Spin States of Mono- and Dinuclear Iron(II) Complexes with Bis(imidazolylimine) Ligands

Bis(imidazolylimine) ligands, H2L (H) and H-2(Me), were prepared from hydrazine and 4-formylimidazole or 2-methyl4-formylimidazole (1:2), respectively. Mononuclear iron(II) complexes, [Fe(H2LH)(2)](CIO4)(2)center dot MeOH and [Fe(H2LMe)(2)](CIO4)(2)center dot 2H(2)O, were in the LS and HS states, respectively, in the temperature range 5-300K. A triple-helicate [Fe-2(H2LMe)(3)](CIO4)(4), showed an abrupt [LS-HS] to [HS-HS] spin transition at 240K, while [Fe-2(H2LMe)(3)](CIO4)(4) remained in the LS state in the temperature range 5-300 K.