Random bimetallic Ni^II_xMn^II_1−x chains with mixed azido and carboxylato triple bridges: A gradual ferromagnetic-to-antiferromagnetic evolution

A series of isomorphous random bimetallic Ni^II-Mn^II compounds with N-methylpyridinium-4-carboxylate (4-mpc) and azide, have been synthesized and characterized. They are of formula [Ni^II_xMn^II_1−x(N₃)₂(4-mpc)] (1−6), (x = 1 (1), 0.86 (2), 0.83 (3), 0.71 (4), 0.56 (5), 0.47 (6)). Compounds 1–6 consist of one-dimensional uniform chains with [(μ-EO-N₃)₂(μ-COO)] triple bridges (EO = end-on). Magnetic measurements reveal that compounds 1–6 behave as antiferromagnets with a gradual ferromagnetic-to-antiferromagnetic evolution by the incorporating of isotropic Mn^II ions into Ni^II chain. The Ni^II-rich compounds 1–3 exhibit field-induced metamagnetism. And the T_N of the heterometallic compounds exhibit a composition-dependence of the content of Ni^II.