), with mono and bidentate HPO42- oxoanions and an OH- anion. [CU2(L-arg)(2)(mu-HPO4-O)(mu-HPO4-O,O')(mu-OH)](-) center dot (H3O)(+) center dot 6H(2)O (1) was prepared and its structure was determined by X-ray diffraction methods. The two independent copper ions are in a distorted square pyramidal coordination, each bonded to one L-arginine molecule. These two CU(L-arg) units are bridged by two monoatomic equatorial-apical oxygen ligands belonging to a monodentate hydrogenphosphate group, and to the hydroxyl group. The copper ions in the dinuclear unit at d = 3.1948(8) angstrom are also connected by two equatorial oxygen belonging to a bidentate hydrogenphosphate. This dinuclear character and bridging scheme, not common for metal-amino acid compounds, is a consequence of the properties of the phosphate anions. The magnetic susceptibility at temperatures between 2 and 300 K and the isothermal magnetization curves at T = 2.29(1) K with applied fields up to 9 T were measured. The magnetic data indicate an antiferromagnetic intradinuclear exchange coupling J/k(B) = -3.7(1) K and using a molecular field approximation we estimated a weaker ferromagnetic, interaction J'/k(B) similar to 0.3 K between neighbour dinuclear units CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO CARLOS CHAGAS FILHO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIRO - FAPERJ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado