Mixed-Valence Cobalt(II/III)–Octacyanidotungstate(IV/V) Ferromagnet

We report a mixed-valence cobalt­(II/III)–octacyanidotungstate­(IV/V)
magnet, [CoII(H2O)]2[CoIII{μ-(R)-1-(4-pyridyl)­ethanol}2]­[WIV(CN)8]­[WV(CN)8]·5H2O. Synchrotron-radiation X-ray single crystal structural analysis,
infrared spectrum, and density-functional theory (DFT) calculation
indicate that this compound has a chiral structure with the P21 space group and both CoII(S = 3/2)–NC–WV(S = 1/2) and CoIII(S = 0)–NC–WIV(S = 0) moieties, which are structurally
distinguishable in the crystal structure. Magnetic measurements reveal
that this compound exhibits ferromagnetism with a Curie temperature
of 11 K and a coercive field of 1500 Oe, which is caused by the coexistence
of the superexchange interaction in the CoII–WV chain and double exchange interaction between the chains.