Symmetry Breaking in Iron(II) Spin-Crossover Molecular Crystals

This review provides an up to date survey of a singular class of iron(II) spin crossover (SCO) molecular materials that undergo high-spin (HS) O low-spin (LS) phase transitions accompanied by crystallographic symmetry breaking (CSB). Particular interest has been focused on a variety of complexes that exhibit one-step or stepwise SCO behavior and CSB. Most of them afford excellent examples of well-ordered 1HS-1LS, 2HS-1LS or 1HS-2LS intermediate phases (IP) and represent an important platform to disclose microscopic mechanisms responsible for cooperativity and ordering in such multistable materials.