The Spin‐Crossover Phenomenon at the Coherent‐Domains Scale in 1D Polymeric Powders: Evidence for Structural Fatigability

Abstract

Abstract The coherent‐domain morphology was determined for a crystalline powder of the 1D polymeric spin‐crossover [Fe(Htrz) 2 (trz)](BF 4 ) {Htrz = 1 H ‐1,2,4‐triazole, trz = deprotonated triazolato(–) ligand} compound. This morphology is in adequacy with the crystal packing and proved that the long axis of the domain corresponds to the iron–triazole chains axis, which gives information on the crystal‐growth process. Furthermore, thermal cycling clearly demonstrated that the coherent‐domain length strongly and continuously decreased as a function of the number of spin‐crossover cycles undergone. The degradation in the crystalline quality corresponds to a break in the [Fe(Htrz) 2 (trz)] + chains. This structural fatigability was confirmed by similar observations on a close spin‐crossover compound, [Fe(NH 2 trz) 3 ](NO 3 ) 2 · H 2 O, showing that a few hundreds of thermal spin‐crossover cycles could destroy the crystalline aspect of the sample.