Topological Ferrimagnetic Behavior of Two New [Mn(L)<sub>2</sub>(N<sub>3</sub>)<sub>2</sub>]<i><sub>n</sub></i> Chains with the New AF/AF/F Alternating Sequence (L = 3-Methylpyridine or 3,4-Dimethylpyridine)
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The reaction of manganese(II) and pyridine derivatives such as 3-methylpyridine (3-Mepy) and 3,4-dimethylpyridine (3,4-Dmepy) led to the new one-dimensional systems trans-[Mn(3-Mepy)2(N3)2]n (1) and trans-[Mn(3,4-Dmepy)2(N3)2]n (2). Compound 1 crystallizes in the monoclinic system, space group P21/n, a = 11.201(3) Å, b = 14.499(4) Å, c = 14.308(4) Å, Z = 6, and compound 2 crystallizes in the triclinic system, space group P1̄, a = 11.502(4) Å, b = 14.246(5) Å, c = 16.200(8) Å, Z = 6. The two compounds show the same general one-dimensional arrangement of double azido bridges between neighboring manganese atoms with the unprecedented −Mn−(μ1,3-N3)2−Mn−(μ1,3-N3)2−Mn−(μ1,1-N3)2−Mn− sequence. Susceptibility and magnetization measurements reveal a ferrimagnetic-like behavior derived from the topology of the chain. A model of the Heisenberg chain, comprising classical spins coupled through alternating exchange interactions J1J1J2... is proposed to describe the magnetic behavior.
