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, [Cu-2(mu(1,3)-N-3)(2)(Et(3)dien)(2)](ClO4)(2) (1) and [Cu-2(mu(1,3)-N-3)(2)(Medpt)(2)](ClO4)(2) (2), and the dinuclear end-on compound [Cu-2(mu(1,1)-N-3)(2)(Medien)(2)](ClO4)(2) (3) (Et(3)dien is triethyldiethylenetriamine, Medpt is methyldipropylenetriamine and Medien is methyldiethylenetriamine). The [Cu(mu-N-3)(2)Cu](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= -JS(1)S(2). 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, tau, and mainly with the Cu-N-3-Cu torsion angle, Delta. 3 shows an unusual antiferromagnetic interaction with J= -16.8 cm(-1) through the end-on azido bridges.