Magnetic properties of a new dinuclear copper (II) amino acid complex: [Cu2(L-arg)2(mu-HPO4-O)(mu-HPO4-O,O')(mu-HO)]-·H3O+·(H2O)6

SANTANA, R. C.; VENCATTO, I.; CARVALHO, J. F.; BORTOLUZZI, A. J.; BARBERIS, G. E.; RAPP, R. E.; PASSEGGI, M. C. G.; CALVO, R.

San Lorenzo, MG, Brasil

Congreso; XXX Encontro Nacional de Física da Matéria Condensada; 2007

Sociedad Brasileira de Física

A novel dinuclear copper(II) complex with the amino acid L-arginine (L-arg), with mono and bidentate HPO4 2- oxoanions and an OH- anion. [Cu2(L-arg)2(l-HPO4-O)(mu-HPO4-O,O`)(mu-OH)]-. (H3O)+ . 6H2O (1) was prepared and its structure was determined byX-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 monodentatehydrogenphosphate group, and to the hydroxyl group. The copper ions in the dinuclear unit at d = 3.1948(8)A 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/kB = -3.7(1) K and using a molecular field approximation we estimated a weaker ferromagnetic interaction J0/kB ~ 0.3 K between neighbour dinuclear units.