An unusual alternating ferro- and antiferromagnetic 1D hydrogen-bonded μ2-1,3-azide-bridged copper(II) complex:: a dominant ferromagnetic coupling

A single-crystal structure analysis of [Cu-2(bben)(2) (N-3)(4)](n) (1) [bben = 1,2-bis(benzylamino) ethane] revealed that the complex consists of double asymmetric mu(2)-1,3-azide-bridged dimeric copper(II) moieties; each copper(II) coordinates with one bben, one terminal azido, and the two bridging azido ligands. The Cu-N-3-Cu torsion angle has a very large value of 47.5degrees. The dimeric units are assembled into 1D chains through N(bben) H...N (azido) hydrogen bonds. The intra- and the interdimeric Cu...Cu distances in the chain are 5.281( 2) and 3.662(2) Angstrom, respectively. Magnetic measurements on 1 have revealed the existence of a dominant ferromagnetic interaction with exchange coupling parameters of J(F) = 16.8 cm(-1), and J(AF) = 3.6 cm(-1), using an alternating ferro- and antiferromagnetic chain model for S = 1/2 local spins. The ferro- and antiferromagnetic interactions are ascribed to the mu(2)-1,3-azide bridges and the hydrogen bonds, respectively; he former interactions are rationalized by the large Cu-N-3-Cu torsion angles.