The development of molecular materials that can be switched between two different spin states through the application of external stimuli is of great interest owing to their potential use in molecular devices and information technology1,2. This switching behaviour can be triggered by different reasons such as a charge/proton transfer, a change in the solid-state structure, or molecular orientation. When the cooperativity between spin centres is strong enough, a region of biostability opens, in which either of the two states can be found depending on the material’s immediate past. This memory effect has been widely exploited in transition metal complexes for their potential application in magnetic data storage, spintronics, sensing etc. Some exciting recent discoveries3-5 of spin-state switching in the Fe(II) based Hofmann type frameworks and Prussian Blue analogues(PBAs) in presence of external perturbation would be discussed. In another class of complexes, cyanido-bridged Fe2Co 2D sheets exhibiting ETCST with simultaneous co-existence of magnetic ordering will be discussed. The complexes exhibit single-chain magnet behaviour where the uncoordinated water molecules act as an exchange-breaking impurity, the removal of which leads to an increase in the number of correlated units in the chain, therefore the length of single-chain magnet can be tuned by the external perturbation like solvent molecules.