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.