A growing family of O2 activating dinuclear iron enzymes with key catalytic diiron(III)-peroxo intermediates: Biological systems and chemical models

• Recently discovered O2 activating dinuclear enzymes.
• Diiron(III)-peroxo intermediates as active species in enzymes catalytic cycles.
• Spectroscopic parameters of hand made diiron(III)-peroxo species.
• Enzymes mechanisms and chemical models.

Discovery of soluble methane monooxygenase (sMMO) in 1966 aroused enthusiastic research on dinuclear iron centers, both in biological systems and chemical models. From this emulation, other O2 activating dinuclear iron enzymes were rapidly discovered and important active intermediates such as peroxo-diiron(III) and diiron(IV)-oxo species were characterized along the different catalytic cycles. For decades solely high-valent iron–oxo species were described as the active species involved in enzyme mechanisms, demoting peroxo-diiron(III) intermediates as a unique role of precursor. Interestingly, recent discovery of new O2 activating diiron enzymes revealed the implication of peroxo-diiron(III) species as active intermediate during catalytic cycles, placing this intermediate in the spotlight and rising new questions about its structure/function relationship. In this review, we describe the entire family of O2 activating diiron enzymes, excluding O2 transportation and iron storage proteins, with a special focus on recently discovered enzymes involving peroxo-diiron(III) species as active intermediate. The various reactivities of these enzymes are placed in the biological context and their mechanisms are discussed on the basis of spectroscopic characterizations of crucial intermediates. Finally, since low molecular weight models are of primary importance for both structural and functional studies, we also give an overview of handmade peroxo-diiron(III) complexes known to date, with a complete list of their UV–vis., resonance Raman and Mössbauer spectroscopic parameters.

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