In an article by Guillon and co-workers, it was found that [Fe(L36)2][BF4]2 (59) (Fig. ) shows higher relative permittivity in the LS state than the HS state (Fig. ), which is in contrast with the general observation in most of the complexes where the relative permittivity is higher in the HS state. DFT calculations were performed on the complex (59) cation, but that also provided contrasting observations where the mean electronic polarizability change was positive, Δα = αHS -αLS = 7.01 a.u. From this, they concluded that counteranion and various intermolecular interactions play a major role in shaping the overall electronic polarizability and, hence, the relative permittivity of molecules in particular spin states . In 2013, Fe(H-L37)(L37)•H2O (60) (Fig. ) was reported to exhibit SCO and dielectric anomaly for the first time in Fe(III) system by Sato and co-workers . They used a thiosemicarbazide-based ligand for this purpose, having N2O2S2 coordination environment around the Fe(III) center. The magnetic data revealed that the complex exhibits a two-step spin transition with a small hysteresis loop (Fig. ). In the dielectric study, it was observed that the it shows dielectric anomaly around 240 K and 270 K, which is where the two-step spin state change happens. Still, the dielectric change is not accompanied by any hysteresis loop (Fig. ). This is most probably due to the less cooperativity in the system. In order to obtain a hysteresis in the dielectric property, a strong cooperative interaction is essential criteria. This becomes more clear when we look at [Fe(H-L38)(L38)](BF4) (61) and its magnetic and dielectric behavior. It shows a robust spin transition with 25 K width of hysteresis loop. In the dielectric property study with respect to temperature, it was found to exhibit a 25 K-wide hysteresis loop and a change large change in the real part of dielectric permittivity. Here also, the LS value is higher than HS state . exhibits very interesting hysteretic SCO behavior. 63R shows a narrow 2 K wide hysteresis loop (Tup = 189 K and Tdown = 187 K) (Fig. ). 63R and 63S also show LIESST effect and 57% and 73% LS to HS conversion, respectively, after light irradiation. Circular dichroism (CD) and vibrational circular dichroism (VCD) spectra show the chiral nature of the complexes. When the dielectric property is measured, the real part of the dielectric constant (ε') exhibits an anomaly around 200 K, indicating a structural phase transition resulting from the SCO. A hysteresis loop is also observed in the dielectric temperature dependence curve having Δε′ = ε′HS -ε′LS = 0.58 for 63R (Fig. ), and this value is 0.46 for 63S. These differences in the dielectric constant at LS and HS are rather higher than usual SCO complexes as the polarizability is coming mainly from the electronic contributions in the SCO complexes. In these chiral molecules, the ligand is polar, and thus, dipolar reorientation can contribute significantly to the dielectric response. So, in these complexes, both SCO and chirality play a major role in the higher Δε′ value of the complexes .