Charge transfer and slow magnetic relaxation in a series of cyano-bridged FeIII4MII2 (M = FeII, CoII, NiII) molecules

The synthesis, single-crystal structures and magnetic properties of three new cyano-bridged complexes [FeIII4MII2] (M = FeII, CoII, NiII) are reported. Electronic absorption spectroscopy reveals the occurrence of intervalence charge transfer for [FeIII4FeII2]. Field-induced slow magnetic relaxation behavior is exhibited for [FeIII4CoII2] and [FeIII4NiII2] which originates from the ferromagnetic interactions between FeIII and MII spin centers of the square.