The magnetic anisotropy and electronic structure of binuclear copper (II) acetate monohydrate

Abstract

The magnetic anisotropy of binuclear copper (II) acetate monohydrate has been redetermined by a null deflexion method at temperatures between 80 and 300 K. The new data establish that all previously reported anisotropy measurements have been seriously in error, presumably due to difficulties in correctly identifying the principal crystal axes. The previous necessity to invoke temperature -dependent values for the exchange integral J eff and the g -factors now disappears and the new experimental anisotropies conform closely to Bleaney & Bowers (1952 b ) theory with constant values for the disposable parameters. The magnetic anisotropy is especially sensitive to anisotropy in the high-frequency term of the susceptibility expressions. This enables the controversial electronic spectrum to be assigned in terms of the ligand field transitions 11000 cm -1 ( d z 2 ← d x 2 - y 2 ); 14400 cm -1 ( d xz , yz ← d x 2 - y 2 ) ; 17000 Cm -1 ( d xy ← d x 2 - y 2 ). The nature of the chemical bonding and exchange interaction is discussed.