Differential scanning calorimetry (DSC) confirmed the appearance of endothermic/exothermic peaks at 258/262 K showing a 4 K wide hysteresis, demonstrating the occurrence of a SCO assisted first-order phase transition. While no change in the space group (P21) during crystallographic studies was observed, suggesting a cooperative effect in the hysteretic SCO of 1. Temperaturedependent magnetic susceptibility measurements were performed to explore the magnetic properties of 1. A reversible spin-transition between the HS (S = 2, T = 3.6-3.7 cm 3 mol -1 K) and LS (S = 0, T  0.3 cm 3 mol -1 K) states were observed with T1/2 = 259 K with 3 K wide hysteresis loop (Fig. ). and .