Structural analysis of spin-crossover materials: From molecules to materials

In molecular spin-crossover materials, the spin-state switching is strongly coupled with changes in the structural degrees of freedom, which play a central role in the alteration of functions and mechanisms of transformation from the molecular scale (bond lengths) to the material scale (volume). This article reviews various techniques currently used, ranging from microscopy to diffraction, to study the structural aspects related to spin crossover at different physical scales. Some of the most important recent advances concern the resolution of complex crystal structures, the determination of microstructures, the study of phase coexistence, temporal studies ranging from second to femtosecond, and the description of multistep transition involving intricate ordering of molecules in different electronic states. (C) 2018 Academie des sciences. Published by Elsevier Masson SAS.