Is Ferromagnetism an Intrinsic Property of the Cu^II/Gd^III Couple? 1. Structures and Magnetic Properties of Two Novel Dinuclear Complexes with a μ-Phenolato−μ-Oximato (Cu,Gd) Core

Two original dinuclear (Cu^II,Gd^III) complexes (1 and 2) deriving from polydentate nonsymmetrical Schiff base ligands LⁱH₂ have been prepared. Formally they differ by the length of the diamino chain. They crystallize in the orthorhombic Pbca (No. 61) (1) and in the monoclinic P2₁/n (No. 14) (2) space groups. The cell parameters are a = 12.6295(7) Å, b = 20.7894(9) Å, c = 18.3301(13) Å, and Z = 8 for 1 and a = 12.7246(16) Å, b = 13.5691(17) Å, c = 14.5310(19) Å, β = 94.629(16)°, and Z = 4 for 2. These structural studies show that in both complexes the Cu^II and Gd^III ions are doubly bridged by a phenolato oxygen atom and an oximato (N−O) pair. The bridging network is not planar. The more important distortions are observed for the complex having the larger diamino chain. Unexpectedly the latter complex presents an antiferromagnetic interaction, but the related J value is small (J ≅ −0.49 cm^-1). In the former complex the interaction is ferromagnetic (J ≅ 3.5 cm^-1) as it is for complexes containing (CuO₂Gd) bridging cores which yield J values varying from 1.4 to 10.1 cm^-1.