Abstract
μ-Nitrido-bridged diiron porphyrins and phthalocyanines are known to be efficient oxidants that are able to oxidize some of the strongest C–H bonds in nature, such as the one in methane. The origin of their catalytic efficiency is poorly understood, and in order to gain insight into the structural and electronic features of this chemical system, we performed a detailed and systematic study into their chemical properties and reactivities using density functional theory. Our work shows that μ-nitrido-bridged diiron porphyrins and phthalocyanines are highly active catalytic oxidants, which react with methane with very low reaction barriers and a rate-determining hydrogen-atom-abstraction step. Furthermore, the μ-nitrido-bridged diiron porphyrin and phthalocyanine complexes react with a free energy of activation that is more than 10 kcal mol–1 lower in energy than that found for cytochrome P450 Compound I, which is known to be one of the most efficient C–H hydroxylating agents in Nature. We have analyzed the ...
Highlights
Cytochrome P450 enzymes are versatile enzymes in human physiology that mainly react with compounds through oxygen atom transfer, including the hydroxylation of C−H bonds
The biodegradation of long chain fatty acids and xenobiotics is catalyzed by P450 liver isozymes through a mechanism that is considered to proceed via an iron(IV)-oxo heme cation radical intermediate called Compound I (CpdI)
We focus on the chemical properties of the μnitrido bound diiron complexes and their reactivity with methane and, in particular, aim to elucidate why A/B react faster by hydrogen atom abstraction than P450 CpdI
Summary
Cytochrome P450 enzymes are versatile enzymes in human physiology that mainly react with compounds through oxygen atom transfer, including the hydroxylation of C−H bonds. P450s activate their substrates with the aim to initiate their metabolism and detoxification but, on the other hand, assist in biosynthetic pathways of e.g., hormones.[1] the biodegradation of long chain fatty acids and xenobiotics is catalyzed by P450 liver isozymes through a mechanism that is considered to proceed via an iron(IV)-oxo heme cation radical intermediate called Compound I (CpdI). To understand the fundamental features of the oxidant in the P450-enzymecatalyzed reaction mechanism, synthetic models have been prepared that model the enzyme active site composition and coordination.[2] These so-called biomimetic model complexes enable one to study the reactivity patterns and the intrinsic chemical properties of iron porphyrins and gain understanding into the intricate structural and electronic features of the active site. Biomimetic work confirmed a high-valent iron(IV)oxo porphyrin cation radical to be the active oxidant in chemical transformations of substrates and ruled out many alternative suggestions.[3]
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