Heteroleptic iron(III) spin crossover complexes; ligand substitution effects

Heteroleptic iron(III) complexes of formula [Fe(qsal-Cl)(thsa)]nMeCN have been synthesized; [Fe(qsal-Cl)(thsa)]MeCN, 1 and [Fe(qsal-Cl)(thsa)], 2. The latter can be obtained by slow evaporation of solutions of compound 1 under ambient conditions, a rare occurrence in nonporous compounds. 1 interestingly shows a unique magnetic profile over the de-solvation temperature range, 300-350 K, in the first cycle, and becomes stable after the third cycle with a hysteresis width of about 20 K. Different de-solvation techniques used on compound 1 give rise to various stable de-solvated phases. Consequently, distinct magnetic profiles, with a larger hysteresis width of about 30 K, are present. Cl substitution on the qsal^- ligand introduces C–H···Cl and P4AE interactions intothe structure which are absent in the related unsubstituted compound, [Fe(qsal)(thsa)]0.5MeCN, 3. Comparisons in structural packing, as well as spin crossover properties between unsubstituted and Cl-substituted ligand compounds, are discussed.