Mononuclear iron complexes relevant to nonheme iron oxygenases. Synthesis, characterizations and reactivity of Fe-Oxo and Fe-Peroxo intermediates.

The new ligand L(6)(2)4E (N,N,N',N'-tetrakis(5-ethyl-2-pyridylmethyl)ethane-1,2-diamine) was designed as a more robust analog of TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethane-1,2-diamine) for which the ability at stabilizing high valent Fe-Oxo and Fe-(hydro)peroxo has been reported. With respect to the latter, the pyridyl beta-substituents in L(6)(2)4E do not modify the Fe coordination chemistry. From the Fe(II) precursor, [FeO](2+) and Fe(III)-(hydro)peroxo intermediates are prepared using the same synthetic methods as those reported for the TPEN analogs.

New example of a non-heme mononuclear iron(IV) oxo complex. Spectroscopic data and oxidation activity.

The green complex S=1 [(TPEN)FeO]2+ [TPEN=N,N,N',N'-tetrakis(2-pyridylmethyl)ethane-1,2-diamine] has been obtained by treating the [(TPEN)Fe]2+ precursor with meta-chloroperoxybenzoic acid (m-CPBA). This high-valent complex belongs to the emerging family of synthetic models of Fe(IV)=O intermediates invoked during the catalytic cycle of biological systems. This complex exhibits spectroscopic characteristics that are similar to those of other models reported recently with a similar amine/pyridine environment.

Very general formation of tetrahydropterin cation radicals during reaction of iron porphyrins with tetrahydropterins: model for the corresponding NO-synthase reaction.

Electron transfer from tetrahydropterins to iron porphyrins, with formation of intermediate tetrahydropterin cation radicals, is a very general reaction that was shown to occur not only with tetrahydrobiopterin, as originally found in NO-synthases, but also with another important biological cofactor, tetrahydrofolate, and various iron porphyrins, either in their ferric state, or in the Fe(II)O(2) state, as in the first model of the corresponding NO-synthase reaction described in this paper.