Observation of Spin Transition in an Octahedrally Coordinated Manganese(II) Compound

The thermal spin transition between a high-spin state (S = 5/2) and an intermediate-spin state (S = 3/2) of the octhahedrally coordinated Mn(II)(3d5) was observed in Rb(I)Mn(II)[Fe(III)(CN)6] with a very wide hysteresis loop over the temperature range of 231 to 304 K. This phenomenon is accompanied by a structural distortion from the face-centered cubic structure to the tetragonal one caused by a cooperative Jahn−Teller effect in the octahedral Fe(III)C6 moiety. To our knowledge, the present spin transition is the first observation in compounds containing a six-coordinated Mn(II).