Exploring the exchange interaction in a mixed valence {CoII4CoIII2} hexanuclear cluster with novel topology

Reaction between [Co 2 (μ-OH 2 )(μ-Piv) 2 (Piv) 2 (HPiv) 4 ] and a (salicylidene)ethanolamine ligand under ambient reaction conditions, affords hexanuclear complexes [Co III 2 Co II 4 (Piv) 8 (HPiv) 2 (L) 2 (OH) 2 ] ( 1 – 2 ). Both products have been characterized crystallographically and found to be mixed-valent, containing divalent and trivalent Co centers. Down to 30 K, the variable-temperature magnetic susceptibility data are dominated by the single-ion properties of high spin Co(II) centers with distorted-octahedral coordination geometries. Below this temperature, the effect of intramolecular ferromagnetic exchange interactions becomes apparent. Magnetic data has been analyzed in terms of ground isolated effective S ˜ = 1 / 2 Kramers doublets where low temperature magnetization data suggests an anisotropic behavior. We have also employed DFT-broken symmetry calculations to evaluate in an isotropic approach the exchange interaction pathways.