Unusual Solvent Dependence of a Molecule‐Based Fe^II Macrocyclic Spin‐Crossover Complex

Abstract

Abstract This work illustrates in detail the reversible hydration–dehydration process of a molecule‐based material, which involves a drastic change of the switchable magnetic properties of the sample. Concretely, the complex [FeL 222 N 3 O 2 (CN) 2 ] · H 2 O exhibits a spin crossover (SCO) accompanied by a change of the coordination number. The dehydration and rehydration of this SCO complex was carried out and monitored by different methods, which include X‐ray diffraction analysis. The corresponding samples display a thermal spin transition as well as a thermal quenching of the metastable high‐spin state at low temperature. In particular it was observed that the rehydrated material exhibits a particularly high temperature of relaxation, T (TIESST), of the metastable high‐spin state. On the other hand, it was shown that this compound exhibits a uncommon correlation between T (TIESST) and the thermal SCO, as compared with other spin‐crossover compounds that do not exhibit a change in coordination number.