Charge Transfer, Change of the Spin Value, and Driving of Magnetic Order by Pressure in Bimetallic Molecular Complexes

The magnetic bimetallic molecular-based compounds attract considerable attention because of their unique characteristics which are very different from those of traditional magnets. We demonstrate the effects of charge transfer as well as spin and magnetic order changes induced by high hydrostatic pressure applied to the two bimetallic multifunctional Prussian blue analogues, K_0.1Co₄[Fe­(CN)₆]_2.7·18H₂O and K_0.5Mn₃[Fe­(CN)₆]_2.14·6H₂O. Two opposite directions of change in their properties under pressure are revealed: (i) the magnetization reduction and magnetic order disappearing for the K_0.1Co₄[Fe­(CN)₆]_2.7·18H₂O compound and (ii) an increase of the magnetization and change of the sign of exchange coupling for the K_0.5Mn₃[Fe­(CN)₆]_2.14·6H₂O compound. It is a first observation of both the magnetic moment increase and transformation from ferrimagnetic order to ferromagnetic order that appear under pressure in Prussian blue analogues. The latter is explained by the charge transfer between the metallic ions resulting in the corresponding spin transitions