Polymorphism-Dependent Spin-Crossover: Hysteretic Two-Step Spin Transition with an Ordered [HS–HS–LS] Intermediate Phase

Abstract

A mononuclear iron(II) complex has been isolated in two polymorphs. Polymorph 1b remains high-spin over all temperatures, whereas polymorph 1a undergoes a cooperative two-step spin crossover accompanied by symmetry breaking, showing an ordered 2:1 high-spin-low-spin intermediate phase.