A novel two-step Fe-Au type spin-crossover behavior in a Hofmann-type coordination complex {Fe(4-methylpyrimidine)2[Au(CN)2]2}.

A Hofmann-type two-step spin-crossover (SCO) complex with a pyrimidine derivative ligand, Fe(4-methylpyrimidine)2[Au(CN)2]2, was synthesized, and this complex shows a two-step SCO phenomenon in the intermediate state. Symmetry breaking also occurs in the intermediate state. These results reveal three spin states within the complex for high-spin (HS), HS0.5LS0.5, and low-spin (LS).