EFFECTS OF ALTERNATION IN SOME QUASI-ONE-DIMENSIONAL MAGNETIC-MATERIALS

Exchange coupling in Cu(II) and Mn(III) compounds with unusual structures is discussed. {[Cu(bipyrimidine)(OH)(H2O)] (ClO4)}n has an alternatingly bridged structure with alternating ferromagnetic (+ 167.6 cm-1 through the hydroxo bridge) and antiferromagnetic (- 79.8 cm-1 through the bipyrimidine bridge) interactions. Copper(II) phthalate monohydrate has alternating next-nearest-neighbor exchange with J = - 12.3 cm-1 and alpha = 0.06. This is the first member of this class. The compound K2[Mn(III) (salicylate)2][Mn(III) (salicylate)2]{CH3OH]2 has manganese ions in two environments alternating along the chain. A modified model for the chain is presented, and exchange coupling is found to be small since magnetic orbitals are not linked by the bridging ligand.