Crystalline, mixed-valence manganese analogue of Prussian blue:: Magnetic, spectroscopic, X-ray and neutron diffraction studies

The compound of stoichiometry Mn(II)(3)[Mn(III)(CN)(6)](2)(.)zH(2)O (Z = 12-16) (1) forms air-stable, transparent red crystals. Low-temperature single crystal optical spectroscopy and single crystal X-ray diffraction provide compelling evidence for N-bonded high-spin manganese(II), and C-bonded low-spin manganese(III) ions arranged in a disordered, face-centered cubic lattice analogous to that of Prussian Blue. X-ray and neutron diffraction show structured diffuse scattering indicative of partially correlated (rather than random) substitutions of [Mn(III)(CN)(6)] ions by (H2O)(6) clusters. Magnetic susceptibility measurements and elastic neutron scattering experiments indicate a ferrimagnetic structure below the critical temperature T-c = 35.5 K.