Characterization of a nonheme mononuclear peroxoiron(III) intermediate by UV Vis and EPR spectroscopy and mass spectrometry

Some nonheme hydroperoxoiron(III) species have been recently characterized by several groups. The reported examples were obtained by adding H2O2 in ex cess to an Fe-II complex with a neutral polypyridine ligand. We show here t hat on deprotonation, the purple low-spin hydroperoxoiron(III) complex [(LF eOOH)-Fe-5-O-III](2+) [L-5 = N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1 ,2-diamine] gives a blue high spin species which we characterized as the et a(2)-peroxoiron(III) species [(LFeO2)-Fe-5-O-III](+). It seems that with su ch an auxiliary ligand, the hydroperoxo group is acidic in contrast with it s basicity when it is coordinated to a heme group.