Structure and magnetic behaviour of the one-dimensional [{Ni2(Medien)2(µ1,1-N3)2(µ1,3-N3)}n][ClO4]n compound with unusually strong ferro-antiferromagnetic alternating interactions

Abstract

A new monodimensional µ-azido-nickel(II) complex of formula [{Ni₂(Medien)₂(µ_1,1-N₃)₂(µ_1,3-N₃)}_n][ClO₄]_n1 [Medien = bis(2-aminoethyl)methylamine] has been synthesized and crystallographically characterised. The nickel atom is placed in an octahedral environment bridged by two end-on azido ligands and one end-to-end azido bridge to the neighbouring nickel atoms, giving an alternated 1-D system. The magnetic behaviour corresponds to an alternating ferro-antiferromagnetic chain. The superexchange parameters have been calculated as J_AF = –34.7 cm^–1 and J_FM = +38.2 cm^–1, α = 1.10, by means of an improved analytical expression for the magnetic susceptibility of the isotropic ferro-antiferromagnetic S = 1 Heisenberg chain in terms of the alternation parameter α = J_FM/|J_AF|. Magnetic properties have been correlated to the structural data.