Conformational effect of a spin crossover iron(II) complex: Bis[N-(2-methylimidazol-4-yl)methylidene-2-aminoethyl]propanediamineiron(II) perchlorate

► A SCO complex [FeII(H2L2-3-2)](ClO4)2 was synthesized for studying its SCO property. ► The complex has the combination of the saturated chelate rings of 5-6-5 for H2L2-3-2. ► The complex showed a gradual and reversible one-step SCO without hysteresis. ► SCO was occurred by changing of ligand conformation and forming of hydrogen bonds. ► In LS state, space group was changed by changing thermodynamic stability of ligand.