Is ferromagnetism an intrinsic property of the Cu-II/Gd-III couple? 1. Structures and magnetic properties of two novel dinuclear complexes with a mu-phenolato-mu-oximato (Cu,Gd) core

Two original dinuclear (Cu-II,Gd-III) complexes (1 and 2) deriving from pol ydentate nonsymmetrical Schiff base ligands (LH2)-H-i have been prepared. F ormally 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 = 20.7 894(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 bot h complexes the Cu-II and Gd-III ions are doubly bridged by a phenolate oxy gen 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 antiferromagneti c 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).