Di- and triheteronuclear Cu-Gd and Cu-Gd-Cu complexes with dissymmetric double bridge.

The study of the Cu-Gd interaction is simplified by the use of heteronuclear Cu-Gd complexes of low nuclearity, such as dinuclear Cu-Gd or trinuclear Cu-Gd-Cu complexes. In the large majority of cases published until now, this interaction presents the advantage of being ferromagnetic. Among the known examples, the complexes with the largest J values have been prepared with use of symmetric Schiff base compartmental ligands, so that the active cores of the molecules involve two phenoxo bridges between the copper and gadolinium ions. Keeping this remark in mind, we decided to synthesize simple complexes in which two different bridges link the copper and gadolinium ions. The structural determinations of a heterodinuclear Cu-Gd and a trinuclear Cu-Gd-Cu complex confirm the asymmetry of the central cores, involving phenoxo and hydroxo bridges. The magnetic studies evidence again the presence of ferromagnetic interactions. These results corroborate preponderance of the planarity of the Cu-O2-Gd core over the dissymmetry of the bridges.