Syntheses, structures and properties of a series of non-heme alkoxide-Fe(III) complexes of a benzimidazolyl-rich ligand as models for lipoxygenase

Abstract

The treatment of Fe(ClO₄)₂·6H₂O or Fe(ClO₄)₃·9H₂O with a benzimidazolyl-rich ligand, N,N,N′,N′-tetrakis[(1-methyl-2-benzimidazolyl)methyl]-1,2-ethanediamine (medtb) in alcohol/MeCN gives a mononuclear ferrous complex, [Fe^II(medtb)](ClO₄)₂·½CH₃CN·½CH₃OH (1), and four non-heme alkoxide–iron(III) complexes, [Fe^III(OMe)(medtb)](ClO₄)₂·H₂O (2, alcohol = MeOH), [Fe^III(OEt)(Hmedtb)](ClO₄)₃·CH₃CN (3, alcohol = EtOH), [Fe^III(OⁿPr)(Hmedtb)](ClO₄)₃·ⁿPrOH·2CH₃CN (4, alcohol = n-PrOH), and [Fe^III(OⁿBu)(Hmedtb)](ClO₄)₃·3CH₃CN·H₂O (5, alcohol = n-BuOH), respectively. The alkoxide–iron(III) complexes all show 1) a Fe(III)–OR center (R = Me, 2; Et, 3; ⁿPr, 4; ⁿBu, 5) with the Fe–O bond distances in the range of 1.781–1.816 Å, and 2) a yellow color and an intense electronic transition around 370 nm. The alkoxide–iron(III) complexes can be reduced by organic compounds with a cis,cis-1,4-diene moiety via the hydrogen atom abstraction reaction.