Spin-crossover compounds with wide thermal hysteresis

Spin-crossover compounds showing wide thermal hysteresis are surveyed, and the factors underlying these properties are discussed. Hysteresis is promoted by large structural rearrangements during the transition and by strong intermolecular interactions involving rigid ligand groups or donor atoms. These observations provide new principles for the design of molecular crystals undergoing spin crossover (or other phase changes) with predefined switching properties.