Is ferromagnetism an intrinsic property of the CuII/GdIII 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 (LH2)-H-i 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 P2(1)/n (No. 14) (2) space groups. The cell parameters are a = 12.6295(7) Angstrom, b = 20.7894(9) Angstrom, c = 18.3301(13) Angstrom, and Z = 8 for 1 and a = 12.7246(16) Angstrom, b = 13.5691(17) Angstrom, c = 14.5310(19) Angstrom, beta = 94.629(16)degrees, 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 phenolate 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 congruent to -0.49 cm(-1)). In the former complex the interaction is ferromagnetic (J congruent to 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).