The iron-mediated activation of dioxygen and nitric oxide are critical processes in a range of biochemical and synthetic pathways. This presentation describes our recent results on the synthesis and reactivity of nonheme iron complexes that activate O2 and NO. A series of new, mononuclear nonheme iron(II) complexes have been synthesized with different biomimetic, nitrogen/sulfur ligand environments. These complexes are designed to bind and activate both O2 and NO. In one case, the same iron(II) complex, based on a triazacyclononane scaffold, activates O2 to give a sequence of metastable ferric-peroxo, high-valent ferryl, and ferric-hydroxo complexes. Other ligand scaffolds yield iron(II) complexes that bind and reduce NO to give N2O, and also react with HNO donors (e.g. Piloty’s acid). Reaction intermediates are thermally trapped and characterized by a range of spectroscopic methods, including UV-vis, Mössbauer, EPR, resonance Raman, and X-ray absorption spectroscopies. A collaboration with the Lancaster group for these studies has been critical to their success. The reactivity of these complexes will be discussed in light of proposed mechanistic steps for the thiol dioxygenases (e.g. CDO), persulfide dioxygenases (e.g. ETHE1), sulfoxide synthases (e.g. EgtB/OvoA), and nitric oxide reductases (e.g. FDP).

Activation of O2 and NO at nonheme, mononuclear, sulfur-ligated iron centers

ACS Spring Meeting 2021

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