Tuning magnetic exchange using the versatile azide ligand

The ability of the azido ligand to generate various chemical architectures and magnetic couplings is surveyed, using Cu(II) and Ni(II) derivatives. Depending on the ratio between the azide salt, the metal salt and the tridentate Schiff base LH (L−:1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato), molecular bimetallic [CuL(μ1,3-N3)]2 (1) and monometallic [NiL(μ1-N3)] (2) as well as extended {[CuL(μ1,1-N3)]}n (3) and {[Ni2(μ1,1-N3)(μ1,3-N3)(L)2(MeOH)2]}n (4) chains were obtained. These systems were fully characterized by X-ray diffraction and magnetic susceptibility measurements. In 1, the asymmetrical double μ1,3-N3 bridge mediates a ferromagnetic exchange whereas 3 and 4 exhibit unusual symmetric and asymmetric single μ1,1-N3 coordination modes that transmit weak ferromagnetic interactions. Ab initio calculations were systematically performed to clarify the origin of the observed magnetic exchanges and to study the role of the asymmetric coordination modes on the magnetic coupling.