Solvent Effects on the Spin Crossover Properties of Manganese (III) (sal‐N‐1,5,8,12) Complexes

Abstract The interplay of host‐guest interactions and controlled modulation of spin‐crossover (SCO) behavior is one of the most exploited topics regarding data storage, molecular sensing, and optical technologies. This study examines the effect of solvents on the spin‐crossover (SCO) behavior of manganese(III) complexes [Mn(sal‐N‐1,5,8,12)]I•S (S=CH 3 OH, C 2 H 5 OH, CH 3 CN) ( 1 ) and [Mn(sal‐N‐1,5,8,12)]I 3 ( 2 ), where (sal‐N‐1,5,8,12) 2− is 2,2′‐((1E,13E)‐2,6,9,13‐tetraazatetradeca‐1,13‐diene‐1,14‐diyl)diphenol synthesized by salicylaldehyde and 1,2‐bis(3‐aminopropylamino)ethane. The complexes, crystallizing in orthorhombic or monoclinic systems, exhibit similar supramolecular arrangements with one‐dimensional cationic chains at low temperatures. Magnetic studies reveal that solvent inclusion sharpens the SCO transition and lowers the transition temperature. Specifically, 1⋅CH 3 OH shows a 13 K thermal hysteresis due to methanol‘s mobility through the channels in the cationic framework. Although the solvent‐free compound was not obtained, compound 2 with a linear I 3 − anion was synthesized, displaying extensive cation‐anion contacts and a distinct 13 K thermal hysteresis upon heating due to altered intermolecular cooperativity. This emphasizes the significant role of solvent introduction and variation in crystal packing and their impact on the SCO properties.