Another exciting physical property associated with spin-state switching is the dielectric property which is the ability of an insulator to store electricity as no free electrons are available to conduct electricity. Although SCO molecules have a paramagnetic metal center, they are surrounded by diamagnetic organic ligands. Thus, overall, molecules are not conducting in nature and behave as insulators. When SCO occurs, the electrons transition from a t2g set of orbitals to eg set of orbitals, and as a result, the bond length increases. During SCO of Fe(II) complexes, Fe-N metal-ligand bond length variation of 5-10% (0.1-0.2 Å) and N-Fe-N angle variation of 0.5-8˚ are observed . This change in bond length and angles leads to a deformation of the local environment around the metal center, and therefore, local electrical dipoles are different in HS and LS states . This change in dielectric property with the spin state of the molecule has been studied with many SCO molecules. As the HS state of the SCO complex is larger in size and has more diffused electron density as compared to the LS state, electronic polarizability should be higher in the HS state than the LS state . Such phenomena were observed in most of the cases, but in some cases reverse phenomena have also been recorded. All these exciting phenomena will be discussed in the review . The main strategy followed by various research groups for introducing and improving the dielectric property in SCO molecules has been to introduce polar and chiral groups that can have different orientations in different spin states, and thus, it will be reflected in their dielectric properties as well . The complex dielectric permittivity is expressed as ε* = ε'-iε'' and is measured in the 10 2 -10 6 Hz frequency range. The real part, ε' represents the effect of a timedependent electric field on the displacement of the bounded charges, and dielectric losses are represented by the imaginary part, ε'' . The first reports of synergy between SCO and dielectric properties were published on mononuclear Mn(III) and Fe(II) complexes, and some of them also exhibit thermal hysteresis in both SCO and dielectric profiles with respect to temperature .