Interaction antiferromagnetic

Concerning molecule-based magnets, the first spin-ladder was synthesized (/ -EPYNN)[Ni (dmit)2] (/ -EPYNN = / -7V-ethylpyridinium o-nitronyl nitroxide). Within the crystal lattice, the radical cation /7-EPYNN units are arranged in ID chains with ferromagnetic interactions. The chains of [Ni(dmit)2] moieties in the ladder formation exhibit coexistent antiferromagnetic interactions.1031,1032... 

The presence of /3-hydrogen in the nitroxide radical may lead to disproportionation reactions. In spin-trapping experiments, N-t-butyl-a-phenyl nitrone yields rather unstable spin adducts. This type of radical can be stabilized by coordination to Nin. The Ni11 complex with N-oxy-A-r-butyl-(2-pyridyl)phenylmethanamine (923) reveals a distorted octahedral geometry with antiferromagnetic interactions between the unpaired electrons of the metal ion and the radical spins.00... 

The magnetic data of the polymeric complex at low temperature (T < 20 K) yield much higher values than those calculated using Eq. 1 and show strong ferromagnetic interactions. The magnetic behavior of the complex is different from those of discrete Cu-Ln complexes, which normally show antiferromagnetic interactions [81-85],... 

The reduced orbital overlap between the radicals reduces the bandwidth and the electronic structures could be better considered as those of a localised rather than itinerant electron system. This poor overlap results in very small antiferromagnetic interactions being observed, and the compounds behave as nearly perfect Curie-Weiss paramagnets. In the cases when improved lateral interactions between the stacks are achieved by change of the substituents85 the compounds behave as weak ID ferromagnets due to the effective orthogonality of the S C interactions. 

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