STRUCTURE AND MAGNETISM OF AN EXCHANGE-COUPLED SYSTEM - AN NMR APPROACH

A binuclear copper(II) complex [Cu(2)L(OH)](ClO4)(2) . 2H(2)O has been synthesized and characterized by X-ray crystallography and H-1-NMR st udies. The crystal structure shows that the bridging angles between Cu (1)-O(1)-Cu(2) and Cu(1)-O(2)-Cu(2) are 98.9(2)degrees and 102.2(2)deg rees respectively. The Cu(1)-Cu(2) distance is 3.0097(12)Angstrom. Thi s indicates that the interaction between the two copper atoms is antif erromagnetic in nature. The geometry around Cu(1) is distorted square- pyramid with one water molecule occupying the axial fifth position, wh ereas, the geometry around Cu(2) is distorted square-planar with weak interactions of one of the perchlorate anion. There are eight molecule s present in the unit cell. There is an interdimer interaction between the dimers. The temperature-dependent H-1-NMR chemical shift studies have been performed on six different protons of this complex which rev eals that the exchange coupling constant(-2J) is same for all protons (208 +/- 1 cm(-1)). However, the hyperfine coupling constant (A') was found to be different in magnitude as well as in sign. We also report solvent dependent NMR properties.