Structural features that modulate the sharpness of the spin crossover transition in [FeIII(5-X-qsal)2]+ based salts

Abstract

This study aimed to unveil the structural modifications that can modulate the SCO transition sharpness, occurring up to room temperature, of Fe^III compounds with general formula [Fe(5-X-qsal)₂]⁺. These compounds are organized in layers of cationic chains. The structure of a series of compounds with different transition progressions were analyzed and compared to extract the structural differences responsible for the change in magnetic behavior. Two structural differences were found to be responsible for the modulation of the magnetic transition sharpness, in direct correspondence with the degree of interactions between the cations in each chain and between chains. The reinforcement of the interchain connectivity was found to contribute towards the sharpness of the transition. On the contrary, the reinforcement of the interlayer interactions resulted in the broadening of the transition. To achieve sharp transitions, it is necessary to obtain structures able to maximize interchain cation–cation interactions at the same time as they minimize the interlayer interactions.