Exploring the exchange interaction in a mixed valence {Co II4Co III2} hexanuclear cluster with novel topology

Abstract

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 2Co 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.