Crystal structures and magnetic properties of a set of dihalo-bridged oxalamidato copper(II) dimers

A set of four copper(II) complexes, L-1-X and L-2-X (X = Cl, Br: L-1 = N-(L-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and L-2 = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide), have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystals and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensional hydrogen bonded networks of dimeric copper(II)-complexes bridged by two halide ions and with the two metal centers 3.44-3.69 angstrom apart. The geometry at each copper(II) atom is ideal or near ideal square pyramidal. EPR and SQUID studies indicate that all complexes exhibit weak anti-ferromagnetic interactions between the Cu(II) paramagnetic centers, with exchange parameter vertical bar J vertical bar similar to 1 cm(-1). Magneto-structural comparisons among similar dihalo-bridged Cu(II) dinuclear complexes are also provided, and a possible correlation has been established.