Molecule-based room-temperature magnets: Catalytic role of V(III) in the synthesis of vanadium-chromium Prussian blue analogues

A new synthetic procedure to obtain vanadium-chromium Prussian blue analogues is presented, using controlled amounts of V-III in solution during the synthesis. The vanadium and chromium oxidation states and the chemical environment of the metal ions in the solids are characterized by infrared and X-ray absorption spectroscopies. The presence of weak amounts of V-III during the synthesis provides materials which are better organized and present reproducible Curie temperature and magnetization at saturation in agreement with the observed V/Cr stoichiometry.