ANTISYMMETRIC AND ANISOTROPIC EXCHANGE AS STUDIED BY EPR IN A MOLECULAR COMPOSITE [NH3-(CH2)-NH3]CUCL4

The monoclinic crystal structure of [NH3-(CH2)(2)-NH3]CuCl4 consists o f two-dimensional (b: c) layers of square planar (CuCl4)(2-) entities, separated from each other by [NH3-(CH2)(2)-NH3](2+) alkylene chain sh eets. Electron Paramagnetic Resonance (EPR) data have been obtained in single crystals of 2C(2)CuCl(4) when rotated around a, b and c -axes , at X-band. Only one EPR exchange-collapsed line was observed for the two magnetically inequivalent copper ions in the lattice. The angular variation of its position and peak-to-peak linewidth were measured in three perpendicular planes. A careful analysis of experimental data p ermits to obtain the principal values of the g-factor g(perpendicular to) = 2.053: g(parallel to) = 2.274. The contributions to the linewidt hs were analyzed in terms of the antisymmetric exchange (d) and the an isotropic exchange (D) and yielded \d(x)/d(y)\ = 0.92 and \(d(2)(2) 2.2D(2))(1/2)/d(y)\ = 0.65. Lineshape studies show that the exchange b etween the two inequivalent copper ions is anisotropic.