High-pressure magnetic susceptibility studies of spin-state transition in Fe(II) complexes

High-pressure magnetic susceptibility measurements have been carried out on Fe(dipy)2(NCS)2 and Fe(phen)2(NCS)2 in the pressure range 1-10 kbar and tempeature range 80-300 K in order to investigate the factors responsible for the spin-state transitions. The transitions change from first order to second or higher order upon application of pressure. The temperature variation of the susceptibility at different pressures has been analysed quantitatively within the framework of available models. It is shown that the relative magnitudes of the ΔG0 of high-spin and low-spin conversion and the ferromagnetic interaction between high-spin complexes determines the nature of the transition