Correlation between the magnetic behaviors and dimensionality of intermolecular interactions in Fe(III) spin crossover compounds

A novel Fe(III) spin crossover (SCO) complex with a linear I3 anion, [Fe(qsal)2]I31 [qsalH=N-(8-quinolyl)-salicylaldimine], was prepared and characterized by the magnetic susceptibilities and crystal structures. 1 exhibited a gradual SCO conversion (TSCO=ca.240 K). The crystal structural analyses for 1 at 50 and 293 K revealed that the two-dimensional (2D) network was constructed by intermolecular π–π interactions between π-ligands of an Fe(III) cation. Since the related complex, [Fe(qsal)2]NCS 2, was known to show a cooperative SCO transition, the crystal structure of 2 at 293 K was also determined. 2 possessed 2D SCO cation arrangement similar to 1, whereas potential π–π interactions between 2D networks in 2 existed. The dimensionality of intermolecular interactions was closely related to SCO behaviors and pressure effects on SCO compounds.