An unusual alternating ferro- and antiferromagnetic 1D hydrogen-bonded µ2-1,3-azide-bridged copper(II) complex: a dominant ferromagnetic couplingElectronic supplementary information (ESI) available: EPR spectra of 1 (Fig. S1) and fit of χMT data with the binuclear model (Fig. S2). See http://www.rsc.org/suppdata/nj/b1/b108511p/

Abstract

A single-crystal structure analysis of [Cu2(bben)2(N3)4]n (1) [bben1,2-bis(benzylamino)ethane] revealed that the complex consists of double asymmetric μ2-1,3-azide-bridged dimeric copper(II) moieties; each copper(II) coordinates with one bben, one terminal azido, and the two bridging azido ligands. The Cu–N3–Cu torsion angle has a very large value of 47.5°. 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) Å, respectively. Magnetic measurements on 1 have revealed the existence of a dominant ferromagnetic interaction with exchange coupling parameters of JF = 16.8 cm−1, and JAF = −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 μ2-1,3-azide bridges and the hydrogen bonds, respectively; the former interactions are rationalized by the large Cu–N3–Cu torsion angles.