ions are present at this temperature. Below 20 K, the T value sharply decreases to a value of 0.641 K cm 3 mol -1 at 2 K. This is probably due to the zero-field splitting and or magnetic anisotropy coming from the residual HS Fe(II) ions. In the heating mode, the T vs T curve follows the same path as that in the cooling mode, which confirms the reversibility of the SCO phenomenon in 1•2DMF without hysteretic behaviour (Figure ). The d(T)/dT vs T plot between 30 and 250 K of 1•2DMF displays a broad maximum at around 127 K (Figure ), representing the T1/2 temperature for the SCO system between LS and HS species in 1•2DMF. The best fit of the T vs. T data were obtained from the ideal solution model, (Figure ) which gives all the important thermodynamic parameters for 1•2DMF as H = 5.18(1) kJ/mol, T1/2 = 125(1) K, S = 41.50 J/K/mol. These results fall within the anticipated range for the iron(II) SCO systems. The field dependence of magnetization studies for 1•2DMF•H2O and 1•2DMF were carried out from 0 to 5 T at 2, 5, 6 K and at 2 K respectively (Figure , left and Figure ). At 2 K and 5 T magnetic field, the magnetization value for