Spin crossover in FeII cyanometallic frameworks

Spin-crossover (SCO) compounds represent a huge class of switchable coordination complexes that can change their electronic configurations under the influence of different external stimuli. SCO provokes a spectacular switch of physical and chemical properties of complexes making them perspective as active elements of sensors, actuators, electronic and optical components, and other devices. In this article we offer a brief overview of cyanometallic frameworks exhibiting SCO properties. Building blocks that tend to provide new materials with desired spin-crossover characteristics are discussed. Special attention is paid on how the host?guest interactions in SCO frameworks affect their transition properties making them suitable for sensing applications. The effect of size reduction to nanometre scale on switchable properties of cyanometallates is described. Additionally, some outstanding features of SCO cyanometallates such as multistep transitions, mechanical actuation and switchable luminescence are highlighted.