A nonheme iron(II) complex that models the redox cycle of lipoxygenase

The air-stable complex [Fe(6-Me-3-TPA) (O2CAr)](+) [1; 6-Me-3-TPA= tris(6-me thyl-2-pyridylmethyl)amine] has been synthesized as a model for the iron(II) site of lipoxygenase. This iron(II) complex reacts with 0.5 equiv ROOH to form a yellow species. which has been formulated as [Fe-III(OH)(6-Me-3-TPA)(O2CAr)](+) (2) by electrospray mass spectrometry. Addition of more ROOH converts 2 into a purple species, which is characterized by electrospray ionization mass spectrometry and resonance Raman spectroscopy as [Fe-III(OOR)(6-Me-3-TPA)(O2CAr)](+). The purple species is metastable and decomposes via Fe-O bond homolysis to regenerate the starting iron(II) complex. These metal-centered transformations parallel the changes observed for lipoxygenase in its reaction with its product hydroperoxide.