Post-synthetic anion exchange in iron(ii) 1,2,4-triazole based spin crossover materials via mechanochemistry.

A facile method for post-synthetic exchange of anions in an iron(ii) spin crossover material using mechanochemistry is described. Dry grinding of the [Fe(atrz)3]Cl2 complex (atrz = 4-amino-1,2,4-triazole) in the presence of an excess of sodium halide salt results in the complete exchange of anions and formation of [Fe(atrz)3]Br2 and [Fe(atrz)3]I2 in a solid-state metathesis reaction. The method represents a new strategy for tuning active switching properties such as the transition temperature in spin crossover systems.

Mechanochemical synthesis of cooperative spin crossover materials.

We describe the synthesis of switchable spin crossover materials via mechanochemistry for the first time. Three chemically diverse spin crossover materials have been produced using solvent-free grinding. Crucially, cooperative spin transition behavior and crystallinity is retained, presenting exciting opportunities for the discovery of new materials with switchable magnetic, optical and structural properties.