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A series of three compounds [Fe(salEen-5-I)2]Cl 1, [Fe(salEen-5-I)2]Br 2, and [Fe(salEen-5-I)2]I 3in which salEen-5-I = 2-{[(2-(ethylamino)ethyl]imino)methyl}-4-iodophenolate is reported. Magnetic studies reveal that 2exhibits an abrupt 2-step spin crossover close to room temperature around 288 K, while 1and 3exhibit gradual incomplete spin crossover spanning over 200 K. The use of structural parameters A–Cto describe the nearest and next nearest neighbor contacts allows us to rationalize not only the abruptness of the spin crossover but also the stepped nature of the spin crossover in 2. Comparisons with previously reported [Fe(salEen-5-Br)2]ClO4and [Fe(salEen-5-I)2]ClO4reveal that this magnetostructural relationship is applicable to a wider range of members of this family of complexes.

Molecular devices based on spin-crossover (SCO) compounds are important targets for molecular electronics. In this study, six air-stable FeIIIcomplexes have been prepared: [Fe(naphBzen)2]Cl (1), [Fe(naphBzen)2]Cl·0.5hexane (1·0.5hexane); [Fe(naphBzen)2]Cl·2CHCl3·1.15hexane (1·2CHCl3·1.15hexane), [Fe(naphBzen)2]Br (2), [Fe(naphBzen)2]Br·0.5hexane (2·0.5hexane), and [Fe(naphBzen)2]Br·2CHCl3(2·2CHCl3). The hexane solvates are isostructural, crystallizing in the tetragonal space group I41/a. Weak van der Waals interactions between the cations result in the Fe1 and Fe2 centers packing into chiral chains and exhibiting two-step SCO. In contrast, the nonisostructural CHCl3solvates have a single Fe center and crystallize in the triclinic space group P1̅ and are LS up to 350 K. The solvent-free systems are also not isostructural with [Fe(naphBzen)2]Cl, crystallizing in the triclinic space group P1̅, while [Fe(naphBzen)2]Br undergoes a phase transition from tetragonal P43to P43212 upon heating from 150 to 280 K. In both cases the compounds are trapped in the LS state. Magnetic data reveals that SCO occurs only in the hexane solvates, indicating that even very weak interactions can be critical in observing spin-crossover behavior.