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

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 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 μ₂-1,3-azide bridges and the hydrogen bonds, respectively; the former interactions are rationalized by the large Cu–N₃–Cu torsion angles.