Anisotropic exchange in a tetranuclear CoII complex

The results of very high-frequency (50-715 GHz) electron paramagnetic resonance (EPR) studies of the tetranuclear CoII complex [Co(hmp)(dmb)Cl]4 (1), are presented. We consider the effect of anisotropic exchange interactions between the effective spin S′ = 1/2 Kramers ions within the tetranuclear complex to understand the origin of the ZFS within the ground state spin multiplet of 1, as well as the slow magnetization relaxation observed from low-temperature hysteresis measurements.