Antiferromagnetic Cu–Gd interactions through an oxime bridge

Abstract

The copper complex of a polydentate non-symmetrical Schiff base ligand [LCu]₂, prepared by template synthesis, has been reacted with the series of lanthanide ions. This complex used as a ligand possesses two functions (phenol and oxime) able to coordinate the Ln ions and, according to the Ln ion, three types of complexes are obtained. From La to Eu, trinuclear [(LCu)₂Ln(NO₃)₃] complexes with a double phenoxo–oximato bridge were isolated. From Gd to Ho, the complexes [(LCu)₂Ln(NO₃)₃(H₂O)] are still trinuclear, with a supplementary water molecule linked to the Ln ion but the Cu^II and Ln^III ions are only bridged by the oximato (N–O) pair, the phenoxo oxygen atom being hydrogen-bridged to the Ln-coordinated water molecule. Then, with heavier Ln ions, dinuclear [(LCu)Ln(NO₃)₃(H₂O)₂] complexes are characterized. The magnetic study demonstrates that the oximato bridge is responsible for the antiferromagnetic character of the Cu–Gd interaction, with J_CuGd = −0.63 cm⁻¹ in [(LCu)₂Gd(NO₃)₃(H₂O)], in contrast to the ferromagnetic Cu–Gd interaction induced by the single oxygen atom phenoxo bridge.