An unprecedented trinuclear FeII triazole-based complex exhibiting a concerted and complete sharp spin transition above room temperature

We report a triazole-based trinuclear complex as the first example that displays a complete one-step first-order [HS–HS–HS] ↔ [LS–LS–LS] spin transition at 318 K. The strong ferro-elastic interactions, between the three metal centers, have been identified as the source of the concerted spin transition in this trinuclear complex.