A neutral mononuclear FeIII complex [FeIII(H-5-Br-thsa-Me)(5-Br-thsa-Me)] H2O (1; H2-5-Br-thsa-Me=5-bromosalicylaldehyde methylthiosemicarbazone) was prepared that exhibited a three-step spin-crossover (SCO) with symmetry breaking and a 14 K hysteresis loop owing to strong cooperativity. Two ordered intermediate states of 1 were observed, 4HS-2LS and 2HS-4LS, which exhibited reentrant phase-transition behavior. This study provides a new platform for examining multistability in SCO complexes. In quite a state: A neutral mononuclear FeIII complex [FeIII(H-5-Br-thsa-Me)(5-Br-thsa-Me)] H2O (thsa=5-bromosalicylaldehyde methylthiosemicarbazone) exhibited a three-step spin crossover with symmetry breaking and a 14 K hysteresis loop owing to strong cooperativity (see picture). The intermediate spin states showed remarkable long-range 4 HS-2 LS and 2 HS-4 LS spin-state ordering (HS=high-spin, red; LS=low-spin, green).
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