Three new dinuclear copper(II) complexes with [Cu(μ1,3-N3)2Cu]2+ and [Cu(μ1,1-N3)2Cu]2+ asymmetrical cores: syntheses, structures and magnetic behaviour

Three new dinuclear copper(II) complexes, derived from end-to-end and end-on azido bridging ligands and triamine derivatives, have been synthesized and their crystal structures have been determined by X-ray diffraction methods. These are the dinuclear end-to-end compounds, [Cu2(μ1,3-N3)2(Et3dien)2](ClO4)2 (1) and [Cu2(μ1,3-N3)2(Medpt)2](ClO4)2 (2), and the dinuclear end-on compound [Cu2(μ1,1-N3)2(Medien)2](ClO4)2 (3) (Et3dien is triethyldiethylenetriamine, Medpt is methyldipropylenetriamine and Medien is methyldiethylenetriamine). The [Cu(μ-N3)2Cu]2+ cores are asymmetrical in all 3 compounds. Variable temperature magnetic susceptibility data were collected and fitted to the appropriate equation derived from the Hamiltonian H = −JS1S2. 1 shows unusual ferromagnetic interactions with J = 9 cm−1 through the end-to-end azido bridges while 2 shows an antiferromagnetic interaction through the end-to-end azido bridges with the highest reported absolute magnitude of J = −105 cm−1. The magnetic data of 1 and 2 have been correlated with the Addison parameter, τ, and mainly with the Cu–N3–Cu torsion angle, Δ. 3 shows an unusual antiferromagnetic interaction with J = −16.8 cm−1 through the end-on azido bridges.