ROLE OF THE TOPOLOGY ON THE MAGNETIC-PROPERTIES OF MIXED-VALENCE TRINUCLEAR MANGANESE CLUSTERS

The magnetic behavior of mixed-valence trinuclear clusters d5-d4-d4 is discussed on the basis of a model that takes into acount the competing effect between valence delocalization and both Heisenberg exchange and distortion of the trimer. For the first time, the different transfer pathways are taken into account. As far as the magnetic properties are concerned, the model anticipates drastic differences depending on the geometry of the entity, with a ferromagnetic behavior in linear trimers and an antiferromagnetic behavior in triangular entities, very similar in appearance to that expected from the valence-trapped model. The sensitivity of the magnetic properties to the electronic delocalization is discussed in both cases.