Copper(II) Complexes with Organic Ligands (VII) Magnetic Properties of Copper (II) Acetate and Copper (П) Salicylate Complexes of Pyridine and Quinoline N- Oxides

I t is well known tha t copper (I I) acetate monohydrate has a binuclear bridged structure [1, 2] in which two copper atoms are bonded by four acetate groups and the water molecules are linked to copper atoms in axial terminal positions (Fig. 1). The salient feature of this structure is the close approach of the neighbouring copper atoms Cu—Cu = 2.64 Á, owing to which there is direct copper—copper bonding, arising most likely [3—7] from the lateral overlap of 3dx*_v* orbitals on each copper atom. Owing to this bonding, the magnetic moment is depressed below the spin-only value 1.73 B. M. for one unpaired electron of 3d configuration of the copper(II) ion to the value 1.40 B. M. a t room temperature [3]. Simultaneously a remarkable temperature dependence of the susceptibility is observed [3, 8, 9] which does not obey the Curie—Weiss law but which is compatible with the antiferromagnetic behaviour. The exchange energy \2J\ determined from this dependence is about 300 cm 1 . The water molecules in the terminal positions in the copper(II) acetate monohydrate structure may be substituted [10—12] by other neutral ligands of available field strength so t ha t the binuclear structure with magnetic interaction between the copper atoms is maintained. Similarly the anions of other carboxylic acids